Staphylococcosis

Staphylococcus aureus infections are common in poultry; the most frequent sites being bones, tendon sheaths, and joints, especially tibiotarsal and stifle joints.

ETIOLOGY The genus Staphylococcus contains approximately 20 species. It is the most important genus in the family Micrococcaceae. The term staphylococcus refers to the morphology of microorganisms in stained smears, which resemble grapelike clusters. Staphylococci frequently isolated from poultry include S. aureus and S. epidermidis.

Natural and Experimental Hosts All avian species are susceptible to staphylococcal infections. Transmission, Carriers, and Vectors The pathogenesis of S. aureus is not completely defined, but for infection to occur, a breakdown in natural defense mechanisms of the host must occur . In most cases, this would involve damage to an environmental barrier, such as a skin wound or inflamed mucous membrane.

Clinical Signs Early clinical signs include ruffled feathers, lameness of one or both legs, drooping of one or both wings, reluctance to walk, and fever. This can be followed by severe depression and death. Birds surviving the acute disease have swollen joints, sit on their hocks and keel bone, and are reluctant or unable to stand.

Gross. Gross lesions of osteomyelitis in bone consist of focal yellow areas of caseous exudate or lytic areas, which cause affected bones to be fragile. Bones and sites most frequently involved are the proximal tibiotarsus and proximal femur.

A. Osteomyelitis of proximal tibiotarsus in a 13-week-old turkey

E. Leghorn, 20-week-old. Multiple foci of necrosis in liver following septicemic staph infection.

DIAGNOSIS Isolation and identification of causative agent

Differential Diagnosis Staphylococcosis can resemble infection with E. coli, Pasteurella multocida, Salmonella gallinarum, Mycoplasma synoviae, reoviruses, or any other infection of bones or joints that is hatchery-related, associated with mechanical trauma, or causes septicemia.

Treatment S. aureus infection sometimes can be treated successfully, but sensitivity tests should always be performed, because antibiotic resistance is common. Drugs used successfully for treatment include penicillin, streptomycin, tetracyclines, erythromycin, novobiocin, sulfonamides, lincomycin, and spectinomycin.