ANDRIAS HOJGAARD, REBECCA J. EISEN, AND JOSEPH PIESMAN

J. Med. Entomol. 45(4): 732Ð736 (2008)

Abstract: Nymphal Ixodes scapularis Say are the principal vectors of Lyme disease spirochetes (Borrelia burgdorferi sensu stricto) in the eastern United States. Physicians frequently face the decision of whether or not to administer prophylactic antibiotics to human tick bite victims in Lyme disease endemic regions, based on the overall probability that such bites will result in infection with B. burgdorferi s.s. We evaluated the transmission dynamics of B. burgdorferi s.s. during the key third day of nymphal I. scapularis feeding, when the risk of transmission rapidly increases. The cumulative probability that 50% of infected ticks transmitted B. burgdorferi s.s. occurred at 68hof tick attachmentandour overall estimate that ahuman tick bite would result in transmission of B. burgdorferi s.s. was 2.4%.