Yes, horses can get brucellosis. While the disease is more commonly associated with cattle, goats, and pigs, horses are natural hosts for several Brucella species and can develop serious infections. The global seroprevalence in horses is estimated at about 1.92%, though rates vary dramatically by region, from effectively 0% in Europe to as high as 10% in parts of Asia.
Which Brucella Species Infect Horses
Three species of the Brucella bacterium are known to cause disease in horses: Brucella abortus (the species most associated with cattle), Brucella suis (typically linked to pigs), and Brucella canis (usually found in dogs). Of these, B. abortus is by far the most common cause of equine brucellosis.
Horses typically pick up the infection through contact with other infected livestock. In regions where horses share grazing land with cattle, sheep, goats, or buffalo, the bacteria can pass between species through contaminated body fluids, birth tissues, or environmental exposure. This is why equine brucellosis is more common in areas with traditional or semi-industrial livestock systems where multiple species are kept together.
How Brucellosis Looks in Horses
Equine brucellosis doesn’t present the way most people expect a systemic infection to look. The hallmark condition is fistulous withers, a painful, draining abscess that develops along the horse’s withers (the ridge between the shoulder blades). The infection settles into the supraspinous bursa, a fluid-filled sac that sits between the vertebral spines and the ligament running along the top of the back. Over time, the bursa becomes infected and swollen, eventually rupturing through the skin and creating one or more draining tracts.
A related condition called poll evil can also occur, involving a similar abscess at the poll (the top of the head, just behind the ears). Both conditions are chronic and difficult to resolve once established. Beyond these signature presentations, infected horses may develop nonspecific lameness from joint infections, and mares can occasionally experience late-term abortions, though this is rare.
Diagnosis
Veterinarians typically diagnose equine brucellosis using blood tests that detect antibodies against Brucella. The two standard screening tests are the Rose Bengal Plate Test, a rapid initial screen, and the Serum Agglutination Test, which confirms the result with greater specificity. A positive antibody test indicates the horse has been exposed to the bacteria and mounted an immune response.
In some cases, the bacteria can be cultured directly from fluid draining from a fistulous withers or poll evil lesion, which provides a definitive diagnosis. Researchers have isolated Brucella abortus biotype 1 from infected foals, confirming that younger horses are also susceptible.
Treatment Is Prolonged and Difficult
Treating equine brucellosis is not straightforward. The recommended approach combines systemic antibiotics with surgical removal of infected tissue and thorough flushing of the wound. Treatment tends to be prolonged because the bacteria can survive inside the horse’s cells, making them difficult for antibiotics to reach. Recurrence after apparent recovery is a known challenge. Some cases of fistulous withers or poll evil require repeated surgical interventions before the infection clears.
Risk to Humans
Brucellosis is zoonotic, meaning it can spread from animals to people. Horses with draining fistulous withers or poll evil lesions pose a potential risk to handlers, farriers, and veterinarians who come into direct contact with contaminated fluids. According to UC Davis School of Veterinary Medicine, B. abortus can be transmitted from horses to humans through contact with contaminated body fluids, tissues, or carcasses, though documented cases of horse-to-human transmission are rare.
In humans, brucellosis causes fever, loss of appetite, headache, back and joint pain, and weight loss. The symptoms can mimic many other illnesses, which sometimes delays diagnosis. Most people recover within three weeks even without treatment, but the infection can become chronic if not properly addressed.
Prevention Through Livestock Management
Because horses almost always acquire brucellosis from other livestock species, the most effective prevention strategy is controlling the disease in cattle, goats, and pigs. Countries that have successfully eradicated bovine brucellosis through vaccination and testing programs see virtually no equine cases. Europe’s 0% seroprevalence in horses reflects this directly.
For horse owners in regions where brucellosis still circulates in livestock, minimizing shared grazing with cattle and other ruminants reduces exposure risk. Any horse that develops unexplained swelling or draining abscesses at the withers or poll should be evaluated for brucellosis, particularly if the horse has had contact with cattle or other potentially infected animals. Wearing gloves when handling drainage from suspicious lesions protects both the handler and helps prevent environmental contamination.