Fatal leptospirosis in free-ranging Eurasian beavers (Castor fiber L.), Switzerland

Leptospirosis was first diagnosed in free-ranging Eurasian beavers (Castor fiber L.) in Switzerland in 2010. Pathologic, serologic, molecular and epidemiologic analyses were carried out on 13 animals submitted for necropsy from 2010 through 2014. Typical lesions included alveolar haemorrhages in the lungs, tubular degeneration and interstitial nephritis in the kidneys. Microscopic agglutination test results were positive for serogroups Icterohaemorrhagiae, Australis, Autumnalis and Sejroe. Molecular analysis identified four distinct profiles belonging to serovar Icterohaemorrhagiae or Copenhageni. The severity and features of the lesions were consistent with a fatal disease associated with leptospires similarly to what has been reported in other animals and humans. The spatiotemporal occurrence of leptospirosis in beavers suggested an upstream spread of the bacteria and coincided with an increased incidence of leptospirosis in dogs and a case cluster in humans. However, an epidemiologic link among beaver cases and among species was not supported neither by the serologic nor molecular data.