Staphylococcosis in Poultry

Staphylococcosis is a bacterial disease caused by gram-positive cocci of the genus Staphylococcus. S aureus and other species are ubiquitous in the environment and are part of the normal flora of the skin and other mucous membranes of poultry and other animals. They typically cause disease when they have access to tissue and the bloodstream after physical barriers, such as skin or mucous membranes, break down. They also cause disease in immunocompromised birds.

There are two major types of staphylococci: 

• systemic infection     

•   localized lesions

•  Septicemia and gangrenous dermatitis are examples of systemic staphylococcal infections.
•  The most common form of staphylococcosis, however, is localized lesions. Examples include arthritis, tenosynovitis, osteomyelitis, and omphalitis. Economic losses may result from decreased weight gain, mortality, and condemnation at slaughter.

Etiology of Staphylococcosis in Poultry:

 

The genus Staphylococcus contains dozens of species, but S aureus is the most pathogenic. S aureus is a gram-positive, catalase-positive, coccoid bacteria that appears in grape-like clusters on stained smears. Most pathogenic strains have been coagulase-positive; however, coagulase-negative Staphylococcus, including S hyicus, S epidermidis, S simulans, and S gallinarum have been reported from clinical cases.

 

Transmission:

• Skin wounds, minor surgical procedures (ie, beak, toe, or comb trimming), vaccine injection, and compromised intestinal mucosa can introduce Staphylococcus to local tissue or into the bloodstream. 
• Infection can also occur in the hatchery as a result of contamination of an open navel. 

• Once in the bloodstream, Staphylococcus can produce systemic disease or localized lesions in tissues. S aureus can invade the metaphyseal area of joints, leading to arthritis and osteomyelitis.

 

Clinical Signs of Staphylococcosis:

Clinical signs can be localized or systemic in this case.

• Localized Infection:

• Bumblefoot (pododermatitis) is more common in heavier birds and in males. Swollen footpads and limping are common clinical signs. The footpad’s subcutaneous tissue becomes contaminated due to injuries frequently. Acute necrotic inflammation results from this, and eventually it turns into a mass of dead tissue. Under a microscope, the lesions show signs of edema, necrosis, and granulomas that could be bacterial colonies.

• Omphalitis, or infection of the yolk sac,caused by S aureus in young chicks. Navel infections can occur in young hatchlings via contamination of open navels and results in elevated mortality. Chicks with omphalitis have moist and dark navels, and affected birds are often lethargic. Infected yolk sacs are retained longer than uninfected yolk sacs, which are normally resorbed by the developing chick within the first week of life. Infected yolks are abnormal in color (dark green to brown), have a doughy consistency, and are odorous.

• Arthritis, synovitis, and osteomyelitis are common forms of staphylococcal infection in poultry. They can begin in the joints, tendons, or bone through systemic infection or through local injury. Clinical signs include swollen, hot joints with limping and reluctance to walk. Increased fluid is present in the joints, tendons and their sheaths are irritated, and bone sections may have isolated pockets of necrosis (osteomyelitis). The proximal head of the tibiotarsus and the femoral head are frequently impacted. Spondylitis may result from further damage to the vertebrae.

 

2. Systemic Infection:

•  Clinical signs included sudden death and a sharp increase of mortality, approaching 1% per day, with signs of cutaneous inflammation and necrosis of comb, wattles, and skin overlying the breast and thigh. Acute septicemic infection lesions in the dead birds include liver necrosis, an enlarged mottled spleen, and petechial hemorrhages in the proventricular glands, brains, and lungs. Following 5–7 days of antibiotic therapy, mortality usually decreases. Affected birds typically perish, resulting in a 5%–10% mortality rate despite little morbidity.

• Lesions that are sequalae of systemic infections are sometimes the only pathologic findings observed in staphylococcal infections. Gangrenous dermatitis is observed, particularly in immunocompromised chickens, affected by infectious bursal disease or chicken anemia virus infection. Gangrenous dermatitis is often due to a combination of S aureus and Clostridium septicum and/or Escherichia coli. Affected areas are usually hemorrhagic and crepitant. Endocarditis can also occur following systemic staphylococcal infections.
• Staphylococcal septicemia can result in green livers or livers with multifocal necrotic granulomas. S aureus has been indicated to be the etiologic agent behind turkey osteomyelitis complex, which causes green discoloration of the liver and inflammatory lesions in the bones, joints, or periarticular soft tissues. Green livers are common in turkeys, leading to increased condemnation in the processing plant. Hemorrhagic enteritis virus, another immunosuppressive agent, is thought to contribute to increased green livers in turkeys.

Diagnosis of Staphylococcosis:

• Infection is confirmed by culture of bacteria from lesions

Although some lesions may be suggestive of a Staphylococcus infection, diagnosis is confirmed by identifying the organisms from lesions cultured on blood agar plates. Phenotyping and genetic techniques have been used to classify strains of poultry S aureus. Differential diagnoses include Streptococcus species, E coli, and Pasteurella multocida as well as other bacterial diseases of poultry. As mentioned, Staphylococcus bacteria are ubiquitous in the environment and cause disease as secondary pathogens. So, the mere isolation of Staphylococcus does not necessarily constitute a disease diagnosis. In fact, it is more often that they are contaminants.

Zoonotic Risk:

S aureus can cause food poisoning in people. Enterotoxin-producing strains are found on clinically healthy poultry, and proper precautions should be taken during the handling and cooking of poultry products. Methicillin-resistant S aureus (MRSA) has been isolated from poultry meat in a number of countries, but the prevalence and significance for human health are incompletely understood.

Treatment of Staphylococcosis :

• Systemic infections respond better to antimicrobial treatment that localized infections
• Improved management can prevent injuries that allow infection to become established

• Staphylococcosis can be successfully treated with antibiotics, but an antimicrobial susceptibility test should be performed. 
• Antibiotics used to treat Staphylococcus infections include penicillin, erythromycin, lincomycin, and spectinomycin. 

Proper management to prevent injury and immunocompromised poultry helps prevent staphylococcosis. Because wounds are the primary route by which Staphylococcus can enter the body, it is important to reduce all potential sources of injury to the bird. Wood splinters in litter, protruding wires from cages, and fighting/cannibalism have been associated with skin wounds and staphylococcosis. Because beak and toe trimming procedures in young chickens and turkeys could result in a staphylococcal septicemia, ensuring that equipment is sanitary will help to prevent outbreaks. Good litter management is important in controlling footpads injuries to prevent bumblefoot. Hatchery sanitation and good egg management practices are also important to reduce navel infections and omphalitis.