McElroy P D, Beier J C, Oster C N, Onyango F K, Oloo A J, Lin X, Beadle C, Hoffman S L
Malaria Program, Naval Medical Research Institute, Bethesda, MD, USA.
Am J Epidemiol. 1997 May 15;145(10):945-56. doi: 10.1093/oxfordjournals.aje.a009054.
Blood-stage level Plasmodium falciparum infection (parasitemia density) is generally elevated prior to, or at the time of, clinical presentation of severe pediatric malaria episodes. Intensity of exposure to infective Anopheles mosquito bites is a suspected determinant of higher density parasitemia. Analyses of entomologic and parasitologic data collected in 1986-1987 were conducted to investigate whether the dose of infective bites predicted the incidence or degree of P. falciparum parasitemia in Kenyan children < 6 years old. At 21 consecutive 30-day intervals, a new cohort (n approximately 50 each) was enrolled, cured of malaria parasites, and monitored over 84 days for recurrent parasitemia. Outcomes included time to parasitemia, time to parasitemia > or = 5,000/microliter, and parasitemia density. Ecologic and individual-level analyses were conducted. The mean infective bite exposure experienced by each cohort was significantly associated with the incidence of parasitemia (age-adjusted r2 = 0.38, p = 0.022) and more strongly associated with the incidence of parasitemia > or = 5,000/microliter (age-adjusted r2 = 0.72, p < 0.001). The infective bite dose, analyzed as a time-dependent covariate, was associated with a 2.8 times higher rate of parasitemia > or = 5,000/microliter among children exposed to > or = 1 infective bite per day as compared with the referent (rate ratio (RR) = 2.82, 95% confidence interval (CI) 2.24-3.56). Cumulative infective bite exposure, exposure duration, and age were significant predictors of recurrent parasitemia density in multiple linear regression analyses. The results support the contention that reductions in P. falciparum transmission intensity, in the absence of complete elimination, will reduce higher level parasitemia among African children.
在严重小儿疟疾发作的临床表现之前或之时，血液阶段的恶性疟原虫感染（寄生虫血症密度）通常会升高。接触感染性按蚊叮咬的强度被怀疑是寄生虫血症密度较高的一个决定因素。对1986 - 1987年收集的昆虫学和寄生虫学数据进行了分析，以调查感染性叮咬的剂量是否能预测肯尼亚6岁以下儿童恶性疟原虫寄生虫血症的发生率或程度。在连续21个30天的间隔期内，招募了新的队列（每个队列约50人），清除疟原虫，并在84天内监测复发性寄生虫血症。结果包括出现寄生虫血症的时间、寄生虫血症≥5000/微升的时间以及寄生虫血症密度。进行了生态学和个体水平的分析。每个队列经历的平均感染性叮咬暴露与寄生虫血症的发生率显著相关（年龄调整后的r2 = 0.38，p = 0.022），并且与寄生虫血症≥5000/微升的发生率相关性更强（年龄调整后的r2 = 0.72，p < 0.001）。作为时间依赖性协变量分析的感染性叮咬剂量，与每天暴露于≥1次感染性叮咬的儿童中寄生虫血症≥5000/微升的发生率相比，参考组高出2.8倍（率比（RR）= 2.82，95%置信区间（CI）2.24 - 3.56）。在多元线性回归分析中，累积感染性叮咬暴露、暴露持续时间和年龄是复发性寄生虫血症密度的显著预测因素。结果支持这样的观点，即在没有完全消除的情况下，降低恶性疟原虫传播强度将降低非洲儿童中较高水平的寄生虫血症。
