A serological prevalence study of important infectious diseases of cattle in rural areas of Kwa Zulu Natal, South Africa

Abstract

In the rural areas of Kwa Zulu Natal small scale farming is the main agricultural activity, which is often carried out in addition to other employment taken on in another location by at least one member of the household. Although Veterinary services (VS) was aware of several diseases occurring in this area and has implemented a dipping strategy for tick borne diseases as well as a regional annual vaccination campaign for Rabies, Anthrax and Black quarter, uncertainty remained about the relative importance of other diseases such as brucellosis, leptospirosis and enzootic bovine leucosis. Further it was of interest to investigate the serological resistance of cattle against the tick borne diseases babesiosis and anaplasmosis. In addition to this veterinary services wanted to increase their understanding of the perceptions and practices of local cattle owners that were relevant for the context of disease control. A serological survey of cattle was carried out between March 2001 and December 2003 to determine the prevalence of the above-mentioned diseases. The survey was designed as a two-stage survey, considering the diptank as the primary sampling unit. The conduction of the questionnaire survey was based on a convenience sample and took place during the dipping procedure. The apparent prevalence at district level was adjusted for clustering, and diagnostic test sensitivity and specificity and displayed in maps. The mean true prevalence of brucellosis varied from zero to 15.8 percent in the north eastern region with the large majority of the districts being disease free. Enzootic Bovine Leukosis (EBL) was widely present in the province at generally low prevalences, except in the central region where the highest prevalence at district level was recorded to be 70 percent. Leptospirosis also occurred frequently with the highest prevalence noted being 62 percent at district level. The southern regions showed a higher leptospirosis prevalence than other areas of the province, while in some of the northern and western districts a lower prevalence is noted. The encountered servovars were pomona, which occurred most frequently, tarrasovi, bratislava, hardjo, canicola and icterohaemorrhagica. While Babesia bovis and anaplasmosis occurred at a high prevalence throughout the province, B. bigemina was found to be much less established and is absent from many of the northern districts. Most prevalences calculated at district level do show large confidence intervals due to uncertainty that arose from the sampling frame and should be interpreted with care.