Centre for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya.
School of Zoological Sciences, Kenyatta University, Nairobi, Kenya.
Parasit Vectors. 2023 Oct 21;16(1):376. doi: 10.1186/s13071-023-05944-5.
Designing, implementing, and upscaling of effective malaria vector control strategies necessitates an understanding of when and where transmission occurs. This study assessed the biting patterns of potentially infectious malaria vectors at various hours, locations, and associated human behaviors in different ecological settings in western Kenya.
Hourly indoor and outdoor catches of human-biting mosquitoes were sampled from 19:00 to 07:00 for four consecutive nights in four houses per village. The human behavior study was conducted via questionnaire surveys and observations. Species within the Anopheles gambiae complex and Anopheles funestus group were distinguished by polymerase chain reaction (PCR) and the presence of Plasmodium falciparum circumsporozoite proteins (CSP) determined by enzyme-linked immunosorbent assay (ELISA).
Altogether, 2037 adult female anophelines were collected comprising the An. funestus group (76.7%), An. gambiae sensu lato (22.8%), and Anopheles coustani (0.5%). PCR results revealed that Anopheles arabiensis constituted 80.5% and 79% of the An. gambiae s.l. samples analyzed from the lowland sites (Ahero and Kisian, respectively). Anopheles gambiae sensu stricto (hereafter An. gambiae) (98.1%) was the dominant species in the highland site (Kimaeti). All the An. funestus s.l. analyzed belonged to An. funestus s.s. (hereafter An. funestus). Indoor biting densities of An. gambiae s.l. and An. funestus exceeded the outdoor biting densities in all sites. The peak biting occurred in early morning between 04:30 and 06:30 in the lowlands for An. funestus both indoors and outdoors. In the highlands, the peak biting of An. gambiae occurred between 01:00 and 02:00 indoors. Over 50% of the study population stayed outdoors from 18:00 to 22:00 and woke up at 05:00, coinciding with the times when the highest numbers of vectors were collected. The sporozoite rate was higher in vectors collected outdoors, with An. funestus being the main malaria vector in the lowlands and An. gambiae in the highlands.
This study shows heterogeneity of anopheline distribution, high outdoor malaria transmission, and early morning peak biting activity of An. funestus when humans are not protected by bednets in the lowland sites. Additional vector control efforts targeting the behaviors of these vectors, such as the use of non-pyrethroids for indoor residual spraying and spatial repellents outdoors, are needed.
设计、实施和扩大有效的疟疾媒介控制策略需要了解传播发生的时间和地点。本研究评估了肯尼亚西部不同生态环境中潜在感染性疟疾病媒在不同时间、地点和相关人类行为下的叮咬模式。
在四个村庄的每所房屋中，从 19:00 到 07:00 连续四个晚上进行每小时室内和室外的人蚊叮咬捕获。通过问卷调查和观察进行人类行为研究。聚合酶链反应 (PCR) 区分冈比亚按蚊复合体和致倦库蚊组内的物种，酶联免疫吸附试验 (ELISA) 确定疟原虫环子孢子蛋白 (CSP) 的存在。
共收集了 2037 只成年雌性按蚊，包括致倦库蚊组（76.7%）、冈比亚按蚊系（22.8%）和库蚊（0.5%）。PCR 结果显示，在低地（Ahero 和 Kisian）分析的冈比亚按蚊系样本中，阿拉伯按蚊分别占 80.5%和 79%。在高地（Kimaeti），优势物种为冈比亚按蚊（98.1%）。分析的所有致倦库蚊均属于致倦库蚊指名亚种（以下简称致倦库蚊）。所有地点的室内冈比亚按蚊系和致倦库蚊的叮咬密度均高于室外。在低地，致倦库蚊无论是室内还是室外，都在清晨 04:30 到 06:30 之间出现高峰叮咬。在高地，冈比亚按蚊的高峰叮咬发生在室内 01:00 到 02:00。超过 50%的研究人群在 18:00 到 22:00 之间留在室外，05:00 醒来，此时收集到的媒介数量最多。在室外收集的媒介中发现了更高的孢子率，致倦库蚊是低地的主要疟疾媒介，冈比亚按蚊是高地的主要疟疾媒介。
本研究表明按蚊分布存在异质性，在低地，户外疟疾传播率高，清晨 04:30 到 06:30 期间是致倦库蚊的高峰叮咬活动时间，此时人类未使用蚊帐。需要针对这些媒介的行为进行额外的媒介控制工作，例如在室内使用非拟除虫菊酯进行滞留喷洒和在室外使用空间驱避剂。
