Horses can be infected with Brucella abortus or B suis. Suppurative bursitis, most commonly recognized as fistulous withers or poll evil (see Fistulous Withers and Poll Evil Fistulous Withers and Poll Evil Bursitis is an inflammatory reaction within a bursa that can range from mild inflammation to sepsis. It is more common and important in horses. It can be classified as true or acquired. True... read more ), is the most common condition associated with brucellosis in horses. Occasionally, abortion has been reported. It is unlikely that infected horses are a source of the disease for other horses, other animal species, or people. Brucellosis in horses is very rare in the USA because of elimination of the disease in cattle.