Veterinary advice should be sought before applying any treatment or vaccine.


Brucellosis is a bacterial disease mainly of cattle and pigs, however there are many documented cases of infection occurring in horses as well. Humans are also at risk of brucellosis, for it is a serious zoonotic disease. Brucellosis is caused by infection with the Brucella abortus and/or B. suis. Horses infected with B. abortus have concurrently developed fistulous withers, poll evil, and other bursal infections, septic arthritis, vertebral osteomyelitis, and abortion in mares. A survey conducted on 85 horses with fistulous withers revealed that B. abortus was isolated from 80% of the affected horses. Of those horses with B. abortus infection, 92% had reported contact with cattle.

How it is Spread to Horses

The main source of infection in horses is infected pigs and cattle. Brucella is spread through ingestion of food, pasture, and water contaminated with urine, plascenta and discharges from infected animals. The organism is moderately resistant to environmental effects, however it is rapidly destroyed with direct sunlight. It can survive in manure, urine and water for 4-6 weeks and much longer in freezing conditions.

Risk Factors

  • Horses in contact with cattle or pigs
  • Housing horses in pastures that were previously used for cattle or pigs.

Causative agent