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. The causes can range from overuse, mild trauma, or severe trauma to sepsis. Bursitis in its various forms is more common and a more important... 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.