Updated 15 January 2015

Cat bites may lead to serious infections

When cats bite, their sharp teeth can inject hard-to-treat bacteria deeply into the skin and joints, increasing the risk of serious infection.


Cat bites may look less serious than dog bites, but beware: They can cause dangerous infections, particularly when they involve the hand, new research indicates.

Although cats have no more germs in their mouths than dogs or people, researchers at the Mayo Clinic found that when cats bite, their sharp teeth can inject hard-to-treat bacteria deeply into the skin and joints, increasing the risk for serious infection.

Cats' teeth are sharp

"Dogs' teeth are blunter, so they don't tend to penetrate as deeply and they tend to leave a larger wound after they bite," study senior author Dr. Brian Carlsen, a Mayo Clinic plastic surgeon and orthopaedic hand surgeon, said in a clinic news release. "Cats' teeth are sharp and can penetrate very deeply. They can seed bacteria in the joint and tendon sheaths."

"It can be just a pinpoint bite mark that can cause a real problem," he said, "because the bacteria get into the tendon sheath or into the joint where they can grow with relative protection from the blood and immune system."

The researchers studied nearly 200 cat bite cases that occurred between 2009 and 2011. The patients involved in the study were all bitten on the hand. The average of the participants was 49 years old, and 69% were women.

About half the patients visited an emergency room, while the rest went to their primary-care physician. The average time people waited between getting bitten and seeking treatment was 27 hours.

Read: Cat scratch disease

Reconstructive surgery

The researchers said 57 of the patients who were bitten needed to be hospitalised, but only 36 had been admitted immediately after seeking medical treatment.

Of those admitted to the hospital, 38 patients needed surgery to clean the wound or remove infected tissue. The study, published in the Journal of Hand Surgery, also revealed that eight patients needed more than one surgical procedure, and some needed reconstructive surgery.

Meanwhile, 80% of the patients were initially prescribed oral antibiotics, the researchers said. For 14% of these patients, outpatient treatment with antibiotics didn't work and they needed to be hospitalised.

In most cases, bites that were positioned directly over the wrist or another joint were more likely to result in hospitalisation than bites to soft tissue, the researchers said.

Cat bites need to be taken seriously

Cat bites need to be taken seriously and carefully evaluated by doctors, the study authors said. This is particularly true when patients develop inflamed skin and swelling. In these cases, the researchers said, the wound should be treated aggressively.

"Cat bites look very benign, but – as we know and as the study shows – they are not," Carlsen said. "They can be very serious."

Read more:
Infections from cat and dog bites
Animal and human bites

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