الفهرس 
Parasitological studyOnly 14 pages are availabe for public view
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Abstract
The present study was carried out on 865 cat fish Clarias lazera. Samples were collected from the River Nile, Kafr El Zayat, Egypt. The examination of the skeletal muscle of a1 1 but one fish revealed the presence of small and large cysts. These encysted metacercariae were situated between the muscle fibers. Identification of these encysted metacercariae is very difficult. Therefore infection of various experimental animals <rats, mice and herons> with the cysts was done to obtain the adults which are easier to identify. The cysts, encysted and excysted metacercariae, one-day-old and two-day-old juvenile worms and adults were described in detail. Adult trematodes recovered from the small intestine of experimental animals were identified as: I> Prohemistomum vivax CSonsino, 1892> Azim, 1933 which belongs to the family Cyathocotylidae. The identification and doubtful presence of another closely resembling parasite Mesostephanus was d i scussed. 2> Cvnodi~lostomum azimi < Gohar , 1933 > Dubois, 1936 which belongs to the family Dip1 ostomidae. The identification and previous descriptions of closely similar parasites, were discussed, In an attempt to find out the safety of these infected fish for human consumption, the present study showed that four days of freezing, deep frying or strong grilling proved to kill the metacercariae. The presence of these encysted metacercariae can cause deleterious effect to the fish host, This was demonstrated, histopathologically, histochemically and biochemically. As regards the histopathological findings, two types of cysts were observed, those of Prohemistomum vivay were small in size and the cyst wall composed of two 1 ayers, an inner nonce1 1u1 ar layer, which is most porbably of parasite origin formed as a defense mechanism against the host, and an outer cellular layer most probably of host origin to limit the lesion caused by the parasite. The cyst of Cvnodi~lostomurrl azimi was larger in size and the wa1 1 formed of the same layers with the addition of a thick hyaline-like middle layer.