A survey of the incidence and importance of the tick-borne diseases heartwater, redwater and anaplasmosis in the heartwater-endemic regions of South Africa

Abstract

In an almost 50% response to a survey questionnaire, farmers in the heartwater-endemic regions of South Africa indicated that they were experiencing losses of 1,3, 0,3 and 0,2% in cattle due to heartwater, redwater and anaplasmosis, respectively. In small stock, the heartwater mortality was 3,8%. Only 35% of cattle farmers and 15% of farmers keeping sheep and goats, vaccinate their animals against heartwater. It would seem that the present vaccine does not control heartwater adequately and, with 9% of farmers claiming poor protection after immunization, it would be difficult to recommend wider use of the heartwater vaccine. Likewise, vaccination against redwater and anaplasmosis on 11,8 and 14,2% of farms, respectively, appears to have had no beneficial effect on the mortality rates of these diseases. Many farmers still believe that very few or no ticks should be seen on cattle. In fact, it would appear that a considerable proportion of farmers find so few ticks on their cattle, that the frequency of acaricidal treatment is in many cases too high. Although there is no correlation between the incidence of heartwater and the intensity of tick control, there is also no serological evidence to support the possibility of an endemically unstable condition. The concept that endemic stability as a means to control heartwater in cattle can be achieved by allowing more ticks on animals, has not yet been established. The overall impression is that farmers do not regard heartwater in cattle as such a serious problem as it is generally believed to be. In small stock, however, heartwater is a severe constraint in the bushveld regions of the Transvaal and in the valley bushveld of the eastern Cape Province. In the latter, it is particularly Angora goats that are affected.