Oral infection of Peromyscus maniculatus with Borrelia burgdorferi and subsequent transmission by Ixodes dammini.

We determined if deer mice (Peromyscus maniculatus) could be infected by Borrelia burgdorferi and develop sufficient spirochetemia to infect larval Ixodes dammini. Ten P. maniculatus were infected orally with 0.05 ml phosphate buffered saline containing approximately 400 B. burgdorferi. On days 21 or 28 after infection (AI) larval I. dammini were fed on the deer mice. Each of the P. maniculatus developed antibodies (up to 7 log2) to B. burgdorferi and B. burgdorferi was isolated from the blood of 1 deer mouse on day 51 AI. Nymphs resulting from these larvae were then allowed to feed on 10 uninfected P. maniculatus. All 10 of these tick-infected P. maniculatus developed antibodies (up to 7 log2) to B. burgdorferi, and B. burgdorferi was isolated from the blood of 1 of the 10 P. maniculatus 15 days after tick feeding and from the pooled organs of another of the tick-infected P. maniculatus. Six of the orally infected P. maniculatus developed clinical signs including ruffled hair coat, inappetence, reluctance to move, and lameness in the rear legs. All P. maniculatus tissues were grossly and histologically normal on necropsy. These findings show that P. maniculatus are susceptible to oral infection and develop sufficient spirochetemias to infect I. dammini larvae.