Borrelia burgdorferi in eastern Virginia: comparison between a coastal and inland locality.

In Virginia, Borrelia burgdorferi was more prevalent in a site along the Atlantic Ocean, near Maryland, than in an inland site near Williamsburg and Yorktown. At the coastal site on Assateague Island, B. burgdorferi was isolated from 4.2% of 475 animals sampled, including four species of small mammals. Serologic tests indicated that 25-37% of the small rodents assayed had been exposed to B. burgdorferi. Immunofluorescence antibody assays specific for B. burgdorferi showed spirochete infection in Ixodes scapularis and Dermacentor variabilis but not in other species of ticks also examined from this site. At another coastal site (Parramore Island), no evidence of Peromyscus leucopus was found, no immature specimens of I. scapularis were collected, and no isolations were made from numerous raccoons or small mammals sampled. Borrelia burgdorferi infection was found in one I. cookei nymph, but not in numerous specimens of I. scapularis or other tick species from this locality. At the inland site between Williamsburg and Yorktown, B. burgdorferi was isolated from two small mammal species and antibodies to B. burgdorferi were found in only 7-10% of the small mammals sampled. Ixodes scapularis were less abundant at this locality than at the Assateague Island site. Borrelia burgdorferi spirochetes were found in I. scapularis and a single nymph of Amblyomma americanum, but not in any of numerous specimens of four other species. Infection with B. burgdorferi was found in 20% of unfed adult I. scapularis from vegetation, but in only 0.2% of numerous adults from hunter-killed deer. Infection in immature ticks was much lower than at Assateague Island. Borrelia burgdorferi may be more prevalent along the Atlantic coast than in inland areas. Isolations, seroprevalence, immature I. scapularis densities, and spirochete infection rates in ticks were higher at the Assateague Island site than the Williamsburg/Yorktown site. Consequently, the risk of human exposure to Lyme disease may be higher in some parts of the coastal area than elsewhere in Virginia. Overall, B. burgdorferi is less intense in Virginia than in the northeastern United States.