(HOST INDUCED VARlATIONS IN Prohemistomum vivax (TREMATODA

Abstract

The identification of parasites depends primary on morphological and anatomical characteristics that may be subjected to many modifications which may lead to misidentification and controversial description of the same parasite . In the present work , host induced morphological variations were studied . Avariety of amphibian (Toad) . reptilian ( crocodyle. , lizard and snake. ) , avian ( falcon , buff- backed heron , 24h old chick and 15 days old domestic duckling and mammalian hosts ( hamster . mouse ard rat ) were experimentally infected with encysted metacercariae of Prohemistomum vivax . to asses the susceptibility of different groups of animals to infection and to detect the host induced morphological variations . Hamsters were considered as experimental control hosts , because the internal organs are well developed with respect to size and position , which is more constant than those of worms reared in other hosts. The prepatent period was shorter and the intrauterine eggs in adult Prohemistomum vivax . as well as the faecal egg count was higher in hamsters than in other animals indicating an early maturation and higher fecundity of the pa asite. Also, the ablility of mature eggs , recovered from the stool of hamsters , to hatch is higher than in eggs recovered from other animals ( El Quisney ,inpress ) All mammalian hosts were susceptible to Prohemistomum vivax infection , the incidence was 100% and the recovery rate of the adult worms was

95- 100% six days post infection. of the birds only falcons were susceptible to Prohemistomum vivax infection , the incidence was 100 % , while the recovery rate was 70 - 80 % six days post infection .