title: Unstable malaria in Sudan: the influence of the dry season. Plasmodium falciparum population in the unstable malaria area of eastern Sudan is stable and genetically complex.
abstract: This paper reviews surveys carried out, over a period of 6 years between 1989 and 1995, to examine Plasmodium falciparum population structure in Asar village in eastern Sudan, an area of unstable malaria, the incidence of which is confined to a few weeks following the short rainy season (June-October). The first phase of the study involved regular cross sectional surveys, between 1989 and 1993 during the seasons of malaria incidence, while the second involved surveys during the malaria-free months of the dry seasons. The parasites were examined for 20 polymorphic loci, including enzyme electrophoretic variants, proteins detected by 2 dimensional polyacrylamide gel electrophoresis, antigens detected by monoclonal antibodies, and in vitro responses to antimalarial drugs. In addition, alleles of the polymorphic genes for merozoite surface proteins 1 and 2 (MSP-1, MSP-2) were examined using the polymerase chain reaction and oligonucleotide probes. Great genetic complexity was observed among the parasites which appeared during the short transmission seasons. A large proportion of the patients who were infected during the transmission season maintained asymptomatic, subpatent parasitaemias throughout the subsequent dry season, often as genetically complex infections.
mesh_terms: D000293:Adolescent; D000328:Adult; D017677:Age Distribution; D000818:Animals; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D014644:Genetic Variation; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology*; D008875:Middle Aged; D010274:Parasitology / Q000379:methods; D010963:Plasmodium falciparum / Q000235:genetics*; D016133:Polymerase Chain Reaction / Q000379:methods; D011891:Rain; D012423:Rural Health; D012621:Seasons; D013397:Sudan / Q000453:epidemiology