Infectious Diseases in European Brown Hares (Lepus europaeus) Found Dead or Moribund in the Netherlands

Information on pathogens, including zoonotic agents, in European brown hares (Lepus europaeus) in the Netherlands is lacking. In this paper, we provide an overview of the most common pathogens found in hares in the Netherlands. Specifically, we assessed whether land use and climatic factors influence the occurrence of a frequently detected pathogen in hares, that is, Yersinia spp., and determined whether there are changes in the occurrence of pathogens in hares between the periods 1966-77 and 2009-21. Postmortem examinations were available for 513 hares from 2009 to 2021 and for 757 hares from 1966 to 1977. Descriptive analysis was performed on these data, assessing hare metadata, pathology, reasons for submission, land use surrounding the location of recovery, and seasonality. A logistic mixed modeling approach was used to identify predictors for the presence of Yersinia spp. In both periods, hares were identified as competent hosts for several pathogens, including zoonotic agents. Yersinia spp. was the most frequently identified pathogen (recent period, 12.1%; historic period, 25.1%). Between 2009 and 2021, Yersinia spp. presence was positively associated with the proportion of agricultural land use and negatively associated with the mean daily minimum temperature. The results presented herein provide a better understanding of pathogens circulating in free-ranging hares in the Netherlands and are relevant to hare health and public health and for wildlife managers and future surveillance strategies. Furthermore, the results emphasize the inherent difficulties associated with retrospective analyses of these types of data.