Opondo Kevin Ochieng', Weetman David, Jawara Musa, Diatta Mathurin, Fofana Amfaal, Crombe Florence, Mwesigwa Julia, D'Alessandro Umberto, Donnelly Martin James
Medical Research Council Unit, PO Box 273, Banjul, The Gambia.
Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, UK.
Malar J. 2016 Mar 15;15:166. doi: 10.1186/s12936-016-1203-z.
Malaria hotspots, areas with consistently higher than average transmission, may become increasingly common as malaria declines. This phenomenon, currently observed in The Gambia, may be caused by several factors, including some related to the local vectors, whose contribution is poorly understood.
Using WHO susceptibility bioassays, insecticide resistance status was determined in vector populations sampled from six pairs of villages across The Gambia, each pair contained a low and high prevalence village.
Three vector species were observed (23.5% Anopheles arabiensis, 31.2% Anopheles gambiae, 43.3% Anopheles coluzzii and 2.0% An. coluzzii × An. gambiae hybrids). Even at a fine scale, significant differences in species composition were detected within village pairs. Resistance to both DDT and deltamethrin was more common in An. gambiae, most markedly in the eastern part of The Gambia and partly attributable to differing frequencies of resistance mutations. The Vgsc-1014F target site mutation was strongly associated with both DDT (OR = 256.7, (95% CI 48.6-6374.3, p < 0.001) and deltamethrin survival (OR = 9.14, (95% CI 4.24-21.4, p < 0.001). A second target site mutation, Vgsc-1575Y, which co-occurs with Vgsc-1014F, and a metabolic marker of resistance, Gste2-114T, conferred additional survival benefits to both insecticides. DDT resistance occurred significantly more frequently in villages with high malaria prevalence (p = 0.025) though this did not apply to deltamethrin resistance.
Whilst causality of relationships requires further investigation, variation in vector species and insecticide resistance in The Gambia is associated with malaria endemicity; with a notably higher prevalence of infection and insecticide resistance in the east of the country. In areas with heterogeneous malaria transmission, the role of the vector should be investigated to guide malaria control interventions.
疟疾热点地区，即疟疾传播持续高于平均水平的地区，可能会随着疟疾发病率的下降而变得越来越普遍。目前在冈比亚观察到的这种现象可能由多种因素引起，包括一些与当地病媒相关的因素，但其作用尚不清楚。
使用世界卫生组织的敏感性生物测定法，对从冈比亚六对村庄采集的病媒种群进行杀虫剂抗性测定，每对村庄包含一个低流行率村庄和一个高流行率村庄。
观察到三种病媒物种（23.5%阿拉伯按蚊、31.2%冈比亚按蚊、43.3%科氏按蚊和2.0%科氏按蚊×冈比亚按蚊杂交种）。即使在小尺度范围内，在村庄对中也检测到物种组成的显著差异。冈比亚按蚊对滴滴涕和溴氰菊酯的抗性更为常见，在冈比亚东部最为明显，部分原因是抗性突变频率不同。Vgsc - 1014F靶位点突变与滴滴涕抗性（比值比=256.7，95%置信区间48.6 - 6374.3，p<0.001）和溴氰菊酯存活（比值比=9.14，95%置信区间4.24 - 21.4，p<0.001）均密切相关。与Vgsc - 1014F共同出现的第二个靶位点突变Vgsc - 1575Y以及抗性代谢标记Gste2 - 114T，对两种杀虫剂均赋予了额外的存活优势。高疟疾流行率村庄的滴滴涕抗性发生率显著更高（p = 0.025），但溴氰菊酯抗性情况并非如此。
虽然各关系的因果性需要进一步研究，但冈比亚病媒物种和杀虫剂抗性的变化与疟疾流行情况相关；该国东部感染率和杀虫剂抗性明显更高。在疟疾传播不均一的地区，应调查病媒的作用以指导疟疾控制干预措施。
