Pig Trader Practices and Prevalence of Bacterial and Viral Zoonoses in Pigs in Uganda

Abstract

Pig numbers in Uganda have grown significantly in the past 30 years, increasing the risk of disease transmission between pigs and humans. However, the presence and prevalence of pig-associated zoonoses is poorly understood. Thus, this thesis aimed to investigate the prevalence and presence of selected zoonoses in pigs in Uganda. A secondary aim was to describe pig trader characteristics and trading practices. Systematic sampling of pigs presenting for slaughter occurred over 4 sampling periods when pork consumption increases. Using qPCR, 10% of pigs had leptospiral DNA in either their reproductive or kidney tissues; Brucella spp. and Coxiella burnetii DNA was not detected. Serotyping revealed circulation of at least 4 distinct Leptospira serovars. Using serological methods and confirmatory tests, 2% of pigs were found to be seropositive to henipaviruses while 7% of pigs were seropositive to ebolaviruses. Risk factors for infection/exposure and the geographic distribution of positive animals were also described for each of the selected zoonoses. During interviews with pig traders, all traders were aware of and observed clinical signs of illness in pigs but lacked clarity on reporting processes. In addition, there was a significant difference in the high price paid per kilogram at farm gate. These results suggest opportunities for inclusion of pig traders in disease mitigation strategies and options for pig farmers to access pork markets and favourable prices for their pigs. This thesis presents the most detailed investigation of selected pig-associated zoonoses in Uganda to date. This includes the first report of the detection of leptospirosis in pigs in Uganda, as well as the first evidence that pigs are exposed to henipaviruses and ebolaviruses in pigs in the East Africa region. Lastly, to support the bourgeoning pork market, areas of investment were identified from interviews with pig traders.