Putaporntip Chaturong, Miao Jun, Kuamsab Napaporn, Sattabongkot Jetsumon, Sirichaisinthop Jeeraphat, Jongwutiwes Somchai, Cui Liwang
Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
Department of Entomology, The Pennsylvania State University, State College, Pennsylvania, United States of America.
PLoS Negl Trop Dis. 2014 Nov 20;8(11):e3336. doi: 10.1371/journal.pntd.0003336. eCollection 2014 Nov.
Malaria control efforts have a significant impact on the epidemiology and parasite population dynamics. In countries aiming for malaria elimination, malaria transmission may be restricted to limited transmission hot spots, where parasite populations may be isolated from each other and experience different selection forces. Here we aim to examine the Plasmodium vivax population divergence in geographically isolated transmission zones in Thailand.
We employed the P. vivax merozoite surface protein 3β (PvMSP3β) as a molecular marker for characterizing P. vivax populations based on the extensive diversity of this gene in Southeast Asian parasite populations. To examine two parasite populations with different transmission levels in Thailand, we obtained 45 P. vivax isolates from Tak Province, northwestern Thailand, where the annual parasite incidence (API) was more than 2%, and 28 isolates from Yala and Narathiwat Provinces, southern Thailand, where the API was less than 0.02%. We sequenced the PvMSP3β gene and examined its genetic diversity and molecular evolution between the parasite populations.
Of 58 isolates containing single PvMSP3β alleles, 31 sequence types were identified. The overall haplotype diversity was 0.77 ± 0.06 and nucleotide diversity 0.0877±0.0054. The northwestern vivax malaria population exhibited extensive haplotype diversity (HD) of PvMSP3β (HD=1.0). In contrast, the southern parasite population displayed a single PvMSP3β allele (HD=0), suggesting a clonal population expansion. This result revealed that the extent of allelic diversity in P. vivax populations in Thailand varies among endemic areas.
Malaria parasite populations in a given region may vary significantly in genetic diversity, which may be the result of control and influenced by the magnitude of malaria transmission intensity. This is an issue that should be taken into account for the implementation of P. vivax control measures such as drug policy and vaccine development.
疟疾防控工作对流行病学和寄生虫种群动态有着重大影响。在致力于消除疟疾的国家，疟疾传播可能局限于有限的传播热点地区，在这些地区，寄生虫种群可能彼此隔离，并经历不同的选择压力。在此，我们旨在研究泰国地理隔离传播区间的间日疟原虫种群分化情况。
基于东南亚寄生虫种群中该基因的广泛多样性，我们采用间日疟原虫裂殖子表面蛋白3β（PvMSP3β）作为分子标记来表征间日疟原虫种群。为研究泰国两个传播水平不同的寄生虫种群，我们从泰国西北部的来兴府获取了45株间日疟原虫分离株，该地的年寄生虫发病率（API）超过2%，并从泰国南部的也拉府和那拉提瓦府获取了28株分离株，该地的API低于0.02%。我们对PvMSP3β基因进行测序，并研究了寄生虫种群间的遗传多样性和分子进化。
在58株含有单个PvMSP3β等位基因的分离株中，鉴定出31种序列类型。总体单倍型多样性为0.77±0.06，核苷酸多样性为0.0877±0.0054。泰国西北部的间日疟原虫种群表现出PvMSP3β广泛的单倍型多样性（HD = 1.0）。相比之下，南部寄生虫种群呈现单一的PvMSP3β等位基因（HD = 0），表明是克隆种群扩张。这一结果揭示，泰国间日疟原虫种群中等位基因多样性的程度在各流行地区有所不同。
特定区域内的疟原虫种群在遗传多样性上可能存在显著差异，这可能是防控的结果，并受疟疾传播强度大小的影响。这是在实施诸如药物政策和疫苗研发等间日疟原虫防控措施时应予以考虑的一个问题。
