How P.vivax parasite maintains multiple infection in areas of low intensity malaria?

在间日疟原虫患者中，即使在低感染强度地区，多重感染也很常见。本研究旨在理解这一悖论。应用两个抗原编码基因（msp 1，sera5）和四个微卫星标记（2.21，3.35，AT，GT）对泰国、土耳其和非洲间日疟原虫分离株进行了单倍型分析和等位基因分析。所有的寄生虫样品显示多个数量的等位基因和高度的单倍型双抗对每个位点。间日疟原虫Ⅳ型血清基因的核苷酸多样性是恶性疟原虫的200倍，可能是来自宿主的免疫压力。间日疟原虫的多重感染可能是由于寄生虫种群的分化所致，可能是正选择的结果。

In P.vivaxpatients, multiple infection is common even in low infection intensity areas. This study was conducted to understand the paradox. Haplotype diversities and the number of allele of the Plasmodium vivaxpopulation isolated from Thailand, Turkey and Africa were analyzed using two antigen coding genes (msp1, sera5) and four microsatellite makers (2.21, 3.35, AT, GT). All parasite samples showed multiple numbers of alleles and high degree of haplotype diversities against each locus. The nucleotide diversity of Group IV sera genes of P.vivax were 200 times higher than those of P.falciparum, implying possible immune pressure from the host. The multiple infection of P.vivax seemed to be caused by the divergent parasite population and it might be result in the positive selection.