Serological and molecular investigation for brucellosis in swine in selected districts of Uganda.

Brucellosis is a notifiable zoonotic disease affecting livestock, humans, and wildlife in Uganda. Pigs can be infected with human pathogenic Brucella suis biovars 1 and 3 and can be a significant source of brucellosis for humans. Uganda has a rapidly growing pig population, and the pork consumption per capita is the highest in East Africa. The objective of this work was to determine the seroprevalence of brucellosis in Ugandan pigs. A cross-sectional serosurvey of pigs was conducted in three of the major pig-keeping districts in Uganda (Masaka (n = 381 samples), Mukono (n = 398), and Kamuli (n = 414)). In addition, pigs originating from these districts were sampled in the major pig abattoir in Kampala (n = 472). In total, 1665 serum samples were investigated by serological and molecular tests. Only three putative brucellosis-positive samples were detected serologically using indirect ELISA. These sera were found negative for Brucella antibodies by CFT; however, two had antibodies against Yersinia enterocolitica as determined by SAT. Presence of antibodies against Yersiniae was confirmed by Y. enterocolitica antibody-specific ELISA. The two Yersiniae ELISA-positive samples were brucellosis negative using real-time PCR. We tested additional 142 sera from the 1665 samples with real-time PCR. All tested negative. Under this type of production system, we expect a maximum B. suis prevalence of less than 1 % at 95 % confidence level, and therefore, the risk of acquiring brucellosis from the pigs or their products is negligible. However, pigs may harbor the zoonotic Y. enterocolitica. This is the first study to investigate the occurrence of brucellosis in pigs in Uganda and the first study to report Y. enterocolitica antibodies in swine in Uganda.

The importance of on-farm biosecurity: Sero-prevalence and risk factors of bacterial and viral pathogens in smallholder pig systems in Uganda.

BACKGROUND: The productivity of pigs in smallholder systems is affected by high disease burden, most of which might not be obvious, with their epidemiology and impact being poorly understood. This study estimated the seroprevalence and identified the risk factors of a range of bacterial and viral pathogens of potential economic and public health importance in domestic pigs in Uganda. A total of 522 clinically healthy pigs were randomly selected from 276 pig farms in Masaka (142) and Lira (134) districts of Uganda in 2015. RESULTS: Overall the highest animal prevalence was found for Streptococcus suis 73.0% (CI95: 67.0-78.3) in Lira and 68.2% (CI95: 62.7-73.4) in Masaka; followed by Porcine circovirus type 2 with 50.8% (CI95: 44.5-57.2) in Lira and 40.7% (CI95: 35.2-46.5) in Masaka and Actinobacillus pleuro-pneumoniae, 25.6% (CI95: 20.4-31.6) in Lira and 20.5% (CI95: 16.2-25.6) in Masaka. Mycoplasma hyopneumonia prevalence was 20.9% (CI95: 16.2-26.6) in Lira and 10.1% (CI95: 7.1-14.1) in Masaka, while Porcine parvovirus was 6.2% (CI95: 4.0-9.7) in Masaka and 3.4% (CI95: 1.7-6.6) in Lira. Less common pathogens were Influenza A, 8.5% (CI95: 5.6-12.8) in Lira and 2.0% (CI95: 0.9-4.5) in Masaka and Porcine Reproductive and Respiratory Syndrome Virus, 1.7% (CI95: 0.7-4.3) in Lira and 1.3% (CI95: 0.5-3.5) in Masaka. Even less common was Rotavirus A with 0.8% (CI95: 0.2-3.0) in Lira and 0.7% (CI95: 0.2-2.5) in Masaka; the same was for Aujeszky virus with 0.4% (CI95: 0.7-2.4) in Lira and 0.0% (CI95: 0.0-0.1) in Masaka. Co-infection with two pathogens was common and there was a significant association of M. hyo and PCV2 co-occurrence (p = 0.016). Multivariate analysis showed that for S. suis the use of disinfectant reduced odds of sero-positivitey (OR = 0.15; p = 0.017) and pigs less than 6 months were more likely to be infected than older pigs (OR = 3.35; p = 0.047). For M. hyo, crossbred pigs had higher odd of infection compared to local breeds (OR = 1.59; p < 0.001). CONCLUSIONS: The studied pathogens have high prevalences in smallholder pig production systems and might be silent killers, thus affecting productivity and there is a possibility that some pathogens could spread to humans. Given the limited knowledge of veterinary workers and the poor diagnostic capacities and capabilities in these systems, the diseases are potentially usually under-diagnosed. These findings constitute baseline data to measure the impact of future interventions aiming to reduce disease burden in the pig production systems in Uganda.