Host-parasite relationship of Bulinus truncatus and Schistosoma haematobium in Iran. 1. Effect of the age of B. truncatus on the development of S. haematobium.

This paper is the first of a series of four on various aspects of the interaction between Bulinus truncatus and the bilharziasis parasite Schistosoma haematobium. It describes laboratory studies conducted to determine the effect of the age of B. truncatus on the development of S. haematobium. The results indicated (1) that the young snails could be infected even if they were one day old; (2) that the infection rates were higher in the snails of two to five weeks of age than in those of one week; (3) that the cercarial-incubation period was shorter in the young snails than in the older ones; (4) that the survival rate of the snails in the cercarial-incubation period was lower in the young snails than in the older ones; (5) that the survival rate of the cercaria-shedding snails was also apparently lower in the young ones than in the older ones; (6) that the maximum life-span for a cercaria-positive snail extended to 329 days after the date of exposure to infection.