Role of Indoplanorbis exustus snails in spreading schistosomiasis in endemic area

Abstract

Indoplanorbis exustus snails were present in ponds, ditches and tanks, Its population was influenced by season reaching toits peak in October with lowest population in May and June, Out of 10 373 Indoplanorbis exustus snails, surveyed at Jabalpurin 3 years, 310 (2.98%) were positive (range 0 to 11.35%) for cercariae of mammalian schistosomes with lowest prevalence inApril, May and June and its peak in October. Shedding of the cercariae from 16 wild positive snails continued till theirdeath with a daily output of 10 to 13,000 cercariae/day a snail and a total cercarial out put between 22.875 to 77.890 by asnail in its life span. Intense schistosome infection shortened life of the positive snails suggesting it to be pathogenic toI. exuslus. Laboratory bred 1. exustus (206) were infected with S. spindale miracidia and all the survived snail's (14)turned positive after 43-47 days of incubation and continued to shed the cercariae till their death (3-22 days). However, thenumber of cercariae (2-1400 cercari ae/day a snail) shed and survival (hence positiveness) of experimentally infected snailswere much less in comparison to positive snails of the wild. Whether this fluctuation in cercarial number related toenvironmental factors or contained in the snail is worth investigating because of its epizootiological importance.