Immunomodulatory and antioxidant responses of African catfish (Clarias gariepinus) to cestode infections: implications for intestinal health and aquaculture management.

Inadequate information exists on host-tapeworm parasite interactions in African catfish (Clarias gariepinus, Burchell 1822). Hence, this study evaluated the natural C. gariepinus severely infected mildly infected, on histopathological features, intestine health, immunological and antioxidant response to cestode parasites infection (Polyonchobothrium clarias (Woodland, 1925) Meggitt, 1930, Proteocephalus sp.). The prevalence of cestodes was 80%, with 26 and 52% of these fish mildly and severely infected, respectively. The prevalence was positively correlated with turbidity (0.64), NO2 (0.58), NO3 (0.63), and total alkalinity (0.57). Data illuminated that mildly and severely infected fish have more harmful effects on intestinal health and hemato-biochemical biomarkers than uninfected fish. Liver and intestinal antioxidant indices showed that the infected fish had higher malondialdehyde (MDA) levels than the uninfected fish. Correspondingly, mildly infected groups' liver and intestine showed significantly higher levels of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH), while severely infected groups showed lower levels. Data clarified that infected fish have significantly upregulated pro-inflammatory genes IL-1β, Tlr1, and C3 expression, especially in mildly infected, than uninfected fish. However, the expression of CAT and SOD genes was significantly downregulated, in the severely infected, along with higher expression of the HSP70 gene than those of the uninfected groups. The histopathological study revealed that fish infected with the cestode parasite had inflammatory and abnormal features, especially in severely infected fish groups. Hence, the study concluded that the cestode parasites induce pathological immunological responses and health status in C. gariepinus.