Methicillin-resistant Staphylococcus aureus is a bacteria that has developed a resistance to many antibiotics, making infections difficult and sometimes impossible to treat. The American Medical Veterinary Association notes that MRSA is the 10th-leading cause of human death in the United States and the most common antibiotic-resistant pathogen reported in hospitals and other health care facilities. Originally thought to be a problem only in humans, MRSA is considered an emerging health concern in veterinary medicine and has been detected in dogs, cats, cows, horses, pet birds and pigs.
Cause and Transmission
A dog that carries MRSA but has no symptoms is considered colonized by the bacteria. MRSA is commonly found on the skin and in nasal passages and is transmitted by direct contact with a colonized animal. Some experts think that dogs are transient carriers of MRSA and that colonization lasts only two or three weeks. In such a case, isolation from at-risk people or animals may be all that is necessary to prevent transmission of the bacteria.
Most healthy dogs will not become infected by MRSA, but some situations may put them at a higher risk. Dogs that live with health care workers, veterinary personnel or immune-compromised humans may be more susceptible to MRSA infection. Additionally, therapy dogs that visit long-term care facilities, hospitals or nursing homes are more likely to come into contact with or become infected with the bacteria. Dogs with a compromised immune system, of course, are at a higher risk of MRSA infection.
Symptoms and Diagnosis
Dogs with MRSA commonly show signs of skin and ear infections. Other symptoms include infected wounds or post-surgical sites. Less commonly, a dog might develop a urinary tract infection, pneumonia or an infection at an IV site. Diagnosis of MRSA in dogs can be difficult, as many veterinary laboratories are still unfamiliar with the bacteria. Cultures to test for S. aureus are run first; if it is found, further testing is done to determine whether MRSA is present.
Asymptomatic dogs colonized with MRSA generally do not require treatment. When symptoms are present, treatment is based on the type of infection and the location. For skin infections, an antibiotic cream on the infected area, oral antibiotics or both may be prescribed. Culture testing is important to determine which antibiotics might be effective. In some cases, drainage and debridement of the area might be necessary.
Good hygiene is an essential component of preventing MRSA outbreaks. Dogs that have been successfully treated for MRSA are not immune from reinfection, and pets and people may pass the bacteria back and forth. When MRSA colonization or infection is confirmed, owners should practice frequent hand-washing; regularly clean dog toys, bones and bowls; and take special care when tending to cuts, scrapes or wounds. Therapy dog owners should also discourage their dog from licking or shaking paws with patients, restrict interaction to patients and families rather than medical personnel, use a towel or pad as a barrier between the dog and any bedding, and avoid visiting patients in isolation units.
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