Mwangoka Grace W, Kimera Sharadhuli I, Mboera Leonard Eg
Ifakara Health Research and Development Centre, Bagamoyo Research and Training Unit, Bagamoyo, Tanzania.
Malar J. 2008 Jul 3;7:117. doi: 10.1186/1475-2875-7-117.
Although recent reports on congenital malaria suggest that the incidence is increasing, it is difficult to determine whether the clinical disease is due to parasites acquired before delivery or as a result of contamination by maternal blood at birth. Understanding of the method of parasite acquisition is important for estimating the time incidence of congenital malaria and design of preventive measures. The aim of this study was to determine whether the first Plasmodium falciparum malaria disease in infants is due to same parasites present on the placenta at birth.
Babies born to mothers with P. falciparum parasites on the placenta detected by PCR were followed up to two years and observed for malaria episodes. Paired placental and infant peripheral blood samples at first malaria episode within first three months of life were genotyped (msp2) to determine genetic relatedness. Selected amplifications from nested PCR were sequenced and compared between pairs.
Eighteen (19.1%) out of 95 infants who were followed up developed clinical malaria within the first three months of age. Eight pairs (60%) out of 14 pairs of sequenced placental and cord samples were genetically related while six (40%) were genetically unrelated. One pair (14.3%) out of seven pairs of sequenced placental and infants samples were genetically related. In addition, infants born from primigravidae mothers were more likely to be infected with P. falciparum (P < 0.001) as compared to infants from secundigravidae and multigravidae mothers during the two years of follow up. Infants from multigravidae mothers got the first P. falciparum infection earlier than those from secundigravidae and primigravidae mothers (RR = 1.43).
Plasmodium falciparum malaria parasites present on the placenta as detected by PCR are more likely to result in clinical disease (congenital malaria) in the infant during the first three months of life. However, sequencing data seem to question the validity of this likelihood. Therefore, the relationship between placental parasites and first clinical disease need to be confirmed in larger studies.
尽管最近关于先天性疟疾的报告表明其发病率正在上升，但很难确定临床疾病是由于分娩前获得的寄生虫，还是出生时受母体血液污染所致。了解寄生虫的获取方式对于估计先天性疟疾的发病时间和设计预防措施至关重要。本研究的目的是确定婴儿首次感染恶性疟原虫疟疾是否归因于出生时胎盘上存在的相同寄生虫。
对通过聚合酶链反应（PCR）检测到胎盘上有恶性疟原虫寄生虫的母亲所生婴儿进行了长达两年的随访，并观察疟疾发作情况。对出生后头三个月内首次出现疟疾发作时的胎盘和婴儿外周血配对样本进行基因分型（msp2），以确定基因相关性。对巢式PCR的选定扩增产物进行测序，并在配对样本之间进行比较。
95名接受随访的婴儿中，有18名（19.1%）在出生后的头三个月内出现了临床疟疾。在14对测序的胎盘和脐带样本中，有8对（60%）基因相关，而6对（40%）基因不相关。在7对测序的胎盘和婴儿样本中，有1对（14.3%）基因相关。此外，在两年的随访期间，初产妇所生婴儿感染恶性疟原虫的可能性高于经产妇和多产妇所生婴儿（P<0.001）。多产妇所生婴儿首次感染恶性疟原虫的时间比经产妇和初产妇所生婴儿更早（相对危险度=1.43）。
通过PCR检测到胎盘上存在的恶性疟原虫更有可能在婴儿出生后的头三个月内导致临床疾病（先天性疟疾）。然而，测序数据似乎对这种可能性的有效性提出了质疑。因此，胎盘寄生虫与首次临床疾病之间的关系需要在更大规模的研究中得到证实。
