Scedosporium prolificans infection associated with arthritis and osteomyelitis in a horse

Scedosporium prolificans was associated with arthritis and degenerative osteomyelitis in a 6-year-old Thoroughbred racehorse. The horse was suspected to have an inflammatory lesion of the interosseous tendon, but treatment had resulted in only a minimal response. Shortly after diagnostic arthrocentesis of the left metacarpophalangeal joint was performed, the joint became severely swollen, and radiography of the area revealed lysis of the distal end of the third metacarpal bone, the proximal sesamoid bones, and the proximal end of the proximal phalanx. The horse did not respond to treatment and was euthanatized. At necropsy, severe erosive arthritis and degenerative osteomyelitis of the left metacarpophalangeal joint were seen. Swab specimens of the ulcerated lesions of the articular cartilage were submitted for microbial culture, and Scedosporium prolificans was isolated. Scedosporium prolificans is a newly recognized opportunistic fungal pathogen of humans and animals. In humans, S prolificans typically causes focal locally invasive infections that primarily involve musculoskeletal tissues; most often, infection is a result of penetrating trauma or surgical incision. In immunocompromised patients, fatal disseminated infection can occur. The fungus is resistant to almost all currently available antimycotic agents.