Mastitis is one of the most economically important diseases in dairy cattle worldwide. Not only does it have a negative effect on milk production, it also is one of the main reasons for culling dairy cattle. Pathogens causing mastitis in dairy cattle can be grouped into either contagious (or host adapted) or environmental pathogens. In different parts of the world it was shown that the prevalence of these differently grouped pathogens is dependent on various risk factors. Furthermore, it was shown that control measures implemented against contagious intramammary infections caused a relative shift over time towards a higher prevalence of environmental intramammary infections. In this study udder health data from the Onderstepoort Milk Laboratory (OML) was compared over two different years, 2008 and 2013, with regards to the prevalence of specified mastitogenic pathogens in total mixed ration (TMR) dairies and pasture-based dairies. Furthermore, the within-herd prevalence of Streptococcus uberis (Str. uberis) in Str. uberis positive herds was compared between the two years and the two management systems. Statistically significant differences were found in the prevalence of most of the major contagious and environmental mastitogenic pathogens between 2008 and 2013 and between the TMR and pasture-based dairies. Coagulase-negative staphylococci (CNS) has the highest prevalence in both TMR and pasture-based for both 2008 and 2013. Streptococcus uberis overall showed an increase in prevalence from 2008 to 2013, with the highest prevalence in pasture-based dairies in 2013. Staphylococcus aureus (S. aureus) showed a statistically significant decrease in TMR and pasture-based dairies from 2008 to 2013. The within-herd prevalence of Str. uberis increased from 2008 to 2013 with the highest within-herd prevalence in pasture-based dairies in 2013. / Dissertation (MMedVet)--University of Pretoria, 2015. / tm2016 / Production Animal Studies / MMedVet

This study is a questionnaire-based, descriptive assessment of informal livestock slaughter practices by small scale farmers in Gauteng. This study aims to assess if the practice of informal slaughter poses a potential risk to public health specifically to brucellosis exposure, a disease of high seroprevalence in Gauteng and South Africa. Informal livestock slaughter from antemortem selection to carcass dressing, butchering and product preparation were descriptively assessed for potential disease exposure and resultant public health risk. This study assessed the frequency of brucellosis testing and the occurrence of livestock abortions as a possible disease indicator. Farmers were asked on the particulars of informal slaughter to ascertain if disease exposure could occur through this practice. The study made use of a questionnaire where 109 study participants were interviewed individually. Questionnaire results were compiled in Microsoft® Excel where data was analysed through descriptive statistics to identify trends and frequency data from the results. The study found that the majority of small-scale farmers participating in the study were older individuals, the majority of whom were not earning an income. It was found that study participants would slaughter livestock informally themselves or with a family member. This would occur only once or twice a year, usually for cultural or religious purposes or for a special occasion. Livestock most commonly owned and slaughtered by small-scale farmers were cattle, carriers of Brucella abortus. Participants rarely made use of adequate protective personal protective equipment (PPE) when slaughtering informally. The use of PPE and the adequacy thereof was however found to increase in frequency with participant age group. Older individuals, elders in their communities were often given the responsibility of livestock slaughter, thus providing some risk mitigation to disease exposure during the process. High risk structures such as lymph nodes and reproductive organs were handled during slaughter, the former frequently consumed with the tripe due to lack of recognition. While some organs previously found to harbour Brucella organisms were consumed raw or only exposed to short cooking times, the majority of slaughter products were exposed to prolonged cooking times, sufficient to reduce bacterial loads, reducing risk through consumption. While many participants recognised brucellosis as a zoonotic disease, the routes of transmission were poorly recognised. Exposure to Brucella spp. through informal slaughter is likely in the current environment of high brucellosis seroprevalence, poor disease control and the unreliable disease history of animals sourced for slaughter, posing a risk to public health. Should a brucella infected animal be slaughtered informally, exposure of those performing the slaughter, dressing the carcass and those involved in food preparation is likely and may lead to brucellosis. / Dissertation (MSc)--University of Pretoria, 2018. / Veterinary Tropical Diseases / MSc / Unrestricted