Malaria Elimination Initiative, Institute of Global Health Sciences, University of California, San Francisco.
Department of Epidemiology and Biostatistics, University of California, San Francisco.
J Infect Dis. 2019 Sep 13;220(8):1346-1354. doi: 10.1093/infdis/jiz305.
To better understand transmission dynamics, we characterized Plasmodium falciparum genetic diversity in Eswatini, where transmission is low and sustained by importation.
Twenty-six P. falciparum microsatellites were genotyped in 66% of confirmed cases (2014-2016; N = 582). Population and within-host diversity were used to characterize differences between imported and locally acquired infections. Logistic regression was used to assess the added value of diversity metrics to classify imported and local infections beyond epidemiology data alone.
Parasite population in Eswatini was highly diverse (expected heterozygosity [HE] = 0.75) and complex: 67% polyclonal infections, mean multiplicity of infection (MOI) 2.2, and mean within-host infection fixation index (FWS) 0.84. Imported cases had comparable diversity to local cases but exhibited higher MOI (2.4 vs 2.0; P = .004) and lower mean FWS (0.82 vs 0.85; P = .03). Addition of MOI and FWS to multivariate analyses did not increase discrimination between imported and local infections.
In contrast to the common perception that P. falciparum diversity declines with decreasing transmission intensity, Eswatini isolates exhibited high parasite diversity consistent with high rates of malaria importation and limited local transmission. Estimates of malaria transmission intensity from genetic data need to consider the effect of importation, especially as countries near elimination.
为了更好地了解传播动态，我们对斯威士兰的恶性疟原虫遗传多样性进行了特征描述，该国的传播水平较低，且由输入性病例维持。
在 2014 年至 2016 年期间，我们对 66%的确诊病例（n=582）进行了 26 个恶性疟原虫微卫星基因分型。利用种群和体内多样性来描述输入性感染和本地感染之间的差异。逻辑回归用于评估多样性指标在分类输入性和本地感染方面的附加价值，超越了流行病学数据。
斯威士兰的寄生虫种群高度多样（预期杂合度[HE]为 0.75）且复杂：67%的多克隆感染，平均感染多重性（MOI）为 2.2，平均体内感染固定指数（FWS）为 0.84。输入性病例与本地病例的多样性相当，但表现出更高的 MOI（2.4 比 2.0；P=0.004）和更低的平均 FWS（0.82 比 0.85；P=0.03）。将 MOI 和 FWS 加入多变量分析并不能提高输入性和本地感染之间的区分度。
与恶性疟原虫多样性随传播强度降低而降低的普遍认知相反，斯威士兰的疟原虫分离株表现出与高疟疾输入率和有限的本地传播相一致的高寄生虫多样性。遗传数据估计疟疾传播强度需要考虑输入性的影响，尤其是在临近消除的国家。
