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Cat bites to the hand can cause serious infections, Mayo study finds

Cats' sharp teeth make relatively deep puncture wounds
MinnPost photo by Corey Anderson
Cats' sharp teeth make relatively deep puncture wounds that are prone to infection.

Cat bites should be taken seriously, for they can lead to difficult-to-treat bacterial infections — in fact, much more so than dog bites — according to a new study by researchers at the Mayo Clinic.

The study, published in the February issue of the Journal of Hand Surgery, found that almost a third of the people who sought treatment at the Mayo Clinic for a cat bite to the hand during a recent three-year period had to be hospitalized. And of the patients who were hospitalized, two-thirds ended up needing surgery to flush out the bacteria and remove infected tissue.

The Mayo Clinic researchers undertook the study to see if they could identify any new risk factors that could help predict which patients who seek treatment for a cat bite to the hand will eventually require hospitalization. Most of what they found, however, simply confirmed what they already knew: Such bites are more likely to lead to hospitalization when they occur over a joint or tendon and are accompanied by swelling, redness and pain. The risk increases for people with existing immune-deficiency disorders.

“The hand surgery community isn’t so shocked by our paper, but I do think the public may be surprised,” said Dr. Brian Carlsen, a hand surgeon at the Mayo Clinic and one of the study’s authors, in a phone interview Monday.

After all, when most people think of dangerous animal bites, they tend to think of dogs, not cats.

Sharper teeth

What is it about cats that make their bite wounds so prone to infection? Their teeth are sharp and make relatively deep puncture wounds. When the bite is on the hand (and other research has shown that up to 85 percent of cat bites occur on the hand or wrist), the puncture may easily pierce a joint or the membrane sheath around a tendon. Joints and tendons have closed spaces, and are thus great growing places for bacteria. And the mouths of cats (like those of dogs — and of humans, for that matter) are home to many types of bacteria.

Dr. Brian Carlsen
Dr. Brian Carlsen

“When bacteria gets into the joints or into the tendon sheaths, that’s a surgical emergency, no matter what the source,” said Carlsen. That’s because antibiotics tend to be unable to reach those infections. Only through surgery can the bacteria be washed out and removed.

If the surgery is delayed too long, patients can develop permanent damage to the hand, including a loss of joint mobility. Those patients may then require reconstructive surgery to replace the damaged tendons or joints.

“I have seen some really bad infections [from cat bites] that have required multiple operations,” said Carlsen. “I had one patient, a farmer, whose tendons were destroyed on the back of his hand by the infection. He couldn’t straighten his fingers out. We had to reconstruct the tendons.”

Study details

For the current study, Carlsen and his colleagues looked at the medical records of people who had shown up at the Mayo Clinic’s emergency room in Rochester with a cat-bite wound to the hand between January 2009 and December 2011. They were interested only in people who had been bitten on the hand because those are the wounds that tend to cause the most problems.

The Mayo Clinic researchers also were interested only in people who had been bitten by house cats, and therefore eliminated three patients from the study who said their wounds had been caused by either a lynx or a bobcat. (Unfortunately, information about how or where those bites occurred wasn’t part of the study. “I was surprised by them, too,” said Carlsen.)

In the end, the researchers identified 193 patients who fit their criteria. They then dug down further into those patient’s medical data. They found that 57 of the patients had been hospitalized. Thirty-six had been hospitalized immediately after showing up in the emergency room so that they could be given antibiotics intravenously. The other 21 had been initially sent home from the emergency room with oral antibiotics, but were subsequently hospitalized when that treatment failed. The average length of hospital stay for all of these patients was three days.

Twenty-six of the 36 people (72 percent) who had been immediately hospitalized and 12 of the 21 (57 percent) who were hospitalized after first trying oral antibiotics ended up requiring surgery. Eight patients required more than one surgery.

The data also revealed that people took an average of 27 hours to seek medical care after their hand was bitten. In addition, the mean age of the patients who showed up at the Mayo Clinic with a cat bite to the hand was 49 years. And most of the patients (69 percent) were women.

Don’t ignore symptoms

Up to 2 percent of all emergency room visits in the United States are for animal bites, according to background information provided in the Mayo Clinic study. Most of those bites (60 percent to 90 percent) involve dogs, but about 10 percent to 15 percent are from cats.

Serious injuries from cat bites are, therefore, relatively rare. Still, if you receive a cat bite, even if it’s a “playful” bite, you should keep alert for signs of infection. Seek medical care if you develop any swelling, redness and pain (particularly pain that worsens), or if you’re having any difficulty moving the hand.

“It takes only a very superficial bite,” said Carlsen. “So, if you have symptoms, don’t ignore them.”

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Comments (9)

One more

…in a list of reasons why I'm not interested in living with a cat.

Speaking for the honor of my cats

What % of people bitten by a cat go to the emergency room? The article doesn't say. If you're going (27 hours later), it's because you've got significant symptoms of infection. I'd venture this is a very tiny percentage of cat bites. I've been bitten many times over my years of cats & never gotten anything more than a short-lived surface infection. Yes it's possible to get a serious infection from a cat bite, but from a risk perspective I'd be hugely surprised if this is more than trivial.

In high school, I knew a kid whose mom tripped in the rain, hit her head, fell unconscious in a puddle and drowned. A horrible event, but it doesn't mean we shouldn't go out in the rain.


I've been bit a few times throughout my lifetime by cats. I would just take some antibiotics if it swelled up too much. I never really got too seriously infected or affected by the bit of a cat until a couple of months ago.
My cat Buster had bit me while having a seizure of sorts. He was 19 years old and had some health issues that brought him to this state where he didn't really know what he was doing. He was tearing around the house and I had to grab him with a towel because he was so crazy. The fit subsided and then came back on. He laid into my wrist so deep, I swear his teeth touched.
I ran him to the vet where they ended his life and suggested I go to the hospital because I was starting to get infected. I went but left without being seen because I wasn't really feeling like being there. It was a traumatic ordeal for both my cat and I.
Over the next couple of hours I continued to swell up, the area was starting to ache and had not stopped bleeding really. Within 6 hours (from time of bit to my second trip to the hospital) I couldn't even touch my thumb and pinky together.
At the hospital they kept me for almost 10 hours. They took xrays,. gave me intravenous antibiotics, and morphine but never flushed out the bite. I was sent home with Amoxicillin, which I never finished taking, but I did take it for a couple of days.
Fast forward two months later (now) and I have developed a weird feeling in my wrist in the past few days. It's not constant and most noticeable when I wake up. It's a kind of pressure type of pain.
Is it possible for this thing going on in my wrist to be associated with the bite? or unlikely after this much time has past?

Bitten badly

I was just bit by a cat that was stuck up in a tree. I had the cat by the neck scruff with leather gloves on. He managed to swing around and sink his fangs in to the top of my hand right at the middle finger knuckle. That night, it swelled up and was very painful. I read this link on the seriousness of cat bites and bacterial infection. Needless to say, I went to the local hospital ER and within no time was admitted and had intravenous antibiotics for 12 hours. It is still swollen around the knuckles and hard to move the fingers but, it is getting better. Bottom line? I learned a lot on what a cat bite can do to you in such a short time. I am still under doctors care along with antibiotics that are so strong they nauseate me and have to see the Ortho doc in 2 days to see if I will be all right. It's nothing to take lightly was the newest lesson in my life.

My own pet Lou bit me

Lou, my cat came upon my lap for a pet and when I reached around my other arm to pet him, he bit me HARD (wrist and mid arm). Two fairly deep puncture wounds that bled, however I cleaned them well and used ointment. When I woke up in the morning, my arm was red, swollen, warm and itchy. I TRULY was not going to go to the Dr. because he was often so frisky with scratching that I just figured it was the same thing, plus to be honest I've had way more painful things happen. My sister is a RNP and MADE me go, sure enough it was infected enough to require antibiotics of which I am not certain yet are working in that day 2 I am still red, hot, sore, itchy and it looks like there is something going on under the skin that needs to be addressed. I have a follow up in the morning but if anyone thinks twice about whether or not to go, I would definitely see the Dr. especially because I feel like the bacteria is trapped and it may need to be opened. The mouths of our cats are sadly very filthy much more so than dogs. I was bit once by our dog and required only a tetanus shot. THIS is a whole other ballgame. I have never not had a cat as a pet, and as many as 4 at once, but Lou is really something else. I suppose the depth is pretty important because they looked like 2 holes until they closed up really quickly. The Dr. said 98% of cat bites become infected, I don't doubt that now!

Cat sitting

I was cat sitting for my sister while she was on an extended vacation.
She had taken my dog last summer while I was on vacation. The cat and dog did great together.
To make a long story short, I was holding the cat when my dog put her nose in the cats butt.

I am sure you all can guess the outcome of that. I was the loser.
I was bitten in my left hand and knuckle with scratches across my face, arm, hand, chest and thigh.

I was told by a co-worker that a cat bite can be dangerous and I should be seen by a Doctor.
I went to the Urgent Care and was seen. I was sent home with antibiotics and was told if the bite started to swell, got red or hurt to go right to the ER. The Urgent Care Doctor said I would probably have "Cat Scratch Fever". I had to giggle, thinking that was a Ted Nugent song. Boy was I wrong. Not only did I have a fever but the pain, redness and swelling started in less than 6 hours after being bitten.

Feeling really stupid for going to the ER for a cat bite, off I went.
Once there they put me into a room and started an IV of high dose antibiotics. From the time I was bitten to the time I was in the ER the red streaks had traveled past my wrist.
After 4 hours in the ER, I had to be admitted for IV meds every 6 hours until this bite cleared.

On the 3rd day of IV antibiotics given every 6 hours the infection was not clearing and a hand surgeon was brought in. The bite had penetrated the sheath of my knuckle. Surgery was the only way to clean the infection. It was done as an emergency basis due to how fast the infection was spreading into my hand and wrist.

The surgeon had to clean out the knuckle and bite marks and put in a drain. My hand started to look and feel better. I was still kept for a 4th day due to the IV meds and pain management.
4 days in the hospital plus another week off work due the an open " wound" where the drain was put in.
A week later the drain came out and my hand started to feel better with less swelling.

I am now back to work, but still have a little pain in my hand while typing. The hand surgeon said this could take up to 4-6 weeks to heal.

Moral of the story~ Have ALL bites checked out !!! It could be a life or death situation.
Or just stay away from cats.

This could have been written about me

Trying to get a feral cat out of my garage basement, I got bit. Went to the clinic first thing next morning, and got oral penicillin and an appointment next day to see a hand surgeon. By the time I got in to see the doctor, my hand was like the Pink Floyd song - a balloon. I was immediately admitted to the hospital and put on IV antibiotics for the next four days, with surgery on the third day. I was extremely lucky, as the bite was in the meaty part of my hand, next to the thumb. No joints or tendons were involved.

Serious cat bite

A month ago, my Siamese was sleeping on my lap, the kitten at my side. All was well for about 15 minutes when the Siamese launched herself at the kitten. I put my hand out to stop her and she bit right through the finger pad on my left middle finger. We squeezed it, ran it under water and put betadine on it. Next morning I went to get oral antibiotics as it was throbbing, within three hours of taking them my finger had swollen to the second knuckle and I went back to the doctor who admitted me for Intravenous antibiotics. Next morning it had tracked into my hand and I was taken for surgery as the area where she bit through had gone black. In total I had 4 surgeries, 2 procedures with morphine in the ward ( pretty gross) a week with a vacuum suction on my finger and a skin graft. I was in hospital for 3 weeks. I had the dressings off today and I need occupational therapy and a special protective dressing for my finger, oh and I still can’t bend the middle joint. So my advice to anyone with a cat bite, go straight away to hospital for treatment, I would hate anyone to go through this and I had it attended to within 12 hours of the bite. As a footnote, they grew Pasteurella Multoceda.

cat bite

while clipping my 18 pound cat claws i hit a nerve and he bit only 1 fang looked like a pin prick at the base of the thumb maybe 1 drop of blood. washed it off.
by the next day it was swollen like a baseball glove called dr and he saw me that morning also was like i had a cold which i had just getting over. got shot of antibiotics and 10 days of pills.but a good side effect i had bouts of ibd for probably 15 yrs at least 10 15 times a yr, since the bite i have only had a rare case of it since over 2 yrs kept the name of the antibiotic pills not sure of the shot. i always had cats and been bitten but this was the first time i had problems . but all said i will always have them there worth the risk but would not keep a mean vishious biter