Müller D A, Charlwood J D, Felger I, Ferreira C, do Rosario V, Smith T
Department of Public Health and Epidemiology, Swiss Tropical Institute, Socinstrasse 57, Postfach CH-4002, Basle, Switzerland.
Acta Trop. 2001 Feb 23;78(2):155-62. doi: 10.1016/s0001-706x(01)00067-5.
The prospective risk of acute morbidity was analysed in relation to multiplicity of Plasmodium falciparum infection in 491 individuals in a peri-urban community in São Tomé. In an initial cross-sectional survey, 40.5% of individuals were recorded by microscopy as infected with P. falciparum, and by PCR 60.5%, with the maximum prevalence in children aged 5-10 years. PCR-RFLP typing of the msp-2 gene of P. falciparum found a mean of 2.4 parasite genotypes per infected person, with little age dependence in this multiplicity and a total of 43 different msp-2 alleles identified. None of these were unique for São Tomé. Study participants were encouraged to report to a project worker whenever they suffered a febrile illness. During the 3 months following the parasitological survey the recorded incidence rates decreased with increasing baseline msp-2 multiplicity, both for P. falciparum-positive episodes and for fever without parasitaemia. While this is consistent with suggestions that multiple P. falciparum infections may protect against super-infecting parasites, confounding by patterns of health service usage is an alternative explanation. The incidence of clinical malaria episodes was only a little higher in children than in adults. This weak age-dependence in clinical immunity might be a consequence of a cohort effect resulting from resurgence of the disease after the breakdown of malaria control programs in the 1980s.
在圣多美一个城郊社区的491名个体中，分析了恶性疟原虫感染的多样性与急性发病的潜在风险之间的关系。在最初的横断面调查中，通过显微镜检查记录到40.5%的个体感染了恶性疟原虫，通过聚合酶链反应（PCR）检测为60.5%，5至10岁儿童的感染率最高。对恶性疟原虫msp - 2基因进行PCR - RFLP分型发现，每个感染个体平均有2.4种寄生虫基因型，这种多样性几乎与年龄无关，共鉴定出43种不同的msp - 2等位基因。这些等位基因在圣多美均不是独特的。研究参与者被鼓励在患发热疾病时向项目工作人员报告。在寄生虫学调查后的3个月里，无论是恶性疟原虫阳性发作还是无寄生虫血症的发热，记录的发病率都随着基线msp - 2多样性的增加而降低。虽然这与多种恶性疟原虫感染可能预防再次感染寄生虫的观点一致，但卫生服务使用模式的混杂因素是另一种解释。临床疟疾发作的发病率在儿童中仅比成人略高。临床免疫中这种微弱的年龄依赖性可能是20世纪80年代疟疾控制项目崩溃后疾病复发所导致的队列效应的结果。
