Serologic analyses of cottontail rabbits for antibodies to Borrelia burgdorferi.

An enzyme-linked immunosorbent assay was developed to detect antibodies to Borrelia burgdorferi in cottontail rabbits captured in Millbrook, N.Y., and New York, N.Y. Five antigenically variable strains of B. burgdorferi were analyzed to determine the variability of serologic test results. In analyses of 79 serum samples, seropositivity ranged from 56% for a strain cultured from kidney tissues of a cottontail rabbit to 68% for a strain isolated from a larva of Ixodes dentatus, a tick that parasitized a cottontail rabbit. There were false-positive results when reference rabbit antisera to B. hermsii and Treponema pallidum were screened against B. burgdorferi. Cross-reactivity with antisera to Leptospira interrogans serovars was less pronounced. Western blot (immunoblot) analyses revealed reactivities of test sera to two or more surface or subsurface proteins of B. burgdorferi with approximate molecular masses of 18, 25 to 27, 34, 36, 41, and 59 kilodaltons. Cottontail rabbits respond immunologically to B. burgdorferi, but the observed variations in serologic test results should not be a limitation in field and laboratory investigations of Lyme borreliosis.