Background: The emergence of important viral diseases and their potential threat to humans has increased the interest in bats as potential reservoir species. Whereas the majority of studies determined the occurrence of specific zoonotic agents in chiropteran species, little is known about actual bat pathogens and impacts of disease on bat mortality. Combined pathological and microbiological investigations in free-ranging bats are sparse and often limited by small sample sizes. In the present study about 500 deceased bats of 19 European species (family Vespertilionidae) were subjected to a post-mortem examination followed by histo-pathological and bacteriological investigations. The bat carcasses originated from different geographical regions in Germany and were collected by bat researchers and bat rehabilitation centers.
Results: Pathological examination revealed inflammatory lesions in more than half of the investigated bats. Lung was the predominantly affected organ (40%) irrespective of bat species, sex and age. To a lesser extent non-inflammatory organ tissue changes were observed. Comparative analysis of histo-pathology and bacteriology results identified 22 different bacterial species that were clearly associated with pathological lesions. Besides disease-related mortality, traumatic injuries represented an additional major cause of death. Here, attacks by domestic cats accounted for almost a half of these cases.
Conclusions: The present study shows that free-ranging bats not only serve as a reservoir of infectious agents, they are also vulnerable to various infectious diseases. Some of these microbial agents have zoonotic potential, but there is no evidence that European bats would pose a higher health hazard risk to humans in comparison to other wildlife.