Patchy Occurrence of Cowpox Virus in Voles from Germany

Cowpox virus (CPXV), genus Orthopoxvirus, family Poxviridae, is a zoonotic pathogen in Eurasian wild rodents. High seroprevalences have been reported previously for vole and murine species in Europe. In contrast, viral DNA was only rarely detected, and very few reservoir-derived CPXV isolates exist. In this study, CPXV DNA and CPXV-reactive antibodies were monitored in wild small mammals for 5 years in four German federal states. Screening of liver tissues of 3966 animals by CPXV real-time PCR (qPCR) revealed five voles of two species positive for CPXV DNA. Two positive bank voles (Myodes glareolus) and two positive common voles (Microtus arvalis) originated from two plots in Baden-Wuerttemberg. One positive bank vole originated from Mecklenburg-Western Pomerania. None of the small mammals from Thuringia and North Rhine-Westphalia was positive in the qPCR. CPXV antigen-based indirect immunofluorescence assays of 654 highly diluted chest cavity fluid samples detected two bank voles and two common voles from the same sites in Baden-Wuerttemberg to be highly seroreactive. Five animals were CPXV DNA positive, and four other animals were orthopoxvirus seropositive. Our study indicates both a very low prevalence and a patchy occurrence of CPXV in common and bank voles and absence in other rodent and shrew species in Germany. The multiple detection of infected voles at one site in Baden-Wuerttemberg and continued detection in a region of Mecklenburg-Western Pomerania classify these regions as potential endemic foci. Cowpox virus (CPXV), family Poxviridae, genus Orthopoxvirus, is a reemerging zoonotic pathogen in Europe (Essbauer et al. 2010). CPXV has a broad host range in Western Eurasia, for example, cats, pet and farm animals, and various zoo animals representing accidental hosts (Essbauer et al. 2010). The transmission to humans is mainly mediated by contact to infected cats, wild rodents, or pet rats (Essbauer et al. 2010, Hoffmann et al. 2015). Contaminated fomites might play an eminent role in the transmission of CPXV and could serve as infectious source for human infection (Andreani et al. 2019). Serological and molecular surveys in Eurasian regions confirmed that various rodent species may act as natural reservoirs for CPXV (Essbauer et al. 2010). Despite high orthopoxvirus seroprevalence rates in wild rodents, molecular detection and isolation of CPXV are rarely reported (Martina et al. 2006, Kinnunen et al. 2011, Franke et al. 2017, Prkno et al. 2017). Previous investigations in Germany indicated orthopoxvirus-reactive antibodies in bank voles (Myodes glareolus) and the striped field mouse (Apodemus agrarius) and resulted in the molecular detection of CPXV in bank voles, common voles (Microtus arvalis), and Norway rats (Rattus norvegicus) (Kurth et al. 2008, Kinnunen et al. 2011, Franke et al. 2017). Here, we evaluated small mammals from Germany for the presence of CPXV DNA and orthopoxvirus-reactive antibodies. During 2010–2014, 4023 small mammals including 3306 rodents, 714 shrews, 2 least weasels (Mustela nivalis), and 1 European mole (Talpa europaea) were collected at four sites (Fischer et al. 2018; Fig. 1 and Table 1). Locations represented different geographic regions, with Mecklenburg-Western Pomerania and North Rhine-Westphalia exhibiting a more maritime climate and Baden-Wuerttemberg and Thuringia a more continental one. A mosaic of forest fragments within an agriculturally dominated landscape characterized all locations. Trapping sites were established in forests and grasslands (Fig. 1) to ensure that a broad spectrum of species, representative of the respective area, was caught.