Persistent infection in Neotoma fuscipes (Muridae : Sigmodontinae) with Ehrlichia phagocytophila sensu lato

Dusky-footed wood rats (Neotoma fuscipes Baird) and two species of Peromysc us mice (P. maniculatus Wagner and P. truci Shufeldt) were collected over a 16-month period from three sites in Sonoma County, California. Blood was c ollected from 93 wood rats and 177 mice and serum or plasma was tested for seroreactivity with Ehrlichia phagocytophila sensu lato (also known as the human granulocytic ehrlichiosis agent). Thirty-five (37.6%) wood rats and 1 5 (8.5%) mice were seropositive. Positive Neotoma serology by site ranged f rom 9.4% to 62.1%. Polymerase chain reaction (PCR) testing for the Ehrlichi a groESL heat shock operon was performed on all the seropositive and select ed seronegative wood rats; 24 (68.6%) seropositive animals were PCR positiv e. Two seroconversions and no seroreversions were detected among 18 of the seropositive wood rats that were recaptured and tested Multiple times (rang e = 2-6). Fourteen (77.8%) of the 18 were also PCR positive with six of the se positive at every testing point (range = 2-6). One wood rat remained ser ologically and PCR positive in six specimens collected over a 14-month peri od. One male of 84 questing adult Ixodes pacificus Cooley & Kohls collected was PCR-positive for E. phagocytophila. Borrelia burgdorferi, the agent of Lyme disease, was cultured from car punch biopsies from six of seven E. ph agocytophila seropositive and one of four seronegative wood rats.