Prevalence of Ehrlichia, Borrelia, and Rickettsial agents in Amblyomma americanum (Acari: Ixodidae) collected from nine states - Mixson, T.R.; Campbell, S.R.; Gill, J.S.; Ginsberg, Howard; Reichard, M.V.; Schultz, T.L.; Dasch, G.A. (Journal of Medical Entomology, 2006)