SEROLOGIC EVIDENCE OF INFECTION WITH EHRLICHIA SPP. IN WILD RODENTS (MURIDAE, SIGMODONTINAE) IN THE UNITED-STATES

Rodent (Muridae: Sigmodontinae) blood and sera collected from 14 state s were tested for seroreactivity to a cultured isolate of the human gr anulocytic ehrlichiosis (HGE) agent by using an indirect immunofluores cence assay, Of the 1,240 samples tested, 136 (11%) were found to be r eactive at titers of greater than or equal to 32. Rodents with HGE age nt-specific antibodies were found in Nem York (23% of 491 samples; geo metric mean endpoint titer [GMT] = 441), Connecticut (11% of 100 sampl es; GMT = 481), California (9% of 32 samples; GMT = 323), Colorado (2% of 212 samples; GMT = 256), Florida (7% of 27 samples; GMT = 362), Ma ryland (7% of 15 samples; titer = 64), New Jersey (4% of 76 samples; t iter = 256), and Wisconsin (13% of 8 samples;titer = 128). Samples fro m Georgia (n = 16), Illinois (n = 27), Nevada (n = 27), North Carolina (n = 52), Ohio (n = 57), and Utah (n = 100) were not reactive. The ea rliest seroreactive sample was from a Peromyscus leucopus mouse collec ted in June 1986 in Connecticut, and the majority of the seroreactive samples (68%) were from this species. Samples from other Peromyscus sp ecies (P. boylii, P. maniculatus, and P. gossypinus) were also found t o be reactive, with a GMT for the genus of 410. Several species of Neo toma woodrats (N. fuscipes, N. lepida, N. albigula, and N. mexicana) f rom California and Colorado had antibodies that reacted with the HGE a gent (genus GMT = 194), suggesting that enzootic cycles of Ehrlichia s pp, exist outside of the areas of confirmed human disease, Attempts to amplify and detect ehrlichial DNA from the limited tissues available (n = 40 animals) were unsuccessful. Further studies are needed to dete rmine the identity of the organisms inducing antibody production in th ese rodent species and to elucidate the epidemiology and public health importance of these agents.