Indian Council of Medical Research-National Institute of Malaria Research, Sector-8, Dwarka, New Delhi 110077, India.
Indian Council of Medical Research-National Institute of Malaria Research Field Unit, Guwahati 781022, Assam, India.
Trans R Soc Trop Med Hyg. 2021 Oct 1;115(10):1198-1206. doi: 10.1093/trstmh/trab017.
Malaria elimination requires targeting asymptomatic and low-density Plasmodium infections that largely remain undetected. Therefore we conducted a cross-sectional study to estimate the burden of asymptomatic and low-density Plasmodium infection using conventional and molecular diagnostics.
A total of 9118 participants, irrespective of age and sex, were screened for malaria using rapid diagnostic tests (RDTs), microscopy and polymerase chain reaction.
Among the participants, 707 presented with symptoms and 8411 without symptoms, of which Plasmodium was present in 15.6% (110/707) and 8.1% (681/8411), respectively. Low-density infection was found in 5.1% (145/2818) of participants and 8327 of 9118 were Plasmodium negative. Endemicity was propotional to asymptomatic infections (high endemicity 11.1% [404/3633] vs low endemicity 5.8% [277/4778]; odds ratio [OR] 2.0 [95% confidence interval {CI} 1.7 to 2.4]) but inversely related to low-density infection (high endemicity 3.7% [57/1545] vs low endemicity 6.9% [88/1273]; OR 1.9 [95% CI 1.4 to 2.7]). The spleen rate in children 2-9 y of age was 17.9% (602/3368) and the enlarged spleen index was 1.6. Children between 8 and 14 y showed higher odds for asymptomatic (adjusted OR [aOR] 1.75 [95% CI 1.4 to 2.2]) and low-density infections (aOR 0.63 [95% CI 0.4 to 1.0)] than adults.
The prevalence of asymptomatic and low-density Plasmodium infection undermines the usefulness of standard diagnostic tools used by health agencies. This necessitates deploying molecular tools in areas where malaria microscopy/RDTs indicate a dearth of infection.
消除疟疾需要针对无症状和低密度的疟原虫感染，而这些感染在很大程度上仍未被发现。因此，我们进行了一项横断面研究，使用常规和分子诊断方法来估计无症状和低密度疟原虫感染的负担。
共筛查了 9118 名年龄和性别不限的参与者，使用快速诊断检测（RDT）、显微镜检查和聚合酶链反应筛查疟疾。
在参与者中，707 人有症状，8411 人无症状，其中分别有 15.6%（110/707）和 8.1%（681/8411）的人存在疟原虫。低密度感染见于 5.1%（145/2818）的参与者中，9118 人中 8327 人疟原虫阴性。流行程度与无症状感染成正比（高度流行地区 11.1%（404/3633）与低度流行地区 5.8%（277/4778）；比值比[OR] 2.0[95%置信区间{CI} 1.7 至 2.4]），但与低密度感染呈反比（高度流行地区 3.7%（57/1545）与低度流行地区 6.9%（88/1273）；OR 1.9[95%CI 1.4 至 2.7]）。2-9 岁儿童的脾脏率为 17.9%（602/3368），脾脏肿大指数为 1.6。8-14 岁儿童无症状（调整比值比[aOR]1.75[95%CI 1.4 至 2.2]）和低密度感染（aOR 0.63[95%CI 0.4 至 1.0]）的可能性均高于成年人。
无症状和低密度疟原虫感染的流行程度削弱了卫生机构使用的标准诊断工具的实用性。这就需要在疟疾显微镜检查/RDT 表明感染不足的地区部署分子工具。
