Fistulous withers, also known as poll evil, is a condition in horses where an abscess forms in the withers region of their back, causing pain and discomfort. There are several synonyms to describe this condition, including suppurative withers, purulent withers, and abscess of the withers. Other descriptive terms may include infected withers or inflamed withers. It's essential to identify and treat fistulous withers as soon as possible to avoid further complications. Treatment typically involves draining the abscess and administering antibiotics to prevent infection. Regular inspections of a horse's withers can help prevent the onset of this condition and ensure the health and well-being of animals.