Dataset describing the biting profile, seasonality and feeding cycle of Anopheles farauti in Haleta village, Solomon Islands

Background: The effectiveness of vector control on malaria transmission by long lasting insecticidal nets (LLINs) and indoor residual spraying (IRS) depends on the vectors entering houses to blood feed and rest when people are inside houses. In the Solomon Islands, significant reductions in malaria have been achieved in the past 20 years with insecticide treated bednets, IRS and improved diagnosis and treatment with artemisinin combination therapies; despite the preference of the primary vector, Anopheles farauti, to feed outdoors and early in the evening and thereby avoid potential exposure to insecticides. Rational development of tools to complement LLINs and IRS by attacking vectors outdoor requires detailed knowledge of the biology and behaviours of the target species.Methods: Malaria transmission in Central Province, Solomon Islands was estimated by measuring the components comprising the entomological inoculation rate (EIR) as well as the vectorial capacity of An. farauti. In addition, the daily and seasonal biting behaviour of An. farauti, was examined and the duration of the feeding cycle was estimated with a mark-release-recapture experiment.Results: Anopheles farauti was highly exophagic with 72% captured by human landing catches (HLC) outside of houses. Three-quarters (76%) of blood feeding on humans was estimated to occur before 21.00 h. When the hourly location of humans was considered, the proportion of exposure to mosquito bites on humans occurring indoors (πi) was only 0.130 ± 0.129. Peak densities of host seeking An. farauti occurred between October and January. The annual EIR was estimated to be 2.5 for 2012 and 33.2 for 2013. The length of the feeding cycle was 2.1 days.Conclusions: The short duration of the feeding cycle by this species offers an explanation for the substantial control of malaria that has been achieved in the Solomon Islands by LLINs and IRS. Anopheles farauti is primarily exophagic and early biting,with 13% of mosquitoes entering houses to feed late at night during each feeding cycle. The 2 day feeding cycle of An. farauti requires females to take 5-6 blood meals before the extrinsic incubation period (EIP) is completed; and this could translate into substantial population-level mortality by LLINs or IRS before females would be infectious to humans with P. falciparum and P. vivax. Although An. farauti is primarily exophagic, the indoor vector control tools recommended by the World Health Organisation (LLINs and IRS) can still provide an important level of control. Nonetheless, elimination will likely require vector control tools that target other bionomic vulnerabilities to suppress transmission outdoors and that complement the control provided by LLINs and IRS.

研究背景：长效杀虫蚊帐（long lasting insecticidal nets, LLINs）与室内残留喷洒（indoor residual spraying, IRS）对疟疾传播的媒介防控效果，取决于媒介在人类居于室内时进入房屋吸血、栖息的行为。所罗门群岛在过去20年间，虽通过经杀虫剂处理的蚊帐、室内残留喷洒以及青蒿素联合疗法（artemisinin combination therapies）优化疟疾诊断与治疗方案，实现了感染率的显著下降，但当地主要传播媒介法鲁按蚊（Anopheles farauti）偏好于户外吸血且在傍晚早期进食，从而规避了杀虫剂暴露风险。若要研发可补充长效杀虫蚊帐与室内残留喷洒、针对户外媒介的防控工具，需对目标媒介的生物学特性与行为模式展开深入研究。

研究方法：通过解析昆虫接种率（entomological inoculation rate, EIR）的构成组分以及法鲁按蚊的媒介能量，估算所罗门群岛中央省的疟疾传播水平。此外，本研究还对法鲁按蚊的昼夜与季节吸血行为开展观测，并通过标记-释放-重捕实验估算其吸血周期时长。

研究结果：法鲁按蚊具有极强的嗜外栖特性，72%的捕获个体通过人饵诱捕法（human landing catches, HLC）在户外获取。据估算，76%的人类吸血行为发生在当日21:00之前。若考量人类每小时的活动位置，人类室内被蚊叮咬的暴露占比（πi）仅为0.130±0.129。法鲁按蚊的宿主搜寻高峰密度出现在10月至次年1月之间。2012年的年度昆虫接种率估算为2.5，2013年则为33.2。该物种的吸血周期时长为2.1天。

研究结论：本研究结果显示，该物种的短吸血周期可解释所罗门群岛通过长效杀虫蚊帐与室内残留喷洒实现疟疾大幅防控的现象。法鲁按蚊主要表现为嗜外栖与早吸血行为，在每个吸血周期中，仅13%的个体进入房屋于深夜吸血。法鲁按蚊的2天吸血周期意味着，雌蚊在完成外潜伏期（extrinsic incubation period, EIP）前需要吸食5~6次血液；这意味着在雌蚊具备感染恶性疟原虫（Plasmodium falciparum）与间日疟原虫（Plasmodium vivax）的能力前，长效杀虫蚊帐或室内残留喷洒可造成种群水平的显著死亡率。尽管法鲁按蚊以嗜外栖行为为主，但世界卫生组织推荐的室内媒介防控工具——长效杀虫蚊帐与室内残留喷洒——仍可发挥重要的防控作用。不过，要实现疟疾消除，仍需研发针对其他生态生物学弱点的媒介防控工具，以抑制户外传播并补充长效杀虫蚊帐与室内残留喷洒的防控效果。