Investigation of known risk factors for bovine tuberculosis in Namibian cattle

Bovine tuberculosis (BTB) is a chronic disease primarily affecting cattle that is caused by a bacterium called Mycobacterium bovis. Though less transmissible in nature, M. bovis is highly potentiated for transmission between animals by its ability to cause chronic disease. The main mode of transmission of M.bovis is through aerosols, however, contaminated pastures and water sources serve as other modes of transmission. BTB is an economically important disease that leads to loss in production in cattle and is of public health concern as it is a zoonosis. There are many risk factors of exposure to BTB in cattle, whilst most of them can be controlled, wildlife contact is a risk factor that remains a persistent challenge in most countries. This project was performed in the 10 cattle farming regions of Namibia to investigate and qualitatively describe the BTB risk factors and their relative importance in Namibian cattle herds. A questionnaire was designed, translated into the main local languages and a pilot study done before commencement of project. The questionnaire consisted of 23 questions which investigated risk factors of BTB in cattle. The questions were in 3 main sections, namely farm demographics, farming practices and disease awareness. The questionnaires were distributed by hand and by electronic mail to farmer participants. The participating farmers were from Omusati, Kavango, Otjozondjupa, Omaheke, Zambezi, Oshana, Ohangwena, Khomas, Oshikoto and Kunene regions. The results were collected, compiled manually and electronically, qualitatively analyzed and presented using descriptive statistics. A total of 254 farmers participated in the questionnaire survey, of these, 178 were communal and 72 were commercial farmers. Proximity to the border was found to be a high risk factor leading to possible interactions between cattle of unknown BTB status across national boundaries, only 18.3% of farmers indicated to being less than 20 km from the nearest border. Since the risk BTB transmission between cattle increases with large herd sizes, this factor was found to be of low risk as 52.7% of farmers had a small herd size of less than 20 cattle. Wildlife species that were observed sharing resources with livestock were warthogs, kudus, mongooses, meerkats, wildebeest, elephants, giraffes and antelopes. Wildlife contact with cattle was the most prevalent risk factor (49.6%), with 27.8% and 33.5% of farmers‘ cattle sharing grazing and water sources with wildlife respectively, 26.4% of commercial farmers confirmed owning wildlife. Distance travelled by cattle in search of grazing was found to be a medium risk as 19.3% of farmers had their cattle moving for at least 10 km, therefore likely to encounter other herds and or wildlife along the way. Within the previous year, there had been high risk factors of exposure to BTB between cattle. The participants with knowledge of BTB were only 39.7% and only 39.5% knew that it is a zoonosis, which poses a risk of possible exposure to disease out of ignorance. Quarantine of cattle was only done by 22.3% of the farmers, mostly in Khomas region, and only 10% of farmers had their meat for home consumption inspected. The low level of cattle quarantine and BTB testing were found to be very significant risk factors of exposure to BTB as diseased cattle were potentially being introduced into healthy herds. Most farmers (62.7%) slaughtered cattle for meat, only 30% of farmers confirmed taking abnormal carcasses to the veterinarian for post-mortem examination. The absence of meat inspection and failure to take abnormal carcasses for meat inspection were significant risk factors for human exposure, since if BTB lesions were present, they could remain unidentified. Milk was found to be a low risk factor of exposure to zoonotic BTB as 67% of farmers confirmed not consuming milk. A total of 12% of farmers confirmed having had a history of human TB in their households, which was a significant finding taking into consideration the possibility of zoonotic M. bovis. There was sufficient evidence from the results that although other risk factors of BTB are present, wildlife is the most threatening common risk factor posing the greatest challenge in Namibia.Mini Dissertation (MSc (Tropical Animal Health))--University of Pretoria, 2020.Veterinary Tropical DiseasesMSc (Tropical Animal Health)Unrestricte