Submicroscopic placental infection by non-<i>falciparum Plasmodium</i> spp.

Background Among the Plasmodium species that infect humans, adverse effects of P. falciparum and P. vivax have been extensively studied and reported with respect to poor outcomes particularly in first time mothers and in pregnant women living in areas with unstable malaria transmission. Although, other non-falciparum malaria infections during pregnancy have sometimes been reported, little is known about the dynamics of these infections during pregnancy. Methods and findings Using a quantitative PCR approach, blood samples collected from Beninese pregnant women during the first antenatal visit (ANV) and at delivery including placental blood were screened for Plasmodium spp. Risk factors associated with Plasmodium spp. infection during pregnancy were assessed as well as the relationships with pregnancy outcomes. P. falciparum was the most prevalent Plasmodium species detected during pregnancy, irrespective either of parity, of age or of season during which the infection occurred. Although no P. vivax infections were detected in this cohort, P. malariae (9.2%) and P. ovale (5.8%) infections were observed in samples collected during the first ANV. These non-falciparum infections were also detected in maternal peripheral blood (1.3% for P. malariae and 1.2% for P. ovale) at delivery. Importantly, higher prevalence of P. malariae (5.5%) was observed in placental than peripheral blood while that of P. ovale was similar (1.8% in placental blood). Among the non-falciparum infected pregnant women with paired peripheral and placental samples, P. malariae infections in the placental blood was significantly higher than in the peripheral blood, suggesting a possible affinity of P. malariae for the placenta. However, no assoctiation of non-falciparum infections and the pregnancy outcomes was observed Conclusions Overall this study provided insights into the molecular epidemiology of Plasmodium spp. infection during pregnancy, indicating placental infection by non-falciparum Plasmodium and the lack of association of these infections with adverse pregnancy outcomes.背景 在感染人类的疟原虫物种中，恶性疟原虫（Plasmodium falciparum）与间日疟原虫（Plasmodium vivax）的不良影响已得到广泛研究与报道，二者尤其可对初产妇以及疟疾传播不稳定地区的孕妇造成不良妊娠结局。尽管妊娠期非恶性疟原虫疟疾感染的案例时有报道，但目前对这类感染在妊娠期的传播动态仍知之甚少。 方法与结果 本研究采用定量PCR（quantitative PCR）技术，对贝宁孕妇的血液样本进行疟原虫属（Plasmodium spp.）筛查，样本采集于首次产前检查（antenatal visit, ANV）以及分娩时的胎盘血。研究评估了妊娠期疟原虫属感染相关的危险因素，以及该感染与妊娠结局的关联。 研究检出的妊娠相关疟原虫物种以恶性疟原虫最为普遍，且检出情况不受产妇产次、年龄及感染发生季节的影响。本研究队列中未检出间日疟原虫感染，但在首次产前检查采集的样本中，观察到三日疟原虫（Plasmodium malariae）感染率为9.2%，卵形疟原虫（Plasmodium ovale）感染率为5.8%。分娩时的产妇外周血样本中同样检出此类非恶性疟原虫感染：三日疟原虫感染率为1.3%，卵形疟原虫感染率为1.2%。值得注意的是，胎盘血中三日疟原虫的检出率（5.5%）显著高于外周血，而卵形疟原虫的检出率在胎盘血（1.8%）与外周血中无明显差异。在同时拥有配对的产妇外周血与胎盘血样本的非恶性疟原虫感染孕妇中，胎盘血内的三日疟原虫感染率显著高于外周血，提示三日疟原虫可能对胎盘具有亲和性。然而，本研究未观察到非恶性疟原虫感染与不良妊娠结局之间存在关联。 结论 本研究整体阐明了妊娠期疟原虫属感染的分子流行病学特征，证实非恶性疟原虫可引发胎盘感染，且这类感染与不良妊娠结局并无关联。