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.

Animals↗

PubMed1965

Transmission of Bilharziasis. 2. Production of Cercariae.

While a knowledge of cercarial infection rates is essential to an understanding of the dynamics of bilharziasis transmission, rather little attention has been paid to methods of determining these rates. The author considers that the most valuable information is likely to be obtained if studies of infectivity are carried out hand in hand with studies of snail population density and structure. Different methods employed in examining snail populations for infection are discussed, together with the patterns of Schistosoma haematobium and S. mansoni cercarial production in relation to natural infections. Other important aspects considered are cercarial shedding in relation to unisexual and bisexual infections, and the use of laboratory animal exposure in natural waters as a means of determining transmission patterns. The author stresses that infection rates and worm burdens obtained from the animal exposure method have to be evaluated carefully in relation to the state of the habitat.

Animals↗

PubMed1965

Natural trends in snail populations in relation to control of bilharziasis in East Africa.

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Africa, Eastern↗

PubMedDate not supplied

Cross protection between a laboratory passaged Chinese strain of Schistosoma japonicum and field isolates of S. japonicum from China.

Our laboratory strain of Schistosoma japonicum has been isolated for 51 years, but is comparable to the indigenous Chinese parasite in terms of its infectivity to both the intermediate and definitive hosts. Vaccination with our strain protects mice against challenge with wild isolates of S. japonicum from China. Thus any defined antigen vaccine developed using our laboratory strain would be expected to protect against S. japonicum in the field in China.

Animals↗