Comparative Study of the Effect of Biological Factors on Helminthes Occurrence in Oreochromis niloticus and Tilapia zilli from Lake Manzala, Port Said, Egypt.

Abstract

Oreochromis niloticus and Tilapia zilli are important sources of protein food for the Egyptians. It provides about 70% of the total fish production in Egypt (EI-Zarka, 1961). Digenetic trematodes and their metacercariae take a great interest as they were one of the most widely distributed parasites infecting fish causing low weight gain, high mortality and some of them may have zoonotic importance (Hernandez et al., 1998). Biotic factors as parasite life cycles and fish age/size and abiotic factors such as water temperature, current and/or depth also affect the distribution of parasites which may be aggregated or over dispersed in the host (Iyaji and Amana, 2015). Ramadan (1991) reported that the host species affect the rate of infection. He recorded the rate of infection in T. nilotca, T .zilli and T. galilaea fish in Lake Manzala. The highest rate of infection was found in T. zilli while, the lowest rate of infection was found in T. nilotica.