Toxocara canis, a zoonotic parasitic nematode and one of the primary pathogens of human toxocariasis, poses a serious threat to public health and biosafety. As a pivotal component of the antioxidant system, superoxide dismutase (sod) promotes parasite resistance to oxidative damage and sustains their survival. This study characterized Tc-sod and investigated its expression patterns and tissue localization. The RNA interference (RNAi) was employed to examine the function of Tc-sod in the growth, development, and pathogenicity of T. canis. The results indicated that Tc-sod is expressed in female, male, and L3 larvae, and the immunofluorescence shows that it is mainly localized in the ovary, uterus, and body wall of T. canis, suggesting that Tc-sod is involved in the growth, development, and reproductive processes of T. canis. Compared with the PBS group, the Tc-sod-siRNA-61 significantly reduced the mRNA transcription and protein expression of Tc-sod, suggesting that siRNA-61 mediated specific silencing of the Tc-sod gene. It further affected the hatching rate of eggs, leading to phenotypic changes, including embryonic development disorders and larvae deformation. The larvae burden rate of infected mice in the Tc-sod-siRNA-61 group was 33.4%, and the motility of larvae was weakened. Mice in the Tc-sod-siRNA-61 group showed reduced haemorrhagic lesions and inflammatory infiltration in the liver, lungs, and brain tissues. These results demonstrate that Tc-sod is crucial in the development and survival of T. canis. It could also be a target candidate for the anti-T. canis vaccine and drugs.

To Cite This Article: Wu TL, Wang BN, Li BY, Hu ZY, You YN, Luo YL, Bi SC and Zhou RQ 2025. Rnai-Mediated silencing of superoxide dismutase in Toxocara canis affects the development and survival of eggs and larvae. Pak Vet J. http://dx.doi.org/10.29261/pakvetj/2025.253