Institute of Infection, Veterinary, and Ecological Sciences, University of Liverpool, Liverpool, L69 7ZB, UK.
Institute of Evolutionary Biology & Centre for Infection, Immunity and Evolution, School of Biological Sciences, University of Edinburgh, Edinburgh, EH9 3FL, UK.
Epidemics. 2021 Jun;35:100451. doi: 10.1016/j.epidem.2021.100451. Epub 2021 Mar 13.
To date, few studies of parasite epidemiology have investigated 'who acquires infection from whom' in wildlife populations. Nonetheless, identifying routes of disease transmission within a population, and determining the key groups of individuals that drive parasite transmission and maintenance, are fundamental to understanding disease dynamics. Gammaherpesviruses are a widespread group of DNA viruses that infect many vertebrate species, and murine gammaherpesviruses (i.e. MuHV-4) are a standard lab model for studying human herpesviruses, for which much about the pathology and immune response elicited to infection is well understood. However, despite this extensive research effort, primarily in the lab, the transmission route of murine gammaherpesviruses within their natural host populations is not well understood. Here, we aimed to understand wood mouse herpesvirus (WMHV) transmission, by fitting a series of population dynamic models to field data on wood mice naturally infected with WMHV and then estimating transmission parameters within and between demographic groups of the host population. Different models accounted for different combinations of host sex (male/female), age (subadult/adult) and transmission functions (density/frequency-dependent). We found that a density-dependent transmission model incorporating explicit sex groups fitted the data better than all other proposed models. Male-to-male transmission was the highest among all possible combinations of between- and within-sex transmission classes, suggesting that male behaviour is a key factor driving WMHV transmission. Our models also suggest that transmission between sexes, although important, wasn't symmetrical, with infected males playing a significant role in infecting naïve females but not vice versa. Overall this work shows the power of coupling population dynamic models with long-term field data to elucidate otherwise unobservable transmission processes in wild disease systems.
迄今为止，很少有寄生虫流行病学研究调查野生动物种群中“谁从谁那里获得感染”。然而，确定疾病在人群中的传播途径，并确定驱动寄生虫传播和维持的关键人群，对于了解疾病动态至关重要。γ疱疹病毒是一组广泛存在的 DNA 病毒，感染许多脊椎动物物种，而鼠γ疱疹病毒（即 MuHV-4）是研究人类疱疹病毒的标准实验室模型，对于其病理学和感染引起的免疫反应有很多了解。然而，尽管进行了广泛的研究工作，主要是在实验室中，但其在其自然宿主种群中的传播途径仍未得到很好的理解。在这里，我们旨在通过将一系列种群动态模型拟合到自然感染 WMHV 的木鼠的现场数据上来了解木鼠疱疹病毒（WMHV）的传播，然后估计宿主种群内和种群间的传播参数。不同的模型考虑了宿主性别（雄性/雌性）、年龄（亚成年/成年）和传播功能（密度/频率依赖性）的不同组合。我们发现，纳入明确性别组的密度依赖性传播模型比所有其他提出的模型更能拟合数据。雄性之间的传播是所有可能的性别内和性别间传播类别的组合中最高的，这表明雄性行为是驱动 WMHV 传播的关键因素。我们的模型还表明，尽管性别间的传播很重要，但并不对称，感染的雄性在感染未感染的雌性方面起着重要作用，但反之则不然。总的来说，这项工作表明将种群动态模型与长期现场数据相结合的方法可以阐明在野生疾病系统中否则无法观察到的传播过程。
