Field trial of an outer surface protein A (OspA) antigen-capture enzyme-linked immunosorbent assay (ELISA) to detect Borrelia burgdorferi in Ixodes scapularis.

Field-collected adult male Ixodes scapularis from Westchester County, New York were bisected and Borrelia burgdorferi infection rates were ascertained by both a direct fluorescent antibody test and an outer surface protein A (OspA) antigen-capture enzyme-linked immunosorbent assay (ELISA). Both assays gave identical antigen positivity rates with 89% concordance between the two assays. Storing dried ticks before ELISA analysis had no significant effect on the ability of the ELISA to determine the presence of OspA compared with assaying live ticks. The OspA antigen positivity rate for dried ticks was 49% compared with 53% for live ticks, with mean OspA antigen spirochete equivalents of 3,388 and 2,823 for dried and live ticks, respectively.