International consensus on terminology to be used in the field of echinococcoses

Echinococcoses require the involvement of specialists from nearly all disciplines; standardization of the terminology used in the field is thus crucial. To harmonize echinococcosis terminology on sound scientific and linguistic grounds, the World Association of Echinococcosis launched a Formal Consensus process. Under the coordination of a Steering and Writing Group (SWG), a Consultation and Rating Group (CRG) had the main missions of (1) providing input on the list of terms drafted by the SWG, taking into account the available literature and the participants’ experience; and (2) providing independent rating on all debated terms submitted to vote. The mission of the Reading and Review Group (RRG) was to give an opinion about the recommendation paper in terms of readability, acceptability and applicability. The main achievements of this process were: (1) an update of the current nomenclature of Echinococcus spp.; (2) an agreement on three names of diseases due to Echinococcus spp.: Cystic Echinococcosis (CE), Alveolar Echinococcosis (AE) and Neotropical Echinococcosis (NE), and the exclusion of all other names; (3) an agreement on the restricted use of the adjective “hydatid” to refer to the cyst and fluid due to E. granulosus sensu lato; and (4) an agreement on a standardized description of the surgical operations for CE, according to the “Approach, cyst Opening, Resection, and Completeness” (AORC) framework. In addition, 95 “approved” and 60 “rejected” terms were listed. The recommendations provided in this paper will be applicable to scientific publications in English and communication with professionals. They will be used for translation into other languages spoken in endemic countries.


Introduction
Echinococcus species (spp.) are parasites of the class Cestoda and belong to the phylum Platyhelminthes; they cause a variety of diseases in humans, most importantly cystic echinococcosis (CE; also found in scientific publications and professional/public communications under "hydatid cyst", or "hydatid disease", "hydatidosis", "echinococcus cysticus", etc.), alveolar echinococcosis (AE; also found under "alveococcosis", "echinococcus alveolaris", "alveolar hydatid", "alveolar hydatidosis", "alveolar hydatid disease", "multilocular hydatid cyst", "multilocular hydatid disease", "multilocular hydatidosis", etc.), and neotropical echinococcosis (NE; also found under "polycystic echinococcosis", "polycystic hydatid disease", "hydatidosis of the New World", etc.) [35]. The simple enumeration of the various alternative names of the diseases, still in use in 2020, readily shows the absence of standardization of the terminology used in this field. Echinococcoses are zoonoses, and the complexity of the life cycle of the various species of Echinococcus involved, the variety of their hosts, as well as the impact of the diseases due to Echinococcus spp. on public health, require the involvement of specialists from nearly all disciplines (medicine and surgery, veterinary medicine, zoology, parasitology, ecology, agriculture, public health, economics, etc.) which have their own history and their own jargon. However, they must cooperate to solve the multiple problems of Echinococcus spp. infection, within the "One-Health" concept. This makes the use of a common vocabulary crucial. Time has thus come for standardization of the terminology in the field of echinococcosis.
From Hippocrates, who first described the cysts in patients more than 2400 years ago [18], to the 20th century, languages of Greek and Latin origin have served to name the parasites/ diseases associated with Echinococcus spp. because in the Western world, countries around the Mediterranean were the known endemic regions for CE, the only recognized Echinococcus-related disease [13]. In the 19th century, physicians and researchers of German and Russian languages and in the 20th century, of French and English languages [18] brought new terms, and AE, then NE, were added to the list of Echinococcus-related diseases. At the end of the 20th century, China was recognized the main endemic region for CE and AE. Meanwhile, publishing in English became more and more common for physicians and scientists working in the field of echinococcosis worldwide, and everyone had to work with the variety of words and expressions describing Echinococcus spp. and echinococcosis in international publications in English [77]. Differences in wording, in the various professional environments, as well as in the various endemic countries, have become sources of misunderstanding, with influences related to the local language of the professionals.
The first decade of the 21st century, with the development of molecular biology techniques and the complete elucidation of the genomes of E. granulosus (Batsch, 1786) [87] and E. multilocularis (Leuckart, 1863) [73], has seen the emergence of new species within the genus Echinococcus, that have increased and refined our taxonomic knowledge of these parasites; such developments have also had an impact on several domains of echinococcosis research including not only genomics, proteomics and metabolomics, but also immunology and epidemiology [81,86]. There has been and still is coexistence of already defined species based on genetic sequences with "types", and "strains", based on morphological characteristics [55]. A better definition of the limits of the species has led to an agreement between specialists on the definition and names of the "new" species, and nine species are now recognized and characterized by the sequences of their genomes, and defined in terms of host species and endemic areas [81]. The application of binomial nomenclature for genera and species is now governed by various internationally agreed codes of rules, of which the "International Code of Zoological Nomenclature (ICZN)" governs the scientific designation of parasites (https:// www.iczn.org/the-code/the-international-code-of-zoologicalnomenclature/the-code-online/). This international system must be followed, and any new species designation has to be registered for its international use. However, the translation of the "new" Echinococcus species defined by specialists into common usage by professionals has not yet been achieved, and many publications still use "E. granulosus" as a single species name responsible for CE.
The situation is also problematic for disease names and all other terms and expressions. This may be due to the status of echinococcoses as "orphan" diseases or "neglected diseases" (e.g., for the World Health Organization they are now recognized as "Neglected Tropical Diseases" (https://www.who.int/ neglected_diseases/diseases/en/), even though most human cases and animal infections are not in tropical areas). For "non-neglected" diseases, authoritative international scientific societies have fixed the terminology and published recommendations that are regularly updated. The World Federation of Parasitologists has endorsed the Standardised Nomenclature of Parasitic Diseases (SNOPAD), initially published in 1988 for animal parasitic diseases by the World Association for the Advancement of Veterinary Parasitology, and has established rules for the names of parasitic diseases [32] (cf. https://www. waavp.org/documents/snopad-guidelines/#.XS9gBvIza00). The disease names are derived from the genus of the parasite with a suffix in "-osis" (e.g., Echinococcus would give "echinococcosis"). The rule is simple and clear; but the application of this rule has not been consistently followed and, especially for echinococcosis, coexistence of various names prevails, with a subsequent impact on database searching and misunderstanding between researchers and professionals [33,34]. Other terms used in the "echinococcosis field" are equally ill-defined.
The "Asociación Internacional de Hidatidología" was founded in 1941 in Colonia del Sacramento (Uruguay), during the first "International South American Conference to Fight against Hydatidosis", aiming at coordinating echinococcosis control, especially in the endemic countries of South America, and organizing conferences. From 1951 to the end of the 1990s, Spanish, French and English were the official languages of the biennial "World Congress of Hydatidology", the main activity of the "International Association of Hydatidology" (IAE). At the 26th congress in Bucharest, Romania, in 2015, the name of the association in English was officially changed to "World Association of Echinococcosis (WAE)", a formal step towards the adoption of "echinococcosis" for the denomination of the diseases (and of the field of research in general). In 1985, the WHO Informal Working Group on Echinococcosis (IWGE) was created, with the double aim of creating a network of scientists working in basic sciences in the realm of echinococcosis, and in standardizing practices for the diagnosis and treatment of Echinococcus spp.related diseases, in line with the priorities of the WHO [18].The group is currently working on a Technical Manual to help clinicians in the care management of patients with echinococcosis. Both professional entities (IAE and IWGE) hold their main meeting at the same location and have always joined efforts to issue manuals on echinococcosis including veterinary aspects, prevention and control [15][16][17], or write and update guidelines for diagnosis and treatment of patients with echinococcosis [10,83]. In a plenary session of the 27th World Congress of Echinococcosis (WCE) in Algiers, Algeria, 2017, the need for harmonizing the terminology of echinococcosis, on sound scientific and linguistic grounds, was stressed; a working group and a consensus process were established to provide recommendations applicable to scientific publications in English, and to the communication between professionals. Such recommendations should then be used as a basis for translation into other languages spoken in endemic countries for communication, teaching and training. This report and its illustrations (Tables and Figures) and Appendix are the ultimate result of the process.

Materials and methods
The methodology proposed to the participants in the working groups established at the 27th WCE was the "Formal consensus" approach, as used by the French "Haute Autorité de Santé" (https://www.has-sante.fr/upload/docs/application/pdf/ 2018-03/good_practice_guidelines_fc_method.pdf), inspired by both the Delphi process [30] and the Consensus Conference methods [19]. As the methodology was initially described to set up guidelines for good clinical practices, the method was slightly modified, as described below, to fit with the objectives of the present work, i.e. an agreement on terminology and good publishing practices. All participants in the various groups involved in the "formal consensus" process are cited as "associated authors" in the final publication (names in Appendix).
Definition and modalities of constitution of the Working Groups Steering and Writing Group (SWG) The mission of the SWG was: (1) to draft the list of words and expressions, and provide a critical analysis of their scientific and linguistic relevance, from the international scientific literature and all available sources (international nomenclature, international recommendations, historical notes, etymology), and submit it to the participants in the Consultation and Rating Group (CRG); (2) to collect and discuss the feedback from the participants in the CRG, and if necessary to submit difficult cases to appropriate external experts; (3) to draft the final lists of words and expressions and submit them to rating by the participants in the CRG; (4) to select 12 experts in the various disciplines of interest to the field of echinococcosis, not involved in the CRG, as members of the Reading and Review Group (RRG); (5) to analyze the rating data and draft the initial version of the Recommendation Paper, including the final tables with recommended terminology, to be submitted to the RRG; (6) to consider the remarks of the RRG on the draft, finalize the paper and the tables with the members of the CRG, and submit it to the appropriate journal; and (7) to ensure the follow-up of the paper and the dissemination of its content to end-users.
The composition of the SWG, chaired by a project manager, was approved by the president and the members of the WAE attending the 27th WCE, and three topics of interest were proposed, each coordinated by two members of the SWG, experts in the area.

Consultation and Rating group (CRG)
The mission of the CRG in the "formal consensus" process was (1) in the first step of consultation, to provide input on the initial list of terms and expressions drafted by the SWG, taking into account the available literature in all fields and the personal experience of the various participants; (2) in the second step of consultation, to participate in the poll, and provide independent rating on all words and expressions submitted to vote by the SWG; and (3) to finalize the text of the paper with the SWG after its evaluation by the RRG, and before its submission to the appropriate journal.
Sub-groups, corresponding to the three topics of interest were composed on a voluntary basis at the 27th WCE, and completed after a call for volunteering launched by email by the SWG after the congress. On their request, participants could belong to more than one subgroup. The list of the CRG participants who were involved in the whole process, and their country/countries of residence and field work, is provided in the Appendix. For the "Species and epidemiology", "Biology and immunology" and "Clinical aspects" subgroups of the CRG, 17, 18, and 14 participants were identified, respectively from 15 countries in total. The project manager coordinated all activities of the groups but was not involved in any rating; however, other members of the SWG who volunteered for the task could be involved in rating but only for those subgroups they were not coordinating.

Reading and Review Group (RRG)
The mission of the RRG, multidisciplinary and multiprofessional, was to give a formal opinion on the content and form of the initial version of the paper and the recommendations it may contain, especially in terms of applicability, acceptability, and readability in their own domain. According to the rules of the "formal consensus" process, the participants in the RRG would offer an advisory opinion on an individual basis, without de novo questioning the decisions from the votes obtained in the first 2 steps of the process. The list of the RRG participants (four experts for each topic) who were involved in the reviewing process, and their country/countries of residence and field of expertise, is given in the Appendix.

Schedule of the process
The time schedule of the process, from October 2017 to February 2020, is given in Figure 1. The main steps included: (1) constitution of the SWG, presentation of the project, and constitution of the CRG; (2) provision of a list of words and expressions, with arguments for their acceptance or rejection, provided by the SWG to the participants in the CRG; (3) input from the participants in the CRG and open discussion; (4) constitution of the RRG by the SWG; (5) a preliminary summary by the SWG, and preparation of three lists of words and expressions for each of the three topics, according to three levels of decision: (a) a priori approved terms, (b) a priori rejected terms, (c) debated issues submitted to vote; (6) vote on "debated issues" by the participants in the CRG; (7) analysis of data and drafting of the Recommendation Paper by the SWG; (8) reviewing of the draft by the RRG; (9) last review by the CRG; (10) submission of the manuscript by the SWG; and (11) follow-up of the publication process and dissemination of the recommendations by the SWG.
Except for the first kick-off meeting at the 27th WCE and the final presentation at the 28th WCE in Lima, Peru, and given the worldwide extent of the consultation group and absence of funding, there were no further face-to-face meetings; all discussions and exchanges were managed by email. The project manager and members of the SWG answered all messages sent by the members of the CRG and all contributions were taken into account at any stage.

Analysis of the poll
Medians and means of the ratings, on a possible agreement range from 1 to 10, were calculated for the answers to each question. A majority of agreement for approval or rejection was considered when more than half of the ratings were equal to or higher than 5, or equal to or lower than 5, respectively. Unanimous approval or rejection was defined as ratings higher than or lower than 5 for all voters, respectively. Agreement for rejection was defined for a median equal to 3.5 or lower, and majority or unanimity of ratings; agreement for approval was defined for a median equal to 7.5 and higher; and majority or unanimity of ratings. A question was deemed "undecided" when the median was between 3.5 and 7.5 and/or there was no majority of ratings. After the poll and when needed, i.e. whenever the result of the votes was "undecided" and/or whenever there was no full agreement on the definition of a term, the SWG submitted the term/expression to further discussion between specialists in order to reach final agreement. To this purpose, subgroups of specialists (e.g., surgeons) were constituted to propose final agreement.

Final composition of the CRG subgroups
For the "Species and epidemiology" subgroup, 1 participant could not be reached by email and 1 never answered emails; the final rating was thus provided independently by 15 participants, from 10 countries. For the "Biology and immunology" subgroup, three participants could not be reached; five participants from the same research team worked together for the final rating; thus the final rating was provided independently by 11/15 participants from 11 countries. For the "Clinical aspects" subgroup, one participant could not be reached and one did not answer emails; 2 participants from the same research group worked together for the final rating; thus the final rating was provided by 11/12 participants from 8 countries.

Results of the first stage of consultation
The first stage of consultation generated numerous comments with associated arguments and references from all participants in the CRG. This input was carefully collated in a summary version of the preliminary tables by the SWG. In case of need, other experts of the specific field were consulted by the coordinators of the subgroups, and their opinion was brought to the attention of the CRG participants. The synthetic tables as well as additional pictures if necessary (especially for the subgroup on "Biology and immunology"), were again sent to all participants to obtain initial evaluation of possible consensus, and set up a list of still "debated issues".
For the "Species and epidemiology" subgroup, it was agreed that the nomenclature of old and new species of Echinococcus should follow the rules of the ICZN. Thus, the names of the species (and their number) listed in the tables reflect the results of current taxonomic research and do not preclude future changes, provided these are based on convincing new evidence. There was also a consensus on the use of the "G" genotypes in cases where genetic differences are apparent, but wherebased on current knowledgethese differences are deemed too small to warrant recognition of the variants as named taxa. In addition, the term "genotype" should be reserved for characterization using molecular biology/sequencing, and "strain" or "type" should be reserved for characterization using morphological and host-range characteristics. Consequently, there were no "debated issues" for this subgroup. However, definitions and clarifications on species names and on other words and expressions regarding this topic were given in provisional tables; they were submitted for approval or rejection in the second stage of the process (with an answer of the "YES/NO" type).
For the "Biology and immunology" subgroup, there was far more debate since there is no official institution in charge of such terminology. Divergences appeared about the various stages of development of the Echinococcus spp. in their intermediate hosts, and particularly on the definition of the term metacestode. Other minor divergences were noted on the use of certain words to designate the cells and components of these parasites, either adult or larval, as well as the host's reaction. References were provided by parasitology and immunology specialists to support data interpretation, thus the use of specific words. From that stage of the consultation, there was general agreement that the adjective "hydatid" should only be used for E. granulosus sensu lato; as this was a sensitive issue, it was however kept in the "debated issues" submitted to vote, both for the "Biology and immunology" and for the "Clinical aspects" subgroups. For details on the names of the various components of the egg of all Echinococcus spp. and of the cyst in CE, it was decided to provide a figure that would fix the definitions of the various words (Figs. 2A, 2B and 2C). The definition of "cyst" was initially the main disagreement between "parasitologists" (2-layer cyst) and "clinicians" (3-layer cyst). At the end of the first stage, it was finally agreed by all experts, whatever their field of expertise, that all cysts due to Echinococcus spp. and, especially for clinicians, those due to E. granulosus s.l., included two "layers" (and not "membranes") of parasite origin and one layer of host origin, thus three layers. This clarification helped when defining several derived terms.
For the "Clinical aspects" subgroup, it was readily agreed that the names of diseases due to the various species of Echinococcus should follow the rules proposed by the SNOPAD and the generic name "echinococcosis" should always be used, irrespective of the species and type of disease. "Cystic" and "Alveolar" should be used as adjectives to designate the diseases due to E. granulosus (Batsch, 1786) sensu lato, and to E. multilocularis (Leuckart, 1963), respectively. Some discussion remained for the use of the adjective "hydatid", and for the names of the diseases due to E. oligarthra (Diesing, 1863) and E. vogeli Rausch and Bernstein, 1972, in South America. Most of the debated issues concerned the names of therapeutic interventions (surgical or using other techniques); however, the common definition of "cyst", shared by parasitologists and clinicians, led to an easier consensus on the meaning of "cystectomy".
Results of the second stage of consultation Agreement for approval or rejection A few terms proposed in the lists for "approval" or "rejection" at the end of the first stage of the process still received objections from participants in the CRG. More precision (or references) were provided in order to reach a final consensus on these terms and their definition. Approved terms were provisionally included in Tables 1A (Genetics and epidemiology), 1B (Biology and immunology) and 1C (Clinical aspects). Rejected terms were provisionally included in Tables 2A (Genetics and epidemiology), 2B (Biology and immunology) and 2C (Clinical aspects).

Poll on debated issues
Among the 39 final participations in the poll about "debated issues" nine were incomplete; the questionnaire was sent back to these participants for completion; precise answers were eventually obtained. The ratings provided for the poll on "debated issues" were analyzed in order to obtain means and medians, and thus a final score for approval or rejection of each term. Results of the median rating for the "debated terms", and whenever useful the agreement between participants, are given in the "Comments" column of Tables 1A-1C and 2A-2C. Objections and concerns on the use of some terms were re-discussed by D.A. Vuitton et al.: Parasite 2020, 27, 41 specialists before making a final decision on their final rejection or approval, and minor modifications in the wording of definitions were made in order to obtain a final consensus. An important result of the poll, since it was distinctly and clearly agreed upon both by the participants in the "Biology and immunology" subgroup and those in the "Clinical aspects" subgroup, was on the word "hydatid". According to the polls, all names of diseases or operations composed from the radical "hydatid" (e.g., in "hydatid-osis" or "hydatid-ectomy", etc.) should be abandoned, and the adjective "hydatid", whenever used, should never be used to qualify entities different from those due to E. granulosus sensu lato, thus never be used for E. multilocularis, E. vogeli and E. oligarthra. A final discussion on the characterization of the surgical procedures aimed at removing CE cysts eventually retained a simple framework that should be used whenever surgical operations are described in publications, with four levels of mandatory qualification, regarding (1) Approach: "laparotomy", "laparoscopy" or "robotic"; (2) Cyst Opening: "non-opened cyst" (NOP) versus "opened-cyst" (OP); (3) Resection type: "cystectomy", "hepatectomy", or "liver transplantation"; and (4) Completeness of resection: "total", "subtotal", and "partial". Description of the AORC unified framework for surgical interventions in CE is given in Figures 3A and 3B. Precise description of the procedure actually performed should complete the mandatory terms (description of the removed parasite layers, area in square centimetres or percentage of cyst actually resected, closure of communications with bile ducts, etc.).

Review by the RRG and meeting at the 28th WCE in Lima, Peru
Feedback from the RRG members usually addressed minor aspects of text readability and/or definitions/descriptions in the Tables. Clarification was provided by the reviewers on the definition of the species and their hosts, especially regarding species involved in NE. The major issues raised by one reviewer (clinician) concerned the definition of the "cyst", and the retention of the adjective "hydatid", even in its very restrictive sense as described in Tables 1B and 1C. However, because of the clear results of the consensus process, these objections could not be taken into account in the final version. At the meeting of the WHO-IWGE held in Lima, Peru, during the 28th WCE, the still debated issues were raised and final adjustments were made between the SWG and the writers of the WHO-IWGE Technical Manual on CE treatment. Words and expressions finally approved and rejected after the poll and the last discussions were added to the list of approved and rejected terms. Terms finally approved (95 items) are thus included in Tables

Discussion
This 2-year multidisciplinary and international exchange of views has allowed physicians, veterinarians and basic science researchers to freely discuss opinions about terms used in all fields relating to Echinococcus spp., and to reach a consensus on the use of the most appropriate ones, based on sound scientific and/or linguistic grounds. When evidence was not available, consensus was based on reasoned arguments, including usage when no suitable alternative was found, confirmed by a poll. This is the first and only endeavour of this type in the domain of echinococcosis; and it is endorsed by the WAE. Definitions of 155 terms and expressions and recommendations provided in Tables 1A-1C and 2A-2C and Figures 2A-2C and  3 should be followed in the future by all scientists writing scientific papers in English; scientific editors and referees/reviewers should recommend article authors to use the approved terms. These recommendations should help the recognized experts, involved in scientific work on echinococcosis at the international level, to set up a similar list of recommended and rejected words in their country language(s), so that similar wording could be used by all professionals. Major advances promoted by the multidisciplinary work on echinococcosis terminology were: (1) the confirmation of the current recognition of nine species of Echinococcus; (2) an agreement on the names of the three types of diseases due to Echinococcus spp. and rejection of all others; (3) the restriction of the adjective "hydatid" to E. granulosus s.l.; and (4) the proposal of the "AORC" framework to describe surgical interventions in CE. The participants involved in the work were representative of the "echinococcosis" scientific community. Half of the 61 participants in the three working groups belonged to the top 50 experts in the area (as cited from their publications retrieved with the key words "echinococcosis": http://expertscape.com/ex/ echinococcosis or "hepatic echinococcosis": http://expertscape. com/ex/echinococcosis%2C+hepatic). Health professionals and young researchers were also involved in the CRG; there was a balanced proportion of researchers and professionals. The participants in the three groups were from 15 endemic countries, and all five continents were represented with a balance of male and female contributors to the debate. Recruitment of the participants in the CRG at the 27th WCE on a volunteer basis enabled researchers and professionals from the Maghreb and Middle East countries, highly endemic countries for CE, to participate in the CRG.  ; must be written in italics with first letter in capital letter; abbreviation "E." (italics followed by a dot) when in a binomen (i.e. a generic name and a specific name) or in a trinomen (a generic name, a specific name and a subspecific namethis is rare).
The genus name Alveococcus (for the species Alveococcus multilocularis (Leuckart, 1863) Abuladze, 1959) was erected to separate E. multilocularis from the other species. There is no longer a taxonomic basis for such a separation, but the name is still used occasionally, particularly in Russian literature. See also Table 2A.
Echinococcus sp. One species within the genus Echinococcus.
The abbreviation "sp." (not italics) stands for a species, the identity of which is not known (e.g. in case of an undetermined Echinococcus isolate) Echinococcus spp. More than one (or all) species within the genus Echinococcus.
The abbreviation "spp." does not indicate a species with the taxonomic definition of "species", but stands for "species pluralis" (the Latin for "multiple species"), hence the roman letters (not italics  The concept of E. granulosus as one species cluster that contains all agents of cystic echinococcosis. "sensu lato" and "sensu stricto" are used, when a species name (here: E. granulosus (Batsch, 1786)) [7] is used in different concepts: in a wider sense (s.l.) that includes e.g. cryptic species, or in a more restricted concept (s.s.) [52]. "sensu lato" should be in italics (although this is debated), without capital letters as first letters. The abbreviation of each word in "sensu lato" is followed by a dot (because it is the abbreviation of Latin words; see e.g., i.e., as examples), thus: "s.l." "granulosus" should be followed by "sensu lato" whenever the precise species has not been determined. For publications on the clinical aspects of echinococcosis, as the clinical descriptions of the disease "cystic echinococcosis"(CE) fits with all those species within E. granulosus sensu lato that are responsible for disease in humans, the use of E. granulosus sensu lato is allowed when there was no identification of the real species. For publications on basic research and epidemiology, molecular identification of the real species is necessary; it should be performed and indicated in the Materials and Methods section.
E. granulosus sensu stricto corresponds to the previous "G1", "G2", a microvariant of "G3", and "G3" genotypes, identified by DNA sequencing (see GenBank: https:// www.ncbi.nlm.nih.gov/genbank/); its cycle usually involves sheep as intermediate hosts and dogs as definitive hosts; cattle and other ungulates may also be infected by E. granulosus sensu stricto A strongly diverging genotype from Africa ("G Omo") is provisionally retained in E. granulosus s.s., but will have to be reclassified in the future [79].
"sensu stricto", which is the equivalent of a species, should be in italics (although this is debated), without capital letters as first letters. The abbreviation of each word in "sensu stricto" is followed by a dot (because it is the abbreviations of Latin words; see e.g., i.e., as examples), thus: "s.s." E. granulosus s.s. belongs to E. granulosus s.l. [66] Echinococcus multilocularis (Leuckart, 1863) A species in the genus Echinococcus.
E. multilocularis (Leuckart, 1863) [50], is the agent of the disease "alveolar echinococcosis" (AE) in humans [35,52] E. multilocularis was clearly distinguished from E. granulosus sensu lato in the middle of the 20th century [18,77]  aqhqa -arthra (joints) which is the plural of ; aqhqom -arthron (joint). The name is therefore not an adjective, but a noun in apposition, which does not change its ending according to the gender of the generic name. This was recognized earlier but subsequently ignored.
E. oligarthra cycle usually involves agouti (Dasyprocta spp.) and occasionally paca (Cuniculus paca), spiny rats (Proechimys spp.), rabbits (Sylvilagus floridanus), and opossums (Didelphis marsupialis) as intermediate hosts and various wild cat species as definitive hosts [65]. It is responsible for a disease in humans distinct from cystic and alveolar echinococcosis, sometimes wrongly called "polycystic echinococcosis" (since it usually presents as a single cyst) [35]. "Neotropical echinococcosis" is the expression recommended to qualify human infection due either to E. vogeli or to E. oligarthra. See also  [85] is a species phylogenetically close to E. multilocularis [52] which was identified in the county of Sêrx€ u (in Tibetan, 石渠县 in Mandarin Chinese (pinyin: Shíqú Xiàn)) in Sichuan province, Qinghai-Tibet plateau region of Western PR China E. shiquicus (pronunciation "seshüicus") infection has not been recognized to be associated with disease in humans up to now [35]. it has also been documented in other rodents such as agouti (Dasyprocta spp.), and the bush dog (Speothos venaticus) and domestic dogs as definitive hosts [65]; E. vogeli is responsible for a disease in humans distinct from cystic and alveolar echinococcosis, often called "polycystic echinococcosis", because of the presentation of the disease [35]. "Neotropical echinococcosis" is the expression recommended to qualify the human infection due either to E. vogeli or to E. oligarthra: see also Table 1C.

G genotypes
Genotypes identified within the species E. granulosus s.l., previously identified as "strains".
Genotypes may be used to differentiate between distinct molecular sequences, within the defined species or complexes; the word "strain" should no longer be used when genetic characterization has been performed [52,55].
Further definition of new species is still possible. Waiting for such definitions, G genotypes should be kept, in addition to the current species name, if necessary.
(Continued on next page) Could be used in clinical or experimental situations when evidence of absence of viability is not obtained by transplantation or in vitro culture.
Distinct from "non-viable"; the definition was approved unanimously by the voters; the adjective "aborted" was preferred to the alternative "died-out" by the majority of voters (median: 10).

*Adult form, Expression
Sexual reproduction stage of Echinococcus spp. parasites in their definitive hosts.
More popular alternative expression to the specific scientific expression "strobilar stage" to designate this step in the development of Echinococcus spp. cestodes; expression coherent with "larval form" in the intermediate hosts.
"Adult" may include all stages of development in the definitive host (fertile or immature worms i.e. with the last segment containing eggs or not). This expression with its definition was approved by the majority of voters (median: 10)

*Adventitial layer, Expression
Partly cellular and fibrous layer of host origin surrounding the inner 2 layers of parasite origin (germinal and laminated layers) of the metacestode in the intermediate host of E. granulosus sensu lato.
The expression was approved in order to have a coherent denomination of the various "layers" of the hydatid cyst, irrespective of their origin (parasite or host).
"Adventitia" was an alternative term; it was rejected by voters (median: 2). The expression "adventitial layer" with its definition was approved by the majority of voters (median: 10) As for "germinal membrane" and "laminated membrane", the use of the expression "adventitial membrane" is not relevant.  The word "genotype" should be used; it is more appropriate than "strain" since it is based on genotyping and not on other techniques (especially morphological) previously used to distinguish between strains [52,55].
Keeping the distinction between genotypes may be necessary for phylogeographic studies and in some circumstances for echinococcosis control (targeting animal hosts and specific cycles) [38,41]. Best target for identification of G1 and G3 seems to be the nad5 gene region [39]. G1 is the most common genotype in sheep; G2 was first described as "Tasmanian sheep strain" but is actually cosmopolitan; G3 was initially identified from water buffalo, but is now also known from other intermediate hosts.
G9 is no longer recognized as a distinct genotype; it is probably a microvariant of G7; the genotypic cluster G6/7 is the second most important agent of human CE worldwide; further distinction between species within the E. canadensis cluster has been proposed, but has not been accepted yet [48,53,54,57].
Genotypes may be used to differentiate between distinct molecular sequences, within the defined species; the word "strain" should no longer be used. For both E. granulosus s.l. and E. multilocularis, structures that surround the laminated layer, at the border with the organ parenchyma.
Alternative term to "boundary" The use of "boundary" was rejected by all voters but one. The noun "border" with its definition was approved by the majority of voters (median: 10).

Brood capsule, Expression
Element budding from the germinal layer which produces protoscoleces.
No synonyms.
In some publications, some confusion may be found with "daughter cysts". The 2 entities are totally different in their origin and their components (see Anatomical entity produced by the growth of the metacestode of Echinococcus spp. distinct from the surrounding organ parenchyma and filled with fluid, which includes (from outside to inside) -Adventitial layer (of host origin, even reduced to a few infiltrating cells or to fibrous tissue) -Laminated layer (of parasite origin) Germinal layer (of parasite origin) -Cyst fluid (and its content, of both parasite and host origin).
The word "cyst" should be reserved to the clinical (or experimental) situation in CE ("hydatid" cyst) or NE; it may be observed by a variety of imaging techniques such as ultrasound imaging, computed tomography, or magnetic resonance imaging.
The international classification of CE cysts is based on ultrasound imaging with 5 CE stages [82] Two types of CE3 cysts (a and b) are now described [10,31].
Should never be used to designate the central necrotic cavity often developed in the AE lesions. "Pseudocyst" should be used for this cavity. All voters supported the restriction of the noun "cyst" to CE or NE, in the context of echinococcosis (median: 10).

*Cyst fluid, Expression
Liquid secreted by the germinal layer of Echinococcus spp. larval form and collected at the center of the "cyst" (for E. granulosus s.l.) or of the "microcysts" (for E. multilocularis).
Should be reserved for in vivo situations: cysts in CE, and NE, and microcysts of AE in human and animal hosts, including experimental models.
The distinction between "vesicle fluid" and "cyst fluid" was approved by all voters (median: 10); they also approved the use of "cyst" for the in vivo situation only.

*Echinococcal, Adjective
Adjective proposed to qualify anything relating to all Echinococcus spp. irrespective of the species, of the pathology, or of the clinical presentation of the disease that occurs in humans or in animal intermediate or definitive hosts.
Completely generic term that does not assume the species and/or stage of Echinococcus spp.
The term "hydatid" is more common, but also more confusing, and should be restricted to E. granulosus s. l. Usage of "echinococcal" with the generic definition was approved by the majority of voters (median: 8).
Based on the recommendations of the World Federation of Parasitologists regarding the names of parasitic diseases [32]. Please see also the definition of "fertile" for the parasitic structures in the intermediate host, and the definition of "immature", in this table.
(Continued on next page) Larval parasitic structure that contains viable protoscoleces and thus allows infection of the definitive hosts through scoleces or in some pathological or experimental circumstances production of newly developed metacestodes in the intermediate host.
Production of protoscoleces by the germinal layer and their release in the parasitic fluid (whatever the species) implies that the metacestode is fertile.
This adjective with its definition for the metacestode in intermediate hosts was approved unanimously by the voters (median: 10).

Germinal layer, Expression
Inner cellular part of Echinococcus spp. metacestode, which includes several types of cells and produces several types of biological components of the metacestode (cyst fluid, brood capsules, and protoscoleces).
The term "layer" should be preferred to "germinal membrane" because of the complexity of the various "layers" of the cyst, and the possible confusion of "membrane" with the cell "membrane", which has a specific definition in biology. Most commonly used expression in the literature, with this definition [47]. However, it must be noted that not all cells of the germinal layer are germinative cells.
The expression was approved by the majority of voters (median: 8) against the alternative "germinal" (median: 3).

Hooks, Noun
Appendices  Following the suggestion of using "hydatid" only to qualify nouns or expressions related to E. granulosus s.l. (see above), this expression should also be restricted to these species. For any other species "fluid" should be preceded by the taxonomic name of the species, or the expression "cyst fluid" (for in vivo situations) or "vesicle fluid" (for in vitro situations) could be used. "Immature" just indicates that the adult form has not fully developed to the stage of egg production; it does not imply that the adult worm will never become fertile, as could suggest the alternative "non-fertile".
See also the entry "non-fertile" in Table 2B regarding the strobilar stage/adult form; and also "nonfertile", approved for the metacestode in the intermediate host, in this table. This adjective was added by the SWG, on experts' suggestion, to the list of approved terms after the poll.

*Infiltrate (periparasitic), Noun
Histological components (cellular and fibrous) of host origin in alveolar echinococcosis; opposite to the "adventitial layer" of CE cysts, the cellular and fibrous infiltrate in AE has no clear limits with the surrounding liver parenchyma.
Alternative term to "infiltration".
The use of "infiltrate" was approved by all voters but one (median: 10).

Laminated layer, Expression
Peripheral acellular outer part of Echinococcus spp. metacestode, mostly composed of mucopolysaccharides.
The laminated layer is produced by the parasite and exerts important functions in the interaction between the metacestode and the intermediate host [21].
The term "layer" should be preferred because of the complexity of the various "layers" of the metacestode, and the possible confusion of "membrane" with the cell "membrane", which has a specific definition in biology. Generally used as a popular equivalent of "metacestode".
All voters but 2 considered that "larva" and "metacestode" were synonymous; however, metacestode should be preferred for scientific communication; see also the entry "larval form".

Larval form, Expression
Asexual reproduction form of Echinococcus spp. parasites in their intermediate hosts.
Expression coherent with the recommended expression "adult form".
The expression may be used as an equivalent of metacestode (or of larva) for communication to the public and to professionals.
(Continued on next page) As the voters did not agree on the definition of "metacestode" (i.e. stages of development included in the definition), this was further discussed by experts after the poll, and the final definition (shown in the second column) was approved.
The approved definition is supported by textbooks of veterinary parasitology [28] and those on Echinococcus spp. [72]. Should be reserved for AE lesions in vivo; may be observed with selected imaging techniques such as Magnetic Resonance Imaging (T2-weighted images) in humans or preclinical models, and/or histological examination in experimental models.
In this situation, "micro" does not refer to "microscopic" but to "small" (from ancient Greek lijqó1 -micros (small)) macroscopic aggregated cysts in AE, opposite to the "big"often isolatedcysts in CE or E. oligarthra-NE or multicystic presentation of E. vogeli-NE. This noun with this definition was approved by 8/10 voters (median: 9).
Microcysts are parasitic structures, distinct from the central necrotic cavity often developed in the AE lesions ("pseudocyst" should be used for this cavity). See also the entry "pseudocyst" in this table. The noun "microcysts" [6] may replace the expression "multiple small round cysts" found in Kodama  A "non-fertile" metacestode may be "viable"; these adjectives are not synonymous [22].  Tissue surrounding the cyst. Regarding echinococcosis, the adjective applies to E. granulosus sensu lato only: tissue/structure (e.g. liver, lung, adrenal gland, brain, etc.) that surrounds the CE cyst which includes: the cyst fluid, the germinal layer, the laminated layer, the adventitial layer.
As the cyst, in E. granulosus sensu lato infection, includes the adventitial layer, the pericyst only corresponds to the organ parenchyma (plus vessels and ducts) which surrounds the cyst.
In the clinical (or animal/ experimental) situation in CE, the noun "pericyst" (or the adjective "pericystic") should not be used to designate the adventitial layer (which is "periparasitic", not "pericystic"). Should not be used in E. multilocularis infection to qualify the tissue/structure that surrounds the lesions.

Periparasitic, Adjective
Tissue surrounding the parasite. For E. granulosus s.l.: tissue/structures that surround the laminated layer of the hydatid.
In the cyst developed in E. granulosus s.l. infection in the intermediate host, the adventitial layer, produced by the host, surrounded by the normal parenchyma (plus vessels and ducts) represents the "periparasitic" tissue.
In the clinical (or animal/ experimental) situation in CE, "periparasitic" (which includes the adventitial layer and the normal parenchyma of the organ) should not be a synonym for "pericystic" (which only includes the normal parenchyma of the organ; see also the definition of "(hydatid) cyst" and Figs. 2A-2C). In the lesion developed in E. multilocularis infection, the inflammatory tissue (granuloma) that surrounds the lesion without clear limit with the organ parenchyma represents the "periparasitic infiltrate".
For E. multilocularis: tissue/ structures that surround the laminated layer of E. multilocularis microcysts.
*Post-oncospheral stage, Expression Stage between the oncosphere and the fully constituted metacestode.
As it textually refers to the "oncosphere", this expression more precisely addresses Echinococcus spp. than "transitional larva" which may apply to any type of larvae. Referring to the Greek origin of the word (ckxssí1: strap), "proglottis (sing), proglottides (plur) should be preferred to "proglottid"; in British English, the original plural of words from other languages is kept, hence "proglottides".

Protoscolex (plural: protoscoleces), Noun
Prefiguration of the scolex, produced by the brood capsules budding to the outside of the germinal layer of Echinococcus spp. metacestode and released in the cyst (CE) or micro-cyst (AE) fluid.
The plural form of scolex (and of all derived words) should definitely be "scoleces".
(Continued on next page) Like its more popular synonym "adult form", it includes all stages of development in the definitive host (fertile or immature worms i.e. with the last segment containing eggs or not).

Suckers, Noun
Appendices of the adult form of Echinococcus spp. parasites which allow them to attach to the intestinal wall of the definitive hosts and to feed from it. The distinction between "vesicle" (in vitro) and cyst (in vivo) and usage of the noun "vesicle" for in vitro cultures only, were approved by all voters but one (median: 10). Used as an even more popular equivalent of "strobilar stage" than "adult form".
May be a source of confusion with non-parasitic worms. However, it is tolerated because it is useful for teaching, reviews for students and professionals, and communication to the public.
* Agreement obtained at the second stage of the consultation (the participants in the Consultation and Rating Group had to rate their approval or rejection of the words/expressions independently on a scale from 0 to 10; whenever relevant, the median of the votes and the nature of the agreement (majority or unanimity) are given in the "Comments" column ** Agreement to recommend a word that was not selected at the first stage of consultation; the approval was obtained at the second stage after further discussion between experts or after recommendation by the RRG. Disease due to E. multilocularis, with multiple microcysts giving an "alveolar" aspect on sectioning of the infected organ.
Widely used since the recognition of the disease in the 19th century [18,78]. From the name of the species "Echinococcus" and the Latin adjective "alveolar", genitive -alveolaris" (composed of or relating to "alveoli"/small holes/air sacs in the lung). The expression conforms to the recommendation of the WFP; the preceding adjective provides precision on the morphology of the lesion (alveolar). The adjective "alveolar" clearly indicates the morphological aspect of the lesions (especially in the liver). Absence of precision regarding the type of disease leads to misunderstanding between experts, stakeholders and policy makers.
Recommended by the WHO-IWGE since its first "Guidelines" [83] Differentiates the disease due to E. multilocularis from that due to E. granulosus sensu lato easily.  [35,81]. In agreement with the international WHO-IWGE classification of cysts due to E. granulosus sensu lato infection, from ultrasound examination (CE1 to CE5) [82].
A majority of voters (and a few RRG members) preferred to use "CE cyst" only and reject the use of hydatid cyst (median 8); however, there was no unanimity (3 voters rating under 6). Because the "Biology and Immunology subgroup supported the use of "hydatid" restricted to E. granulosus s.l., at least temporarily, because of the widely used expressions "hydatid cyst" and "hydatid fluid", both expressions will be tolerated. Using "CE cyst" is highly recommended. Clinical definition. Complications may be: -Rupture (outside or in structures of the infected organ), -Compression or invasion of internal structures of the infected organ or of neighboring organs, -Superinfection of the CE/NT cyst or of the AE pseudo-cyst with bacteria or fungi, -Anaphylactic (IgE-dependent allergic) reactions due to echinococcal antigens, -Compression or invasion of internal structures/tissues (e.g. for bone or brain) in CE/NE and AE [35].
The adjective "complicated", for echinococcosis, should not be used to designate the simple growth of the parasite (with or without pain) if there are no consequences on the structures of the infected organ or on the neighboring organs. The large size of the cyst and its proximity to bile ducts or vessels in the liver (or bronchi or vessels in the lung, or vital structures in the brain) are not "per se" complications; even though they make the surgical treatment more difficult or impossible, they are just anatomical particularities. The term, with this definition, was accepted unanimously by the voters (median: 10).
(Continued on next page) From the ancient Greek jύrsi1, -cystis-(anatomical bladder), and ἐjsolή, -ectomè/ ectomia-(to cut out; to cut and remove), the suffix "-ectomy", in surgical vocabulary, refers to any type of removal of an organ or a lesion. So, literally it means "removal of the cyst". The context must be clear so that there may be no confusion between a CE cyst and any other types of cysts. In addition, the cystectomy should be qualified by the type of surgical technique, the type of cyst opening, and the extent of cyst removal.
Should never be used alone, without qualification, in a scientific/medical publication. The recommended order for qualification follows the AORC framework:  Disease due to E. granulosus sensu lato.
The expression conforms to the recommendation of the WFP; the preceding adjective, from the Middle French "cystique", from the ancient Greek jύrsi1, -cystis-(anatomical bladder), provides precision on the morphology of lesion (cystic). Absence of precision regarding the type of disease leads to misunderstanding between experts, stakeholders and policy makers.

Recommended by the WHO-Informal Working
Group on Echinococcosis (WHO-IWGE) since its first "Guidelines" [83]. Differentiates the disease due to E. granulosus sensu lato, from those due to E. multilocularis, E. oligarthra and E. vogeli, respectively.
From the ancient Greek eἶdo1 -eïdos-(shape), the suffix "-id" (with the infix "-o-" whenever useful in a given language) refers to anything "which has the shape of ... something"; thus "cystoid": which has the shape of a cyst (without being a real cyst).
This adjective was proposed and published for the classification of AE lesions at computed tomography (CT) scanning in 2016 [23] and used thereafter in other publications. Although the adjective "pseudocystic" was preferred by the majority of voters (median: 9 for the "Biology-Immunology group and 7 for the "Clinical Aspects group), the adjective "cystoid" was maintained after the poll to describe cyst-like images observed using computed tomography scanning and which cannot be attributed unequivocally to the necrotic cavity present in advanced lesions of AE.
In AE, the cystoid structures observed on imaging may be due to the central, liquefied necrosis in advanced AE lesions or to other cyst-like components such as conglomerate of microcysts or in very small lesions, occasionally, a hypodense solid necrosis. As these structures do not correspond to a parasitological entity, a specific word should differentiate these pathological cyst-like macroscopic structures from the real parasitic "cysts" of CE. All suggested names for this metacestode structure were rejected by the majority of voters (median for "daughter cyst", daughter hydatid, and daughter vesicle: 2, 1 and 3, respectively; means 4.63, 1.72 and 4.70, respectively). The word "daughter" evokes sexual reproduction (which does not exist for the metacestode), and "cyst" a complete CE cyst structure, with a fully developed adventitial layer (which is generally hardly present in this structure). However, the adjective "secondary" was considered by the participants in the CRG to be irrelevant for this situation (used for the growth of new cysts after protoscolex spillage), and the noun "vesicle" was accepted by biologists with restricted use for in vitro culture of the metacestode; hence the decision of the SWG to keep the "historical", albeit inexact, wording.
(Continued on next page) In CE and AE diagnostic procedures, no exploration of the pancreatic ducts is performed, but the acronym ERCP is commonly used even though the pancreatic exploration is not performed.
Performance of the ERCP may be only for diagnostic purposes; however, usually it has a therapeutic intent and is the first step of perendoscopic biliary drainage. In scientific publications, this distinction should be clearly stated.
Ex-vivo liver resection with autotransplantation (ELRA), Expression Surgical operation which includes: -Total hepatectomy followed by -Ex-vivo resection of the pathological parts of the liver associated with -Various types of reconstruction of the bile ducts and/or vessels then by -Re-implantation ("autotransplantation") of the liver orthotopically.
Surgical technique used for the treatment of advanced AE. The expression includes all steps of the procedure; so it should be preferred to partial expressions such as "ex-vivo liver resection" or "autotransplantation". The abbreviation was proposed by the surgical team that has performed most of these procedures and includes all main terms of the expression [2].
The numerous alternative expressions and acronyms should no longer be used.

Hepatectomy
Removal of the liver or part of it.
From the ancient Greek ήπaq, -hepar; genitive ήpaso1 -hepatos (liver), and the suffix ἐjsolή, -ectomè/ectomia-(to cut out; to cut and remove); in the surgical vocabulary it refers to any type of removal of an organ or a lesion. So, literally it means "removal of the liver" (which is literally correct only in liver transplantation). Various types are described, valid for all types of diseases subject to liver surgery.
Should always be qualified, according to the usual definitions of hepatic surgery, and of the liver segments; definitions are valid for the application to all types of diseases, including echinococcosis [29].
(Continued on next page) From the ancient Greek ύdasí1 -hydatis-, genitive -ύdasído1 -hydatidos (vesicle/bladder full of water). According to the definition of "hydatid" (as an adjective), the expression should be restricted to designate a cyst /cysts due to infection with E. granulosus s.l. in the intermediate host (including humans).
As it adds to confusion in epidemiological and clinical studies, it should never be used to designate the anatomical lesion due to E. multilocularis infection. The definition was approved by the unanimity of voters (median: 10). A majority of voters preferred to totally reject the use of "hydatid cyst" (median 8 for the specific question; see above "CE cyst"). As there was no unanimity and as the "Biology and Immunology" subgroup supported the use of "hydatid" restricted to E. granulosus s.l., at least temporarily, because of the widely used expression "hydatid cyst", both expressions will be tolerated. Nevertheless, the use of "CE cyst" is highly recommended.
As it designates an anatomical lesion and not a disease, it should never be used as an alternative name for Echinococcus spp.-related infection ("echinococcosis").
To designate the diseases due to Echinococcus spp. the noun "echinococcosis" qualified by the type of disease (cystic, alveolar or neotropical) should be used (abbreviations CE, AE, NE; see above).

**Laparoscopy, Noun
Surgical approach performed for operations in the abdomen or pelvis using small incisions (usually 0.5-1.5 cm) with the aid of a camera.
Qualifies any surgical intervention performed under laparoscopy. To be preferred to "coelioscopy", more used in gynecology.
Should be added to the noun or expression describing any type of intervention, if this surgical intervention is performed by laparoscopy. See also Figure 3 and the description of the AORC framework with the definition of its various components in liver CE surgery.

**Laparotomy, Noun
Surgical approach which includes a large opening of the abdomen.

Qualifies any surgical intervention performed under laparotomy.
Should be added to the noun or expression describing any type of intervention, if this surgical intervention is performed by laparotomy. See also Figure 3 and the description of the AORC framework with the definition of its various components in liver CE surgery.

Modified catheterization technique, Expression
Mo-CAT, Acronym Percutaneous procedure for treatment of CE cysts that results in removal of the cyst layers, possibly including daughter cysts, in addition to the cyst fluid and protoscoleces.
Similar techniques (such as PEVAC) previously described are no longer in use [36,71,81]. The name of the procedure and the acronym "Mo-CAT" clearly distinguish this procedure from the conventional PAIR and from the "standard catheterization technique" [3,61] The mode of percutaneous puncture guidance (e.g. ultrasound-guided, CTguided) should also be given, as well as the type/size of catheterization and aspiration. The expression and its acronym were accepted by the majority of voters (median: 10).

*Multicystic (echinococcosis; images), Adjective
Any type of echinococcosis with multiple aggregated cysts observed on imaging or during surgery in the same organ.
Avoids the confusing use of "polycystic", which currently refers both to cystic or alveolar echinococcosis with multiple large size-cysts observed on imaging, and to E. vogeli infection; also avoids confusion with polycystic liver (and kidney) disease.
The adjective "multicystic" should not be used to qualify the usual "alveolar" aspect of the aggregated "microcysts" in AE. It should not be used to qualify cases of CE or NE with multiple separated and independent cysts observed on imaging or during surgery in the same organ or different organs; see the definition of "multiple cyst-". This term was accepted by the majority of voters (median: 10). See also "polycystic", the rejected term, in Table 2C.
**Multiple cyst-, Expression used as Adjective Any type of echinococcosis (except AE) with multiple separated and independent cysts observed on imaging or during surgery in the same organ or different organs.
Clearly distinguishes the "multicystic" aspect of lesions and the presence of multiple cysts.
Should not be used to qualify cases of AE with multiple lesions. Should not be used to qualify cases with aggregated cysts in the same organ (i.e. "multicystic" CE or NE); see the definition of "multicystic".  Conforms to the recommendation by the WFP (echinococcosis); the preceding adjective provides precision on the particularity of the diseases (neotropical) [36]. "Neotropical" evokes the unique geographic distribution of the Echinococcus spp. involved (in the tropical areas of the New World).
Although the expression does not give any information on the morphology of the lesion ("polycystic" in E. vogeli infection; "unicystic" in E. oligarthra infection), it has been in use for a while in the literature and was approved by the South American Working Group on E. vogeli and E. oligarthra; it usefully distinguishes the diseases caused by these species from CE and AE (see definitions above).

**New CE cyst(s), Expression
Appearance of a new CE cyst in a location different from where a CE cyst was diagnosed before.
The definition covers all new cysts that have appeared in a patient after a first diagnosis; the new cyst may have appeared spontaneously (e.g. during a "Watch and Wait" period of follow-up) or after any type of treatment.
This expression was added by the SWG after the poll, in agreement with the writers of the WHO-IWGE Technical Manual. It excludes all cases of cyst recurrence or reactivation, as well as "secondary echinococcosis" (see the definitions of "reactivation" "recurrence", and secondary echinococcosis" in this Table 1C).
**Non-opened cyst (total cystectomy), Expression NOC, Acronym Surgical operation which does not include cyst opening before cyst removal (cystectomy). Only applies to CE, and for total cystectomy; it is not relevant for AE.
Linguistically more correct than "close(d) cystectomy" (a cyst can be "non-opened" during the surgical procedure, a cystectomy cannot be close or closed) [81]. This expression clearly describes the situation of the cyst (non-opened) and the highly reduced risk of dissemination of protoscoleces or germinal membrane fragments related to the surgical procedure.
Newly introduced expression, resulting from the discussion between members of the "Clinical aspects" subgroup of the CRG. The adjective expression "non-opened cyst", its acronym "NOC" and its definition, to qualify more precisely the total cystectomy, were accepted by a majority of voters (median: 10) See also Figure 3 and  Linguistically more correct than "open cystectomy" (a cyst can be opened during the surgical procedure, a cystectomy cannot) [81].
Newly introduced expression, resulting from the discussion between members of the "Clinical aspects" subgroup of the CRG. The adjective expression "opened cyst", its acronym "OC", and its definition, to qualify more precisely the total cystectomy, were accepted by a majority of voters (median: 10) See also Figure 3 and the description of the AORC framework with the definition of its various components in liver CE surgery.
This expression clearly describes the situation of the cyst (opened) and the potential risk of dissemination of protoscoleces or germinal membrane fragments related to the surgical procedure.
(Orthotopic) Liver transplantation, Expression OLT, Acronym Removal of the recipient's liver followed by the transplantation of the donor's liver (or part of liver) at the same anatomical location.
Surgical technique used for the treatment of advanced cases of AE, and more rarely of CE. Often used for "allotransplantation of the liver"; does not include auto-transplantation.
The adjective "orthotopic" (and its abbreviation "O") is facultative, since the great majority of liver transplantations in humans are orthotopic.
PAIR, Acronym for Puncture, Aspiration, Injection of protoscolecide, Reaspiration, Expression Percutaneous treatment of CE cysts using needle puncture and use of protoscolecide agents.
Accepted name and acronym to designate the procedure, since its description by Ben Amor et al., 1986 [8] in French (same acronym), and its first publication in English by Gargouri et al., in 1990 [20]. It describes the 4 steps of the procedure which does not include catheterization of the cyst. The procedure was evaluated and its indications clarified by the WHO-IWGE [10].
The name and acronym must be used only for the initially described procedure, with needle puncture, manual syringe aspiration, without catheterization or other associated techniques.
(Continued on next page) Opposite to "subtotal" which only leaves parts of the adventitial layer in place, this may include a partial removal of any layer (including parts of the germinal layer and laminated layer); usually only the adventitial layer is left.
By definition, in this situation, the CE cyst has to be opened (first or second intent opening). The adjective and its definition were accepted by a majority of voters (median: 8); however, a complementary discussion was necessary to precisely agree on the differences between "subtotal" and "partial". See also Figure 3 and  For the treatment of AE, this expression is preferred to "cavity drainage" since it refers to the typical "pseudocyst" resulting from the necrosis of AE lesions; "cavity drainage" is more commonly used for the drainage/ treatment of the postoperative cavities after surgery for CE (cystectomy). In AE, such drainage has no temporal relationship with any other interventional treatment.
The expression was accepted by the majority of voters (median: 10). No acronym was fixed. In any description of the procedure, the mode of percutaneous puncture guidance (e.g. ultrasoundguided, CT-guided) should also be given, as well as the type/size of catheterization and aspiration. A clearly different expression for the drainage of the cystoid necrotic cavity in AE versus the treatment of CE with postoperative residual cavity was considered useful. The "post-surgery" temporal performance of such drainage is clearly indicated in the expression.
This expression was added by the SWG after the poll, after recommendation by the RRG, in order to clearly distinguish the respective situations in AE and CE. In any description of the procedure, the mode of percutaneous puncture guidance (e.g. ultrasound-guided, CT-guided) should also be given, as well as the type/size of catheterization and aspiration.

Perendoscopic biliary drainage Expression
Non-surgical interventional technique used for the drainage of the biliary tree, through ERCP.
The procedure, which applies both to CE and AE, may or may not include biliary stenting [4,71].
The procedure does not include a curative action on the CE cyst or on the AE lesion; it only treats complications of the diseases and/or of their surgical treatment. In scientific publications, if biliary stenting is associated with the procedure, this should be specifically mentioned, as well as the type, size, and number of stents.
*Peri-adventitial (cystectomy), Adjective Total cystectomy performed without opening the cyst, and which uses the dissection space between the adventitial layer and the "normal" liver parenchyma to remove the cyst totally.
The adjective indicates more precisely that the resection is performed outside the adventitial layer (i.e. the adventitial layer is included in the resected cyst) [37,81].
The use of this adjective for the description of cystectomy is facultative. The adjective "periadventitial" and its definition, to qualify more precisely the total cystectomy, were accepted by a majority of voters (median: 10) See also Figure 3 and the description of the AORC framework with the definition of its various components in liver CE surgery.
Protoscolecide, Noun protoscolecidal, Adjective Compound (natural or chemical) which is able to kill the protoscoleces.
Should be used instead of "scolicide", "scolecide" and "protoscolicide". See also  Additional contributors opinion, if any */**Pseudocyst, Noun, and pseudocystic, Adjective (Noun and Adjective common to "Biology-Immunology" and to "Clinical Aspects") Irregular cyst-like anatomical entity due to the central necrosis in AE lesions at advanced stages.
From the ancient Greek "wetdή1" -"pseudès-(= false, deceptive, misleading) that designates something which looks like something but is not; thus "pseudocyst": anatomical entity which looks like a cyst but is not a cyst. The terms differentiate the cystlike necrotic cavity in AE from the real "cyst" of CE (with its parasitic structure including the 3 layers). This structure does not correspond to a parasitological entity. In medicine, the term "pseudocyst" is generally used for the necrotic cavities that develop after episodes of pancreatitis in the pancreas.
The terms were approved by the majority of voters (median: 9). The context and the organ being different from pancreatitis, and the formation of the cavity also being due to liquefied necrosis of an inflammatory lesion, it was considered that the words "pseudocyst" and "pseudocystic" could also be used in AE. However, the adjective "cystoid" was maintained to qualify cyst-like structures (irrespective of their anatomical nature) observed at imaging (especially at CT-scan) in AE lesions.
PTBD, Acronym, for Percutaneous Transhepatic Biliary Drainage, Expression Non-surgical interventional technique used for the drainage of the biliary tree, which is used in AE or complicated CE, after percutaneous puncture.
No synonyms. Expression and acronym widely used in the medical literature, whatever the application. The procedure applies both to CE and AE and does not include a curative action on the CE cyst or on the AE lesion.
The mode of percutaneous puncture guidance (e.g. ultrasound-guided, CTguided) should also be given, as well as the type/size of catheterization.

**Reactivation, Noun
Appearance of daughter cyst (s) in the solid matrix of spontaneously inactivated CE4 cysts that shows an evolution towards a CE3b stage.
The term "reactivation" is reserved for spontaneously inactivated cysts (observed after an initial diagnosis of CE4 cyst, with or without formal "Watch and Wait" follow-up).
This term was added by the SWG after the poll, in agreement with the writers of the WHO-IWGE Technical Manual, in order to clearly distinguish the various situations regarding new lesions or changes in lesions that appeared spontaneously or after attempts at treatment.

**Recurrence, Noun
Appearance of an active CE cyst (types CE1-3, usually CE3b) in the same location where a treated cyst was located, independently of the type of previous treatment.
Following its definition in oncology, the term "recurrence" is reserved for the post-therapeutic situation; the term "reactivation" applies to non-treated cysts.
This term was added by the SWG after the poll, in agreement with the writers of the WHO-IWGE Technical Manual, in order to clearly distinguish the various situations regarding new lesions or changes in lesions that appeared spontaneously or after attempts at treatment. NB: the occurrence of a post-surgical cavity needs to be excluded before a diagnosis of recurrence is made (cf. the definition of "percutaneous post-surgical cavity drainage", in this Table 1C).

**Secondary cyst, Expression
Newly formed cysts from the dissemination of protoscoleces or germinal layer fragments, in the serosal cavities, spontaneously, accidentally or after surgery or cyst puncture.
Mode of formation distinct from that of daughter cysts; the adjective "secondary" should, however, be restricted to the appearance of new CE cysts in the peritoneum, pleura or meningeal space because of spontaneous or per-treatment spillage of the cyst content.
This expression was added by the SWG after the poll, to clearly distinguish this situation from the development of "daughter cyst". The expression was approved by the writers of the WHO-IWGE Technical Manual, in order to clearly distinguish the various situations regarding new CE cysts or changes in CE cysts that appeared spontaneously or after attempts at treatment. (Continued on next page) The name of the procedure and the acronym "S-CAT" clearly distinguish this procedure from the conventional PAIR and from the "modified catheterization technique" ("Mo-CAT") [3,35].
The expression and its acronym were accepted unanimously by the voters (median: 10) It was also proposed to complete the description by the following mentions: -One-session S-CAT: the catheter is removed during the first procedure; -Multiple-session S-CAT: the catheter is removed at another session. The mode of percutaneous puncture guidance (e.g. ultrasound-guided, CTguided) should also be given, as well as the type/size of catheterization.
*/**Sub-total (cystectomy), Adjective Nearly total cystectomy with incomplete removal of the adventitial layer of a CE cyst Situation that occurs when limited parts of the cyst cannot be removed safely because of the proximity of blood vessels or other anatomical structures (e.g. bile ducts, bronchi, brain anatomical structures with critical functions). To be qualified of "subtotal", the cystectomy must remove the totality of the germinal and laminated layer; only limited parts of the adventitial layer are left.
By definition, in this situation (as in "partial cystectomy), the cyst has to be opened (second intent opening). The adjective and its definition were accepted by a majority of voters (median: 10); however, a complementary discussion after the poll was necessary to precisely agree on the differences between "subtotal" and "partial". See also Figure 3 and the description of the AORC framework with the definition of its various components in liver CE surgery.

*Total (cystectomy), Adjective
Complete removal of a CE cyst, including the content (fluid and protoscoleces) and all layers of the cyst (germinal, laminated and adventitial layers. The adjective "total" insists on the complete removal of the CE cyst by the surgical operation (the "C", for "completeness" of the AORC framework). It does not prejudge of the opening or not of the cyst at any time of the procedure. This operation, when performed on a non-opened cyst, was sometimes called "peri-cystectomy"; however, a proper definition of the CE cyst is against the use of this word (see Tables 1B and 2C and Figs. 2A-2C).
The adjective "total", speaking of cystectomy, and its definition were accepted by all voters but one (median: 10). See also Figure 3 and the description of the AORC framework with the definition of its various components in liver CE surgery. * Agreement obtained at the second stage of the consultation (the participants in the Consultation and Rating Group had to rate their approval or rejection of the words/expressions independently on a scale from 0 to 10; whenever relevant, the median of the votes and the nature of the agreement (majority or unanimity) are given in the "Comments" column. ** Agreement to recommend a word that was not selected at the first stage of consultation; the approval was obtained at the second stage after further discussion between experts or after recommendation by the RRG. */** Agreement obtained at the second stage of the consultation; however the final definition was obtained after further discussions with the members of the RRG. E. multilocularis (Leuckart, 1863) belongs to the Echinococcus genus [50,67]. The International Code for Zoological Nomenclature should be followed (see Table 1A) [52].
There is no longer a taxonomic basis for this different genus name.
Only those approved species names in the genus Echinococcus mentioned in Table 1A should be used.

Echinococcus alveolaris, Expression
Non-valid species name sometimesand even recently used in the German and Turkish literature to designate either the species Echinococcus multilocularis or the disease "alveolar echinococcosis" [60].
To designate the cestode, the International Code for Zoological Nomenclature should be followed (see Table 1A) Should definitively be abandoned.
To designate the disease, the recommendations of the World Federation of Parasitologists (WFP) should be followed (see Table 1C)

Echinococcus cysticus, Expression
Non-valid species name sometimes used in the German and Turkish literature to designate either the species Echinococcus granulosus s.l. or the disease "cystic echinococcosis" [44] To designate the cestode, the International Code for Zoological Nomenclature should be followed (see Table 1A) Should definitively be abandoned.
To designate the disease, the recommendations of the World Federation of Parasitologists (WFP) should be followed (see Table 1C).

Echinococcus granulosis
Non-valid species name with wrong orthography, often found in publications.
To designate the cestode, the International Code for Zoological Nomenclature should be followed (see Table 1A).
Simply wrong. Recently proposed species names should not be used, unless a case can be made (e.g. by molecular studies) that they merit recognition as separate species.

Echinococcus
Only those approved species names in the genus Echinococcus mentioned in Table 1A should be used.

Echinococcus oligarthrus, Echinococcus oligarthus, Expressions
Non-valid names of the species among Echinococcus spp. which is responsible for one of the clinical forms of "neotropical echinococcoses" Often referred to as E. oligarthrus (or even oligarthus), the species was originally described as Taenia oligarthra (Diesing, 1863) by Diesing [14].
In this case, there was no mistake in the original name of species given by Diesing; variants were used mistakenly afterwards in the scientific literature. However, the genus "Echinococcus" was subsequently identified and replaced the genus "Taenia".
The component a ; 0 qhqaarthra (joints)is the plural of a ; 0 qhqom -arthron (joint). The name is therefore not an adjective, but a noun in apposition, which does not change its ending according to the gender of the generic name. This was recognized earlier but subsequently ignored.
The expression was rejected by a majority of voters (median: 3). Adult worm may be considered redundant, since worms are adult forms of helminths. In addition, "adult form" in the definitive host corresponds to "larval form" in the intermediate host.

*Adventitia, Noun
Fibrous and cellular layer between the laminated layer of the hydatid in E. granulosus s.l. infection and the normal parenchyma of the host organ where the metacestode developed.
Word of Latin origin, "adventitia" is the outermost connective tissue covering of an organ, vessel, or other biological structure. In the CE cyst, this poorly cellular and mostly fibrous layer results from the host immune reaction to E. granulosus sensu lato metacestode.
As "adventitia" may be used for any biological structure, the use of "adventitial layer", which refers to the parasite "germinal layer" and "laminated layer", was preferred by the voters for this structure of host origin (median: 2, for "adventitia"). Alternative noun to "border"; "border" is more common in pathology terminology.
Rejected because of usage (median: 0). *Died-out (cyst, lesion), Adjective Non-viable parasitic structure as evidenced by imaging (complete calcification in AE, CE5 cyst in CE) or histological examination (absence of viable parasitic cells).
Could be used in clinical or experimental situations when evidence of absence of viability is not obtained by transplantation or in vitro culture.
Rejected by a majority of voters (median: 10, for rejection).

*Germinal cell, Expression
Pluripotent somatic stem cell with some homologies but also differences to neoblasts of freeliving flatworms. Germinative cells are the only mitotically active cells in the metacestode and give rise to all differentiated cells.
Alternative expression to designate germinative cells. Same adjective as in the expression "germinal layer" where these cells are located. However, not all cells in the germinal layer correspond to this definition.
The germinal layer also contains other cell types such as muscle cells, nerve cells, and calcareous corpuscleproducing cells. This was an argument to reject the adjective "germinal" for such cells (median: 3).

Germinal membrane, Expression
Inner cellular layer of the Echinococcus spp. metacestode. This term should be avoided and the term "layer" should be preferred because of the complexity of the various "layers" of the hydatid, and the possible confusion of "membrane" with the cell "membrane", which has a specific definition in biology.
Germinal layer is the recommended expressions to designate the inner cellular "layer" of parasite origin in the Echinococcus spp. metacestode.

Hooklets, Noun
Appendices of the adult worm of Echinococcus spp. parasites allowing them to attach to the intestinal wall of the definitive hosts.
This term, a diminutive of "hooks", is also used to designate these structures of the scolex and adult form of Echinococcus spp.; it should be avoided because the term "hooklet" infers a smaller version of a hook, i.e. that two forms are present, a larger "hook" and a smaller "hooklet" as in the haptor of some Monogenean parasites.  Should not be used in English.
*Infiltration (periparasitic), Noun Histological components (cellular and fibrous) from host origin in alveolar echinococcosis Alternative noun to "infiltrate"; infiltrate is more common in pathology terminology; infiltration has a slightly different meaning (systemic homing of inflammatory in the whole organ).

Laminated membrane, Expression
Outer acellular layer of the Echinococcus spp. metacestode.
This term should be avoided and the term "layer" should be preferred because of the complexity of the various "layers" of the hydatid, and the possible confusion of "membrane" with the cell "membrane", which has a specific definition in biology.
Laminated layer is the recommended expression to designate the outer acellular "layer" of parasite origin in the Echinococcus spp. metacestode.

Neoblast, Noun
Somatic stem cell type which shares homologies with germinative cells from Echinococcus spp. metacestodes, but also display significant differences.
Specific of planarians (and other free-living flatworms).
Should not be used for Echinococcus spp.
**Non-fertile (adult form or worm), Expression Adult form/worm of Echinococcus spp. whose last segment does not contain eggs.
Alternative to "immature" (adult form or worm). However, non-fertile could imply that this worm is not able to become fertile (which is wrong for the majority of adult Echinococcus spp. forms, especially in the definitive host in vivo).
In vitro-reared adult forms of Echinococcus spp. do not contain eggs; they exhibit some differences from the in vivo developed adult forms, and they are presumably non-fertile [56]. However, the adjective "non-fertile" cannot be accepted for the usual situation of in vivo developed Echinococcus spp. adult forms/worms.

Primary cells, Expression
All cells that result from lytic digestion of the Echinococcus spp. metacestode and can be kept in culture using the "primary cell cultivation system".
"Primary cell" is not a specific cell type of Echinococcus spp. metacestode, but a "culture system" [70].
Primary cells are a mixture of "germinative cells" (~80% at the beginning), muscle cells and nerve cells [45]. Proglottid is an alternative to proglottis in several dictionaries; the plural "proglottids" is commonly used in the USA (American English).
Referring to the Greek origin of the word, "proglottis (sing), proglottides (plur) should be preferred.
This spelling was rejected by a majority of voters (7/10; median: 3) Protoscolices (Plural of protoscolex), Noun Prefiguration ("proto") of the "scolex", produced by the brood capsules budding from the germinal layer of Echinococcus spp. metacestode and released in the cyst fluid.
Protoscoleces is the correct plural form, according to the etymology of the word.
Scoleces is the correct plural form, according to the etymology of the word.

Totipotent somatic stem cell, Expression
Stem cells in the germinal layer of Echinococcus spp. metacestode.
Alternative to "germinative cells"; however, the real totipotent cell, with specific markers, has not been identified yet [45].
Pending a better definition of the really totipotent cells in the germinal layer of Echinococcus spp. metacestode, a single expression "germinative cell" should be kept.
(Continued on next page) Alternative expression to "post-oncospheral" stage, but less precise to qualify a stage of a metacestode since it may apply to any larva. In addition, "transitional" may qualify any other stages of development (e.g. when brood capsules produce protoscoleces).
Rejected by all voters but 2 (median: 0). * Agreement to reject the term obtained at the second stage of the consultation (the participants in the Consultation and Rating Group had to rate their approval or rejection of the words/expressions independently on a scale from 0 to 10; whenever relevant, the median of the votes is given in the "Comments" column). ** Agreement to reject a term that was not selected at the first stage of consultation; the agreement was obtained at the second stage after further discussion between experts or after recommendation by the RRG. Total cystectomy (usually performed without opening the cyst) which uses the dissection space between the adventitial layer and the "normal" liver parenchyma to remove the cyst more easily.
The adjectives do not indicate clearly if the resection is performed inside or outside the adventitial layer.

Alveococcosis, Noun
Disease related to infection with E. multilocularis.
Historical name for the infection due to E. multilocularis in Russia/Russian language and Russia-related countries. Not compliant with the recommendations of the World Federation of Parasitologists (WFP), since it is built from the name of a wrong genus.
Not in use in other countries/ languages than Russia/Russian The only recommended name is "Alveolar echinococcosis (AE)" (see Table 1C).
*Anti-infectious, *Anti-infective, (therapy/treatment/drug), Drug treatment (usually chemical) of echinococcosis, opposed to or associated with surgery (on the model of infectious diseases therapy).
Although they are commonly used for the treatment of infectious diseases, these adjectives infer prevention as well as (and even rather than) treatment."Anti-parasitic" is more exact, and more appropriate for parasitic diseases.

Chemotherapy, Noun
Drug treatment (usually chemical) of echinococcosis, opposed to or associated with surgery (on the model of cancer therapy) The word was used at the first trials of mebendazole/albendazole, for the treatment of echinococcosis, in the 1980s, to stress the "chemical" nature of the treatment and oppose this treatment to surgery which was the only therapeutic option. Has been used commonly thereafter.
Even though echinococcosis shares some particularities with cancer, the word "chemotherapy" has gained a strong cancerrelated meaning which may cause confusion, especially when echinococcosis occurs in cancer patients because of the immunosuppressive effect of the anti-cancer chemotherapy. In addition, not all drugs against echinococcosis are chemical (cf. immunotherapy and other biotherapies). It should be abandoned for the use of "antiparasitic" therapy (or treatment, or drugs). See also Table 1C.
(Continued on next page) Widely used by surgeons; however, linguistically incorrect: a cystectomywhich is an interventioncannot be "closed", and a cyst is rather "nonopened" than "closed" (the surgeon does not close the cyst, he/she may have it non-opened) [81].
The majority of voters rejected the expression (median: 3).The expression should be replaced by "non-opened cyst (NOC) -cystectomy". See also Table 1C and Figure 3 and  Alternative term to "daughter cyst". As a literal translation, the use of "vesicle" would fit with the initial description by Dévé ("vésicule fille" in French).
The majority of voters rejected all suggested names for this metacestode structure (median: 3; mean: 4.7, for "daughter vesicle"). The arguments which prevailed to reject "daughter vesicle" and eventually approve the historical expression "daughter cyst" was first the worldwide usage and second the agreement by the participants in the subgroup "Biology and immunology" to restrict the use of "vesicle" to the metacestode of Echinococcus spp. in vitro only, whatever the species.

Echinococcus alveolaris, Expression
Disease related to infection with E. multilocularis.
Name for the infection due to E. multilocularis sometimes used in German-speaking countries.
Mix of the name of the genus and the adjective qualifying the disease (in Latin. . .).
Not compliant with the recommendations of the WFP.
Name for the infection due to E. granulosus s.l. sometimes used in German-speaking countries Mix of the name of the genus and the adjective qualifying the disease (in Latin. . .) Not compliant with the recommendations of the WFP.
Should not be used in English.

Hydatid disease, Expression
Disease related to infection with Echinococcus spp.
Commonly used alternative name to designate either all diseases due to Echinococcus spp. or the diseases due to E. granulosus sensu lato. This disease name does not fit with the unified recommendations of the WFP.
This noun should not, in any cases, be used for alveolar echinococcosis or neotropical echinococcosis; it should not be used for E. granulosus s.l. infection in humans either: the only recommended name is "Cystic echinococcosis (CE)" (see Table 1C). In addition, usage of this name increases confusion among clinicians and decision makers between the diseases due to E. granulosus sensu lato and E. multilocularis, respectively.
Use of "hydatid" as an adjective should be restricted to infection due to E. granulosus s.l. (see Tables 1B and 1C) in the intermediate hosts.
The adjective "multicystic" is now proposed as a non-specific description of any type of cystic echinococcosis when several/many macroscopic cysts are present and visible at imaging (see Table 1C). Use of "hydatid" as an adjective should be restricted to infection due to E. granulosus s.l. (see Table 1C) in the intermediate hosts.
(Continued on next page) From the definition of "hydatid" (see Table 1B), this noun could replace "partial cystectomy", with less ambiguity (especially regarding surgeon's evaluation between "subtotal" and "partial").
Scientifically correct, but not established by use. The term with this definition was rejected by the majority of voters (median: 0).

Hydatidosis, Noun
Disease related to infection with Echinococcus spp.
Commonly used name to designate the diseases due to Echinococcus spp. This disease name does not fit with the recommendations of the WFP This noun should not, in any cases, be used for alveolar echinococcosis or neotropical echinococcosis; it should not be used for E. granulosus s.l. infection in humans either: the only recommended name is "Cystic echinococcosis (CE)" (see Table 1C).
In addition, usage of this name increases confusion among clinicians and decision makers between the diseases due to E. granulosus s.l. and E. multilocularis, respectively.

*Open cystectomy, Expression
Surgical operation which includes cyst opening before cyst removal (cystectomy). Only applies to CE; may be at first or second intent; it is not relevant for AE.
Expression widely used by surgeons; however, linguistically incorrect: a cystectomy cannot be "open", but a cyst may be "opened" (the surgeon does open the cyst) [81].
The majority of voters rejected the expression (median: 3). The expression should be replaced by "non-opened cyst cystectomy" (NOC). See also Table 1C and Figure 3 and the description of the AORC framework with the definition of its various components in liver CE surgery.

Pericystectomy
Removal of a CE cyst which includes all layers of the cyst (including the adventitial layer).
Wrongly used to designate the operation which includes the adventitial layer of the cyst in CE. The prefix "peri" is not useful, since the adventitial layer is part of the cyst; "cystectomy" is thus the appropriate word. Stricto sensu, the "pericyst" is the normal organ parenchyma that surrounds the cyst (see Figs. 2A-2C) [68].
See Table 1C for alternative wording regarding surgery of CE. The only noun recommended is "cystectomy". See also Figure 3 and the description of the AORC framework with the definition of its various components in liver CE surgery.

Polycystic echinococcosis, Expression
Disease related to infection with E. vogeli (stressing the multicystic type/presentation of E. vogeli infection).
The expression is sometimes wrongly used in medical publication to designate diseases due both to E. vogeli, which is most often polycystic/multicystic and E. oligarthra, which usually presents with single cysts similar to those of CE, in humans and in animal intermediate hosts [11,35] but may also be multicystic or even microcystic (AE-like) [69].
The only recommended name for the diseases due to E. vogeli and E. oligarthra is "Neotropical echinococcosis (NE)" (see Table 1C).
In addition, "polycystic" may cause confusion between the disease due to E. vogeli and "polycystic" clinical types of E. granulosus and E. multilocularis infections. The adjective "polycystic" is widely used to designate a genetic nonparasitic disease of the liver and kidney, adding to the confusion.
The adjective "multicystic" is now proposed as a non-specific description of any type of cystic echinococcosis when several/many macroscopic cysts are present and visible at imaging (see Table 1C).

Polycystic, Adjective
Constituted of several cysts (used to qualify the imaging and operative aspect of various types of echinococcosis).
The adjective "polycystic" is not specific to echinococcosis; "polycystic" is widely used to qualify a genetic non-parasitic disease of the liver and kidney; in addition, it has been used to distinctly qualify the disease due to E. vogeli (see below).
The adjective "multicystic" is now proposed as a non-specific description of any type of cystic echinococcosis when several/many macroscopic cysts are present and visible at imaging (see Table 1C). Additional colleagues, especially from South America and China, were solicited after the congress. However, only Chinese colleagues answered positively, which resulted in a relatively low participation of South American colleagues in the "Clinical aspects" subgroup, perhaps because of language issues: Spanish and Portuguese are the publication languages of most South American clinicians; publications in English from South America are mostly in biology and public health. All members of the RRG were selected by the SWG on the basis of their international academic recognition in the fields of CE, AE and NE. Despite the absence of face-to-face meetings to discuss the undecided questions, open email discussions were initiated by the coordinators of the subgroups, and this procedure was very efficient. If there were missing values for the poll, the project manager actively and individually contacted the voters in question in order to ask them to provide their opinion. Feedback from the RRG members was also followed by active discussions in order to reach consensus on important terms and to revise and finalize this paper.

Major outcomes and conclusions
Currently, a precise genetic definition is available for nine species: E. granulosus (Batsch, 1786)   Compound (natural or chemical) which is able to kill the protoscolex.
Synonym for protoscolecide. The protoscolex is the final stage of the metacestode of Echinococcus spp, able to produce a scolex then an adult form of the parasite in the definitive host, or to reproduce a metacestode in the intermediate host. From the ancient Greek "rjὠken"-scolex (worm), genitive: rjὠkejo1-scolecos, and not scolicos; plural rjὠkeje1, scoleces, and not scolices), with the prefix "pqxso1"-protos (first/before), and the Latin suffix -"-cide", from "caedere" (to kill).
Should be abandoned for "protoscolecide" (see Table 1C); protoscolecides (protoscolecidal agents) are used to kill the protoscoleces and/or prevent secondary cysts after surgery.
**Relapse, Noun Any type of echinococcosis lesions that appeared after the implementation of any type of treatment.
The definition is vague and covers several types of lesion appearing after attempts of treatment. More precise definitions of lesions observed in this situation should be used.
Should be abandoned for specific terms/ expressions covering the various situations encountered by clinicians (see in Table 1C the definitions of "new CE cyst", "reactivation", "recurrence", and "secondary echinococcosis").
Scolecide, Noun; Scolecidal, Adjective Compound (natural or chemical) that is able to kill the scolex.
The scolex is the head of the adult form of Echinococcus spp. From the ancient Greek "rjὠken", genitive: rjὠkejo1-scolecos; plural rjὠkeje1, scoleces). Such compounds are used to kill protoscoleces, produced by the metacestode in intermediate hosts, not scoleces in the definitive hosts. Usage of "scolecide" is thus scientifically inexact (killing concerns the protoscoleces, not the scoleces).

Scolicide, Noun;
Scolicidal, Adjective Compound (natural or chemical) that is able to kill the scolex.
Should be abandoned for "protoscolecide/protoscolecidal" (see Table 1C). * Agreement to reject the term obtained at the second stage of the consultation (the participants in the Consultation and Rating Group had to rate their approval or rejection of the words/expressions independently on a scale from 0 to 10; whenever relevant, the median of the votes is given in the "Comments" column). ** Agreement to reject a term that was not selected at the first stage of consultation; the agreement was obtained at the second stage after further discussion between experts or after recommendation by the RRG. 1863), responsible for neotropical echinococcosis; the responsibility of some of the species (e.g., E. equinus (Williams and Sweatman, 1963) or E. shiquicus Xiao et al., 2005) in human infection is still being questioned; this does not challenge the genetic definition of these species (Table 1A). Recognition of additional species within E. canadensis and E. granulosus s.s. is to be expected (Table 1A). Thus, distinct Echinococcus spp. genotypes within the E. canadensis cluster may move to full species status, and the names E. intermedius (for G6/7), E. borealis (for G8) and E canadensis (for G10) have been proposed; however, no conclusion on the number and names of these species has yet been reached [57]. Variations around the radical "hydatid" have long been used to designate diseases due to Echinococcus spp. The presence of "hydatid" cysts had long been recognized as a feature of a parasitic disease when the natural cycle of the parasite responsible for its occurrence was identified in the middle of the 19th century [18,77]; the species was first named Taenia echinococcus before becoming Echinococcus granulosus. In humans, the disease was clearly not a "taeniasis", and "hydatid disease", "hydatidosis" (if the disease was considered) or "hydatid cyst" (if the lesion was considered) thus prevailed. It took another century before the Echinococcus sp. which causes AE was identified as a distinct species, E. multilocularis [18,77]. It is thus easy to understand why several terms, not related to the current name of the genus, were used for centuries, and why they were used to designate both diseases, alveolar and cystic echinococcosis. The inappropriate use of "hydatid" has been a source of confusion, both for disease surveillance and treatment indication [10,35]. Until recently, echinococcosis surveillance by the European Centre for Disease Control (ECDC) did not distinguish between the two diseases [23]. A clear distinction between three types of diseases, with a single name for each of them, will make all studies on epidemiology, socio-economic burden, and care management more reliable. There was total agreement to never use terms based on the "hydatid" root to designate any disease due to Echinococcus spp., and to strictly restrict the use of "hydatid" to qualify a lesion or part of a lesion due to E. granulosus s.l. in intermediate hosts, entirely excluding its use to qualify anything regarding (1) E. granulosus s.l. infection of the definitive host, and (2) AE and NE. With regards to a cystic lesion, "CE cyst" should be preferred to "hydatid cyst" since the large majority of voters preferred to use this term, and did not wish to keep both names for E. granulosus s.l.-related cysts.
Although specialists of the genetics of Echinococcus spp. rapidly agreed on the correct spelling of the species E. oligarthra on historical and linguistic arguments (and not oligarthrus, as commonly spelled in the last few decades; see e.g., [5,17]), clinicians were more hesitant on the names of the diseases that E. oligarthra and E. vogeli may cause in humans. There was no term/expression entirely satisfactory to designate both diseases. Because both are infections of the "tropical areas of the New World", "neotropical" has been commonly used in the scientific literature and was presented at the WHO-Forum in 2015 to be included among the U50-U99 "Codes for research and alternative subclassifications" of the International Statistical Code of Diseases and Related Health Problems (https://apps.who.int/ iris/bitstream/handle/10665/246208/9789241549165-V2-eng. pdf), as: U51X: "Infection due to Neotropical Echinococcosis". The suggestion of South American specialists, which was confirmed by the poll, was thus to keep this denomination. To avoid the confusion with "polycystic liver and kidney disease", a genetic disease, the adjective "polycystic" (of Greek origin) should definitively be replaced by "multicystic" (of Latin origin, but with exactly the same meaning) when multiple aggregated cysts are observed on imaging, regardless of the species; "multiple cyst-" characterizes the co-existence of several separated and independent cysts in the same organ or different organs.
It was agreed that the current international classifications already approved by the WHO-IWGE, i.e. the "CE" classification of CE cysts [82], and the PNM classification of AE lesions [37], would not be questioned, and that further work on the refinement of imaging classification of AE would not proceed until fixing of international recommendations. However, an unexpected and extremely useful outcome of the terminology discussions was the agreement on a new and internationally recognized system to describe surgical operations in CE, the "AORC" framework ( Fig. 3), with consensus on the single word "cystectomy" to describe the removal of the CE cyst, thus excluding "pericystectomy" when it consists of the removal of the three layers of the cyst without "pericystic" liver. This recommendation will help professionals to share a common description that is relevant in terms of perioperative risks and the risk of CE recurrence after operation. A precise description of the procedure actually performed by the surgeon for a given patient should accompany the mandatory terms (description of the removed parasite layers, area in square centimeters or percentage of cyst actually resected, closure of communications with bile ducts, content of the cyst if it was opened, etc.); this is beyond the objectives of a work on terminology and will be further discussed in the "Technical Manual" for the diagnosis and treatment of CE, which is currently being prepared by the WHO-IWGE. For non-surgical CE interventions, the clear distinction between the PAIR (puncture, aspiration, injection, reaspiration, through a needle, without catheterization), S-CAT (standard catheterization), and Mo-CAT (modified catheterization) techniques provides accepted acronyms and will also help professionals to better understand the specific indications of each technique and the results of clinical trials.
The work in terminology aimed to cover all fields of echinococcosis; it was the first attempt at standardizing scientific and medical language in a specific area of parasitic diseaseechinococcosis. However, it did not claim to solve all points of debate and/or to address everything definitively. The words and expressions reported in Tables 1A-1C and 2A-2C do not encompass all technical aspects; such details should be considered by subgroups of specialists. Regular updating will also be necessary, following future advances in scientific and medical knowledge. Apparently "easy-to-solve" dilemmas were in fact more difficult to resolve when several disciplines reported on their own usages. This was the case for the debate between "daughter cyst" and "daughter vesicle". Purists will certainly regret that "daughter cyst" will stay in use, despite the paradoxical female gender, explained by the use of the feminine "vésicule" (vesicle) in the first descriptions in French. Although "daughter" is not justified in English, the alternative adjective "secondary" cannot replace it since it is widely used to designate new cysts developed in the peritoneum, pleura or meningeal space after cyst rupture and/or protoscolex spillage Although "cyst" was not fully justified either, because it has no fully developed adventitial layer, biologists readily agreed to keep the noun "vesicle" with restricted use for the in vitro situation. The results of the poll (Tables 1C and 2C) confirmed the problematic nature of the issue: "daughter cyst" was not preferred, "daughter vesicle" was not either, and the alternative expression "daughter hydatid" was unequivocally rejected; it was thus agreed to keep the "historical wording", i.e. "daughter cyst". We recommend the constitution of a permanent group on "terminology" common to the WAE and the WHO-IWGE so that such "unresolved" issues may be further discussed, and that the certainly numerous new terms used in the field in the future may be handled in a timely manner.