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See also chapter 12.

(214) This disease is caused by the bacterium Brucella suis, which is one of the six different species of brucella. Brucella suis does not exist in the UK, Ireland and in some other EU countries, but is widespread through most of the rest of the pig rearing world and is an important disease not least because some strains of it cause a nasty disease in people. It can be spread by venereal infection and the boar is a major source either by direct contact at mating or via artificial insemination. Pigs can also be infected via the conjunctiva, through the nose or by mouth. The organism can survive outside the pig for long periods of time particularly at or near freezing temperatures. The hare in Northern Europe can also be infected where it is considered a natural host. It can be an important source of infection to the pig.

When a female becomes infected, the organism is plentiful in the blood, causing a bacteraemia, which persists over a period of 3-6 weeks. It is during this period of time that the organism establishes itself in the placenta, causing inflammation and ultimately abortion. B. suis infects the testicles and accessory reproductive glands, and can be excreted via semen. The disease can be transmitted to people and is serious.

Clinical signs
These include infertility and abortions which may occur at any time. If the sow is infected via the boar at mating, the abortions occur early, often before day 35 and delayed returns will be experienced. Sows aborting after day 30 may show a bloody vaginal discharge that contains high numbers of organisms. In sucking and weaned pigs, B. suis can infect bones and soft tissues causing paralysis of the hind legs. A carrier state persists for long periods of time.

This can be readily carried out by isolation of the organism. Serology is used to detect carrier sows but cross reactions can occur quite extensively due to another organism called Yersinia enterocolitica. The serum agglutination test (SAT) is used and results in excess of 31 international units (iu) are considered positive. The complement fixation test (CFT) is used in conjunction with the SAT for export testing purposes within the EU.

Standards used with the EU for intra community trade.

- Serum agglutination test (SAT) - More than 31iu classified as a failure.
- Complement fixation test (CFT) More than 25iu classified as a failure.


  • There is no effective treatment. Antibiotics give a poor response.
Management control and prevention
  • This is based on identifying herds free from B. suis infection and maintaining them by purchasing pigs only from herds free of disease. In some countries eradication programmes are being carried out by identifying infected herds and removing them.
  • Once a country is declared free of the disease, serological testing of incoming breeding stock has proved highly effective in preventing disease spread.

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