Trematode Infections and Histopathological Effects in <i>Chrysichthys nigrodigitatus</i> from the Polluted Andoni River, Niger Delta, Nigeria

This study evaluated the prevalence, histopathological effects, and environmental drivers of trematode metacercariae in Chrysichthys nigrodigitatus from the Andoni River in the Nigerian Niger Delta. One hundred specimens were examined for parasitic cysts and associated tissue pathology, while physicochemical parameters of water samples from fish landing sites were analyzed following American Public Health Association protocols. The results revealed a 74% prevalence of infection, with metacercariae predominantly located in the gills, intestines, and muscle tissues. Infected fish exhibited significant histopathological alterations, including lamellar fusion, mucosal necrosis, goblet cell hyperplasia, myofibre degeneration, and fibrotic encapsulation. The condition factor was significantly lower in infected individuals, indicating impaired physiological status. Water quality analysis showed elevated concentrations of nitrates, phosphates, BOD₅, and turbidity, all of which were positively correlated with parasite prevalence. To our knowledge, this is the first documented assessment in the Niger Delta that integrates prevalence, histopathological alterations, and quantified environmental drivers of trematode infection in C. nigrodigitatus, offering an ecological and public health perspective rarely addressed in African inland fisheries research. These findings highlight the role of environmental stressors in promoting parasitic infections, and underscore the value of fish health indicators for monitoring aquatic ecosystem integrity and zoonotic risk in fish-consuming communities. Consequently, consumption of C. nigrodigitatus from the Andoni River may pose public health concerns.