A prevalence study of bovine tuberculosis and brucellosis in Malawi

Abstract

A study was performed in 1986 to identify the prevalence and distribution of tuberculosis and brucellosis infections in cattle in Malawi. The cattle were obtained through multistage random sample consisting of administrative districts, dip tanks and/or dairy cooperative bulking groups within district, and then farm and/or animal sampling within group. The single intradermal comparative cervical (SIDCC) tuberculin test was used to assess tuberculosis status, and the rose bengal test followed by the tube agglutination test for brucellosis status. Data on each sampled animal included age, breed, sex, owner, dip tank or bulking-group identification, and district, as well as the outcomes for tuberculosis and brucellosis. The study included 2032 cattle selected from dip tanks and 1449 dairy cattle from bulking groups; all of these were tested for tuberculosis, and 2017 of them were tested for brucellosis. Overall, the prevalence of tuberculosis reactions was 3.85%. The prevalence varied by district, by group (dip tank cattle had a higher prevalence than cattle from bulking groups), breed and sex (males higher than females). Age was not related to prevalence. The change in skin thickness on the SIDCC test was influenced by original skin thickness, those with thicker skin tending to give a larger response. Most of the differences in prevalence by district were explained by differences in breed and sex. The overall prevalence of brucellosis was 0.3%. Sixteen animals were rose bengal test positive and six of these were slide agglutination test positive. Only two reactors came from the same herd.