Infectious Diseases Research Collaboration, Kampala, Uganda.
London School of Hygiene and Tropical Medicine, London, UK.
Malar J. 2022 Dec 19;21(1):388. doi: 10.1186/s12936-022-04413-1.
Methods used to sample mosquitoes are important to consider when estimating entomologic metrics. Human landing catches (HLCs) are considered the gold standard for collecting malaria vectors. However, HLCs are labour intensive, can expose collectors to transmission risk, and are difficult to implement at scale. This study compared alternative methods to HLCs for collecting Anopheles mosquitoes in eastern Uganda.
Between June and November 2021, mosquitoes were collected from randomly selected households in three parishes in Tororo and Busia districts. Mosquitoes were collected indoors and outdoors using HLCs in 16 households every 4 weeks. Additional collections were done indoors with prokopack aspirators, and outdoors with pit traps, in these 16 households every 2 weeks. CDC light trap collections were done indoors in 80 households every 4 weeks. Female Anopheles mosquitoes were identified morphologically and Anopheles gambiae sensu lato were speciated using PCR. Plasmodium falciparum sporozoite testing was done with ELISA.
Overall, 4,891 female Anopheles were collected, including 3,318 indoors and 1,573 outdoors. Compared to indoor HLCs, vector density (mosquitoes per unit collection) was lower using CDC light traps (4.24 vs 2.96, density ratio [DR] 0.70, 95% CIs 0.63-0.77, p < 0.001) and prokopacks (4.24 vs 1.82, DR 0.43, 95% CIs 0.37-0.49, p < 0.001). Sporozoite rates were similar between indoor methods, although precision was limited. Compared to outdoor HLCs, vector density was higher using pit trap collections (3.53 vs 6.43, DR 1.82, 95% CIs 1.61-2.05, p < 0.001), while the sporozoite rate was lower (0.018 vs 0.004, rate ratio [RR] 0.23, 95% CIs 0.07-0.75, p = 0.008). Prokopacks collected a higher proportion of Anopheles funestus (75.0%) than indoor HLCs (25.8%), while pit traps collected a higher proportion of Anopheles arabiensis (84.3%) than outdoor HLCs (36.9%).
In this setting, the density and species of mosquitoes collected with alternative methods varied, reflecting the feeding and resting characteristics of the common vectors and the different collection approaches. These differences could impact on the accuracy of entomological indicators and estimates of malaria transmission, when using the alternative methods for sampling mosquitos, as compared to HLCs.
在估计昆虫学指标时，采样蚊子的方法很重要。人体诱捕（HLC）被认为是收集疟疾媒介的黄金标准。然而，HLC 劳动强度大，会使采集者面临传播风险，并且难以大规模实施。本研究比较了在乌干达东部替代 HLC 收集疟蚊的方法。
2021 年 6 月至 11 月，在托罗罗和布西亚区的三个教区中随机选择的家庭中收集蚊子。每隔 4 周，在 16 户家庭中使用 HLC 在室内和室外收集蚊子。每隔两周，在这 16 户家庭中，使用 prokopack 吸气器在室内和室外收集蚊子。每隔 4 周，在 80 户家庭中使用 CDC 灯诱在室内收集蚊子。使用形态学鉴定雌性疟蚊，并使用 PCR 对冈比亚按蚊进行种系鉴定。使用 ELISA 进行恶性疟原虫裂殖子检测。
共收集到 4891 只雌性疟蚊，其中 3318 只为室内采集，1573 只为室外采集。与室内 HLC 相比，CDC 灯诱（4.24 比 2.96，密度比[DR]0.70，95%置信区间 0.63-0.77，p<0.001）和 prokopack（4.24 比 1.82，DR 0.43，95%置信区间 0.37-0.49，p<0.001）的蚊虫密度较低。虽然精度有限，但室内方法的裂殖子率相似。与户外 HLC 相比，使用陷阱收集的蚊虫密度更高（3.53 比 6.43，DR 1.82，95%置信区间 1.61-2.05，p<0.001），而裂殖子率较低（0.018 比 0.004，率比[RR]0.23，95%置信区间 0.07-0.75，p=0.008）。Prokopack 收集的冈比亚按蚊比例（75.0%）高于室内 HLC（25.8%），而陷阱收集的按蚊 Arabiensis 比例（84.3%）高于户外 HLC（36.9%）。
在这种情况下，替代方法收集的蚊虫密度和种类存在差异，反映了常见媒介的摄食和休息特征以及不同的收集方法。与 HLC 相比，使用替代方法采样蚊子时，这些差异可能会影响昆虫学指标的准确性和疟疾传播的估计。
