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Host-parasite relationship of Bulinus truncatus and Schistosoma haematobium in Iran. 2. Effect of exposure dosage of miracidia on the biology of the snail host and the development of the parasites.

Laboratory experiments were carried out to study the development of Bulinus truncatus and the larval stages of Schistosoma haematobium after the snails had been exposed to various numbers of miracidia. The results showed: (1) that in the cercarial-incubation period the growth and survival rate of snails was not influenced by the development of the larval stages of S. haematobium, but that in the cercaria-shedding period the life-span of the infected snails was shorter than that of the non-infected controls; (2) that reduction of oviposition was proportional to the exposure of miracidia; (3) that the length of the cercarial-incubation period in snails was inversely proportional to the exposure number of miracidia; (4) that all the snails exposed to 20 miracidia (the maximum exposure number used) shed cercariae; (5) that snails exposed to one miracidium each shed fewer cercariae than those exposed to two or more miracidia each; and (6) that the peak of cercaria-shedding occurred 40 to 90 days after the shedding had started, varying in different groups.

Animals↗

[Argyrophilic structures of the larval forms of 2 strains of Paramphistomum microbothrium: 1 a parasite of Isidora guernei and Ovis aries, the other a parasite of Isidora truncata and Bos taurus].

The life cycle of a Paramphistome from North Senegal is completed starting from cercariae shed by naturally infected Isidora guernei: a sheep and then uninfected Isidora guernei were successively infected experimentally. Adults obtained were identifiable as P. phillerouxi or as P. microbothrium. Species determination cannot be made on the basis of argentophilic structures in the miracidium. Morphology of sporocysts and rediae differs from that observed in P. phillerouxi but is undistinguishable from that described in P. microbothrium. Cercarial chaetotaxy differs from that of P. phillerouxi. Mollusc host: Isidora guernei belongs to the same genus as Isidora truncata and I. alluaudi, reported hosts to P. microbothrium. Therefore the material is provisionally identified as P. microbothrium. To confirm this, a strain of P. microbothrium from naturally infected Bos taurus in Egypt was studied. Miracidia were used to experimentally infect Isidora truncata; cercariae obtained were identical to those previously described for this species from I. truncata and I. alluaudi. Cercarial chaetotaxy was not significantly different from that of material from North Senegal. They represent therefore two strains of Paramphistomum microbothrium.

Animals↗