It is the Swedish University of Agricultural Sciences and Umeå University that have studied why the number of sork fever cases can vary greatly between the winters in Sweden.
One explanation for increased cases is how many forest vultures there are, but that is not the only explanation.
- We saw that the more precipitation that fell as rain during the months of November, the greater the degree of infection in forest voles, says Saana Sipari, postdoctoral fellow at the Department of Game, Fish and Environment at SLU in Umeå.
Heavy rain during the middle of winter (December – March) had no effect on the degree of infection in the voles.
The period before there is a protective snow cover, often November, therefore seems to be most sensitive to the spread of infection.
"Crowded in small spaces"
But there are several aspects that cause the virus to spread among the voles, including the so-called rain-on-snow events with ice bark formation as a result probably lead to forest voles being crowded in small areas of land and that the virus thrives better in such an environment.
- Many studies predict an increased risk of outbreaks of animal diseases in a future and increasingly warmer climate, especially in northern regions.
However, our study shows that this has actually already happened, says Frauke Ecke, senior lecturer at SLU in Umeå.