Linard Catherine, Tersago Katrien, Leirs Herwig, Lambin Eric F
Department of Geography, Université Catholique de Louvain, Place Pasteur 3, B-1348 Louvain-la-Neuve, Belgium.
Int J Health Geogr. 2007 Dec 14;6:55. doi: 10.1186/1476-072X-6-55.
Non-vector-borne zoonoses such as Puumala hantavirus (PUUV) can be transmitted directly, by physical contact between infected and susceptible hosts, or indirectly, with the environment as an intermediate. The objective of this study is to better understand the causal link between environmental features and PUUV prevalence in bank vole population in Belgium, and hence with transmission risk to humans. Our hypothesis was that environmental conditions controlling the direct and indirect transmission paths differ, such that the risk of transmission to humans is not only determined by host abundance. We explored the relationship between, on one hand, environmental variables and, on the other hand, host abundance, PUUV prevalence in the host, and human cases of nephropathia epidemica (NE). Statistical analyses were carried out on 17 field sites situated in Belgian broadleaf forests.
Linear regressions showed that landscape attributes, particularly landscape configuration, influence the abundance of hosts in broadleaf forests. Based on logistic regressions, we show that PUUV prevalence among bank voles is more linked to variables favouring the survival of the virus in the environment, and thus the indirect transmission: low winter temperatures are strongly linked to prevalence among bank voles, and high soil moisture is linked to the number of NE cases among humans. The transmission risk to humans therefore depends on the efficiency of the indirect transmission path. Human risk behaviours, such as the propensity for people to go in forest areas that best support the virus, also influence the number of human cases.
The transmission risk to humans of non-vector-borne zoonoses such as PUUV depends on a combination of various environmental factors. To understand the complex causal pathways between the environment and disease risk, one should distinguish between environmental factors related to the abundance of hosts such as land-surface attributes, landscape configuration, and climate - i.e., host ecology, - and environmental factors related to PUUV prevalence, mainly winter temperatures and soil moisture - i.e., virus ecology. Beyond a threshold abundance of hosts, environmental factors favouring the indirect transmission path (soil and climate) can better predict the number of NE cases among humans than factors influencing the abundance of hosts.
诸如普马拉汉坦病毒（PUUV）之类的非媒介传播人畜共患病可以通过受感染宿主与易感宿主之间的直接身体接触直接传播，也可以通过以环境为媒介间接传播。本研究的目的是更好地理解比利时林姬鼠种群中环境特征与PUUV流行率之间的因果关系，进而理解其对人类的传播风险。我们的假设是，控制直接和间接传播途径的环境条件不同，因此向人类的传播风险不仅取决于宿主数量。我们一方面探讨了环境变量与另一方面宿主数量、宿主中PUUV流行率以及人类流行性肾病（NE）病例之间的关系。对位于比利时阔叶林的17个野外地点进行了统计分析。
线性回归表明，景观属性，特别是景观格局，会影响阔叶林中宿主的数量。基于逻辑回归，我们表明，林姬鼠中PUUV的流行率与有利于病毒在环境中存活的变量，即间接传播，更相关：冬季低温与林姬鼠中的流行率密切相关，而高土壤湿度与人类NE病例数相关。因此，对人类的传播风险取决于间接传播途径的效率。人类的风险行为，例如人们前往最有利于病毒生存的林区的倾向，也会影响人类病例数。
诸如PUUV之类的非媒介传播人畜共患病对人类的传播风险取决于多种环境因素的综合作用。为了理解环境与疾病风险之间复杂的因果途径，应该区分与宿主数量相关的环境因素，如地表属性、景观格局和气候，即宿主生态学，以及与PUUV流行率相关的环境因素，主要是冬季温度和土壤湿度，即病毒生态学。超过宿主数量的阈值后，有利于间接传播途径（土壤和气候）的环境因素比影响宿主数量的因素能更好地预测人类NE病例数。
