Experimental infection of dusky-footed wood rats (Neotoma fuscipes) with Ehrlichia phagocytophila sensu lato.

Dusky-footed wood rats, Neotoma fuscipes, have bean implicated in the natural maintenance of Ehrlichia phagocytophila sensu lato, the agent of human granulocytic chrlichiosis (HGE), in northern California based on high seroprevalence and amplification of E. phagocytophila s.l. DNA from wood rat blood. In order to further assess granulocytic chrlichiosis in wood rats, we examined wild-caught wood rats for infection and then performed experimental intra-peritoneal infections with E. phagocytophila s.l. in horse or wood rat blood. and tested animals for 120 davs by polymerase chain reaction (PCR) and serology. Of 15 wood rats collected from northern California, three were antibody and PCR-positive for E. phagocytophila s.l. at the time of capture. The naturally infected wood rats remained PCR-positive for a mean of 52 days (+/-SD). Experimental IP passage of E. phagocytophila s.l. in wood rat blood was successful in three of four wood rats and the mean duration of PCR-positivie was 75 davs (+/-21.2 SD). Experimental infection with E. phagocytophila s.l. in horse blood succeeded in all four of the recipients and the mean duration of PCR-positivity of 81 davs (+/-17.5 SD). No infected individual appeared to be ill based on feeding behavior, activity, and hydration status. These data confirm that wood rats are susceptible to E. phagocytophila s.l., may develop prolonged infection without clinical ehrlichiosis, and may play a role in maintaining E. phagocytophila s.l. in nature.