Landscape and climatic characteristics associated with human alveolar echinococcosis in France, 1982 to 2007

M Piarroux,A Gerard,J Knapp,J Beytout,Collective The Francechino Network,J Dumortier,R Piarroux,M Wallon,B Faucher,A Abergel,S Bresson-Hadni,K Bardonnet,F Grenouillet,D A Vuitton,J Gaudart,J Watelet

doi:10.2807/1560-7917.es2015.20.18.21118

Abstract

Human alveolar echinococcosis (AE) is a severe hepatic disease caused by Echinococcus multilocularis. In France, the definitive and intermediate hosts of E. multilocularis (foxes and rodents, respectively) have a broader geographical distribution than that of human AE. In this two-part study, we describe the link between AE incidence in France between 1982 and 2007 and climatic and landscape characteristics. National-level analysis demonstrated a dramatic increase in AE risk in areas with very cold winters and high annual rainfall levels. Notably, 52% (207/401) of cases resided in French communes (smallest French administrative level) with a mountain climate. The mountain climate communes displayed a 133-fold (95% CI: 95-191) increase in AE risk compared with communes in which the majority of the population resides. A case-control study performed in the most affected areas confirmed the link between AE risk and climatic factors. This arm of the study also revealed that populations residing in forest or pasture areas were at high risk of developing AE. We therefore hypothesised that snow-covered ground may facilitate predators to track their prey, thus increasing E. multilocularis biomass in foxes. Such climatic and landscape conditions could lead to an increased risk of developing AE among humans residing in nearby areas.

Highlights

Echinococcus multilocularis is a cestode parasite that exhibits a dixenic life cycle involving circulation between canids and rodents
Humans represent an aberrant host of the parasite, they sometimes become infected with E. multilocularis larvae after ingesting parasite oncospheres
When E. multilocularis infects humans, E. multilocularis metacestode cells proliferate in the liver and eventually lead to alveolar echinococcosis (AE), a rare but severe hepatic disease resembling a slow-growing liver cancer [1]

Summary

Introduction

Echinococcus multilocularis is a cestode parasite that exhibits a dixenic life cycle involving circulation between canids and rodents. E. multilocularis sylvatic life cycle involves foxes (the main definitive host) and rodents such as Arvicola terrestris, Microtus arvalis, M. agrestis or Ondatra zibethicus (the main intermediate hosts). A study by the EurEchinoReg network showed that 235 of 559 (42%) European AE cases reported from 1982 to 2000 were observed in France [2]. Since 2000, the French registry of human AE cases has been maintained by the FrancEchino network. In France, for this period, high-risk areas included the Massif Central and north-eastern regions of the country (Figure 1), where most cases either resided in rural communes (smallest French administrative level) or resided in towns but worked as farmers or tended gardens [3]

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