Since Davis and Cox (1) first isolated the causative agent of Q fever from Dermacentor andersoni, several species of ticks have been incriminated in the epidemiology of this disease in various parts of the world. Investigations implicating the following species were reviewed by Kohls in 1948 (2): in Australia, Haemaphysalis humerosa and H. bispinosa, Ixodes holocyclus, Rhipicephalus sanguineus and Boophilus microplus; and in the United States, Dermacentor occidentalis, Amblyomma americanum, Haemaphysalis leporis-palustris, Ixodes dentatus, Ornithodoros moubata and O. hermsi.
Recently Q fever has been demonstrated to occur sporadically in Panama (3, 4). However, there are no data available concerning the possible vectors in this area. We decided, therefore, to attempt experimental transmission by Amblyomma cajennense, a tick ideally suited for this purpose in Panama, due to its abundance and wide host range (5). The JD strain of Rickettsia burneti, isolated locally (6), was employed as the infective agent and the guinea-pig as the experimental animal.