Research work into heartwater, a disease of sheep, goats and cattle caused by Rickettsia ruminantium (Cowdry 1926) has been hampered to a very great extent by the lack of a susceptible small laboratory animal. Up to the present all efforts to infect the guinea pig, rabbit, rat, and mouse have been quite unsuccessful. It was, therefore, decided to procure one or more strains of the typhus group of rickettsias, which are pathogenic for guinea pigs, to serve as a positive control for certain technique and experimental methods.
During the course of this work other rickettsia were encountered and ultimately were compared with a strain of fièvre boutonneuse kindly supplied by Dr. Balozet of Tunis. The present series of papers is presented to record the observation that have been made, in the hope that the data may be of value in helping to clarify the somewhat confused position of the South African rickettsias in the current literature.