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All issues Volume 32 (2025) Parasite, 32 (2025) 24 Full HTML
Open Access
Issue
Parasite
Volume 32, 2025
Article Number 24
Number of page(s) 12
DOI https://doi.org/10.1051/parasite/2025019
Published online 09 April 2025

© O. Vosála et al., published by EDP Sciences, 2025

Licence Creative CommonsThis is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Introduction

The dog roundworm Toxocara canis (Werner, 1782) (Nematoda: Toxocaridae) is commonly described as a single-host intestinal parasite of canids [42, 51]. However, this parasite utilizes a broad spectrum of species, including humans [7, 51], as paratenic hosts. In them, L3 larvae undergo somatic migration, targeting predominantly the central nervous system (CNS). While T. cati seems to accumulate in the cerebellum, T. canis prefers the hemispheres [8, 22]. In mice, the first L3 larvae appear in the CNS as soon as 1 week post-infection (WPI) [41], but likely as a consequence of brain immune milieu modulation [36, 46], they remain viable up to several years [1]. Their traumatic migration through the CNS parenchyma is marked by macroscopic surface hemorrhage formation [22]. Moreover, typical hallmarks of neural destruction are observed: demyelination [40], which could be correlated with behavioral changes [23, 37], and axonal damage as indicated by the increase in amyloid-β precursor protein (AβPP) [40, 45].

AβPP can undergo a process called amyloidogenesis, resulting in the production of amyloid-β (Aβ). This small peptide is most often associated with being the main building block of “senile plaques” [50], an infamous pathological hallmark of Alzheimer’s disease (AD). However, Aβ still has some physiological functions [30, 35], including the proposed role of antimicrobial peptide in CNS innate immunity response [20, 44]. Given this role, an infectious hypothesis (IH) of AD, connecting physiological overproduction due to neuroinfection with pathological neurocytotoxicity of Aβ, was formed. IH was initially based on prion research data [49], which were later accompanied by virological studies [3, 4, 13, 26, 48]. Although in vitro and in vivo data collected from experimentally infected animals suggest that viral presence in CNS might increase Aβ production, the robust and conclusive connection between infections and AD development has not been described so far [2, 16, 28, 53]. Apart from viruses, both prokaryotic and eukaryotic unicellular pathogens were also investigated as potential triggers of Aβ overproduction, possibly leading to AD symptomatology. Importantly, increased levels of Aβ were detected in mouse brains infected by Porphyromonas gingivalis or Candida albicans [15, 52]. However, neither experiments with pathogenic bacteria [33, 38, 47], yeasts [39, 52], or even protozoan Toxoplasma gondii [9, 43] brought irrefutable evidence to credit IH.

As for neurotropic helminths, it was speculated that T. canis could be associated with the development of neurodegenerative disorders, including AD [18], mainly due to the chronic nature of the infections and worldwide distribution. Notably, in vivo data indicated increased production of AβPP [10, 40] and Aβ [10] resulting from chronic (14–20 WPI) neurotoxocarosis in mice. However, the data are scarce and lack more complex insight, which would enable a better understanding of the link between T. canis infection, Aβ production, and AD symptomatology. Here, we investigated whether the chronic infection of mice with T. canis triggers increased Aβ production and AD-related behavioral changes. Additionally, the effects of Aβ on T. canis larvae both in vitro and in vivo were assessed to test its potential antimicrobial properties.

Materials and methods

Ethics statement

Animal experiments were performed following European and Czech legislation (EU Directive 2010/63/EU, Act No 246/1992). The project was approved by the animal welfare committees of the Faculty of Science, Charles University, and the Ministry of Education, Youth and Sports of the Czech Republic (MSMT-1573/2022-5). Intraperitoneal ketamine (250 mg/kg) and xylazine (25 mg/kg) injection and subsequent exsanguination by transcardial perfusion were combined to euthanize the mice. All animals were euthanized at the end of the experiments and no untimely euthanasia was needed due to worsening of their health status (e.g., loss of 20% of original body weight).

Animals

BALB/cOlaHsd females (ENVIGO, UK) were housed in the Centre for Experimental Biomodels, First Faculty of Medicine (Charles University, Prague); they were used for experiments examining the presence of Aβ in the infected CNS. Heterozygous B6;C3-Tg(APPswe,PSEN1dE9)85Dbo/Mmjax mice (Jackson Laboratory, Farmington, CT, USA; further referred to as “APP/PS1”) and wild type (WT) littermates were bred and genotyped at the Institute of Molecular Genetics (Czech Academy of Sciences, Prague) and housed at the Faculty of Science (Charles University, Prague). APP/PS1 mice overproduce Aβ [19], so they were used to monitor the effect of Aβ on the course of neurotoxocarosis. All mice were caged in groups (4–6 animal per cage) and provided access to food and water ad libitum, unless an infection was performed as described below. The mice were given regular care and enrichment (paper shelters, wooden sticks, nesting material) with daily checks of their health status. Allocation of animals to experimental groups was made randomly by a blinded animal technician. The persons performing the experiments were blinded to the experimental group (control, infected) or animal genotype (WT, APP/PS1).

Culture of Toxocara canis larvae

Adult females of T. canis were obtained from naturally infected dogs from dog shelters following anthelmintic treatment. Female worms were collected, and Toxocara eggs were isolated by sieving female internal organs through a tea strainer and dissolving redundant tissue with 0.2 N H2SO4 [5]. Hatching of L3 larvae was performed by modified protocols of Fairbairn [17] and De Savigny et al. [14] using glass beads to disrupt the eggshell mechanically. Then, vital larvae were separated using Baermann’s apparatus with a 40 μm cell strainer (Corning, Corning, NY, USA). Hatched L3 larvae were placed in cultivation flasks in serum-free RPMI-1640 (Sigma-Aldrich, St. Louis, MO, USA) supplemented by 100 IU/mL penicillin, 250 μg/mL streptomycin, 0.1 IU/mL L-glutamine and 12 mM HEPES. They were used for infection of mice or in vitro experiments no later than 30 weeks after hatching. The culture medium containing Toxocara excretory-secretory (TES) antigen produced by L3 larvae was collected at weekly intervals according to Novák et al. [34] and further used as antigens in ELISA tests.

In vivo experimental design

In vivo experiments were conducted to examine if (a) infection with T. canis affects Aβ levels in the CNS of BALB/c mice (n = 5–7 per group) or facilitates AD-like behavioral changes in APP/PS1 mice (n = 3–6 per group), and if (b) Aβ overproduction affects the course of T. canis infection in APP/PS1 mice (n = 7–11 per group). The infected and control mice were continuously monitored and terminally harvested 8 or 16 WPI. Blood and CNS were collected for downstream analyses as described below. The actual number of animals was decided based on preliminary experiments and is indicated in the figures. The study design is summarized in Figure 1.

thumbnail Figure 1

Experimental design of in vivo experiments. (A) BALB/c mice were infected with 1,000 L3 larvae and harvested for further analyses 8 and 16 weeks post infection (WPI). (B) APP/PS1 mice were behaviorally tested –1, 1 and 16 WPI, when they were harvested for further analyses.

Infection of mice

Infection of 8-week-old female mice was performed similarly to Novák et al. [34]. Briefly, 1 day before infection, mice were denied water to boost their subsequent fluid intake. On the day of infection, L3 larvae were washed with phosphate-buffered saline (PBS) and distributed in glass tubes (1,000 L3 in 1 mL of PBS per mouse). After 4 h, the tubes were checked and refilled if necessary to ensure intake of the entire infection dose. The control group received only PBS. The day after the infection, mice were weighed and returned to cages.

Behavioral tests

APP/PS1 and control WT female mice were behaviorally tested repeatedly at three time points: T1 (1 week before the infection by T. canis), T2 (1 WPI), and T3 (16 WPI). This design was adopted due to limited access to APP/PS1 animals. The absence of uninfected controls (both WT and APP/PS1) did not allow us to assess the effect of the infection on the behavioral outcome. However, we were still able to evaluate the effect of the genotype linked to increased Aβ production, which corresponds to the study objectives. All mice underwent three behavioral tests in the following order.

Elevated plus maze (EPM)

The plus-shaped apparatus made from white plastic consisted of two opposite open arms and two closed arms (5 × 30 cm; 15 cm high walls) and was elevated 43 cm above the floor. Illumination ranged between ~130 lux (closed arms) and ~320 lux (open arms). The mouse was placed in the central part of the apparatus facing an open arm and left undisturbed for 5 min. The frequency of open arm visits as a measure of anxiety and total walked distance as a measure of locomotor activity were assessed.

Open field (OF)

The mouse was placed in the center of the square, white-laminated chipboard arena (50 × 50 cm) with opaque walls (40 cm high) and was left to freely explore for 10 min. The arena was illuminated from ~205 lux (walls) to ~270 lux (center). Locomotor activity (measured by total walked distance) and anxiety (measured by time spent in the center of the arena) were assessed.

Y-maze

The apparatus consisted of three identical arms labeled A, B, and C (6 × 35 cm; 20 cm high walls; illuminated ~ 150 lux) made from white plastic. The mouse was placed at the end of the A arm facing the center and was left free to explore the maze for 8 min. Spontaneous alternation (in %) was calculated as the number of correct triads of arm entries (ABC, BCA, CAB, ACB, CBA, BAC) divided by the number of all triads. Spontaneous alternation is a measure of working memory as it is assumed that mice prefer to alternate between the visited arms if they remember past choices. Activity was measured as total arm visits.

The apparatuses were always cleaned with a water-ethanol mixture between individual sessions and dried with paper cloths. All three tests were performed during the same day in the light phase of the daily cycle of the animals. Mice behavior was recorded by an overhead camera (Logitech C920) using Logitech Webcam software. Data were analyzed offline automatically in EthoVision software (Noldus Information Technology, Wageningen, Netherlands; EPM and OF), or manually (Y-maze).

Sample harvest

Mice were euthanized, blood for serum samples was collected, and transcardial perfusion with heparinized PBS (“unfixed” samples) or PBS and 4% formaldehyde (“fixed” samples) was performed. Lastly, intact brains were extracted. The brains of “unfixed” mice were used for larval burden examination and Aβ concentration measurement (BALB/c and APP/PS1 mice); the brains of “fixed” mice were used for immunofluorescent staining of Aβ (BALB/c mice).

Serum preparation and anti-Toxocara ES IgG ELISA

Clotted blood was centrifuged (1,500 × g, 10 min), and collected sera were stored at −80 °C. Levels of specific anti-TES IgG antibodies were measured by ELISA as already described [34].

Parasite burden

The brains of “unfixed” mice were sliced in half, and one hemisphere, half of the cerebellum, and the brain stem were individually weighed and placed into PBS at 4 °C overnight. Small parts of neural tissue were then compressed between two microscopic slides, and larvae were counted under the light microscope.

Neural tissue Aβ ELISA

Amyloid beta 42 Mouse ELISA Kits (Invitrogen, Waltham, MA, USA) were used to measure Aβ concentration in the other half of “unfixed” brains. The tissue was homogenized by sonication in 5 M guanidine-HCl/50 mM Tris (pH 8.0), and the soluble fraction was further processed and analyzed according to the manufacturer’s instructions.

Immunohistochemical staining

The “fixed” samples of mouse CNS were prepared and processed as previously described by Macháček et al. [32]. Cryosections (10 μm) were incubated overnight with primary antibodies (polyclonal rabbit anti-mouse Aβ, Rockland; 1:1,000). Anti-rabbit goat secondary antibodies with a fluorophore (Alexa Fluor® 488/594, Cell Signaling Technology, 1:1,000) were subsequently allowed to bind for one hour. Lastly, the slides were mounted in VectaShield with DAPI (VectorLabs, Newark, CA, USA) and observed under the fluorescence microscope (BX 51, Olympus).

In vitro experiments and larval viability

Thirty T. canis L3 larvae in the cultivation medium were placed into individual wells of the 96-well plate and were treated with recombinant mouse Aβ1-42 (Sigma-Aldrich; dissolved in ddH2O) in final concentrations of 5, 50, or 125 μg/mL. The treatment lasted 2 or 7 days, and 12 h before the end, a vital dye fluorescein diacetate (FDA) (Sigma-Aldrich, 0.4 μg/mL) was added. Propidium iodide (PI) (Sigma-Aldrich, 20 μg/mL) was employed as a non-vital dye. For easier observation, the larvae were immobilized by 0.4% formaldehyde. Larvae viability was assessed under the fluorescence microscope: FDA+ larvae were considered viable, PI+ larvae were considered dead. Additionally, we monitored the larval morphology: viable larvae were curled and intact, while dead larvae were characteristically taut and/or visibly damaged.

Scanning electron microscopy

L3 larvae were fixed for one hour using 0.1 M cacodylate buffer solution (CBS) containing 2.5% glutaraldehyde and 1% formaldehyde. Then, triple 5-minute CBS rinsing followed. One-hour post-fixation employing 1% osmium tetroxide (in CBS) was again followed with three times CBS rinsing. The larvae were subsequently dehydrated in the increasing ethanol series (30%, 50%, 75%, 85%, 95%, 2 × 100%; 5 min each). Critical point drying was performed in acetone by Leica EM CPD300; the larvae were then mounted and coated with a 3 nm layer of Pt using Leica EM ACE600, and later 3 nm Au using Bal-Tec SCD 050. Imaging was performed on a JEOL 6380 LV scanning electron microscope.

Statistical analysis and data visualization

All quantitative data were statistically analyzed and visualized in GraphPad Prism 10 (Dotmatics), showing individual data along with group medians. The data were checked for normality (Shapiro-Wilk test, QQ-plot) and analyzed as specified in the figure legends (1- or 2-way ANOVA or mixed-effects model followed by post hoc tests or Kaplan-Meier curve & Mantel-Cox test for survival). Statistical significance is indicated by asterisks: *p ≤ 0.05, **p ≤ 0.01, ***p ≤ 0.001, ****p ≤ 0.0001.

Results

Chronic murine neurotoxocarosis did not elevate Aβ concentrations in the CNS

Infection of BALB/c mice with Toxocara canis did not significantly affect gain in body weight when compared to healthy controls (Fig. 2A). Only one infected mouse died 3 WPI, and three infected mice showed a remarkable drop in body weight after 4 WPI (marked with crosses in Fig. 2A). They also exhibited certain behavioral changes (tumbling motion and body posture, stereotypic movements) and two of them died 13 WPI. However, no significant alteration in probability of survival was noticed between control and infected mice (p = 0.07). All infected mice harvested 8 or 16 WPI showed significantly increased serum levels of anti-TES IgG (Fig. 2B). Total larval burden in the CNS was higher in the hemispheres than in the cerebella or brain stems; more larvae were found 8 WPI than 16 WPI (Fig. 2C). However, no changes in Aβ concentration were detected in infected hemispheres either 8 or 16 WPI (Fig. 2D); similar results were obtained for the cerebella (data not shown).

thumbnail Figure 2

Characterization of chronic neurotoxocarosis in BALB/c murine model. (A) Relative weight changes did not differ between infected and control groups. Crosses (“+”) indicate mice that showed body weight drop; two of them died 13 WPI. The graph contains mice pooled from two experiments (harvest 8 and 16 WPI). (B) Levels of serum anti-T. canis IgG antibodies were significantly elevated in infected mice at both time points. (C) T. canis larvae accumulated mostly in hemispheres at both time points. Overall, more larvae were found in the group sacrificed 8 WPI. The values show larval burden in half of the freshly harvested organ as the other half was used for Aβ measurement (see next). (D) Chronic neurotoxocarosis did not alter Aβ production in the hemispheres. Individual data are shown along with the group median. For statistical analysis, a mixed-effects model (A) or 2-way ANOVA (B–D) followed by Holm-Šidák’s multiple comparisons test were used. Significant differences among the infected groups are indicated by asterisks (*p ≤ 0.05, ****p ≤ 0.0001). Aβ, amyloid-β; CNS, central nervous system; Ctrl, control (uninfected) group; OD, optical density; WPI, weeks post infection.

Aβ was associated with the outer surface and intestine of T. canis larvae in the CNS

Although increased Aβ concentration was not observed in the infected CNS, an attempt was made to localize Aβ in the nervous tissue to assess whether Aβ is somehow associated with the migrating larvae. This could remain unnoticed by the ELISA quantification, but could still indicate relevant host-parasite interplay. Hence, Aβ immunofluorescence staining was performed on control and infected animals 8 and 16 WPI. In infected brains, the only observed signal for Aβ was on the larval surface and likely in the intestine (Fig. 3). No signs of Aβ plaques were detected throughout the neural tissues. The specificity of staining was monitored by incubation of larvae-positive slides with negative rabbit serum as well as without either primary or secondary antibodies (not shown). Uninfected mice were also investigated for Aβ signal in CNS in both time points, but there were no noticeable sources of signal (not shown).

thumbnail Figure 3

Immunohistochemical localization of Aβ associated with T. canis larvae in BALB/c CNS. Signal for Aβ was located only on the surface and in the intestine of found larvae in 8 WPI (A) and 16 WPI (B) as well. The position of sectioned larvae is depicted by white lines in the bright field photos. Beyond the round shape in the cross section, the larvae can be distinguished by smaller nuclei packed more densely within the parasite tissues. Three mice per time point and at least three larvae-positive slides per mouse were analyzed. Aβ, amyloid-β; WPI, weeks post infection. Scale bars: 20 μm.

Recombinant Aβ1-42 did not alter the viability of T. canis larvae in vitro

As Aβ was associated with both the outer and inner surfaces of T. canis larvae in the brain, Aβ capacity to injure them was tested in vitro. However, incubation with physiological Aβ concentrations did not reveal any changes in parasite morphology (Fig. 4A) or staining by vital (FDA) and non-vital (PI) dyes (Fig. 4B). This suggests the absence of Aβ larvicidal capacity both after 2 and 7 days of treatment. This conclusion was also confirmed by observation of the treated larvae by scanning electron microscopy, which did not indicate any surface changes or damage (Fig. 4C).

thumbnail Figure 4

Viability assessment of T. canis larvae after in vitro treatment with recombinant Aβ1-42. After one week of treatment, neither morphology (A) or staining with vital (fluorescein diacetate; FDA) and non-vital (propidium iodide; PI) dyes (B) showed alterations in larval viability. Moreover, the 7-day treatment did not disrupt the surface of larvae as revealed by scanning electron microscopy (C). For statistical analysis, 1-way ANOVA followed by Dunnett’s multiple comparisons test were used to compare the treated groups to the respective negative control. Significant differences are indicated by asterisks (****p ≤ 0.0001). Scale bars: 10 μm.

Overproduction of Aβ in APP/PS1 mice did not control T. canis neuroinfection

To evaluate the effect of increased Aβ concentration on T. canis larvae in vivo, APP/PS1 mice overproducing Aβ were infected and harvested 16 WPI. No significant changes in weight gain were detected between infected WT and APP/PS1 mice, except for a drop in APP/PS1 mice at 16 WPI (Fig. 5A). Somewhat decreased probability of survival was noticed in APP/PS1 mice as two mice died during the infection (3 and 7 WPI, p = 0.05). Interestingly, infected APP/PS1 individuals had higher serum levels of anti-TES IgG (Fig. 5B). Compared to BALB/c mice, the total larval burden was generally lower in WT and APP/PS1 animals. Of note, significantly more larvae were found in the hemispheres of APP/PS1 mice than in WT littermates (Fig. 5C). However, the infection did not markedly change Aβ concentration in the CNS (Fig. 5D).

thumbnail Figure 5

Characterization of chronic neurotoxocarosis in APP/PS1 murine model. (A) Relative weight changes differ between infected and control groups and also between infected WT and APP/PS1 mice at 16 WPI. The graph contains only data from mice that did not undergo behavioral testing. (B) Levels of serum anti-T. canis IgG antibodies were elevated both in infected WT and APP/PS1 mice, the latter showing even significantly higher values. (C) T. canis larvae mostly preferred the hemispheres in both groups. Interestingly, more larvae were found in the APP/PS1 group. The values show larval burden in half of the freshly harvested organ as the other half was used for Aβ measurement (see next). (D) Chronic neurotoxocarosis did not alter Aβ production in the hemispheres, higher levels of Aβ were observed in the APP/PS1 groups as expected. Individual data are shown along with the group median. For statistical analysis, a mixed-effects model (A) or 2-way ANOVA (B–D) followed by Holm-Šidák’s multiple comparisons test were used. Significant differences among the infected groups are indicated by asterisks (*p ≤ 0.05, ***p ≤ 0.001). Aβ, amyloid-β; CNS, central nervous system; Ctrl, control (uninfected) group; OD, optical density; WPI, weeks post infection.

Behavioral tests

Elevated plus maze

APP/PS1 mice and their WT counterparts differed in their frequency of open arm visits (Fig. 6A), as evidenced by a significant interaction between the factors of time point and genotype (p = 0.0045). Prior to and a week after infection, APP/PS1 mice entered open arms rather less often, suggesting more anxious behavior, while 16 WPI, they visited open arms much more often than WT mice, suggesting lower anxiety. Total distance walked was affected by neither genotype nor time point, showing normal locomotor abilities (Fig. 6B). However, we observed frequent stereotypic behaviors and postural problems, including falls from the open arms, in both groups at 16 WPI.

thumbnail Figure 6

Influence of neurotoxocarosis on behavior of APP/PS1 mice. (A) Frequency of open arm visits was lower in APP/PS1 compared to WT mice –1 WPI, but notably increased 16 WPI. (B) Total distance walked was altered by neither genotype nor time point. (C) APP/PS1 mice spent more time at the center of the open field compared to WT across all time points; this parameter was notably increased 16 WPI in both groups. (D) Total distance walked in the open field was comparable between WT and APP/PS1, with a dramatic increase 16 WPI seen in both groups. (E) Spontaneous alternation was not affected by genotype but differed across time points. (F) Total arm visits were affected by neither time point nor genotype. Individual data are shown along with the group median. A mixed-effects model was used along with Holm-Šidák’s multiple comparisons test to detect differences at particular time points. Significant differences among WT and APP/PS1 mice are indicated by asterisks (*p ≤ 0.05). If the animal fell from the apparatus (EPM) or was not moving (Y-maze), it was excluded from the data sets, which explains lower n indicated in some cases.

Open field

APP/PS1 mice spent more time in the central part of the apparatus, the difference was statistically significant at 16 WPI (Fig. 6C), suggesting decreased anxiety in APP/PS1 animals. Interestingly, the time spent in the center notably increased in both groups 16 WPI. Locomotor activity was not affected by the genotype but changed between time points, with a mild decrease at 1 WPI and a dramatic increase at 16 WPI (Fig. 6D). The latter might be attributed to frequent stereotypic behavior (circling) in chronically infected mice.

Y-maze

Spontaneous alternation changed between time points, but the effect of genotype was not significant (Fig. 6E). No significant effects were found in the total number of arm visits (Fig. 6F). This suggests that both working memory and locomotor activity were not affected by genotype.

An overview of the behavioral data suggests that prior to and immediately after infection, APP/PS1 exhibited normal locomotor activity. They were more anxious in the elevated plus maze, but less anxious in the open field. This difference may reflect a specific response to anxiogenic stimuli particular to a given task: fear of heights and avoidance of open spaces, respectively. At 16 WPI, the behavior of the animals in both groups was severely affected by the infection, with stereotypic movements and disruption of normal behavioral patterns. APP/PS1 mice exhibited lower anxiety (more frequent open arm visits, and more time spent in the central part). However, the small sample size at 16 WPI makes any conclusions tentative.

Discussion

AD has been recognized for over a century, yet its triggers remain largely unknown, limiting prevention and treatment strategies. While pathological processes such as Aβ overproduction and tau hyperphosphorylation are well documented [29], their initiating factors remain unclear. Here, we used a mouse model of chronic neurotoxocarosis to investigate the emerging hypothesis that infections contribute to AD pathogenesis via Aβ’s antimicrobial properties.

Toxocara canis has been proposed as a possible AD-triggering infectious agent, especially due to its global prevalence and persistence in the host CNS [18]. Supporting this view, Chou et al. [10] recorded by a semi-quantitative Western blot the increased signal of Aβ in the hippocampus of infected mice 8–20 WPI. However, our quantitative study, using ELISA to detect total soluble Aβ, shows no elevated Aβ concentration in the CNS (neither hemispheres nor cerebella) of chronically infected mice – despite the presence of considerable larval burden, particularly in the hemispheres. Moreover, no Aβ deposits were seen throughout the infected CNS, including the hippocampus, when examined by immunohistochemistry. This corroborates the data ascribing the increased levels of AβPP, the Aβ precursor detected in T. canis infected brains, to axonal injury, not AD-like pathology [21, 40]. This type of interpretation is further supported by the downregulation of the “Alzheimer disease-amyloid secretase pathway” noted on 16 WPI [45]. Collectively, our data seem to contradict the hypothesis that chronic neurotoxocarosis would facilitate Aβ accumulation, at least within 16 WPI, even in the mouse model naturally overproducing Aβ.

However, it must be acknowledged that our study tracks the effects of T. canis infection only up to 16 WPI, which may not be sufficient to capture delayed or progressive AD-like pathology in mice. This follow-up period could limit our ability to detect potential long-term effects of the infection. Additionally, the absence of age-matched healthy controls at 16 WPI and the small sample sizes in the behavioral tests limit the interpretation and statistical power to detect possible subtle effects. Therefore, future studies with extended timeframes and larger sample sizes are needed to fully assess the long-term impact of T. canis infection.

Interestingly, while Aβ levels did not increase in the brain tissue, immunofluorescence staining revealed Aβ localized on the surface and within the intestine of migrating T. canis larvae. A similar phenomenon of Aβ binding onto the pathogen surface has been observed in viruses, bacteria, and yeasts [16, 27, 38, 39]. This could be related to the proposed role of Aβ in brain innate immunity, which attempts to sequester or injure the invading pathogens [24, 44]. However, our in vitro experiments do not support the view that Aβ has anthelmintic activities as both the morphology and viability of Aβ-treated T. canis larvae remained unchanged, even after 7-day Aβ treatment. Additionally, the larval burden was not decreased in APP/PS1 mice that naturally overproduce Aβ in the CNS [19], which we also confirmed by ELISA. The lack of antiparasitic activity can be explained by the complex, multi-layered nature of the nematode cuticle, which provides robust resistance against antimicrobial peptides [6, 11]. Additionally, it cannot be excluded that TES containing peptidases [12] help the larvae to remove the surface-bound Aβ. Also, the brain immune milieu is shifted to anti-inflammatory response in infected mice [46], which might decrease Aβ production. As for the Aβ detected in the larval intestine, we speculate that it originates from active feeding of the parasites on the nervous tissue, which was also demonstrated, e.g., in the neurotropic schistosome Trichobilharzia regenti [31]. Overall, our data show that Aβ is not detrimental to the parasite and that Aβ might not function as a defense mechanism against helminth neuroinfection.

Conclusion

Altogether, our robust experimental data show that T. canis infection does not trigger AD-like pathology in mice and Aβ does not act as an antiparasitic agent. The absence of Aβ elevation in response to T. canis infection challenges the notion that parasitic infections can directly exacerbate AD-like pathology through Aβ accumulation [18]. Additionally, this aligns with the recent epidemiologic report showing no strong association between Toxocara exposure and AD in humans [25]. Likewise, we found no experimental evidence supporting the hypothesis that Aβ acts as an antimicrobial agent limiting nematode neuroinfections [44]. By demonstrating that T. canis is likely not significantly involved in disease etiology in the mouse model, we do not however disprove the AD infectious hypothesis as a whole.

Funding

The study was supported by the Charles University Grant Agency (B-BIO 405022), and Charles University institutional funding (Cooperatio Biology, SVV 260687, SVV 260664, UNCE24/SCI/011). The authors acknowledge the Imaging Methods Core Facility at BIOCEV, institution supported by the MEYS CR (LM2023050 Czech-BioImaging), for their assistance with preparation of SEM samples.

Conflicts of interest

The authors declare that they have no competing interests.

References

  1. Beaver PC. 1962. Toxocarosis (visceral larva migrans) in relation to tropical eosinophilia. Bulletin de la Société de Pathologie Exotique, 55, 555–576. [Google Scholar]
  2. Bocharova O, Pandit NP, Molesworth K, Fisher A, Mychko O, Makarava N, Baskakov IV. 2021. Alzheimer’s disease-associated β-amyloid does not protect against herpes simplex virus 1 infection in the mouse brain. Journal of Biological Chemistry, 297, 100845. [CrossRef] [Google Scholar]
  3. Bourgade K, Garneau H, Giroux G, Le Page AY, Bocti C, Dupuis G, Frost EH, Fülöp T. 2015. β-Amyloid peptides display protective activity against the human Alzheimer’s disease-associated herpes simplex virus-1. Biogerontology, 16, 85–98. [CrossRef] [PubMed] [Google Scholar]
  4. Bourgade K, Le Page A, Bocti C, Witkowski JM, Dupuis G, Frost EH, Fülöp T. 2016. Protective effect of Amyloid-β peptides against herpes simplex virus-1 infection in a neuronal cell culture model. Journal of Alzheimer’s Disease, 50, 1227–1241. [CrossRef] [Google Scholar]
  5. Bowman DD, Mika-Grieve M, Grieve RB. 1987. Circulating excretory-secretory antigen levels and specific antibody responses in mice infected with Toxocara canis. American Journal of Tropical Medicine and Hygiene, 36, 75–82. [CrossRef] [PubMed] [Google Scholar]
  6. Bowman DD, Oaks JA, Grieve RB. 1993. Infrastructure of the infective-stage larva of Toxocara canis (Nematoda:Ascaridoidea). Journal of the Helminthological Society of Washington, 60, 183–204. [Google Scholar]
  7. Brill R, Churg J, Beaver PC. 1953. Allergic granulomatosis associated with visceral larva migrans; case report with autopsy findings on Toxocara infection in a child. American Journal of Clinical Pathology, 23, 1208–1215. [CrossRef] [PubMed] [Google Scholar]
  8. Burren CH. 1971. The distribution of Toxocara larvae in the central nervous system of the mouse. Transactions of the Royal Society of Tropical Medicine and Hygiene, 65, 450–453. [CrossRef] [PubMed] [Google Scholar]
  9. Cabral CM, McGovern KE, MacDonald WR, Franco J, Koshy AA. 2017. Dissecting amyloid beta deposition using distinct strains of the neurotropic parasite Toxoplasma gondii as a novel tool. ASN Neuro, 9, 175909141772491. [CrossRef] [Google Scholar]
  10. Chou CM, Lee YL, Liao CW, Huang YC, Fan CK. 2017. Enhanced expressions of neurodegeneration-associated factors, UPS impairment, and excess Aβ accumulation in the hippocampus of mice with persistent cerebral toxocariasis. Parasites & Vectors, 10, 620. [CrossRef] [PubMed] [Google Scholar]
  11. Ciudad S, Puig E, Botzanowski T, Meigooni M, Arango AS, Do J, Mayzel M, Bayoumi M, Chaignepain S, Maglia G, Cianferani S, Orekhov V, Tajkhorshid E, Bardiaux B, Carulla N. 2020. Aβ(1-42) tetramer and octamer structures reveal edge conductivity pores as a mechanism for membrane damage. Nature Communications, 11, 3014. [CrossRef] [PubMed] [Google Scholar]
  12. da Silva MB, Urrego JRA, Oviedo Y, Cooper PJ, Pacheco LGC, Pinheiro CS, Ferreira F, Briza P, Alcantara-Neves NM. 2018. The somatic proteins of Toxocara canis larvae and excretory-secretory products revealed by proteomics. Veterinary Parasitology, 259, 25–34. [CrossRef] [PubMed] [Google Scholar]
  13. De Chiara G, Piacentini R, Fabiani M, Mastrodonato A, Marcocci ME, Limongi D, Napoletani G, Protto V, Coluccio P, Celestino I, Li Puma DD, Grassi C, Palamara AT. 2019. Recurrent herpes simplex virus-1 infection induces hallmarks of neurodegeneration and cognitive deficits in mice. PLoS Pathogens, 15, e1007617. [CrossRef] [PubMed] [Google Scholar]
  14. De Savigny DH, Voller A, Woodruff AW. 1979. Toxocariasis: Serological diagnosis by enzyme immunoassay. Journal of Clinical Pathology, 32, 284–288. [CrossRef] [PubMed] [Google Scholar]
  15. Dominy SS, Lynch C, Ermini F, Benedyk M, Marczyk A, Konradi A, Nguyen M, Haditsch U, Raha D, Griffin C, Holsinger LJ, Arastu-Kapur S, Kaba S, Lee A, Ryder MI, Potempa B, Mydel P, Hellvard A, Adamowicz K, Hasturk H, Walker GD, Reynolds EC, Maull RLM, Curtis MA, Dragunow M, Potempa J. 2019. Porphyromonas gingivalis in Alzheimer’s disease brains: Evidence for disease causation and treatment with small-molecule inhibitors. Science Advances, 5, eaau3333. [CrossRef] [PubMed] [Google Scholar]
  16. Eimer WA, Vijaya Kumar DK, Navalpur Shanmugam NK, Rodriguez AS, Mitchell T, Washicosky KJ, György B, Breakefield XO, Tanzi RE, Moir RD. 2018. Alzheimer’s disease-associated β-amyloid is rapidly seeded by Herpesviridae to protect against brain infection. Neuron, 99, 56–63.e3. [CrossRef] [PubMed] [Google Scholar]
  17. Fairbairn D. 1961. The in vitro hatching of Ascaris lumbricoides eggs. Canadian Journal of Zoology, 39, 153–162. [CrossRef] [Google Scholar]
  18. Fan CK, Holland CV, Loxton K, Barghouth U. 2015. Cerebral toxocariasis: Silent progression to neurodegenerative disorders? Clinical Microbiology Reviews, 28, 663–686. [CrossRef] [PubMed] [Google Scholar]
  19. Finnie GS, Gunnarsson R, Manavis J, Blumbergs PC, Mander KA, Edwards S, Van den Heuvel C, Finnie JW. 2017. Characterization of an “Amyloid only” transgenic (B6C3-Tg (APPswe, PSEN1dE9) 85Dbo/Mmjax) mouse model of Alzheimer’s disease. Journal of Comparative Pathology, 156, 389–399. [CrossRef] [PubMed] [Google Scholar]
  20. Gosztyla ML, Brothers HM, Robinson SR. 2018. Alzheimer’s amyloid-β is an antimicrobial peptide: A review of the evidence. Journal of Alzheimer’s Disease, 62, 1495–1506. [CrossRef] [PubMed] [Google Scholar]
  21. Heuer L, Beyerbach M, Lühder F, Beineke A, Strube C. 2015. Neurotoxocarosis alters myelin protein gene transcription and expression. Parasitology Research, 114, 2175–2186. [CrossRef] [PubMed] [Google Scholar]
  22. Janecek E, Beineke A, Schnieder T, Strube C. 2014. Neurotoxocarosis: Marked preference of Toxocara canis for the cerebrum and T. cati for the cerebellum in the paratenic model host mouse. Parasites & Vectors, 7, 194. [CrossRef] [PubMed] [Google Scholar]
  23. Janecek E, Waindok P, Bankstahl M, Strube C. 2017. Abnormal neurobehaviour and impaired memory function as a consequence of Toxocara canis- as well as Toxocara cati-induced neurotoxocarosis. PLoS Neglected Tropical Diseases, 11, e0005594. [CrossRef] [PubMed] [Google Scholar]
  24. Kagan BL, Jang H, Capone R, Teran Arce F, Ramachandran S, Lal R, Nussinov R. 2012. Antimicrobial properties of amyloid peptides. Molecular Pharmaceutics, 9, 708–717. [CrossRef] [PubMed] [Google Scholar]
  25. Khatir AA, Mousavi F, Sepidarkish M, Arshadi M, Arjmandi D, Aldaghi M, Rostami A. 2024. Association between Alzheimer’s disease and Toxocara infection/exposure: A case-control study. Transactions of the Royal Society of Tropical Medicine and Hygiene, 118, 744–751. [CrossRef] [PubMed] [Google Scholar]
  26. Kristen H, Santana S, Sastre I, Recuero M, Bullido MJ, Aldudo J. 2015. Herpes simplex virus type 2 infection induces AD-like neurodegeneration markers in human neuroblastoma cells. Neurobiology of Aging, 36, 2737–2747. [CrossRef] [PubMed] [Google Scholar]
  27. Kumar DKV, Choi SH, Washicosky KJ, Eimer WA, Tucker S, Ghofrani J, Lefkowitz A, McColl G, Goldstein LE, Tanzi RE, Moir RD. 2016. Amyloid-β peptide protects against microbial infection in mouse and worm models of Alzheimer’s disease. Science Translational Medicine, 8, 139–148. [Google Scholar]
  28. Lapeyre L, Piret J, Rhéaume C, Pons V, Uyar O, Préfontaine P, Rivest S, Boivin G. 2024. Herpes simplex virus 1 infection does not increase amyloid-β pathology in APP/PS1 mice. Journal of Alzheimer’s Disease, 97, 171–178. [CrossRef] [Google Scholar]
  29. Long JM, Holtzman DM. 2019. Alzheimer disease: An update on pathobiology and treatment strategies. Cell, 179, 312–339. [CrossRef] [PubMed] [Google Scholar]
  30. Lovell MA, Robertson JD, Teesdale WJ, Campbell JL, Markesbery WR. 1998. Copper, iron and zinc in Alzheimer’s disease senile plaques. Journal of the Neurological Sciences, 158, 47–52. [CrossRef] [PubMed] [Google Scholar]
  31. Macháček T, Leontovyč R, Šmídová B, Majer M, Vondráček O, Vojtěchová I, Petrásek T, Horák P. 2022. Mechanisms of the host immune response and helminth-induced pathology during Trichobilharzia regenti (Schistosomatidae) neuroinvasion in mice. PLoS Pathogens, 18, e1010302. [CrossRef] [PubMed] [Google Scholar]
  32. Macháček T, Šmídová B, Pankrác J, Majer M, Bulantová J, Horák P. 2020. Nitric oxide debilitates the neuropathogenic schistosome Trichobilharzia regenti in mice, partly by inhibiting its vital peptidases. Parasites & Vectors, 13, 426. [CrossRef] [PubMed] [Google Scholar]
  33. Miklossy J, Kis A, Radenovic A, Miller L, Forro L, Martins R, Reiss K, Darbinian N, Darekar P, Mihaly L, Khalili K. 2006. Beta-amyloid deposition and Alzheimer’s type changes induced by Borrelia spirochetes. Neurobiology of Aging, 27, 228–236. [CrossRef] [PubMed] [Google Scholar]
  34. Novák J, Panská L, Macháček T, Kolářová L, Horák P. 2017. Humoral response of mice infected with Toxocara canis following different infection schemes. Acta Parasitologica, 62, 823–835. [CrossRef] [PubMed] [Google Scholar]
  35. Rahman MM, Westermark GT, Zetterberg H, Härd T, Sandgren M. 2018. Protofibrillar and fibrillar amyloid-β binding proteins in cerebrospinal fluid. Journal of Alzheimer’s Disease, 66, 1053–1064. [CrossRef] [PubMed] [Google Scholar]
  36. Resende NM, Gazzinelli-Guimarães PH, Barbosa FS, Oliveira LM, Nogueira DS, Gazzinelli-Guimarães AC, Gonçalves MTP, Amorim CCO, Oliveira FMS, Caliari MV, Rachid MA, Volpato GT, Bueno LL, Geiger SM, Fujiwara RT. 2015. New insights into the immunopathology of early Toxocara canis infection in mice. Parasites & Vectors, 8, 354. [CrossRef] [PubMed] [Google Scholar]
  37. Serra-de-Oliveira N, Boilesen SN, Prado de França Carvalho C, LeSueur-Maluf L, Zollner RL, Spadari RC, Medalha CC, Monteiro de Castro G. 2015. Behavioural changes observed in demyelination model shares similarities with white matter abnormalities in humans. Behavioural Brain Research, 287, 265–275. [CrossRef] [PubMed] [Google Scholar]
  38. Soscia SJ, Kirby JE, Washicosky KJ, Tucker SM, Ingelsson M, Hyman B, Burton MA, Goldstein LE, Duong S, Tanzi RE, Moir RD. 2010. The Alzheimer’s disease-associated amyloid β-protein is an antimicrobial peptide. PLoS One, 5, e9505. [CrossRef] [PubMed] [Google Scholar]
  39. Spitzer P, Condic M, Herrmann M, Oberstein TJ, Scharin-Mehlmann M, Gilbert DF, Friedrich O, Grömer T, Kornhuber J, Lang R, Maler JM. 2016. Amyloidogenic amyloid-β-peptide variants induce microbial agglutination and exert antimicrobial activity. Scientific Reports, 6, 32228. [CrossRef] [PubMed] [Google Scholar]
  40. Springer A, Heuer L, Janecek-Erfurth E, Beineke A, Strube C. 2019. Histopathological characterization of Toxocara canis- and T. cati-induced neurotoxocarosis in the mouse model. Parasitology Research, 118, 2591–2600. [CrossRef] [PubMed] [Google Scholar]
  41. Strube C, Waindok P, Raulf MK, Springer A. 2020. Toxocara-induced neural larva migrans (neurotoxocarosis) in rodent model hosts. Advances in Parasitology, 109, 189–218. [CrossRef] [PubMed] [Google Scholar]
  42. Taylor EL. 1924. On the ascarids of the dog and cat. Annals of Tropical Medicine and Parasitology, 18, 243–251. [CrossRef] [Google Scholar]
  43. Torres L, Robinson SA, Kim DG, Yan A, Cleland TA, Bynoe MS. 2018. Toxoplasma gondii alters NMDAR signaling and induces signs of Alzheimer’s disease in wild-type, C57BL/6 mice. Journal of Neuroinflammation, 15, 57. [CrossRef] [PubMed] [Google Scholar]
  44. Vojtechova I, Machacek T, Kristofikova Z, Stuchlik A, Petrasek T. 2022. Infectious origin of Alzheimer’s disease: Amyloid beta as a component of brain antimicrobial immunity. PLoS Pathogens, 18, e1010929. [CrossRef] [PubMed] [Google Scholar]
  45. Waindok P, Janecek-Erfurth E, Lindenwald DL, Wilk E, Schughart K, Geffers R, Strube C. 2022. Toxocara canis- and Toxocara cati-induced neurotoxocarosis is associated with comprehensive brain transcriptomic alterations. Microorganisms, 10, 177. [CrossRef] [PubMed] [Google Scholar]
  46. Waindok P, Strube C. 2019. Neuroinvasion of Toxocara canis- and T. cati-larvae mediates dynamic changes in brain cytokine and chemokine profile. Journal of Neuroinflammation, 16, 147. [CrossRef] [PubMed] [Google Scholar]
  47. Wang XL, Zeng J, Feng J, Tian YT, Liu YJ, Qiu M, Yan X, Yang Y, Xiong Y, Zhang ZH, Wang Q, Wang JZ, Liu R. 2014. Helicobacter pylori filtrate impairs spatial learning and memory in rats and increases β-amyloid by enhancing expression of presenilin-2. Frontiers in Aging Neuroscience, 6, 66. [PubMed] [Google Scholar]
  48. White MR, Kandel R, Tripathi S, Condon D, Qi L, Taubenberger J, Hartshorn KL. 2014. Alzheimer’s associated β-amyloid protein inhibits influenza a virus and modulates viral interactions with phagocytes. PLoS One, 9, e101364. [CrossRef] [PubMed] [Google Scholar]
  49. Wisniewski HM, Moretz RC, Lossinsky AS. 1981. Evidence for induction of localized amyloid deposits and neuritic plaques by an infectious agent. Annals of Neurology, 10, 517–522. [CrossRef] [PubMed] [Google Scholar]
  50. Wong CW, Quaranta V, Glenner GG. 1985. Neuritic plaques and cerebrovascular amyloid in Alzheimer disease are antigenically related. Proceedings of the National Academy of Sciences of the United States of America, 82, 8729–8732. [CrossRef] [PubMed] [Google Scholar]
  51. Wu TK, Bowman DD. 2022. Toxocara canis. Trends in Parasitology, 38, 709–710. [CrossRef] [PubMed] [Google Scholar]
  52. Wu Y, Du S, Johnson JL, Tung HY, Landers CT, Liu Y, Seman BG, Wheeler RT, Costa-Mattioli M, Kheradmand F, Zheng H, Corry DB. 2019. Microglia and amyloid precursor protein coordinate control of transient Candida cerebritis with memory deficits. Nature Communications, 10(1), 58. [CrossRef] [PubMed] [Google Scholar]
  53. Zhao M, Ma G, Yan X, Li X, Wang E, Xu XX, Zhao JB, Ma X, Zeng J. 2024. Microbial infection promotes amyloid pathology in a mouse model of Alzheimer’s disease via modulating γ-secretase. Molecular Psychiatry, 29, 1491–1500. [CrossRef] [PubMed] [Google Scholar]

Cite this article as: Vosála O, Šmídová B, Novák J, Svoboda J, Petrásek T, Vojtěchová I & Macháček T. 2025. No evidence of Alzheimer’s disease pathology in mice infected with Toxocara canis. Parasite 32, 24. https://doi.org/10.1051/parasite/2025019.

All Figures

thumbnail Figure 1

Experimental design of in vivo experiments. (A) BALB/c mice were infected with 1,000 L3 larvae and harvested for further analyses 8 and 16 weeks post infection (WPI). (B) APP/PS1 mice were behaviorally tested –1, 1 and 16 WPI, when they were harvested for further analyses.
In the text
thumbnail Figure 2

Characterization of chronic neurotoxocarosis in BALB/c murine model. (A) Relative weight changes did not differ between infected and control groups. Crosses (“+”) indicate mice that showed body weight drop; two of them died 13 WPI. The graph contains mice pooled from two experiments (harvest 8 and 16 WPI). (B) Levels of serum anti-T. canis IgG antibodies were significantly elevated in infected mice at both time points. (C) T. canis larvae accumulated mostly in hemispheres at both time points. Overall, more larvae were found in the group sacrificed 8 WPI. The values show larval burden in half of the freshly harvested organ as the other half was used for Aβ measurement (see next). (D) Chronic neurotoxocarosis did not alter Aβ production in the hemispheres. Individual data are shown along with the group median. For statistical analysis, a mixed-effects model (A) or 2-way ANOVA (B–D) followed by Holm-Šidák’s multiple comparisons test were used. Significant differences among the infected groups are indicated by asterisks (*p ≤ 0.05, ****p ≤ 0.0001). Aβ, amyloid-β; CNS, central nervous system; Ctrl, control (uninfected) group; OD, optical density; WPI, weeks post infection.
In the text
thumbnail Figure 3

Immunohistochemical localization of Aβ associated with T. canis larvae in BALB/c CNS. Signal for Aβ was located only on the surface and in the intestine of found larvae in 8 WPI (A) and 16 WPI (B) as well. The position of sectioned larvae is depicted by white lines in the bright field photos. Beyond the round shape in the cross section, the larvae can be distinguished by smaller nuclei packed more densely within the parasite tissues. Three mice per time point and at least three larvae-positive slides per mouse were analyzed. Aβ, amyloid-β; WPI, weeks post infection. Scale bars: 20 μm.
In the text
thumbnail Figure 4

Viability assessment of T. canis larvae after in vitro treatment with recombinant Aβ1-42. After one week of treatment, neither morphology (A) or staining with vital (fluorescein diacetate; FDA) and non-vital (propidium iodide; PI) dyes (B) showed alterations in larval viability. Moreover, the 7-day treatment did not disrupt the surface of larvae as revealed by scanning electron microscopy (C). For statistical analysis, 1-way ANOVA followed by Dunnett’s multiple comparisons test were used to compare the treated groups to the respective negative control. Significant differences are indicated by asterisks (****p ≤ 0.0001). Scale bars: 10 μm.
In the text
thumbnail Figure 5

Characterization of chronic neurotoxocarosis in APP/PS1 murine model. (A) Relative weight changes differ between infected and control groups and also between infected WT and APP/PS1 mice at 16 WPI. The graph contains only data from mice that did not undergo behavioral testing. (B) Levels of serum anti-T. canis IgG antibodies were elevated both in infected WT and APP/PS1 mice, the latter showing even significantly higher values. (C) T. canis larvae mostly preferred the hemispheres in both groups. Interestingly, more larvae were found in the APP/PS1 group. The values show larval burden in half of the freshly harvested organ as the other half was used for Aβ measurement (see next). (D) Chronic neurotoxocarosis did not alter Aβ production in the hemispheres, higher levels of Aβ were observed in the APP/PS1 groups as expected. Individual data are shown along with the group median. For statistical analysis, a mixed-effects model (A) or 2-way ANOVA (B–D) followed by Holm-Šidák’s multiple comparisons test were used. Significant differences among the infected groups are indicated by asterisks (*p ≤ 0.05, ***p ≤ 0.001). Aβ, amyloid-β; CNS, central nervous system; Ctrl, control (uninfected) group; OD, optical density; WPI, weeks post infection.
In the text
thumbnail Figure 6

Influence of neurotoxocarosis on behavior of APP/PS1 mice. (A) Frequency of open arm visits was lower in APP/PS1 compared to WT mice –1 WPI, but notably increased 16 WPI. (B) Total distance walked was altered by neither genotype nor time point. (C) APP/PS1 mice spent more time at the center of the open field compared to WT across all time points; this parameter was notably increased 16 WPI in both groups. (D) Total distance walked in the open field was comparable between WT and APP/PS1, with a dramatic increase 16 WPI seen in both groups. (E) Spontaneous alternation was not affected by genotype but differed across time points. (F) Total arm visits were affected by neither time point nor genotype. Individual data are shown along with the group median. A mixed-effects model was used along with Holm-Šidák’s multiple comparisons test to detect differences at particular time points. Significant differences among WT and APP/PS1 mice are indicated by asterisks (*p ≤ 0.05). If the animal fell from the apparatus (EPM) or was not moving (Y-maze), it was excluded from the data sets, which explains lower n indicated in some cases.
In the text

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