Kyle Colin H, Liu Jiawei, Gallagher Molly E, Dukic Vanja, Dwyer Greg
Am Nat. 2020 Mar;195(3):504-523. doi: 10.1086/707138. Epub 2020 Jan 15.
In deterministic models of epidemics, there is a host abundance threshold above which the introduction of a few infected individuals leads to a severe epidemic. Studies of weather-driven animal pathogens often assume that abundance thresholds will be overwhelmed by weather-driven stochasticity, but tests of this assumption are lacking. We collected observational and experimental data for a fungal pathogen, , that infects the gypsy moth, . We used an advanced statistical-computing algorithm to fit mechanistic models to our data, such that different models made different assumptions about the effects of host density and weather on epizootics (epidemics in animals). We then used Akaike information criterion analysis to choose the best model. In the best model, epizootics are driven by a combination of weather and host density, and the model does an excellent job of explaining the data, whereas models that allow only for weather effects or only for density-dependent effects do a poor job of explaining the data. Density-dependent transmission in our best model produces a host density threshold, but this threshold is strongly blurred by the stochastic effects of weather. Our work shows that host-abundance thresholds may be important even if weather strongly affects transmission, suggesting that epidemiological models that allow for weather have an important role to play in understanding animal pathogens. The success of our model means that it could be useful for managing the gypsy moth, an important pest of hardwood forests in North America.
在传染病的确定性模型中，存在一个宿主丰度阈值，超过该阈值，引入少数受感染个体就会引发严重疫情。对受天气驱动的动物病原体的研究通常假定，丰度阈值会被天气驱动的随机性所掩盖，但缺乏对这一假设的检验。我们收集了一种感染舞毒蛾的真菌病原体的数据，既有观测数据，也有实验数据。我们使用一种先进的统计计算算法，将机理模型与我们的数据进行拟合，使得不同模型对宿主密度和天气对动物流行病（动物中的传染病）的影响做出不同假设。然后，我们使用赤池信息准则分析来选择最佳模型。在最佳模型中，动物流行病是由天气和宿主密度共同驱动的，该模型在解释数据方面表现出色，而仅考虑天气影响或仅考虑密度依赖影响的模型在解释数据方面表现较差。我们最佳模型中的密度依赖传播产生了一个宿主密度阈值，但这个阈值因天气的随机效应而严重模糊。我们的研究表明，即使天气对传播有强烈影响，宿主丰度阈值可能仍很重要，这表明考虑天气因素的流行病学模型在理解动物病原体方面可发挥重要作用。我们模型的成功意味着它可能有助于管理舞毒蛾，这种害虫对北美硬木森林很重要。
