a1 Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT, UK
a2 National Institute for Medical Research, Ifakara Centre, Box 53, Ifakara, Tanzania
a3 Department of Biology, Imperial College, Prince Consort Road, London SW7 2BB, UK
The genetic structure of a population of the malaria parasite Plasmodium falciparum has been examined in a village in Tanzania. Seventeen alleles of the merozoite surface protein MSP-1 and 23 of MSP-2 were detected by the polymerase chain reaction (PCR) among the blood parasites of the inhabitants. Most infections contained mixtures of genetically distinct parasite clones. PCR was then used to examine individual P. falciparum oocysts, the products of fertilization events, in wild-caught mosquitoes. Forty-five out of 71 oocysts were heterozygous for one or both genes, showing that crossing between clones was taking place frequently, following uptake of mixtures of gametocytes by the mosquitoes. The frequency of heterozygous forms showed that random mating events probably occurred within mosquito bloodmeals between gametes belonging to different parasite clones.
(Received December 22 1993)
(Revised March 11 1994)
(Accepted March 11 1994)
p1 Reprint requests to Dr D. Walliker, Institute of Cell, Animal and Population Biology, University of Edinburgh, West Mains Road, Edinburgh EH9 3JT.