pet connection

I just attended a session on MRSA: Emergence of a bad bug–treatment, infection control and public health challenges. Here’s a recap of my notes. Christie, I’d hoped to find something that would be useful for you, but I’m not sure that I did.

Dr. Jeff Bender, a public health specialist at the University of Minnesota, believes that MRSA (methicillin-resistant staphylococcus aureus) infections are increasing in frequency and that pets with MRSA most likely acquire it from their owners.

A little background: MRSA is the leading cause of pneumonia, surgical wound and bloodstream infections in hospital patients. In the 1990s, a new manifestation emerged among patients that hadn’t been hospitalized. About 29 percent of the U.S. population is colonized by Staphylococcus aureus. The prevalence of MRSA colonization is about 1.5 percent.

One of the first cases evidencing human-to-animal transmission was in the Netherlands. MRSA was cultured from the nose of a healthy dog whose owner, a nurse, was colonized with MRSA while working in a Dutch nursing home. Molecular characterization revealed that the dog and human strains were indistinguishable.

The nurse was treated twice with antibiotics. Because MRSA is uncommon in Europe, the second treatment triggered an environmental investigation of the home and family members, and both the child and dog were also identified as having MRSA. All three were treated and the infection was eventually eliminated.

Staph (S. pseudointermedius) is the most common skin flora among dogs and cats. On the plus side, no MRSA was identified in 102 dogs enrolled in human hospital visitation programs. For the most part, the percentage of animals that have it is quite low. But, Dr. Bender says, “I’m hearing disturbing trends regarding the number of cases that some folks are seeing.”

What are the risk factors for S. aureus (not MRSA) colonization of owners? An occupation in health care; the presence of other animals; sex of the dog (females are at greater risk); and size of household. Regarding household size, the theory is that in a larger household with lots of people, dogs may receive less attention. In a smaller household, the dog may receive more physical attention, such as being kissed. A higher risk of colonization wasn’t associated with frequent contact, including kissing, allowing the dog to lick the face, or sleeping on the bed.

Dr. Bender went on to discuss several cases and studies from the University of Minnesota. From 2003 to 2008, they saw 29 clinical MRSA cases identified in 7 cats, 20 dogs and 2 horses. The majority were nonhealing soft tissue or postsurgical infections. Owners were asked about potential risk factors: recent hospitalization, occupation, previous MRSA infections, visits to long-term care facilities and, surprisingly, sports participation.

One of those cases was a Beagle hit by a car. He suffered a degloving injury, resulting in nonhealing skin lesions. The owner worked in a mortuary, so that was a possible source of infection. A family cat developed septic arthritis that persisted for several months. How the cat acquired the infection is unclear. The owner had previously cared for a severely ill family member, so it’s a possible example of human to animal transmission.

One study looked at animal-assisted activities in health care settings. In it, 10 therapy dogs were sampled weekly for 10 weeks. Handlers, who also gave samples, completed a questionnaire covering location, length and frequency of visits, and types of interactions. MRSA was recovered from two dogs and their handlers. All isolates were healthcare-associated strains and were indistinguishable. This therapy dog group worked in one particular hospital so that strain might have been in circulation at that hospital at that time.

Risk factors for canine infections included visits to health care centers and interaction with children. Drum roll for funniest line: “The most dangerous animal on the planet is a child.”

Dog behaviors related to acquiring MRSA infection were licking patients and being given treats by patients.

The takeaway

Do visitation animals transmit disease? No reported outbreaks have been attributed to visitation animals, but they can carry infectious agents and they can acquire infectious agents while visiting.

MRSA infection is increasing in frequency.

Pets with MRSA most likely acquire the infection from their owners.

Pets with MRSA appear to be transiently colonized and don’t need treatment; that doesn’t apply, of course, to animals with clinical infections.

Emphasize hand hygiene to decrease potential risk of transmission from and/or to pets.

Discourage dogs from licking human patients.

Consider asking patients to wash their hands.

Further research is needed to quantify household risk, length of carriage in pets, and evaluation of treatment options for pets.

In general, disinfection procedures that we currently have are sufficient to control this bug.

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