Swine brucellosis

Swine brucellosis is a venereal disease that infects pigs during mating.

Farmed domestic pigs have not had any new cases of swine brucellosis in Queensland since 1991. In feral pigs, however, the disease hasn't been eradicated (completely removed). Breeding stock should be purchased only from a 'clean' pig herd.

Scientific name

Brucella suis


Bacterium Brucella suis



Affected animals

  • pigs

Clinical signs

  • Infertility (failure to conceive)
  • Irregular oestrus cycle
  • Abortion
  • Birth of stillborn, mummified or weak piglets
  • Sows aborting usually once and, after that, breeding normally but remaining carriers, shedding the bacteria in milk and uterine discharge
  • Swelling of 1 or both testicles of infected boars and reduced sexual drive
  • Boars and sows become lame or even paralysed in the hindquarters.
  • Arthritis occurs in lame and paralysed pigs

How it is spread

In contrast to brucellosis in cattle, swine brucellosis is a venereal disease and pigs are infected during mating.

Infected boars that keep their sex drive infect sows at mating which prevents them conceiving or causes them to abort. In reverse, infected sows shed bacteria in discharge from their uterus, which infects boars during mating. These discharges are rarely seen as abnormal.

Brucellosis is not solely spread through genital contact. Pigs can also be infected by bacteria they take in via the mouth. This occurs when sows eat aborted foetuses, or when the boars and sows encounter vaginal or uterine discharges during courting before mating. Producers running sows and gilts outdoors for all or part of their production cycle should be aware of the risk posed by feral pigs and implement an appropriate biosecurity program.

Monitoring and action

Brucellosis symptoms (above) are not unique to the disease. All except testicle swelling occur relatively regularly in individual pigs.

Brucellosis is mainly diagnosed by a laboratory test performed on serum (the liquid part of blood that remains after clotting). The test is not reliable when you only test individual animals, as the results will sometimes be negative after they have become infected. However, the test is accurate if you collect samples from all the breeders in a herd.

Laboratories may also diagnose brucellosis by growing the bacteria that causes the disease from the suspect animal, such as a boar with swollen testicles.

Post-mortem may show chronic inflammation of the uterus with white nodular appearance and abscess.


  • No treatment exists for brucellosis in pigs. To control the disease, you should slaughter all affected animals
  • You should only purchase breeding stock from a brucellosis-clean herd
  • Our Brucella suis accredited herd scheme makes this possible. The scheme, based on herd history, herd security and risk assessment, is accepted by all states and has been used in Queensland since 2001
  • When buying breeding stock you should seek the advice of your veterinary consultant to confirm that you are buying from herds free of brucellosis and ideally registered in this scheme

Further information