Open Access
Research note
Issue
Parasite
Volume 19, Number 3, August 2012
Page(s) 281 - 283
DOI https://doi.org/10.1051/parasite/2012193281
Published online 15 August 2012

© PRINCEPS Editions, Paris, 2012, transferred to Société Française de Parasitologie

Licence Creative Commons
This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Bovine tropical theileriosis (Theileria annulata infection) is a tick-borne disease that has been described in three continents: Europe, Asia, and Africa. T. annulata infection represents a major constraint to pure bred cattle development in endemic countries. The control of this disease can be carried out by the implementation of one or more of the three control options: (i) acaricide application on cattle and on the barn walls, (ii) roughcasting of the outer and inner wall surfaces of the barn, inducing destruction of the nymphs lodgings, (iii) vaccination with local attenuated cell line vaccine (Brown, 1990; Darghouth et al., 2003). The development of a simple and low cost T. annulata culture technique is useful in several fields: epidemiology, immunology, molecular biology and vaccinology. The aim of the present study was to evaluate the effectiveness of a rapid and simple technique for in vitro T. annulata isolation from infected animal blood and to compare this protocol to the classical parasite culture technique based on isolation of peripheral blood monocytes by Ficoll gradients (Pipano et al., 1990).

Material and Methods

In order to compare the two techniques we used two groups of animals. The animals were purchased from a tropical theileriosis and Hyalomma detritum detritum free farm and they were kept in a tick-free isolation unit at the national veterinary school at Sidi Thabet:

  • Group 1: 20 Holstein-Friesian bovines aged between five and ten months.

  • Group 2: 22 Holstein Friesian calves aged between three and six months.

The animals were infected by subcutaneous injection of a lethal dose of 1.8 and 0.25 equivalent ticks using ground up tick supernates (GUTS) of the Jdaida 4 (Ta3/2 isolate), respectively.

Ficoll (Histopaque© 1077, Sigma) was used for the isolation of peripheral blood monocytes (PBM), as recommended by the supplier. This technique is considered as the reference technique.

Culture media were prepared according to the protocol described in Brown (1981). Briefly, sterile RPMI-1640 (Gibco Invitrogen Australia Ltd, Victoria, Australia) was mixed with Heparin (Sigma) at the final concentration of 100 IU/ml, 2-Mercaptoethanol (Sigma) (10-5 M) and penicillin-streptomycin at the concentrations of 105 IU/ml and 0.1 g/ml, respectively. The media was filtrated through a 0.2 µm Millipore® filters and mixed with 10 % foetal calf serum (Gibco Invitrogen Australia Ltd, Victoria, Australia) at the concentration and 100 µM/ml L-Glutamine (Gibco Invitrogen Australia Ltd, Victoria, Australia).

Around day 12 post-infection, the animals of both groups presented typical clinical signs of tropical theileriosis. Blood samples were taken at the onset of clinical signs consistent with the onset of an episode of acute tropical theileriosis. Whole blood was aseptically collected in heparinised tubes (Vacutainer©).

For Ficoll (Histopaque© 1077, Sigma) PBM isolation, ten millilitres of blood were aseptically collected in heparinised sterile tubes (Vacutainer©), peripheral blood monocytes were isolated as recommended by the supplier. For the whole blood technique only one millilitre of blood was mixed with complete RPMI-1640 (Gibco Invitrogen Australia Ltd, Victoria, Australia) in a 25 cm3 cell culture vial in vertical position. All cell cultures were incubated at 37 °C, 90 % humidity and 5 % CO2 for two weeks.

The cell cultures were monitored by making cytospin smears three times a week. The Giemsa stained cell culture smears were examined microscopically for T. annulata schizont infected cells. To compare the two techniques, six indicators were estimated:

  1. Cell culture effectiveness is the number of positive cell cultures at the end of the survey divided by the number of starting cells.

  2. Range of first day of passage is the minimum delay to obtain a schizont index (SI) superior to 50 %. SI is the ratio of infected WBC/examined WBC.

  3. Number of contaminated vials.

  4. Schizont index at day 9.

  5. First-day of schizont detection.

  6. Costs difference = cost of reference technique - cost of the rapid method (the labour costs and laboratory equipments were ignored).

Results and Discussion

Compared to the reference technique, the rapid protocol is more effective, saving both time and money (Table I).

Table I.

Comparison of two Theileria annulata isolation techniques: culture of whole blood and following Ficoll purification.

The control of tropical theileriosis is not possible until effective control policies are implemented, particularly vaccination with local attenuated cell line vaccines. To simulate the field conditions when the veterinarian will be called to examine clinically infected bovine, the animals were sampled at the beginning of the clinical signs corresponding to day 12 of infection.

Cells cultures were negative at day 0 and 3 indicating that the proportion of infected cells is low to zero. This can be attributed to the small quantity of stained samples when using the cytospin® (30 µl per sample).

At day 6, the cultures showed a high proliferation rate, at day 9, the schizont index increases dramatically for all the animals, and reached 80 to 90 % at day 15. The index schizont progresses similarly to the conventional cell culture methods.

The parasite cultures isolated by Ficoll were successful for 19 out of 22 samples. Pipano et al. (1990) estimated the effectiveness of Ficoll isolation to 50%. However, they examined less severe clinical cases than those used in the present study. Indeed, they worked on animals challenged with T. annulata contaminated blood, whereas in our study the animals were challenged with the Jed 4 GUTS at the lethal dose of 1.8 to 2.5 tick equivalents. It has been established that infection with sporozoïtes induces a more severe infection than inoculation of T. annulata present in blood (Darghouth, 2000).

When considering the new rapid protocol, the day of first passage (first day when the schizont index is equal or higher than 50%) was estimated to either day 6 or day 9, whilst the first passage is realised from day 11 to 21 (median: day 15) for Ficoll. Cell culture from total blood allows a more rapid development of infected cells, since they are suspended in whole blood containing several growth factors leading a rapid growth of the cells and good output of cultures. Indeed, the T. annulata-infected cells can activate and induce non-specifically the proliferation of non-infected autologous T cells (Glass & Spooner, 1990), known as Theileria mixed lymphocyte reaction (Theileria MLR). In MLR, the non-specifically recruited lymphocytes produce cytokines that enhance the expansion of infected cells with a dramatic increase of INFγ (gamma interferon) and TNFα (tumour necrosis factor alpha) concentrations (Glass, 2001). These cytokines increases the proliferation of young schizonts and induce the production of activated macrophages that will secrete IL-2. During the early infection stage, exogenous IL-2 secreted by non-infected lymphocytes contributes to the initiation of infected cells transformation (Dobbelaere et al., 1990).

The present technique offers a good environment to the cells, since they are not washed and centrifuged. Cell washing can lead to the loss of infected cells and decrease the output of cell cultures with an increase risk of contamination. Indeed, three out of 22 Ficoll treated samples were contaminated. One contamination was even observed before the first passage, whilst the two others were observed later.

The new technique leads to a dramatic saving in time, since it can be performed in few minutes, whereas the conventional technique requires two to three hours. In addition, the protocol saves € 3.06 per sample when compared to the conventional technique. Combined, they could encourage the use of this new technique for the isolation of T. annulata from infected animals and its validation under field conditions, where T. annulata-infected cattle are in a carrier state.

Acknowledgments

This study received financial support from the “Laboratoire d’Épidémiologie des Infections Enzootiques des Herbivores en Tunisie (Ministère de la Recherche Scientifique et de la Promotion des Compétences, Tunisie)”.

References

  1. Brown C.G.D. Application of in vitro techniques to vaccination against theileriosis, in: Advances in the control of theileriosis. Irvin A.D., Cunningham M.P. & Youg A.S. (Eds), Martinus Nijhof, La Haye, 1981, 104–119. [CrossRef] [Google Scholar]
  2. Brown C.G.D. Control of tropical theileriosis (Theileria annulata infection of cattle). Parassitologia, 1990, 32, 23–31. [PubMed] [Google Scholar]
  3. Darghouth M.A. La theilériose tropicale des bovins (Theileria annulata) en Tunisie : caractérisation des états d’endémie et développement de lignées leucocytaires infectées de schizontes atténués. Thèse de troisième cycle. Institut National Polytechnique de Toulouse, 2000, 242 p. [Google Scholar]
  4. Darghouth M.A.,Ben Miled L., Bouattour A., Melrose T.R., Brown C.G.D. & Kilani M. A preliminary study on the attenuation of Tunisian schizont infected cell lines of Theileria annulata. Parasitol Res, 1996, 82, 647–655. [CrossRef] [PubMed] [Google Scholar]
  5. Darghouth M.A., Kilani M. & Bouattour A. Les Theilérioses, in: Lefèvre PC, Provost A & Blancou.J (Eds). Les maladies infectieuses et parasitaires du bétail des régions chaudes. Masson, Paris, 2003, 1585–1603. [Google Scholar]
  6. Dobbelaere D.A., Prospero T.D., Roditi I.J., Kelke C., Baumann I., Eichhorn M., Williams R.O., Ahmed J.S., Baldwin C.L., Clevers H. & Morrison W.I. Expression of Tac antigen component of bovine interleukin-2 receptor in different leukocyte populations infected with Theileria parva or Theileria annulata. Infect Immun, 1990, 58, 3847–3855. [PubMed] [Google Scholar]
  7. Gharbi M. Vaccination contre la theilériose tropicale en Tunisie (Theileria annulata) : analyse économique et essai d’immunisation par ADN. Thèse de l’Institut National Polytechnique de Toulouse, 2006, 156 p. [Google Scholar]
  8. Gharbi M., Sassi L., Dorchies P. & Darghouth M.A. Infection of calves with Theileria annulata in Tunisia: economic analysis and evaluation of the potential benefit of vaccination. Vet Parasitol, 2006, 137, 231–241. [CrossRef] [PubMed] [Google Scholar]
  9. Glass E.J. The balance between protective immunity and pathogenesis in tropical theileriosis: what we need to know to design effective vaccines for the future Res Vet Sci, 2001, 70, 71–75. [CrossRef] [PubMed] [Google Scholar]
  10. Pipano E. Shkap V. & Frank M. Comparison of three methods for initiating in vitro cultures of Theileria annulata schizonts. Revue Élev Méd Vét Pays Trop, 1990, 4, 529–533. [Google Scholar]
  11. Shkap V., Frank M., Fish L. & Pipano E. Theileria annulata: in vitro cultivation of schizont-infected bovine hymphocytes. Vet Parasitol, 1995, 65, 11–20. [CrossRef] [Google Scholar]
  12. Tsur I. & Adler S. The cultivation of lymphoblastoïd cells and Theileria annulata schizonts from infected blood. Refuah Veterinarith, 1965, 22 60–62. [Google Scholar]
  13. Van Den Ende M. & Edlinger E. Culture des lignées lymphocytaires bovines infectées par Theileria annulata. Archives de l’Institut Pasteur de Tunis, 1971, 1–2, 45–54. [Google Scholar]

All Tables

Table I.

Comparison of two Theileria annulata isolation techniques: culture of whole blood and following Ficoll purification.

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.