Prevalence of Yersinia pestis in rodents and fleas associated with black-tailed prairie dogs ( Cynomys ludovicianus ) at Thunder Basin National Grassland, Wyoming
Rodents (and their fleas) that are associated with prairie dogs are considered important for the maintenance and transmission of the bacterium ( Yersinia pestis ) that causes plague. Our goal was to identify rodent and flea species that were potentially involved in a plague epizootic in black-tailed prairie dogs at Thunder Basin National Grassland. We collected blood samples and ectoparasites from rodents trapped at off- and on-colony grids at Thunder Basin National Grassland between 2002 and 2004. Blood samples were tested for antibodies to Y. pestis F-1 antigen by a passive hemagglutination assay, and fleas were tested by a multiplex polymerase chain reaction, for the presence of the plague bacterium. Only one of 1,421 fleas, an Oropsylla hirsuta collected in 2002 from a deer mouse, Peromyscus maniculatus , tested positive for Y. pestis . Blood samples collected in summer 2004 from two northern grasshopper mice, Onychomys leucogaster , tested positive for Y. pestis antibodies. All three positive samples were collected from on-colony grids shortly after a plague epizootic occurred. This study confirms that plague is difficult to detect in rodents and fleas associated with prairie dog colonies, unless samples are collected immediately after a prairie dog die-off.