Limited genetic diversity of Plasmodium falciparum in field isolates from Honduras.

Abstract

The genetic diversity displayed by Plasmodium falciparum field isolates, the occurrence of variant forms of the parasite at different frequencies in different geographic areas, and the complexity of the infections represent major obstacles for the development of effective malaria control measures. However, since most of the existing studies have been performed in regions where P. falciparum transmission is high, little is known about the diversity and complexity of parasite populations circulating in areas of low malaria endemicity. We investigated the extent of genetic polymorphism in P. falciparum field isolates from Honduras, a region where its transmission is low and seasonal. Allelic diversity was analyzed in the highly polymorphic parasite genes encoding the merozoite surface proteins-1 (MSP-1) and-2 (MSP-2) and the glutamate-rich protein (GLURP) by the polymerase chain reaction. Gene polymorphism was also assessed in the EB200 region derived from the highly size polymorphic Pf332 gene. Limited size polymorphism was detected in all genes analyzed, with four and three variants for the MSP-1 and MSP-2 alleles, respectively, and two size variants for the GLURP and Pf332 genes. Moreover, based on the studied genetic markers, most infections consisted of only a few genetically distinct parasite clones. These results suggest that the P. falciparum parasite populations circulating in this region are genetically homogeneous and point to an association between the extent of parasite genetic diversity and the intensity of malaria transmission.

Genetic diversity of Plasmodium falciparum field samples from an isolated Colombian village.

“…Nonetheless, given the analytic method used, we cannot rule out the possibility that subtle differences in the size of the amplified fragments or specific changes in the sequence went unobserved. This limited polymorphism is in keeping with what was reported for areas of low endemicity, such as French Guiana, 16 Honduras, 17 and Vanuatu, 18 and contrasts with what was found in Senegal 4 and Thailand. 3 The particular features of the study zone-namely, geographic isolation and a closed population-may cause the low introduction of new allelic types via migration, which could be a probable cause of the limited polymorphism observed.…”

Polymorphism of the Merozoite Surface Protein-1 Block 2 Region in Plasmodium Falciparum Isolates from Symptomatic Individual Living in Rural Area of Senegal

“…This study also revealed the predominance of K1 type alleles at study site level or throughout the parasite population compared to Mad20 and Ro33 over year. Similar results were found in several studies conducted in Gabon [17][18][19][20][21], in Central Africa or in Honduras [22] in Central America. Ours results showed also that the msp1_Mad20 family was less frequent except in 2008 where this pattern was more frequent than msp1_RO33.…”

Plasmodium falciparum parasites in French Guiana: limited genetic diversity and high selfing rate.

“…This contrasts with observations made in Senegal, 8,11,20,21,26 Tanzania, 10,19,22 and Papua New Guinea, 9,17 or in low endemicity areas such as Colombia, 6 Sudan, 7,12,13,19 or Honduras. 28 The limited genetic polymorphism observed in French Guiana indicates that the P. falciparum population is small enough and the transmission rate low enough to result in local reduction in the genetic diversity due to a strong genetic drift effect, resulting in loss of alleles. A probable illustration of such an effect was the loss of the MAD20 MSP-1 allele during the study period, shown in the upper panel of Figure 2.…”

“…2,11,19,22 In Colombia, Brazil, or Honduras, areas where endemicity is lower and asymptomatic carriage is rare, an incidence of mixed infections of approximately 30% has been reported. 6,28,29 In Sudanese villages where the entomologic inoculation rate is less than 1 infective bite/person/year, 20% of the blood samples collected from symptomatic cases contained more than 1 P. falciparum clone. 19 Mixed infections are a prerequisite for cross-fertilization, and a source for novel genotype combinations, and novel alleles.…”