Distribution of the two forms of Plasmodium falciparum erythrocyte binding antigen-175 (eba-175) gene in Lao PDR

The erythrocyte binding antigen 175 (EBA-175) is a 175 kDa antigen of Plasmodium falciparum and plays a major role in erythrocyte recognition by the parasite. The antigen is also supposed to be partly responsible for the invasion of erythrocytes by merozoites. EBA-175 has been sequenced from the FCR-3 and CAMP strains of P. falciparum. The sequences were identical in most parts of the gene. Differences were apparent in a 423 bp segment in the FCR-3 strain, the F-Fragment, that is not found in the CAMP-strain and a 342 bp segment, the C-Fragment, which is present in the CAMP-strain but not in the FCR-3-strain. The aim of this study was to assess the distribution of the two EBA-175-alleles in the Lao PDR. Altogether, 240 blood-samples were collected in two areas of the country: Attapeu in the south and Lung Namtha in the north. Subsequently, the material was scanned for the F-and C-fragments. In the whole study population, 52% carried the F-fragment, and 41% the C-fragment while seven percent of the patients were infected with at least two parasite strains and showed both alleles. Distribution of the alleles showed significant differences between the north and the south province. Reasons for this include possible importation of different parasite strains from neighbouring countries.