MRSA infections that are transmitted from dogs and cats to their human handlers, and vice-versa, are increasing—with infections of the skin, soft-tissue, and surgical infections the most common.

MRSA, or methicillin-resistant Staphylococcus aureus, is a term often used to describe staph infections that are resistant to antibiotics. This and other bite-related and septic syndromes caused by cats and dogs are discussed in a Review in the July 2009 edition of The Lancet Infectious Diseases, written by Dr. Richard Oehler and colleagues at the USF College of Medicine and James A. Haley Veterans’ Hospital.

In the United States, dog and cat bites make up roughly 1 percent of emergency room visits yearly, with similar numbers reported in Europe. Women and the elderly are most at risk of being bitten by a cat. Men in general and those younger than 20 of both sexes are most likely to be injured. Most bite exposures occur in young children, involve unrestrained dogs on the owner’s property, and about 20 percent involve a non-neutered dog.

Risk is highest in young boys ages 5 to 9, because of their small size and lack of understanding of provocative behaviour, the authors write. Children, due to their small height, often receive bites to the face, neck, or head. Adults are most frequently bitten on the hand, followed by face, scalp, neck, thigh or leg.

Proper treatment of dog and cat bites should involve treatment of the immediate injury (whether superficial or deep) and then management of the risk of acute infection, including washing with high pressure saline if possible, and antibiotics in selected cases.

Severe infections can develop in about 20 percent of all cases, and are caused by Pasteurella, Streptococcus, Fusobacterium, and Capnocytophaga bacteria from the animal’s mouth, plus possibly other pathogens from the human’s skin. In countries with endemic rabies, rabies prophylaxis should be considered.

Sepsis can be a severe complication of bite wounds, particularly those infected with C canimorsus, P multocida, Staphylococcus spp (including MRSA), and Streptococcus spp. Meningitis, endocarditis, and peritonitis can also complicate bite-wound infections. Several other species, including Bacteroides, Fusobacterium, Neisseria, and Prevotella, might also produce bite-wound sepsis in individuals with leukaemia and lupus, and in those receiving chronic steroids.

As community-acquired strains of MRSA increase in prevalence, 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. MRSA colonization has been documented in companion animals such as horses, dogs, and cats, and these animals have been viewed as potential reservoirs of infection.

MRSA-related skin infections of pets seem to occur in several manifestations, including simple dermatitis, and even perineal cellulitis, and can be easily spread to owners. Some people carry MRSA germs in their noses or on their skin without realizing it, but the bacteria do not cause infection unless they enter the body — through a bite or open wound, for instance.

Specific therapy for pet-associated MRSA infections is similar to regimens used in most community-acquired MRSA syndromes. “Much more remains to be learned about MRSA and pet-associated human infections,” the authors write.

“Pet owners are often unaware of the potential for transmission of life-threatening pathogens from their canine and feline companions. 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,” they conclude.

“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.”

Other USF/VA authors of the The Lancet Infectious Diseases review were Dr. Sandra Gompf, Dr. Ana Velez, and Dr. Jorge Lamarche.

– Source: Press Release from The Lance Infectious Diseases