Cytological studies on heartwater II : Rickettsia ruminantium in the tissues of ticks capable of transmitting the disease

Abstract

The evidence observed in favour of a causative relationship between Rickettsia ruminantium and the production of heartwater falls under the following headings: (1) The discovery of Rickettsia ruminantium in the tissues of goats, sheep, and cattle suffering from heartwater; the close association between their presence in these three species and the febrile reaction; their disappearance soon after the fever has commenced to decline corresponding to the loss in infectivity of the blood; and their absence in control animals (Part 1 of this Report). (2) The appearance of the same Rickettsia, easily identifiable by their very characteristic morphology and staining reactions in two series of ticks (607 and 614) which had fed upon cases of heartwater and which, before feeding, did not contain them; and their non-appearance in three series of control ticks (604, 605, and 606) from the same parent stock which had fed upon normal animals. (3) The fact that the ticks containing Rickettsia in their alimentary tracts when fed upon susceptible animals, produced in them typical attacks of heartwater, which the control ticks, devoid of Rickettsia, failed to do. (4) The completion of the cycle by the recognition of the same Rickettsia in the tissues of these animals (sheep 8049 and goat 9651) which contracted heartwater as a result of having been bitten by the infective ticks containing Rickettsia.