Brucellosis
Also called Contagious abortion, Bang's disease (cattle); undulant fever (people)
A bacterial disease whose main sign is abortion late in pregnancy. Infected animals can stay infected for years and spread it through birth fluids and milk, and people can catch it too.
Cause and spread
- Cause
- Bacteria of the genus Brucella: Brucella abortus mainly in cattle and buffalo, Brucella melitensis mainly in goats and sheep.
- How it spreads
- Through vaginal discharges, aborted calves and lambs and the afterbirth, and through milk. Animals take it in by licking or eating contaminated material or through broken skin. People catch it from infected animals, their tissues and unpasteurised milk products.
- People
- Brucellosis spreads from animals to people through contact with birth products or raw milk and cheese. Wear gloves when handling aborted material and drink only pasteurised or boiled milk.
Signs to watch for
- Abortion, usually in the second half of pregnancy
- Stillbirths and weak calves or kids born alive that may die soon after
- Retained afterbirth and womb infection afterwards
- Swollen testicles in bulls (orchitis, epididymitis)
- Joint swelling and hygromas in long-standing infection
- Lower milk yield
Many diseases look alike. Only a laboratory test can tell them apart, so please see a veterinarian for any sick animal.
How it is diagnosed
Abortion has several causes, so the cause has to be proved. Antibodies in the blood (ELISA) are the usual screening test for the herd, and PCR or culture of aborted material, vaginal swabs or milk confirms the bacteria. Infected animals can be missed by blood tests, especially if infected when young, so herd additions are tested and kept apart first.
- Usually the first testBrucellosis ELISADetects antibodies. The usual screening test for a herd or after an abortion.
- Confirms the diseaseBrucellosis PCRFinds the bacteria themselves in aborted material, milk or swabs.
- Supports the diagnosisAbortion Panel (Brucellosis, Neospora, BVD) (panel)Looks for brucellosis and two other common causes of abortion together.
Prevention and control
- Buy replacement animals only from tested, brucellosis-free herds, and quarantine and re-test new animals before they join the herd
- Remove and destroy afterbirth, aborted calves or lambs and soiled bedding quickly, and disinfect the area
- Keep animals that have just aborted away from the rest of the herd
- Do not use the offspring of infected animals as replacements
- Vaccination of calves is used in areas where the disease is common; ask your veterinarian
Where this information comes from
- Brucellosis: Brucella abortus (factsheet) · Center for Food Security and Public Health, Iowa State University
- Brucellosis: Brucella melitensis (factsheet) · Center for Food Security and Public Health, Iowa State University
- Brucellosis in Cattle · Merck Veterinary Manual
General information for animal owners and veterinarians, last checked October 2026. It does not replace the advice of your veterinarian, who should decide which tests and treatment your animal needs.