Muskrats as carriers of pathogenic leptospires in The Netherlands.

Leptospires were isolated from 24 of 327 (7%) muskrats (Ondatra zibethicus) caught in The Netherlands. All isolates were identified as Leptospira interrogans. One isolate was typed as serovar copenhageni in the Icterohaemorrhagiae serogroup, one as serovar lora in the Australis serogroup. Twenty-one isolates showed a close relationship with serovars grippotyphosa, valbuzzi, muelleri and ratnapura from the Grippotyphosa serogroup. One isolate was lost. Sera from 196 muskrats were examined by the microscopic agglutination test. Forty-five (23%) sera reacted positively (titers greater than or equal to 1:160), 42 (21%) of these 45 sera to Grippotyphosa and 3 (2%) to Sejroe serogroup antigens. This is the first report of serological and cultural evidence of leptospira infection in muskrats in The Netherlands.