SEASONAL-CHANGES IN THE PLASMODIUM-FALCIPARUM POPULATION IN INDIVIDUALS AND THEIR RELATIONSHIP TO CLINICAL MALARIA - A LONGITUDINAL-STUDY IN A SUDANESE VILLAGE

Residents of Daraweesh village in Sudan were monitored for Plasmodium falciparum infection and malaria morbidity in 3 malaria seasons from 1 993 to 1996. Malaria parasites were detected microscopically and by po lymerase chain reaction (PCR) in a series of cross-sectional surveys. PCR revealed submicroscopical infections during the dry season, partic ularly among individuals who had recovered from a malaria episode foll owing successful drug treatment. Clinical and subclinical infections w ere contrasted by assaying for allelic polymorphism at 2 gene loci, MS P-1 and GLURP and 2 hypotheses examined with reference to these data: that clinical malaria is associated with infection with novel parasite genotypes not previously detected in that host, or alternatively, tha t clinical malaria episodes are associated with an increased number of clones in an infection. We detected more mixed infections among clini cal isolates, but people carrying parasites during the dry season were not found to have an increased risk of disease in the following malar ia season. There was a clear association of disease with the appearanc e of novel parasite genotypes.