MRSA was long thought to be a disease that only affected humans. However, in 1972, veterinarians reported the infection in a dairy cow. Since then, MRSA has been found in other farm animals, dogs, cats and pet birds.

Staphylococcus aureus (S. aureus, or “staph”) is a bacterium that often lives on the skin and in the nose. Methicillin-resistant S. aureus (MRSA) refers to strains of the bacteria that have developed resistance to methicillin, a penicillin-type antibiotic, and other common antibiotics.

The Centers for Disease Control and Prevention estimates about one-third of Americans have S. aureus bacteria on their skin at any time. Most people don’t develop an infection from it.

When infection occurs, patients can develop a red, swollen, painful lump on the skin. The area may be warm to the touch or contain pus or fluid. Patients also often have a fever. About one percent of people with a staph infection have MRSA.

The exact incidence of MRSA in pets isn’t known. However, a recent Canadian study of 122 households over a two month period found 1.5 percent of dogs were colonized with MRSA (i.e., the bacteria was obtained from their nostrils, but the animals had no symptoms of infection). MRSA wasn’t found in any cats.

In pets, the most common sites of a MRSA infection are the skin and ears. MRSA is more likely to occur in pets that are given certain antibiotics, have an IV catheterization, urinary tract infection, pneumonia, skin or ear infection, are admitted to a vet clinic or receive some type of surgical implant. In another study, dogs with MRSA were hospitalized for a mean of 3.4 days. 40 percent of the animals required surgery for treatment of the infection.

MRSA is not very common in pets, but it thrives in humans. Therefore, when a pet gets MRSA, the most likely source of infection is a human. Daniel Morris, D.V.M., M.P.H., Veterinary Dermatologist with the University of Pennsylvania School of Veterinary Medicine in Philadelphia, PA, says the bacteria are spread through saliva and body secretions or through contact with an open wound. Pets become contaminated when they lick a human’s body or a human with contaminated skin snuggles with or pets the animal’s fur.

Animal MRSA is more common in homes where one or more of the human occupants have an infection. Morris says dogs can carry the bacteria on their body and not have any signs of infection. Cats can carry the bacteria for an even longer time. Thus, even after the human has gotten over the infection, it’s possible for the animal to give MRSA back.

To reduce the risk of transmission between humans and pets, Morris recommends following good hygiene. Humans who are infected should stay away from pets and not allow the animals to lick wounds or the face. The American Veterinary Medical Association recommends taking a pet for testing whenever any human in the home has a MRSA infection to ensure the animal is not a carrier of the bacteria.

If a pet develops MRSA, topical or oral antibiotics can often be administered to cure the infection. To prevent spread to humans, the pet should be isolated from any human who is ill or recovering from an illness (including a MRSA infection). Pet owners should wear disposable gloves when cleaning the pet’s wounds. Wash hands frequently with warm soap and water and disinfect all surfaces the animal touches, including floors and bedding. Morris also recommends frequent cleaning of food and water dishes and keeping the pet off the bed until the infection is cleared.

For information about MRSA in pets, go here.