Horses can be infected with Brucella abortus or B suis. Suppurative bursitis, most commonly recognized as fistulous withers 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 or poll evil (bursitis) is the most common condition associated with brucellosis in horses (often with Actinomyces bovis infection also). Occasionally, abortion has been reported. It is unlikely that infected horses are a source of the disease for other horses, other animal species, or humans. Brucellosis in horses is very rare in the US because of elimination of the disease in cattle.