Toxocara canis is widely distributed parasite that not only presents in definitive hosts but also occurs in paratenic hosts including human. Larvae migrate throughout the somatic tissue causing severe inflammatory and pathological reactions. This study aims to detect the effect of infection with Toxocara canis on testis of rats regarding histopathological, histochemical and immunohistochemical changes and amelioration of these changes with either vaccination with gamma radiation-attenuated embryonated eggs or with herbal treatment with thyme. The study was conducted on eighty rats classified into four groups (20 each): Group A (normal control); Group B (infected control); Group C infected and treated with thyme oil (thyme-treated); and Group D vaccinated with 800 Gy gamma radiation-attenuated embryonated eggs, and challenged with the same number of eggs (vaccinated-challenged). Testicular tissues were stained with Haematoxylin and Eosin (H &E) for histopathological study. Periodic acid Schiff’s (PAS), bromophenol blue (BPB) and Feulgen’s reaction for carbohydrates, proteins and DNA, respectively were done to examine histochemical changes. Immunohistochemical study was done through expression of TGF-β1 and caspase-3. Infected control group B showed severe histopathological changes with marked decrease in PAS +ve materials, total proteins and DNA and enhanced expression of Transforming growth factor- β1 (TGF-β1) and caspase-3. Moderate changes were observed in testicular tissues of group C treated with thyme. Slight changes were detected in vaccinated-challenged group D. It was concluded that Toxocara canis infection causes marked hispathological, histochemical and immunohistochemical changes in testicular tissues of rats that can be ameliorated by vaccination with radiation-attenuated infective stage or treated with thyme; however vaccination is more effective in protection.

Toxocara canis is a major parasite that infects many animals with high risk of human infections. This study aims at assessing the immunization with gamma radiationattenuated infective stage on rats challenged with non-irradiated dose. Level of vaccine protection was evaluated in liver and lung regarding parasitological, histopathological, biochemical and molecular parameters. Fifty rats were enrolled in three groups: group A (10 rats) as normal control; group B (20 rats) subdivided into subgroup B1 (infected control) and subgroup B2 infected then challenged after 14 days with the same dose of infection (challenged infected control); and group C (20 rats) subdivided into subgroup C1 vaccinated with a dose of 800 gray (Gy) gamma-radiated infective eggs (vaccine control) and subgroup C2 vaccinated then challenged on 14th day with same number of infective eggs (vaccinated-challenged). Tissues were stained with Haematoxylin and Eosin (H&E) for histopathological studies. Biochemical studies through detection of nitric oxide (NO) and Caspase-3 were conducted. Extent of DNA damage by Comet assay was assessed. Vaccinated-challenged subgroup revealed a marked reduction in larvae in tissues with mild associated histological changes. In addition there was accompanied reduction of NO, Casepase-3 level and DNA damage compared to the control infected group. It could be concluded that vaccination of rats with a dose of 800Gy gamma radiation-attenuated infective stage improves immune response to challenge infection and drastically reduces the morbidity currently seen.