Immunological status of some edible fishes exposed to parasitic infections in relation to heavy metals pollution.

In this study, six heavy metals (Pb, Fe, Cu, Ni, Cd, and Mn) have been measured in water, and muscles from mullet (Mugil cephalus), tilapia (Oreochromis niloticus), and African catfish (Clarias gariepinus) collected from Lake Manzal, Egypt. In addition, the existence of different encysted metacercariae in fish muscle with an evaluation of cell-mediated immune response in infected muscles was also investigated. Water samples generally contained less than the permissible level of heavy metals. The metal accumulation levels in muscle were: Pb > Ni > Cd > Cu > Fe > Mn. The levels of Pb and Ni in the muscles exceed the permissible limits, while the concentration of Mn varied significantly (p < 0.05) depending on fish species. Based on the estimated weekly intake in this study, the EWI values of these heavy metals are below the established Provisional Permissible Tolerable Weekly Intake. On the other hand, Prohemistomum vivax encysted metacercaria were found in the muscle of O. niloticus and C. gariepinus with the intensity of 1-10 cyst per 1 cm of muscle. While M. cephalus was found to be infected with Heterophyes heterophyes EMC. TNF- α1 was 10 folds upregulated in O. niloticus than in control fish. IL-1β expression in O. niloticus was upregulated by 15 folds compared with the control one. By examining C. gariepinus, the MHC II gene expression was increased by 15-fold in comparison to the control group. © Indian Society for Parasitology 2022.