Transmission of Bilharziasis. 1. Some essential aspects of Snail population dynamics and their study.

Accurate quantitative assessment is essential to any study of disease transmission; in relation to the transmission of bilharziasis the most important characteristics that have to be determined include density, reproduction and mortality rates, the age and sex structure of the population, dispersion and the intrinsic rate of natural increase (the biotic potential). The author discusses techniques that have been developed to yield this and other information and stresses the need to evaluate such techniques objectively.Some basic principles of population ecology are defined and discussed in relation to the control of transmission. It is considered that laboratory studies can be usefully carried on in conjunction with field work but that they cannot be substituted for field investigations in determining the parameters of bilharziasis transmission for a given area.