Water vole (Arvicola terrestris Scherman) density as risk factor for humanalveolar echinococcosis

Concern is growing in Europe about alveolar echinococcosis (AE) with the in crease in grassland rodent and red fox populations, intermediate and defini tive hosts for Echinococcus multilocularis, respectively. The objective of this study was to assess the influence of rodent densities on human AE dist ribution. Spatial Poisson regression analyses were performed with geomorpho logic features, landscape composition, climatic characteristics, and water vole density as independent variables. The outcome consisted of AE cases di agnosed over the period 1980-1992. High vole density yielded a 10-fold risk (relative risk [RR] = 10.34, 95% confidence interval [CI] = 2.78-38.39), a nd the first plateau (400-700 m altitude) compared with the plain (200-400 m) was associated with a large increase in risk (RR = 7.10, 95% CI = 1.30-3 8.63). These results confirm that human AE is strongly influenced by the de nsities of arvicolid species. Foxes feeding almost exclusively on grassland rodents when the latter expand could mediate this relation.