Relating increasing hantavirus incidences to the changing climate: the mast connection

Jan Clement,Piet Maes,Geneviève Ducoffre,Marc Van Ranst,Jurgen Vercauteren,Anne-Mieke Vandamme,Willem W Verstraeten,José M Barrios

doi:10.1186/1476-072x-8-1

Abstract

BackgroundNephropathia epidemica (NE), an emerging rodent-borne viral disease, has become the most important cause of infectious acute renal failure in Belgium, with sharp increases in incidence occurring for more than a decade. Bank voles are the rodent reservoir of the responsible hantavirus and are known to display cyclic population peaks. We tried to relate these peaks to the cyclic NE outbreaks observed since 1993. Our hypothesis was that the ecological causal connection was the staple food source for voles, being seeds of deciduous broad-leaf trees, commonly called "mast". We also examined whether past temperature and precipitation preceding "mast years" were statistically linked to these NE outbreaks.ResultsSince 1993, each NE peak is immediately preceded by a mast year, resulting in significantly higher NE case numbers during these peaks (Spearman R = -0.82; P = 0.034). NE peaks are significantly related to warmer autumns the year before (R = 0.51; P < 0.001), hotter summers two years before (R = 0.32; P < 0.001), but also to colder (R = -0.25; P < 0.01) and more moist summers (R = 0.39; P < 0.001) three years before. Summer correlations were even more pronounced, when only July was singled out as the most representative summer month.ConclusionNE peaks in year 0 are induced by abundant mast formation in year-1, facilitating bank vole survival during winter, thus putting the local human population at risk from the spring onwards of year 0. This bank vole survival is further promoted by higher autumn temperatures in year-1, whereas mast formation itself is primed by higher summer temperatures in year-2. Both summer and autumn temperatures have been rising to significantly higher levels during recent years, explaining the virtually continuous epidemic state since 2005 of a zoonosis, considered rare until recently. Moreover, in 2007 a NE peak and an abundant mast formation occurred for the first time within the same year, thus forecasting yet another record NE incidence for 2008. We therefore predict that with the anticipated climate changes due to global warming, NE might become a highly endemic disease in Belgium and surrounding countries.

Highlights

Nephropathia epidemica (NE), an emerging rodent-borne viral disease, has become the most important cause of infectious acute renal failure in Belgium, with sharp increases in incidence occurring for more than a decade
Hantaviruses are worldwide emerging hemorrhagic fever viruses which are transmitted to humans via aerosolized excreta of chronically infected rodents, the main reservoir in nature
In Europe and Russia, the most important hantavirus is Puumala virus (PUUV), which is spread by a common wild rodent, the bank vole (Myodes glareolus) [13]

Summary

Introduction

Nephropathia epidemica (NE), an emerging rodent-borne viral disease, has become the most important cause of infectious acute renal failure in Belgium, with sharp increases in incidence occurring for more than a decade. Bank voles are the rodent reservoir of the responsible hantavirus and are known to display cyclic population peaks. In Europe and Russia, the most important hantavirus is Puumala virus (PUUV), which is spread by a common wild rodent, the bank vole (Myodes glareolus) [13]. PUUV infection causes nephropathia epidemica (NE), a mild form of hemorrhagic fever with renal syndrome (HFRS), the general denomination of hantavirus disease in the rest of the Old World [1,2,3]. The preferred habitats of Myodes glareolus are temperate deciduous broad leaf forhttp://www.ij-healthgeographics.com/content/8/1/1 ests that can be mixed with pine trees. This vole species is common in boreal forests or taiga.

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