Studies of the relationships betweenSchistosomaand their intermediate hosts. 1. The genusBulinusandSchistosoma haematobiumfrom Egypt

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Abstract
The susceptibility ofBulinus truncatus, B. tropicus, B. natalensis, B. coulboisi, B. globosus, B. cernicusandB. wrightitoSchistosoma haematobiumfrom Egypt were examined. Eighteen different populations ofB. truncatuswere investigated.A new method of measuring the compatibility between schistosomes and the intermediate snail hosts, the total cercarial production per 100 exposed snail, is introduced.AllB. truncatuspopulations became infected and could be divided in four groups according to the total cercarial production per 100 exposed snails. In the first group the cercarial production varied from 250 000 to 500 000 and in the last group between 5000 and 20 000. The first group had a high infection rate of 62 to 100% and a low mortality of approximately 10% and the last group showed a very low infection rate and a high mortality.B. globosus(Rhodesia),B. cernicusandB. wrightibecame infected, whileB. globosus(Zaire),B. coulboisi, B. natalensisandB. tropicuswere refractory.The shortest prepatent period was 26 days at a room temperature of 26°C. The maximum cercariae production for one snail in one day was 600 and the longest duration of infection was 200 days.Experimenting with different doses of miracidia, 5 to 50 per snail, resulted in a one hundred per cent infection and a low mortality of 10%. There was only a slight variation in the cercarial production.