Studies on Bovine petechial fever and ovine tick-borne fever

Abstract

A comparative study was made of tick -borne fever in sheep in àcotland, and bovine petechial fever in sheep and cattle in Kenya. The results obtained demonstrated the similarity of the two diseases. Both are caused by rickettsia -like organisms observable principally in the neutrophils, and tentatively classified in the genus Cytoecetes. These were considered to be morphologically identical.Clinical signs and necropsy lesions of experimental animals were noted. The parameters of normal infections with both diseases were defined, with reference to haematological, febrile, and parasitaernic res,:onses. The distribution of the causative organisms in infected hosts at different stages of reaction was investigated by infectivity studies; spleen and lung were found to contain the highest titres.A latent infection was a more common sequel to tick -borne fever than to bovine petechial fever.A complement fixation test was deve-loped for tick -borne fever, antigen being prepared from infected leucocytes. Sirnilar methods proved only partially successful for bovine petechial fever.A hitherto unsuspected breed difference in susceptibility to bovine petechial fever was observed, and thereafter Sahiwal cross cattle were used routinely.Investigations were made into the potential role of wild ruminants in the epidemiology of bovine petechial fever, by experimental inoculation of captive wild animals. several species were found to allow multiplication; as a corollary to this, isolates of the causative organism were made from wild bushbuck in an enzootic area.Three antibiotics were compared in the treatment of patent bovine petechial fever reactions in sheep, and the most efficacious of these (d.ithiosemicarbazone) was used successfully to treat the disease in cattle.The similarities between the two diseases were so marked that it was concluded that the diseases my well be caused by different strains of the one microorganism.