Oreochromis spp. and Clarias Lazera as a Source of Transmitting Encysted Metacercariae to Man

A total of 135 freshwater fish samples (Oreochromis spp. <85> and Clarias lazera <50>) were collected from different localities (shops and fish markets) in Alexandria Province-Egypt and examined for the presence of parasitic larval stages. The obtained data found the overall mean of the infestation with encysted metacercariae was 71.1% in the examined fish. The rates of infestation with encysted metacercariae were 72.9% and 68.0% in the examined Oreochromis spp. and Clarias lazera, respectively. The highest prevalence of the encysted metacercariae was found in summer (81.8%) in case of Oreochromis spp. and in winter (92.3%) in case of Clarias lazera, all these seasonal differences are statistically significant. The rate of infestation of encysted metacercariae in the anterior third, middle third and posterior third of Oreochromis spp. was found to be 82.3%, 74.2% and 95.2%, respectively, while 88.2%, 88.2% and 91.2%, respectively, in Clarias lazera. Moreover, the rate of infestation of encysted metacercariae in eyes, gills, liver, kidney and branchial cavity of Oreochromis spp. was 91.9%, 70.9%, 20.9%, 46.8% and 32.2%, respectively. In Clarias lazera the infestation rate was found to be 47.1%, 70.6%, 8.8% and 38.2% in the gills, liver, spleen and kidney, respectively. The zoonotic and public health importance of the encysted metacercariae are causes severe visceral pain, abdominal discomfort, intermittent bloody diarrhoea and colic after consumption of inadequately cooked fish especially Tilapia spp. (Oreochromis spp.).