ON CERTAIN ASPECTS OF THE BIOLOGY AND HOST-PARASITE RELATIONSHIPS OF FASCIOLA SPP. IN EGYPT

Abstract

The susceptibility of Lymnaea natalensis, Hiomphalaria alexandrina, Bulinus truncatus and Physa acuta to the infection with Fasciola gigantica from Egyptian buffaloes, cows and sheep and F. hepatica from European cows was studied. L. natalensis proved to be susceptible to F. gigantica from Egyptian hosts, but the degree of susceptibility varied according to the source of infection. The mortality rate, prepatent period and metacercariae production were recorded for the infected snails. However, L natalensis snails exposed to F. hepatica miracidia from European cows appeared non­ susceptible to the infection. Similarly, Biomphalaria alexandrina, Bulinus truncatus and Physa acuta exposed to F. gigantica from Egyptian hosts and F. hepatica from European cows were non­ susceptible to infection. Moreover, schistosome-cercariae-shedding B. a!exandrina and B. truncatus also proved non-susceptible to the infection.

In order to investigate the infectivity of Fasciola gigantica and F. hepatica miracidia to the previous pulmonate snails, histological sections were taken in these snails, after exposure to miracidia of both species. Snails were fixed for sectioning at 3,5,12 and 24 hours, and 3,9,15, and 27 days post exposure. The examination of histological sections of exposed snails revealed that the miracidia of both species failed to penetrate the tissues of B. alexandrina, B. truncatus and P. acuta. The miracidia!penetration and the intramolluscan larval development occmTed only in L. natalensis exposed to F. gigantica miracidia.