Higher biodiversity leads to reduced risk of infection

– When one species is allowed to become dominant, the incidence of infection increases. If there is competition between species, it drops, explains Hussein Khalil. He is the main author of the study, which has been published in Scientific Reports.

The research team, made up of ecology researchers from SLU Umeå and a virologist from Umeå University, have studied the link between biodiversity and the incidence of the Puumala virus, which can cause epidemic nephropathy in humans. The study was conducted in Sweden.

The virus is transmitted to humans by bank voles when voles carrying the virus get into houses and outbuildings.

Since the 1970s, SLU has caught and collected small rodents through the national environmental monitoring of small rodents. In this samples bank, researchers have now been able to analyse the presence of infected bank voles and relate this to the presence of competing species and predators. Results from the monitoring show that bank voles have become increasingly dominant in the forest ecosystem, as important competitors such as field voles and the grey-sided vole have dropped in numbers. In addition, parallel studies show that the number of Tengmalm's owls, the main predator of bank voles, has also dropped.

– It is obvious that both the share and the total number of infected bank voles has increased in line with the reduced numbers of Tengmalm's owls and competitors such as grey-sided vole and field voles, says Hussein Khalil.

Researchers have also noted that the presence of common shrews is an important factor affecting the number of infected voles. Shrews attack bank voles in their nests, which has an inhibitory effect on the movement patterns of voles and the spread of the virus.

Outbreaks of epidemic nephropathy are relatively common in northern Sweden, and more so in the last few years. In addition to taking precautions related to buildings in order to protect against contamination, the research team has some other suggestions for actions that may reduce the number of infected voles.

– Putting up nest boxes for Tengmalm's owls may be a good way to help. Conventionally managed forests offer few natural cavities for nesting, explains Birger Hörnfeldt, who has long been working on monitoring small rodents and their predators.

– We also suspect that it is not a good idea to have relatively young, single-species forests close to human dwellings. Competitors such as grey-sided vole prefer multi-story forests, and field voles prefer open spaces such as clearcuts. We will be looking closer at the importance of forest structure in a future study, adds Hussein Khalil.

The study was published in Scientific Reports . Authors are Hussein Khalil, Frauke Ecke, Magnus Evander, Magnus Magnusson and Birger Hörnfeldt. All except Magnus Evander are from the Department of Wildlife, Fish, and Environmental Studies at SLU. Magnus Evander is a professor at the Department of Clinical Microbiology, Umeå University.