In vitro synergy and in vivo efficacy of Melia azedarach–Millettia pachyloba leaf extracts against Trichodina nigra infection and oxidative stress in juvenile white-spotted catfish ( Clarias fuscus )

Trichodinosis and infection-associated oxidative stress can impair fish health. We evaluated ethanolic leaf extracts of chinaberry (Melia azedarach; EMA), fish-poison plant (Millettia pachyloba; EMP), and their fixed 1:1 combination (EMA+EMP) against the trichodinid parasite Trichodina nigra and in experimentally infected juvenile white-spotted catfish (Clarias fuscus). Antioxidant activity was assessed using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical-scavenging assay and the ferric reducing antioxidant power (FRAP) assay. EMA+EMP produced higher mean DPPH and FRAP responses than either extract alone. At 72 h, EMA+EMP inhibited parasite growth by 60.1–84.6% and yielded combination-index values of 0.31–0.59, indicating in vitro synergy under the tested fixed-ratio conditions. The 500 + 500 ppm formulation was then evaluated for 28 days in vivo. On Day 28, mean skin and gill burdens were 95.9% and 94.7% lower, respectively, than in infected untreated fish. EMA+EMP also produced the highest mean body-weight gain and specific growth rate among active treatments, with 40/40 terminal survival. At the tested 1:1 ratio, EMA+EMP therefore showed in vitro antitrichodinal synergy and favorable laboratory in vivo outcomes in infected juvenile C. fuscus.