Roper C, Elhassan I M, Hviid L, Giha H, Richardson W, Babiker H, Satti G M, Theander T G, Arnot D E
Division of Biological Sciences, University of Edinburgh, Scotland.
Am J Trop Med Hyg. 1996 Apr;54(4):325-31. doi: 10.4269/ajtmh.1996.54.325.
We have used the nested polymerase chain reaction (PCR) to assay for low level Plasmodium falciparum infections that were below the threshold of detection of blood film examination. This revealed a substantial group of asymptomatic, submicroscopically patent infections within the population of a Sudanese village present throughout the year although clinical malaria episodes were almost entirely confined to the transmission season. In our September, January, April, and June surveys, the PCR-detected prevalences were 13%, 19%, 24%, and 19%, respectively. These figures reveal a much higher prevalence of dry season infection than previous microscopic surveys have indicated. Furthermore, 20% of a cohort of 79 individuals were healthy throughout the September to November transmission season but were PCR-positive for P. falciparum in a least one of a series of samples taken in the ensuing months. Levels of exposure to P. falciparum infection were therefore higher than was previously believed in this region, highlighting the fact that many individuals were infected but healthy for most of the year. The reservoir parasite population was thus larger and more stable than previously thought, a finding that is consistent with the high levels of genetic variation at polymorphic loci reported from analysis of P. falciparum parasites in this area.
我们运用巢式聚合酶链反应（PCR）来检测低于血涂片检查检测阈值的低水平恶性疟原虫感染情况。这揭示了在苏丹一个村庄的人群中，尽管临床疟疾发作几乎完全局限于传播季节，但全年都存在大量无症状、镜下不可见的显性感染。在我们9月、1月、4月和6月的调查中，PCR检测到的患病率分别为13%、19%、24%和19%。这些数据显示旱季感染的患病率比以往显微镜检查所表明的要高得多。此外，在79人的队列中，20%的人在9月至11月的传播季节全程健康，但在随后几个月采集的一系列样本中，至少有一份样本的恶性疟原虫PCR检测呈阳性。因此，该地区恶性疟原虫感染的暴露水平高于此前的认知，这突出表明许多人虽被感染，但一年中的大部分时间都是健康的。由此可见，寄生虫储存宿主群体比之前认为的更大且更稳定，这一发现与该地区恶性疟原虫寄生虫多态性位点的高水平遗传变异分析结果一致。
