Influence of crude extracts from different thermally treated Hysterothylacium thalassini L3 larvae on liver pathology and immune responses in C57BL/6 mice.

Hysterothylacium thalassini third-stage larvae (L3), commonly found in marine fish, are known to induce liver injury, oxidative stress, and immune disturbances when transmitted to mammalian hosts. This study investigated the pathological effects of purified crude extracts derived from fresh, heat-treated, and frozen L3 larvae on liver function, oxidative status, and immune responses in a murine model. Thirty Saurida tumbil fish were examined for L3 larvae, which were processed under three conditions: fresh (24 ± 2 °C for 60 min), heat-treated (100 °C for 60 min), and frozen (-20 °C for 24 h). Twenty male C57BL/6 mice were randomly allocated into four groups and inoculated with larval extracts at a 14-day interval. Mice exposed to fresh larval extracts exhibited significant weight loss, elevated liver enzymes (ALT, AST, ALP), hyperglycemia, and reduced total protein levels, alongside severe hepatic damage characterized by necrosis and inflammatory infiltration. Antioxidant enzyme activities (CAT and SOD) were markedly decreased, whereas oxidative stress markers (NO and H₂O₂) were increased. Additionally, there was significant upregulation of iNOS, TNF-α, and IL-10 gene expression, accompanied by elevated iNOS, IL-10, and IgE protein levels, indicating strong inflammatory and Th2-type immune responses. In contrast, extracts from heat-treated and frozen larvae resulted in attenuated pathological effects, including improved liver function, reduced oxidative stress, and moderated immune responses. These findings demonstrate that untreated L3 larval extracts exert pronounced hepatotoxic and immunomodulatory effects, while thermal and freezing treatments significantly reduce their pathogenicity and support immune homeostasis, highlighting potential strategies to mitigate parasite-induced host damage.