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.

Economic losses occurring due to brucellosis in Indian livestock populations

Brucellosis is a serious public health issue in India. Estimation of economic losses occurring due to brucellosis is required to help formulate prevention and control strategies, but has not been done in India. We estimated economic losses due to brucellosis by sourcing prevalence data from epidemiological surveys conducted in India. Data for livestock populations were obtained from official records. Probability distributions were used for many of the input parameters to account for uncertainty and variability. The analysis revealed that brucellosis in livestock is responsible for a median loss of US $ 3.4 billion (5th-95th percentile 2.8-4.2 billion). The disease in cattle and buffalo accounted for 95.6% of the total losses occurring due to brucellosis in livestock populations. The disease is responsible for a loss of US $ 6.8 per cattle, US$18.2 per buffalo, US $ 0.7 per sheep, US $ 0.5 per goat and US $ 0.6 per pig. These losses are additional to the economic and social consequences of the disease in humans. The results suggest that the disease causes significant economic losses in the country and should be controlled on a priority basis.

Clinical and histological features of brucellin skin test responses in Brucella suis biovar 2 infected pigs

Current serological tests for swine brucellosis detect antibodies to the Brucella O-polysaccharide (O/PS). However, when infections by bacteria carrying cross-reacting O/PS occur, these tests suffer from false positive serological reactions (FPSR), and the skin test with Brucella soluble protein extracts is the best diagnostic alternative to differentiate true Brucella suis infections from FPSR in pigs. Since this test has been seldom used in B. suis infected swine, the clinical and histological features involved have not been described properly. Here, we describe the clinical and histological events in B. suis biovar 2 infected pigs skin tested with a cytosoluble O/PS free protein extract from rough Brucella abortus Tn5::per mutant. A similar extract from rough Ochrobactrum intermedium was also used for comparative purposes. No relevant differences were evidenced between the homologous and heterologous allergens, and the main clinical feature was an elevated area of the skin showing different induration degrees. Moreover, an important vascular reaction with hyperemia and haemorrhage was produced in most infected sows 24-48 h after inoculation, thus facilitating the clinical interpretation of positive reactions. Histologically, combined immediate (type III) and delayed (type IV) hypersensitivity reactions were identified as the most relevant feature of the inflammatory responses produced.