Beech Fructification and Bank Vole Population Dynamics - Combined Analyses of Promoters of Human Puumala Virus Infections in Germany

Abstract

The transmission of wildlife zoonoses to humans depends, amongst others, on complex interactions of host population ecology and pathogen dynamics within host populations. In Europe, the Puumala virus (PUUV) causes nephropathia epidemica in humans. In this study we investigated complex interrelations within the epidemic system of PUUV and its rodent host, the bank vole (Myodes glareolus). We suggest that beech fructification and bank vole abundance are both decisive factors affecting human PUUV infections. While rodent host dynamics are expected to be directly linked to human PUUV infections, beech fructification is a rather indirect predictor by serving as food source for PUUV rodent hosts. Furthermore, we examined the dependence of bank vole abundance on beech fructification. We analysed a 12-year (2001-2012) time series of the parameters: beech fructification (as food resource for the PUUV host), bank vole abundance and human incidences from 7 Federal States of Germany. For the first time, we could show the direct interrelation between these three parameters involved in human PUUV epidemics and we were able to demonstrate on a large scale that human PUUV infections are highly correlated with bank vole abundance in the present year, as well as beech fructification in the previous year. By using beech fructification and bank vole abundance as predictors in one model we significantly improved the degree of explanation of human PUUV incidence. Federal State was included as random factor because human PUUV incidence varies considerably among states. Surprisingly, the effect of rodent abundance on human PUUV infections is less strong compared to the indirect effect of beech fructification. Our findings are useful to facilitate the development of predictive models for host population dynamics and the related PUUV infection risk for humans and can be used for plant protection and human health protection purposes.

Heterogeneous Puumala orthohantavirus situation in endemic regions in Germany in summer 2019

“…Beech fructification intensity was estimated between July and August 2018 as the percentage of fruiting beech trees older than 49 years, classified in absent, scarce, common and abundant fructification. Beech fructification is assessed annually by State Forest Authorities and reported as a mean value for each Federal State (Reil et al, ).…”

“…Puumala orthohantavirus (PUUV) is the most relevant hantavirus in Europe: It causes the majority of human hantavirus disease cases in Europe and is distributed in several parts of the continent. The number of human cases in Fennoscandia, Belgium, France and Germany oscillates among outbreak and non‐outbreak years (Ettinger et al, ; Heyman, Ceianu, Christova, Tordo, & Vaheri, ; Olsson, Leirs, & Henttonen, ; Reil, Imholt, Eccard, & Jacob, ; Reil et al, ). Human PUUV infections lead to a mild to moderate course of symptoms called nephropathia epidemica (NE) characterized by an acute onset of high fever, headache, myalgias, gastrointestinal symptoms and thrombocytopenia (Latus et al, ).…”

Spatial and Temporal Epidemiology of Nephropathia Epidemica Incidence and Hantavirus Seroprevalence in Rodent Hosts: Identification of the Main Environmental Factors in Europe

“…Three studies (Piechotowski et al., ; Schwarz et al., ; Zeimes et al., ) reported a positive association with NE incidence; no association was found in the study of Reil et al. (). However, selecting a single plant species among all those consumed by bank voles hinders the identification of the underlying causes of the observed association (food‐versus‐shelter effect) (Schwarz et al., ; Zeimes et al., ).…”

“…Finally, to quantify food availability, a few authors estimated directly the ‘mast production’, that is the quantity of seeds produced by beech ( F. sylvatica ) or/and oak ( Quercus robur and Q. petraea ). A positive association was systematically found between NE incidence and mast production estimated from the year before (Clement et al., ; Haredasht et al., , ; Piechotowski et al., ; Reil et al., ,b; Schwarz et al., ; Tersago et al., ). This indicator reflects only food availability regardless of shelter, but, again, does not take into account the entire rodent diet.…”

“…As for host seroprevalence, indirect measures of single plant species were used to estimate the importance of food availability in connection to NE incidence: per cent of area covered by beech (Piechotowski et al., ; Reil et al., Schwarz et al., ) or by spruce ( Picea abies ) (Zeimes et al., ; ). Three studies (Piechotowski et al., ; Schwarz et al., ; Zeimes et al., ) reported a positive association with NE incidence; no association was found in the study of Reil et al.…”