A comparison of devices for direct sampling of avian schistosome cercariae.

Abstract

Density and distribution of cercariae of digenetic trematodes are poorly understood because adequate methods for sampling this larval stage in a natural setting have not been developed. The purpose of the present study was to design an apparatus and develop a technique to determine relative numbers of avian schistosome cercariae along a lake shore. Three devices (with modifications) were designed and tested in both the laboratory and the field. The most efficient apparatus was a water pump used in conjunction with a column of 8-inch diameter sieves with mesh sizes ranging 1000-25 microns stacked top to bottom respectively. In laboratory trials, 79% of the cercariae were recovered in the 25-micron sieve. This technique shows great promise for both the prediction and control of swimmer's itch.