Biomphalaria Alexandrina: cellular responses of susceptible and resistant snails to Schistosma manson infection

ABSTRACT

The distribution pattern of Schistosoma mansoni miracidia among exposed Biomphalaria alexandrina determined by the level of host susceptibility/resistance and the basic cellular responses observed during the parasite development were studied. Several snail stocks showed a wide spectrum of host reaction to the parasite. From the present study, a vigorous "resistant-type" cellular response to invade miracidia was observed in the histological sections of the non- susceptible snails. In this respect, they were classified in this study as "resistant snails". B. alexandrina experimentally infected with S. Mansoni exhibited a wide range of histopathological and immunological changes. The rate of phagocytosis as well as the actual number of hemocytes were determined in different groups of snails during the infection cycle. The significant fluctuation [increase and/or decrease] in circulating hemocyte number was only correlated with a shift in the hemocyte populations in the first two days after the exposure to the infective stage. The in vitro phagocytic activity of the resistant snail hemocytes was found to be higher than that observed in the susceptible snails