Cui Jing-An, Chen Fangyuan, Fan Shengjie
School of Science, Beijing University of Civil Engineering and Architecture , Beijing, China .
Vector Borne Zoonotic Dis. 2017 Aug;17(8):599-609. doi: 10.1089/vbz.2016.2059. Epub 2017 Jul 5.
Most emerging zoonotic pathogens originate from animals. They can directly infect humans through natural reservoirs or indirectly through intermediate hosts. As a bridge, an intermediate host plays different roles in the transmission of zoonotic pathogens. In this study, we present three types of pathogen transmission to evaluate the effect of intermediate hosts on emerging zoonotic diseases in human epidemics. These types are identified as follows: TYPE 1, pathogen transmission without an intermediate host for comparison; TYPE 2, pathogen transmission with an intermediate host as an amplifier; and TYPE 3, pathogen transmission with an intermediate host as a vessel for genetic variation. In addition, we established three mathematical models to elucidate the mechanisms underlying zoonotic disease transmission according to these three types. Stability analysis indicated that the existence of intermediate hosts increased the difficulty of controlling zoonotic diseases because of more difficult conditions to satisfy for the disease to die out. The human epidemic would die out under the following conditions: TYPE 1: [Formula: see text] and [Formula: see text]; TYPE 2: [Formula: see text], [Formula: see text], and [Formula: see text]; and TYPE 3: [Formula: see text], [Formula: see text], [Formula: see text], and [Formula: see text] Simulation with similar parameters demonstrated that intermediate hosts could change the peak time and number of infected humans during a human epidemic; intermediate hosts also exerted different effects on controlling the prevalence of a human epidemic with natural reservoirs in different periods, which is important in addressing problems in public health. Monitoring and controlling the number of natural reservoirs and intermediate hosts at the right time would successfully manage and prevent the prevalence of emerging zoonoses in humans.
大多数新出现的人畜共患病原体都来自动物。它们可以通过自然宿主直接感染人类，也可以通过中间宿主间接感染人类。作为桥梁，中间宿主在人畜共患病原体的传播中发挥着不同的作用。在本研究中，我们提出了三种病原体传播类型，以评估中间宿主对人类流行病中新出现的人畜共患病的影响。这些类型如下：类型1，无中间宿主的病原体传播作为对照；类型2，以中间宿主作为放大器的病原体传播；类型3，以中间宿主作为基因变异载体的病原体传播。此外，我们根据这三种类型建立了三个数学模型，以阐明人畜共患病传播的潜在机制。稳定性分析表明，中间宿主的存在增加了控制人畜共患病的难度，因为疾病消亡需要满足更苛刻的条件。在以下条件下人类流行病将会消亡：类型1：[公式：见原文]和[公式：见原文]；类型2：[公式：见原文]、[公式：见原文]和[公式：见原文]；类型3：[公式：见原文]、[公式：见原文]、[公式：见原文]和[公式：见原文]。用相似参数进行的模拟表明，中间宿主可以改变人类流行病期间感染人类的峰值时间和数量；中间宿主在不同时期对控制有自然宿主的人类流行病的流行也有不同影响，这在解决公共卫生问题方面很重要。适时监测和控制自然宿主和中间宿主的数量将成功管理和预防新出现的人畜共患病在人类中的流行。
