Investigating the probability of establishment of Zika virus and detection through mosquito surveillance under different temperature conditions

Because of the increasing threat that Zika virus (ZIKV) poses to more sub-tropical area due to increased global travel, there is a need for better understanding of the effect(s) of temperature on the establishment potential of ZIKV within these subtropical, temperate, and/or seasonal Ae. aegypti populations. The first step to determining risk establishment of ZIKV in these regions is to assess ZIKV's ability to infect mosquitoes at less tropical temperatures, and thus be detected through common surveillance programs. To that end, the effect of two rearing temperatures (RT) and extrinsic incubation temperatures (EIT) on infection and dissemination rates was evaluated, as well as the interactions of such. Total, there were four combinations (RT24-EIT24, RT24-EIT28, RT28-EIT24, RT28-EIT28). Further, a stochastic SEIR framework was adapted to determine whether observed data could lead to differential success of establishment of ZIKV in naive mosquito populations. There was no consistent pattern in significant differences found across treatments for either infection or dissemination rates (p>0.05), where only a significant difference was found in infection rates between RT24-EIT24 (44%) and RT28-EIT24 (82.6%). Across all temperature conditions, the model predicted between a 76.4% and 95.4% chance of successful establishment of ZIKV in naive mosquito populations under model assumptions. We further show that excluding the maximum observed infection and dissemination rates likely overestimates the probability of local establishment of ZIKV. These results indicate that 1) there is no straightforward relationship between RT, EIT, and infection/dissemination rates, 2) in more temperate climates, ZIKV may still have the ability to establish in populations of Aedes aegypti, 3) despite an overall lack of significant differences in infection/dissemination rates, temperature may still alter the kinetics of ZIKV within the mosquito enough to affect the likelihood of infection establishment and detection within the context of mosquito surveillance programs, and 4) both the temporal and magnitude qualities of vector competence are necessary for parameterization of within-mosquito virus kinetics.

由于全球旅行增多导致寨卡病毒（Zika virus, ZIKV）对更多亚热带区域的威胁日益加剧，学界亟需更深入地理解温度对亚热带、温带及季节性埃及伊蚊（Ae. aegypti）种群中寨卡病毒定殖潜力的影响。确定寨卡病毒在上述区域的定殖风险的首要环节，是评估寨卡病毒在非热带温度条件下感染蚊虫的能力，进而可通过常规监测项目实现病毒检测。为此，本研究评估了两种饲养温度（rearing temperature, RT）与外潜伏期温度（extrinsic incubation temperature, EIT）对蚊虫感染率与播散率的影响，以及二者的交互作用。实验共设置四组温度组合：RT24-EIT24、RT24-EIT28、RT28-EIT24、RT28-EIT28。此外，本研究采用随机SEIR框架，以探究观测数据是否会导致寨卡病毒在易感蚊种群中出现差异化的定殖成功概率。针对感染率与播散率的组间显著差异分析未发现一致模式（p>0.05），仅在RT24-EIT24（44%）与RT28-EIT24（82.6%）两组间的感染率存在显著差异。在所有温度条件下，基于模型假设的预测结果显示，寨卡病毒在易感蚊种群中成功定殖的概率介于76.4%至95.4%之间。本研究进一步证实，排除观测到的最高感染率与播散率后，很可能会高估寨卡病毒的本地定殖概率。上述结果表明：1）饲养温度、外潜伏期温度与感染/播散率之间并无直接的简单关联；2）在温带气候区域，寨卡病毒仍有可能在埃及伊蚊种群中完成定殖；3）尽管感染与播散率整体未呈现显著差异，但温度仍可显著改变寨卡病毒在蚊体内的动力学特征，足以影响蚊虫监测项目背景下的病毒感染定殖与检测概率；4）媒介效能的时序特征与强度特征均是蚊体内病毒动力学参数化的必要条件。