Brucellosis due to brucella suis in a swine herd associated with a human clinical case in the state of São Paulo, Brazil

Brucella suis was the most frequent agent of human brucellosis in many areas free of B. melitensis infection, but with changes in swine management the occurrence of swine brucellosis has decreased, and so did the incidence of B. suis infection in humans.  An outbreak of swine brucellosis affecting one herd in the municipality of Jaboticabal, State of São Paulo, Brazil, was detected in July 2006. The herd was composed by approximately 300 sows and 1,500 fattening animals.  Many sows aborted and many showed posterior paralysis and lameness.  Among 270 sows, 206 (76.3%) tested positive for brucellosis by the complement fixation, and among 62 randomly bled fattening animals, 17 (27.4%) tested positive.  B. suis biovar 1 was cultured from 14 aborted fetuses (stomach content, lung, spleen, liver) and 6 sows (lymph nodes, spleen, liver).  Brucella growth was obtained on Brucella-agar plus 10% rabbit serum, and incubation at 37°C with 10% of CO₂.  Brucella identification was accomplished by morphology, growth in atmosphere with and without CO₂, growth on media containing antibiotics, thionin, fuchsin and acriflavine, H₂S production, and urease activity.  Thirteen persons working in the farm were tested by the agglutination test, and 3 of them had antibody titers: one 39 years old woman, who worked at the pig maternity ward and had direct contact with aborted fetuses, presented a titer of 480 IU/mL and clinical signs (intermittent fever, night profuse sweattening, weakness, malaise); one 27 year old man, that also had contact with aborted fetuses, had agglutinating antibody titer of 200 IU/mL, but does not show clinical signs; and one 25 years old man had a titer of 60 IU/mL without clinical signs. These informations indicate that in spite of the reduction of swine brucellosis prevalence in Brazil, B. suis infection still occurs, posing a risk to animal and human health.