Genetic complexity of Plasmodium vivax infections in Sri Lanka, as reflected at the merozoite-surface-protein-3alpha locus.
The presence of genetically different strains of malarial parasites in cases of human malaria is a severe drawback in the successful control of the disease. In Sri Lanka, although this species accounts for 60%-80% of all of the cases of clinical malaria that occur each year, the genetic complexity of Plasmodium vivax on the island remains to be elucidated. In recent studies based on PCR-RFLP and the parasites' merozoite-surface-protein-3alpha locus, the genetic structure of 201 clinical isolates of P. vivax, from two malaria-endemic areas and a non-endemic area of the island, was investigated. Although the PCR only produced amplicons of three sizes [1900 (72.6%), 1500 (25.9%) and 1200 (1.5%) bp], the RFLP analysis based on HhaI or AluI digestion yielded 22 and 26 restriction patterns, respectively, with 51 combined patterns recorded. The distribution of the prominent PCR-RFLP haplotypes was area-specific. The probability that an investigated case had a multiple-clone infection (MCI) was higher among the cases from the endemic areas (20.0%) than among those from the non-endemic area (13.8%) but this difference was not statistically significant. Since 17 single-clone isolates produced only 11 different PCR-RFLP haplotypes but (after sequencing) 13 distinct nucleotide haplotypes, it is clear that the results of the PCR-RFLP were not revealing all of the diversity that existed at the nucleotide level. Four mass blood surveys in a malaria-endemic area demonstrated that seasonal changes in the prevalences of human infection with P. vivax may influence the occurrence of MCI.
Wickramarachchi
T
T
Department of Zoology, Faculty of Science, University of Colombo, Colombo, Sri Lanka.
Premaratne
P H
PH
Dias
S
S
Handunnetti
S M
SM
Udagama-Randeniya
P V
PV
D000818:Animals; D000953:Antigens, Protozoan / Q000032:analysis / Q000235:genetics*; D000954:Antigens, Surface / Q000032:analysis / Q000235:genetics; D016054:DNA, Protozoan / Q000032:analysis; D014644:Genetic Variation / Q000235:genetics*; D006801:Humans; D016780:Malaria, Vivax / Q000453:epidemiology / Q000235:genetics*; D010966:Plasmodium vivax / Q000235:genetics* / Q000302:isolation & purification; D016133:Polymerase Chain Reaction / Q000379:methods; D012150:Polymorphism, Restriction Fragment Length; D015800:Protozoan Proteins / Q000235:genetics*; D012621:Seasons; D017422:Sequence Analysis, DNA; D013188:Sri Lanka / Q000453:epidemiology
D000953:Antigens, Protozoan; D000954:Antigens, Surface; D016054:DNA, Protozoan; D015800:Protozoan Proteins; C089133:merozoite surface protein 3, Plasmodium