Migration Pattern and Tissue Tropism of Toxascaris leonina (Linstow, 1902) Larvae: An in vivo Evaluation.

Background: : The role of Toxascaris leonina in visceral larva migrans is controversial. This study aimed to investigate the migratory behavior of T. leonina larvae across different organs in mice. Methods: Six-week-old Swiss albino mice (n = 26) were randomly allocated into six experimental groups and one control group. Each mouse in the experimental groups was orally inoculated with 1,000 embryonated T. leonina eggs. The animals were euthanized at 2, 5, 10, 15, 20 and 30 dpi (days post-infection). Tissue samples were examined for larval presence and associated pathological changes using digestive and histopathological methods. The squash method was used for brain tissue analysis. Results: T. leonina larvae were recovered from the small intestinal wall, lungs, liver, and striated muscles. No larvae were detected in the kidneys, heart, spleen, and brain using digestive or squash methods. Histological examination revealed granulomatous reactions, inflammatory cell accumulation, and larval presence in the isolated tissues. Larval concentration in the striated muscles increased over time, demonstrating the potential of Swiss albino mice to serve as paratenic hosts in toxocariasis. Conclusion: Our study exhibits that Swiss albino mice are susceptible to T. leonina infection, with larvae localizing primarily in the small intestinal wall, liver, lungs, and striated muscles.