A Pet's Bite Can Pass on MRSA

The spread of methicillin-resistant staphylococcus aureus (MRSA) infections between pets and humans is increasing, with the most common being infections of the skin, soft-tissue and surgical infections, say researchers who conducted a review of clinical evidence.

"Pet owners are often unaware of the potential for transmission of life-threatening pathogens from their canine and feline companions," Dr. Richard Oehler, of the University of South Florida College of Medicine in Tampa, and colleagues wrote in the July issue of The Lancet Infectious Diseases.

Dog and cat bites account for about 1 percent of emergency department visits each year in the United States and Europe. Severe infections occur in about 20 percent of all cases and are caused by bacteria from the animal's mouth, plus possibly other bacteria from the human patient's skin, the study authors pointed out.

The researchers noted that most pets do not carry MRSA -- in fact, one study found that just one in every 10 dogs or cats that carried any kind of staphylococcus carried the S. aureus strain. And of this group, only about a third (35 percent) were found to carry the MRSA strain, according to a study done at the University of Pennsylvania Veterinary School.

Still, increasing prevalence of community-acquired MRSA in humans has been accompanied by MRSA colonization in domestic animals. This makes the animals potential reservoirs of MRSA infection, the researchers said.

In fact, the study found that in some cases, pets may be picking the pathogen up from humans. "A growing body of clinical evidence has documented MRSA colonization in domestic animals, often implying direct acquisition of S. aureus infection from their human owners," the team noted. MRSA-related skin infections in pets can then easily spread back to humans, the article noted.

Not all MRSA infections are isolated to the skin. Sepsis, a potentially fatal bloodstream infection, can be a complication following bite wounds from a pet infected with MRSA, as well as a number of other types of bacteria, the team noted.

"Bite injuries are a major cause of injury in the USA and Europe each year, particularly in children. Bites to the hands, forearms, neck and head have the potential for the highest morbidity," the study authors concluded. "Health-care providers are at the forefront of protecting the vital relationships between people and their pets. Clinicians must continue to promote loving pet ownership, take an adequate pet history, and be aware that associated diseases are preventable via recognition, education, and simple precautions."

Treatment of MRSA infections in pets is similar to that used in humans, the experts said. And for the most part, the danger to pet owners -- even those most vulnerable to MRSA -- remains low.

"Contact with an asymptomatic pet is not a risk factor for sensitive or immunocompromised patients for acquiring S. aureus, because most household pets are not likely to be MRSA colonized," the researchers wrote.

More information

The U.S. National Institute of Allergy and Infectious Diseases has more about MRSA.

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