Centre for Population Health, Burnet Institute, Melbourne, Australia.
Malar J. 2010 Nov 23;9:336. doi: 10.1186/1475-2875-9-336.
The South West Pacific nation of Papua New Guinea has intense year round transmission of Plasmodium falciparum on the coast and in the low-lying inland areas. Local heterogeneity in the epidemiology of malaria suggests that parasites from multiple locations will need to be surveyed to define the population biology of P. falciparum in the region. This study describes the population genetics of P. falciparum in thirteen villages spread over four distinct catchment areas of Papua New Guinea.
Ten microsatellite loci were genotyped in 318 P. falciparum isolates from the parasite populations of two inland catchment areas, namely Wosera (number of villages (n) = 7) and Utu (n = 1) and; and two coastal catchments, Malala (n = 3) and Mugil (n = 3). Analysis of the resultant multilocus haplotypes was done at different spatial scales (2-336 km) to define the genetic diversity (allelic richness and expected heterozygosity), linkage disequilibrium and population structure throughout the study area.
Although genetic diversity was high in all parasite populations, it was also variable with a lower allelic richness and expected heterozygosity for inland populations compared to those from the more accessible coast. This variability was not correlated with two proxy measures of transmission intensity, the infection prevalence and the proportion multiple infections. Random associations among the microsatellite loci were observed in all four catchments showing that a substantial degree of out-crossing occurs in the region. Moderate to very high levels of population structure were found but the amount of genetic differentiation (FST) did not correlate with geographic distance suggesting that parasite populations are fragmented. Population structure was also identified between villages within the Malala area, with the haplotypes of one parasite population clustering with the neighbouring catchment of Mugil.
The observed population genetics of P. falciparum in this region is likely to be a consequence of the high transmission intensity combined with the isolation of human and vector populations, especially those located inland and migration of parasites via human movement into coastal populations. The variable genetic diversity and population structure of P. falciparum has important implications for malaria control strategies and warrants further fine scale sampling throughout Papua New Guinea.
太平洋西南部的巴布亚新几内亚，在沿海和低地内陆地区终年都有恶性疟原虫传播。疟疾在当地的流行情况存在异质性，这表明需要调查来自多个地点的寄生虫，以确定该地区恶性疟原虫的种群生物学。本研究描述了分布在巴布亚新几内亚四个不同集水区的 13 个村庄中恶性疟原虫的种群遗传学。
在两个内陆集水区（沃塞拉，村庄数量（n）= 7；乌图，n = 1）和两个沿海集水区（马拉拉，n = 3；穆吉尔，n = 3）的寄生虫群体中，对 318 株恶性疟原虫分离株的 10 个微卫星位点进行了基因分型。在不同的空间尺度（2-336 公里）上对所得的多位点单倍型进行分析，以定义整个研究区域内的遗传多样性（等位基因丰富度和预期杂合度）、连锁不平衡和种群结构。
尽管所有寄生虫群体的遗传多样性都很高，但与更容易到达的沿海地区相比，内陆群体的等位基因丰富度和预期杂合度较低。这种可变性与两个传播强度的替代指标，即感染率和多重感染比例，没有相关性。在四个集水区都观察到微卫星位点之间的随机关联，表明该地区存在大量的异交。发现了中度至非常高的种群结构水平，但遗传分化（FST）的数量与地理距离无关，这表明寄生虫种群是碎片化的。在马拉拉地区的村庄之间也发现了种群结构，一种寄生虫种群的单倍型与邻近的穆吉尔集水区聚类。
该地区恶性疟原虫的观察到的种群遗传学可能是高强度传播与人类和媒介种群的隔离相结合的结果，特别是那些位于内陆地区和寄生虫通过人类活动迁移到沿海地区的种群。恶性疟原虫遗传多样性和种群结构的可变性对疟疾控制策略有重要影响，需要在整个巴布亚新几内亚进行进一步的精细采样。
