Myonecrosis and cutaneous infarction associated with Salmonella serovar Infantum infection in a horse

A 5-year-old Quarter Horse mare was referred for evaluation of oral ulcers, limb edema, weight loss, and weakness. There was marked diffuse swelling extending from the stifle region to the tarsal region of the left hind limb, and the horse had a left hind limb lameness. Firm swellings ranging from 2 to 15 cm in diameter and consisting of nodules, plaques, and discrete masses were palpated on both sides of the neck, over the right shoulder region, over the left elbow region, and over the left caudoventral aspect of the abdomen. Laboratory abnormalities included hypoproteinemia, neutrophilia, and hyperfibrinogenemia. Results of ultrasonographic examination of the left hind limb and masses were suggestive of muscle edema, necrosis, and hemorrhage. Histologic examination of a biopsy specimen from a subcutaneous mass revealed necrotizing, suppurative myositis. The horse's condition gradually deteriorated, and the horse was euthanatized. Necropsy revealed myonecrosis, cutaneous infarcts, hepatic abscesses, and cholangitis. Salmonella serovar Infantum was cultured from liver and muscle lesions, and a diagnosis of Salmonella myonecrosis was made.