A rickettsialike microorganism in the tick Ornithodoros savignyi; Observations on its structure and distribution in the tissues of the tick

A rickettsialike microorganism is described, for the first time, from the tick Ornithodoros savignyi collected from camels in Egypt. The microorganism is found in the cells of the anterior half of the Malpighian tubules, except those of the anteriormost region of the organ, in both male and female ticks, and in the oocytes. It is not observed in the male gonads. In smears of infected organs stained with Giemsa or Macchiavello's stain, the microorganism appears as threads and chains of variable lengths, occurring either singly or in bundles, as well as in coccoid and short-rod forms. Light and electron microscopy of the microorganism in infected tissues show close similarities in appearance and fine structure to certain Rickettsia and to other rickettsialike symbiotes naturally occurring in ticks and other arthropods.