Pathophysiological impact of Euclinostomum heterostomum infection in Nile tilapia (Oreochromis niloticus): a multidisciplinary investigation revealing immune-oxidative stress interactions

Euclinostomum heterostomum, a digenetic trematode, represents an emerging threat to tilapia aquaculture, yet its immunological impacts remain inadequately characterized. This comprehensive study employed an integrated approach combining morphological, molecular, biochemical, and histopathological analyses to elucidate the pathophysiological consequences of natural E. heterostomum infection in Nile tilapia (Oreochromis niloticus). Metacercariae were isolated from kidney tissue of farmed tilapia with 18% prevalence (n = 100), and species identity was confirmed through morphological examination and internal transcribed spacer (ITS) region sequencing (100% identity with GenBank reference sequences). Biochemical profiling revealed significant (P < 0.05) disruption of protein metabolism, with infected fish showing decreased total protein (3.05 ± 0.08 vs 5.28 ± 0.13 g/dL), albumin (0.75 ± 0.05 vs 2 ± 0.06 g/dL), and globulin (2.3 ± 0.1 vs 3.3 ± 0.16 g/dL) compared to controls. Hepatic dysfunction was evidenced by elevated ALT (46.7 ± 1.5 vs 14.41 ± 0.62 U/mL) and AST (90.01 ± 3.2 vs 30.24 ± 1.5 U/mL), while renal impairment manifested as increased creatinine (1.33 ± 0.07 vs 0.51 ± 0.03 mg/dL) and uric acid (53.2 ± 1.5 vs 30.88 ± 1.31 mg/L). Oxidative stress was indicated by elevated MDA levels (17.7 ± 0.24 vs 12.15 ± 0.28 nmol/mL). Quantitative RT-PCR analysis revealed significant immune activation with upregulation of TNFα (5.4-fold), IL-1β (7.4-fold), and MHC-IIα (8.8-fold), contrasting with downregulation of antioxidant enzymes SOD2 (0.09-fold) and Cat (0.1-fold). These molecular alterations underscore the host’s immune activation alongside oxidative stress burden, highlighting the complex pathophysiological interplay associated with E. heterostomum infection in Nile tilapia. Histopathological examination demonstrated severe renal alterations including glomerular atrophy, tubular necrosis, and extensive fibrosis surrounding encysted metacercariae. These findings provide crucial insights into host-parasite interactions and establish baseline data for developing targeted therapeutic interventions and management strategies for E. heterostomum infections in aquaculture systems.