Department of Environmental Health & Ecological Sciences, Ifakara Health Institute, Ifakara, Tanzania.
Institute of Biodiversity, Animal Health and Comparative Medicine, University of Glasgow, Glasgow, UK.
Malar J. 2022 Jun 3;21(1):161. doi: 10.1186/s12936-022-04189-4.
It is often assumed that the population dynamics of the malaria vector Anopheles funestus, its role in malaria transmission and the way it responds to interventions are similar to the more elaborately characterized Anopheles gambiae. However, An. funestus has several unique ecological features that could generate distinct transmission dynamics and responsiveness to interventions. The objectives of this work were to develop a model which will: (1) reconstruct the population dynamics, survival, and fecundity of wild An. funestus populations in southern Tanzania, (2) quantify impacts of density dependence on the dynamics, and (3) assess seasonal fluctuations in An. funestus demography. Through quantifying the population dynamics of An. funestus, this model will enable analysis of how their stability and response to interventions may differ from that of An. gambiae sensu lato.
A Bayesian State Space Model (SSM) based on mosquito life history was fit to time series data on the abundance of female An. funestus sensu stricto collected over 2 years in southern Tanzania. Prior values of fitness and demography were incorporated from empirical data on larval development, adult survival and fecundity from laboratory-reared first generation progeny of wild caught An. funestus. The model was structured to allow larval and adult fitness traits to vary seasonally in response to environmental covariates (i.e. temperature and rainfall), and for density dependency in larvae. The effects of density dependence and seasonality were measured through counterfactual examination of model fit with or without these covariates.
The model accurately reconstructed the seasonal population dynamics of An. funestus and generated biologically-plausible values of their survival larval, development and fecundity in the wild. This model suggests that An. funestus survival and fecundity annual pattern was highly variable across the year, but did not show consistent seasonal trends either rainfall or temperature. While the model fit was somewhat improved by inclusion of density dependence, this was a relatively minor effect and suggests that this process is not as important for An. funestus as it is for An. gambiae populations.
The model's ability to accurately reconstruct the dynamics and demography of An. funestus could potentially be useful in simulating the response of these populations to vector control techniques deployed separately or in combination. The observed and simulated dynamics also suggests that An. funestus could be playing a role in year-round malaria transmission, with any apparent seasonality attributed to other vector species.
人们通常认为，疟疾病媒按蚊（Anopheles funestus）的种群动态、其在疟疾传播中的作用以及对干预措施的反应方式与特征更为复杂的冈比亚按蚊（Anopheles gambiae）相似。然而，按蚊（An. funestus）具有一些独特的生态特征，这些特征可能会产生不同的传播动态和对干预措施的反应。本研究的目的是开发一种模型，该模型将：（1）重建野生按蚊（An. funestus）在坦桑尼亚南部的种群动态、存活率和繁殖力，（2）量化密度依赖性对动态的影响，（3）评估按蚊（An. funestus）种群季节性波动。通过量化按蚊（An. funestus）的种群动态，该模型将能够分析其稳定性及其对干预措施的反应可能与冈比亚按蚊（An. gambiae sensu lato）有何不同。
本研究基于蚊类生活史，建立了一个贝叶斯状态空间模型（SSM），并将其拟合到在坦桑尼亚南部收集的两年内按蚊（An. funestus sensu stricto）雌性丰度的时间序列数据上。将从实验室饲养的野生捕获按蚊（An. funestus）第一代幼虫的发育、成虫存活率和繁殖力的经验数据中得出的适合度和人口统计学的先验值纳入模型。该模型的结构允许幼虫和成虫的适合度特征随环境协变量（即温度和降雨量）季节性变化，并允许幼虫密度依赖性。通过对照没有这些协变量的模型拟合情况，来衡量密度依赖性和季节性的影响。
该模型准确地重建了按蚊（An. funestus）的季节性种群动态，并在野外生成了其生存、幼虫发育和繁殖力的生物学上合理的值。该模型表明，按蚊（An. funestus）的存活率和繁殖力的年度模式在全年变化很大，但无论降雨量还是温度，都没有表现出一致的季节性趋势。虽然包括密度依赖性会略微提高模型拟合度，但这只是一个相对较小的影响，表明该过程对按蚊（An. funestus）的重要性不如对冈比亚按蚊（An. gambiae）种群的重要性。
该模型准确重建按蚊（An. funestus）动态和人口统计学的能力可能有助于模拟这些种群对单独或联合部署的蚊虫控制技术的反应。观察到的和模拟的动态也表明，按蚊（An. funestus）可能在全年传播疟疾中发挥作用，任何明显的季节性都归因于其他媒介物种。
