DETECTION OF EHRLICHIA-RISTICII, THE AGENT OF POTOMAC HORSE FEVER, INFRESH-WATER STREAM SNAILS (PLEUROCERIDAE, JUGA SPP.) FROM NORTHERN CALIFORNIA

Ehrlichia DNA was identified by nested PCR in operculate snails (Pleur oceridae: Juga spp.) collected from stream mater in a northern Califor nia pasture in which Potomac horse fever (PHF) is enzootic. Sequencing of PCR-amplified DNA from a suite of genes (the 16S rRNA, groESL heat shock operon, 51-kDa major antigen genes) indicated that the source o rganism closely resembled Ehrlichia risticii, the causative agent of P RF. The minimum percentage of Juga spp. harboring the organism in the population studied was 3.5% (2 of 57 snails). No ehrlichia DNA was fou nd in tissues of 123 lymnaeid, physid, and planorbid snails collected at the same site. These data suggest that pleurocerid stream snails ma y play a role in the life cycle of E. risticii in northern California.