الفهرس 
Effect of temperature on trematode infectionOnly 14 pages are availabe for public view
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Abstract
The rapidly growing population in Egypt and the accompanied demand for an available source of animal protein, urged the government to encourage fish farms. Fish represent one of the best nutritious, relatively cheap food stuff, if compared with other animal sources. In Egypt, fresh water fish were found to be infected with trematode metacercariae that are transmittable to ma~ninals and fish eating birds. Fish pathogens may only cause problems when fish are weakened by some predisposing factors. Therefore it is essentially important to find out such factors and control them through programs of good management, and this will lead to the production of an annual healthy fish population. In the present study, Prohemistomum vivax was chosen as a model of a trematode parasite the metacercariae of which was frequently reported in the skeletal muscles of Nile fishes and the adult inhabit the intestine of fish eating birds and inaininals including man. This parasite was reported to harm both its final and intermediate hosts. The life cycle of P. vivax was experimentally completed starting with metacercariae fiom naturally infected Claras gariepinus, these infective stages were fed to golden hamsters and adult worms began to deposit eggs one week post-infection. Eggs \yere developed in vitro and infective miracidia emerged after ten. Active ~niracidia were used to infect C. bulmoides snails (first intermediate host) and cercarial shedding started 60 days post-infection. Active cercariae were used to infect G. aflnis (second intermediate host). Cercariae developed in fish muscle and became infective metacercariae 28 days post-infection at 30 * 2 ’ ~ . These metacercariae were used to infect golden hamsters and adult worms were recovered from the small intestine five days post-infection. Regarding the factors affecting the susceptibility of G. afjnis to infection with P. viva cercariae the present results showed that: 1 - The incidence of infection was higher in large fish (2.5) than in smaller ones (1.2). Also smaller fish showed higher tolerance to metacercarial infection. 2 - The incidence of infection and the mortality rate was the same in both sexes. 3 - The incidence of metacercariae and mortality rate of fish was higher in crowding fish population (10 fish infected all together with 500 cercariae) than when each fish was infected individually with 50 cercariae. 4 - Regarding the effect of the density of cercarid infection on the maintenance and distribution of P. vivax metacercariae within the fish host, the :results showed that with the increase in the number of crecariae the incidence of infection and mortality rate increased while the recovery rate decreased. Metacercarial distribution varied at different exposure levels. - 5 - Fish fed on Sera diet (vitamins rich diet) were the best to tolerate the parasitic infection followed by best diet (proteins rich diet), while all fish fed on plain bread (carbohydrate rich diet) died within the experimental period. 6 - At high temperature (30 5 ~OC) cercariae reached the skeletal muscles, became encysted, infective and succeed to infect hamsters 28 days post-infection. At low temperature (15 * 2 ’ ~ ) cercariae become encysted but never reached the infective stage and failed to infect hamsters. 7 - With increasing the concentration of CuSOq, the incidence of infection decreased due to the reduction in the infective ability of cercariae to fish. Histopathological study: Histopathological study revealed that infected fish showed haemorrhagic spots that marked sites of cercarial penetration. Encysted metacercariae in the skeletal muscles and in the connective tissue surrounding the. eyeball caused variable degrees of tissue reaction. Haeinorrhage was accompanied by inflammation in the sites of cercarial penetration. Encysted metacercariae in between the muscle fibers were surrounded with a double layered capsules. The muscle tissue around the cysts was disrupted. Variable degrees of cellular infiltration and fibrous tissue formation was observed in the vicinity of the parasite. Biochemical study: As regards the biochemical findings, the total lipid content of the skeletal muscle of infected fishes did not show any significant change compared with uninfected ones. A signi licant decrease was observed in the total muscle protein content of the infected skeletal muscle. The total body weight was significantly lower in infected fish while body water content showed significant increase in infected fish than in uninfected ones.