Survey for zoonotic pathogens in Norway rat populations from Europe

BACKGROUND The Norway rat Rattus norvegicus is an important reservoir of various zoonotic pathogens, such as cowpox virus and Leptospira, but also for agents of no or unknown zoonotic potential. We describe a survey of 426 Norway rats originating from five European countries and different habitats for Leptospira spp., rickettsiae, orthopox virus (OPV), avian metapneumovirus subtype A and B (aMPV), and rat polyomavirus (rat PyV). RESULTS Leptospira DNA was detected in 60 of 420 (14.3%) rats and Rickettsia DNA was found in three of 369 (0.8%) rats investigated. PCR-based typing resulted in the identification of L. interrogans sequence type 17, serogroup Icterohaemorrhagiae, and Rickettsia helvetica, respectively. Rat PyV DNA was detected in 103 of 421 (24.5%) rats. OPV DNA and aMPV RNA were detected in none of the rats, but OPV-specific antibodies in three of 388 (0.8%) rats. The frequency of single Leptospira and rat PyV infections and co-infections was, independent of sex, greater for adults compared to juveniles/subadults and greater at rural sites compared to urban areas. CONCLUSIONS Study results indicate a broad geographical distribution of Leptospira DNA in rats within Europe underlining the need to further investigate potential mechanisms leading to increased prevalence in rural habitats and to assess the relevance to public health. In contrast, rickettsia and OPV infections rarely occurred in wild rat populations. The potential influence of rat PyV on the susceptibility to infections with other pathogens should be investigated in future studies.