Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
Malar J. 2013 Aug 6;12:275. doi: 10.1186/1475-2875-12-275.
Plasmodium vivax infections in pregnancy are associated with low birth weight and anaemia. This parasites species is also characterised by relapses, erythrocytic infections initiated by the activation of the dormant liver stages, the hypnozoites, to mature. Genotyping of P. vivax using microsatellite markers has opened the way to comparative investigations of parasite populations. The aim of the study was to assess whether there were any differences between the parasites found in pregnant and non-pregnant patients, and/or between the admission infections and recurrent episodes during follow-up.
Blood samples were collected from 18 pregnant and 18 non-pregnant patients, who had at least two recurrent episodes during follow-up, that were recruited in two previous trials on the efficacy of chloroquine treatment of P. vivax infections on the Thai-Myanmar border. DNA was purified and the P. vivax populations genotyped with respect to eight polymorphic microsatellite markers. Analyses of the genetic diversity, multiplicity of infection (MOI), and a comparison of the genotypes in the samples from each patient were conducted.
The P. vivax parasites present in the samples exhibited high genetic diversity (6 to 15 distinct allelic variants found for the 8 loci). Similar expected heterozygosity (He) values were obtained for isolates from pregnant (0.837) and non-pregnant patients (0.852). There were modest differences between the MOI values calculated for both admission and recurrence samples from the pregnant patients (2.00 and 2.05, respectively) and the equivalent samples from the non-pregnant patients (1.67 and 1.64, respectively). Furthermore, the mean number of distinct alleles enumerated in the admission samples from the pregnant (6.88) and non-pregnant (7.63) patients were significantly lower than that found in the corresponding recurrent episodes samples (9.25 and 9.63, respectively).
The P. vivax populations circulating in inhabitants along the Thai-Myanmar border, an area of low malaria transmission, displayed high genetic diversity. A subtle increase in the multiplicity of P. vivax infections in pregnant patients suggests a higher susceptibility to infection. The higher allelic diversity in the relapse as compared to the admission samples in both patient groups is consistent with the hypothesis that a febrile episode promotes the activation of hypnozoites.
孕妇感染间日疟原虫与低出生体重和贫血有关。这种寄生虫还具有复发的特点，即休眠的肝脏阶段（休眠子）被激活，开始成熟为红细胞感染。使用微卫星标记对间日疟原虫进行基因分型为寄生虫种群的比较研究开辟了道路。本研究旨在评估孕妇和非孕妇患者之间、随访期间的入院感染和复发发作之间是否存在差异。
从在泰国-缅甸边境进行的两项氯喹治疗间日疟原虫感染疗效的临床试验中招募的 18 名孕妇和 18 名非孕妇至少有两次复发的患者中采集血样。提取 DNA 后，用 8 个多态性微卫星标记对间日疟原虫种群进行基因分型。对遗传多样性、感染倍数（MOI）进行分析，并对每位患者样本中的基因型进行比较。
样本中存在的间日疟原虫寄生虫具有高度遗传多样性（8 个位点发现 6 至 15 个不同等位基因变异）。从孕妇（0.837）和非孕妇（0.852）患者分离的寄生虫获得的预期杂合度（He）值相似。从孕妇入院和复发样本（分别为 2.00 和 2.05）和非孕妇入院和复发样本（分别为 1.67 和 1.64）计算得出的 MOI 值存在微小差异。此外，孕妇（6.88）和非孕妇（7.63）入院样本中计数的不同等位基因数量平均值明显低于相应的复发样本（9.25 和 9.63）。
在低疟疾传播地区泰国-缅甸边境的居民中循环的间日疟原虫种群显示出高度遗传多样性。孕妇感染间日疟原虫的倍数略有增加，表明孕妇更易感染。与两组患者的入院样本相比，复发样本的等位基因多样性更高，这与发热发作促进休眠子激活的假设一致。
