KEMRI-Wellcome Trust Research Programme, Kilifi, Kenya.
Centre for Tropical Medicine and Global Health, Nuffield Department of Clinical Medicine, University of Oxford, Oxford, UK.
Malar J. 2020 Jun 17;19(1):210. doi: 10.1186/s12936-020-03286-6.
Malaria transmission has recently fallen in many parts of Africa, but systematic descriptions of infection and disease across all age groups are rare. Here, an epidemiological investigation of parasite prevalence, the incidence of fevers associated with infection, severe hospitalized disease and mortality among children older than 6 months and adults on the Kenyan coast is presented.
A prospective fever surveillance was undertaken at 6 out-patients (OPD) health-facilities between March 2018 and February 2019. Four community-based, cross sectional surveys of fever history and infection prevalence were completed among randomly selected homestead members from the same communities. Paediatric and adult malaria at Kilifi county hospital was obtained for the 12 months period. Rapid Diagnostic Tests (CareStart™ RDT) to detect HRP2-specific to Plasmodium falciparum was used in the community and the OPD, and microscopy in the hospital. Crude and age-specific incidence rates were computed using Poisson regression.
Parasite prevalence gradually increased from childhood, reaching 12% by 9 years of age then declining through adolescence into adulthood. The incidence rate of RDT positivity in the OPD followed a similar trend to that of infection prevalence in the community. The incidence of hospitalized malaria from the same community was concentrated among children aged 6 months to 4 years (i.e. 64% and 70% of all hospitalized and severe malaria during the 12 months of surveillance, respectively). Only 3.7% (12/316) of deaths were directly attributable to malaria. Malaria mortality was highest among children aged 6 months-4 years at 0.57 per 1000 person-years (95% CI 0.2, 1.2). Severe malaria and death from malaria was negligible above 15 years of age.
Under conditions of low transmission intensity, immunity to disease and the fatal consequences of infection appear to continue to be acquired in childhood and faster than anti-parasitic immunity. There was no evidence of an emerging significant burden of severe malaria or malaria mortality among adults. This is contrary to current modelled approaches to disease burden estimation in Africa and has important implications for the targeting of infection prevention strategies based on chemoprevention or vector control.
在非洲的许多地区，疟疾传播最近有所下降，但对所有年龄段的感染和疾病进行系统描述的情况却很少见。在此，我们呈现了一项在肯尼亚沿海地区对 6 个月以上儿童和成人的寄生虫流行率、与感染相关的发热发生率、严重住院疾病和死亡率进行的流行病学调查。
在 2018 年 3 月至 2019 年 2 月期间，在 6 个门诊（OPD）医疗机构进行了前瞻性发热监测。在来自同一社区的随机选定的居民中完成了四次基于社区的发热史和感染流行率的横断面调查。在基利菲县医院获得了 12 个月期间的儿科和成人疟疾。社区和 OPD 中使用 CareStart™ RDT 检测 HRP2 特异性恶性疟原虫，医院中使用显微镜。使用泊松回归计算粗发病率和年龄特异性发病率。
寄生虫流行率从儿童期逐渐增加，到 9 岁时达到 12%，然后在青少年期到成年期下降。OPD 中的 RDT 阳性率的发生率与社区中感染的流行率相似。来自同一社区的住院疟疾发生率集中在 6 个月至 4 岁的儿童中（即，12 个月监测期间所有住院和严重疟疾的 64%和 70%）。只有 3.7%（12/316）的死亡直接归因于疟疾。6 个月至 4 岁的儿童疟疾死亡率最高，为每 1000 人年 0.57 例（95%CI 0.2，1.2）。15 岁以上严重疟疾和疟疾死亡率可忽略不计。
在低传播强度的情况下，对疾病的免疫力和感染的致命后果似乎在儿童期继续获得，而且比抗寄生虫免疫力更快。在成年人中没有发现严重疟疾或疟疾死亡率出现显著负担的证据。这与目前非洲疾病负担评估的模型方法相反，对基于化学预防或病媒控制的感染预防策略的目标具有重要意义。
