The significance of recent highlights in heartwater research.

Many of the objectives identified earlier, with regard to research on cowdriosis, have been achieved during the past decade. Some contributions such as the development of Cowdria specific DNA probes and the attenuation of the organisms are still in the experimental stage but others, such as in vitro cultivation, are already well established practices in many laboratories. Serological techniques are now more widely used since other methods and other sources of antigen became available. However, persistent cross reactions with Ehrlichia still complicate the interpretation of epidemiological data. Biochemical studies to identify, isolate and characterize antigenic proteins present in Cowdria organisms revealed definite immunodominant proteins that could prove to be suitable antigens for serological tests. Despite these significant research advances, practical methods to diagnose and control the disease have remained virtually unchanged. Control is still based on either intensive tick control or in some cases on the establishment and maintenance of endemic stability. The infection and treatment method using infected blood or prophylactic treatment with tetracyclines, remains the backbone of disease control in South Africa. Heartwater will remain a threat to the American mainland for as long as Amblyomma variegatum is present in the Caribbean and eradication of the tick from that region seems indicated.