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

Abstract

Background: 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.

Materials & methods: 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.

Results: 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.

Conclusion: 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.

Figure 1

Study sites in Lao PDR

Figure 2

Differences in the distribution of the F/ C- Fragment and mixed infections in the south and north of Lao PDR