Smith T, Charlwood J D, Kitua A Y, Masanja H, Mwankusye S, Alonso P L, Tanner M
Swiss Tropical Institute, Basel.
Am J Trop Med Hyg. 1998 Aug;59(2):252-7. doi: 10.4269/ajtmh.1998.59.252.
To study incidence of clinical Plasmodium falciparum malaria in relation to exposure to parasites, attendance of children less than eighteen months old at a village dispensary in a highly endemic area of Tanzania was recorded. Entomologic inoculation rates (EIRs), estimated as a function of time period and place of residence, exceeded one sporozoite positive bite per adult per night in some village neighborhoods during the wet season. Incidence of clinical P. falciparum malaria, defined either as fever with parasitemia or as fever with hyperparasitemia, increased with the EIR over the whole range of exposures. Each 10-fold increase in the EIR corresponded to a 1.6-fold increase in incidence of fever plus parasitemia (95% confidence interval = 1.4-2.0). Therefore reduction of human-vector contacts will probably reduce morbidity incidence even at very high exposures. Incidence showed little relationship to estimated cumulative numbers of inoculations since birth, but decreased steeply with estimated cumulative time infected with trophozoites. This suggests that clinical immunity depends mainly on the extent of exposure to blood-stage antigens, not on the diversity of inocula seen, and thus temporary reductions in human-vector contacts are unlikely to result in subsequent increases in morbidity.
为研究恶性疟原虫临床疟疾的发病率与寄生虫暴露之间的关系，记录了坦桑尼亚一个高度流行地区某乡村诊疗所18个月以下儿童的就诊情况。根据时间段和居住地点估算的昆虫接种率（EIRs）显示，在雨季期间，某些村庄社区的EIRs超过每晚每成年人1次子孢子阳性叮咬。以伴有寄生虫血症的发热或伴有高寄生虫血症的发热定义的恶性疟原虫临床疟疾发病率，在整个暴露范围内均随EIRs升高而增加。EIRs每增加10倍，伴有寄生虫血症的发热发病率相应增加1.6倍（95%置信区间 = 1.4 - 2.0）。因此，即使在暴露程度非常高的情况下，减少人与媒介的接触也可能降低发病几率。发病率与自出生以来估算的累计接种次数关系不大，但随估算的滋养体感染累计时间急剧下降。这表明临床免疫力主要取决于血期抗原的暴露程度，而非所接触接种物的多样性，因此人与媒介接触的暂时减少不太可能导致随后发病率上升。
