Bovine brucellosis in Argentina and bordering countries: update.

Bovine brucellosis is a zoonotic disease spread worldwide. The infection in cattle is predominantly caused by Brucella abortus and is usually detected in pregnant females through abortions. The disease is endemic in Argentina; however, infection in humans is underestimated and often not reported. The prevalence of bovine brucellosis in countries bordering Argentina is quite variable: 0.04% in Uruguay, 10.20% in the north and 0.06% in the south of Brazil, 0.2% in Chile, 3.15% in Paraguay and 2.27% in Bolivia. In 1999, the Argentine National Control and Eradication Program was implemented. Its strategies include identification of vaccinated animals, compulsory vaccination with B. abortus S19 of 100% of 3- to 8-month-old females, negative serological tests before animal movements and categorization of farms in terms of their brucellosis status. The epidemiological surveillance in milk is performed through the milk ring test and the indirect ELISA. The result of a national brucellosis survey performed in 2004 indicates that 12.4% (95% CI: 10.89-14.0) of Argentine beef farms are seropositive to Brucella and that the apparent prevalence in cattle is 2.10% (95% CI: 1.90-2.40). The official serological diagnostic tests are as follows: buffered plate antigen test, as screening, serum agglutination test, 2-mercaptoethanol and fluorescence polarization assay, competitive ELISA, as confirmatory tests, and complement fixation test, as definitive test. Santa Fe and a district in Córdoba have 'Outstanding Plans'. Tierra del Fuego is a 'Zone free from bovine brucellosis'. One question arising when studying the Argentine situation is why the disease remains endemic if good regulations exist to control and eradicate it. In future, some different aspects might be evaluated to understand it, and further studies should be performed to prioritize, select and refine control strategies.