The ecology of schistosome transmission foci.

The study of cercarial populations in the field can provide a useful means of locating schistosome transmission foci and of evaluating the success of bilharziasis control programmes. It also provides a means of learning about certain aspects of transmission that have hitherto been neglected.In recent years six techniques have been successfully field-tested or employed in field research on the biology of the cercarial stage of schistosomes. They include several variations of paper filtration of the water, the use of phototaxy for separating cercariae from water, and bioassay by exposing mice to infective water. The various advantages and disadvantages of each method are discussed in this paper. The author suggests that an approach to the ideal cercariometric method may be achieved by combining a paper filtration technique with mouse exposure.