A survey of Brucellosis and Bovine Tuberculosis at a human-domestic animal-wildlife interface in Zimbabwe.

Abstract

A cross sectional study was conducted to determine the risk of emergence or the presence and risk factors of bovine tuberculosis and brucellosis in human populations at the human-domestic animal-wildlife interface areas within the South East Lowveld (SEL) of Zimbabwe. A three dimensional risk assessment approach; the release, exposure and consequences assessment was adopted. The release assessment explored the presence or evidence of exposure to Brucella species and Mycobacterium bovis in cattle, milk and meat including game. The exposure assessment investigated disease knowledge and perception by farmers, abattoir and game workers using a structured questionnaire. The consequence assessment analysed human health data collected from health centres in the SEL for tuberculosis, malaria and acute febrile illnesses (AFIs). Three study sites were selected based on the type of domestic animal–wildlife interface: Malipati, Chikombedzi and Chiredzi peri-urban as high, medium and low interface, respectively. This study demonstrated that there was evidence of exposure to brucellosis in cattle, where seroprevalence was highest at the high interface (Malipati) where contact between cattle and wildlife occurs compared to the medium and low interface areas. Bovine tuberculosis was not isolated in cattle. The knowledge, attitude and practices study revealed that 67.4 % (130/193) of the respondents were aware of zoonoses. Fewer cattle owners from a high interface area were aware of zoonoses compared to other areas due to combined effects of limited education and other factors disadvantaging these marginalised areas. This could increase their risk of exposure to zoonoses, considering that consumption of raw meat and milk is common. Analysis of human health data showed that the lack of diagnostic capacity makes estimates of the prevalence of zoonotic TB and the aetiologies of AFIs imprecise and largely unknown. From inference if all cases of extra-pulmonary tuberculosis were treated as M. bovis this would give a prevalence of 4.1%. Noteworthy up to 88% of AFIs cases were not confirmed by laboratory tests. In conclusion, the observed high seroprevalence of brucellosis at the high interface compared to other areas suggested that the interface is a possible nexus for amplification of animal brucellosis. Further, the lack of awareness of zoonoses among farmers, coupled with the presence of risky practices could predispose them to infection by brucellosis. Thus, the contribution of animal derived zoonotic infections to the AFIs observed in the areas could not be ruled out. Therefore, further research is required to determine the public health importance of bovine brucellosis and bTB, and to establish the exact causes of AFIs in these areas. The implementation of brucellosis control measures in these areas could reduce the incidence of brucellosis in cattle and the risk of zoonotic infections. Continued surveillance at abattoirs and slaughter poles by trained animal health personnel would allow early detection of bovine tuberculosis should it arise.