Cat-scratch disease, a bacterial infection spread through scratches and possibly bites from cats, occurs more often and sends more people to the hospital than health officials previously believed, the Centers for Disease Control and Prevention (CDC) reported this week.
But there’s no need for any cat lovers to panic. The CDC report also makes clear that the infection is rare.
Still, cat owners should know the symptoms of cat-scratch disease, particularly since the infection can sometimes be serious — and even fatal — if left untreated.
But, let me emphasize again: that likelihood is quite rare.
How you get infected
Cat-scratch disease is caused by a bacterium (Bartonella henselae), which is spread by cat fleas. Cats get infected when a flea bites them or when flea “dirt” (feces) gets into a wound. The bacterium can also get under the cats’ nails or between their teeth when they scratch or bite at the fleas.
Cats spread the bacterium to people when they break human skin, either by scratching or biting, or when they lick a person’s existing wound.
Cats do not usually appear sick when they are infected. And such infections are quite common. Forty percent of cats carry the B. henselae bacterium at some time in their lives, according to the CDC. Kittens and young cats (up to six months old) are particularly likely to be carriers.
People show symptoms of cat-scratch disease from three to 14 days after being infected. Early symptoms include swelling and a small raised pimple-like lesion at the scratch or bite site, as well as fever, headache and fatigue. Later, lymph nodes near the infection site may become swollen and painful.
In serious cases, the infection may spread to the eyes, bone, brain or heart. Such complications are most likely to occur in children under the age of 5 and in people with weakened immune systems.
Treatment for mild cases of cat-scratch disease usually involves taking over-the-counter medications to reduce the fever and swelling. In more serious cases, antibiotics and other drugs may be prescribed.
Tracking down the numbers
The purpose of the new CDC report was to get a better idea of the overall picture of cat-scratch disease in the United States. How many people are getting infected, and which groups are most at risk?
To answer those questions, the CDC researchers dug through a medical claims database from 2005-2013 that contained the medical records of almost 40 million Americans under the age of 65.
They found 13,273 diagnosed cases of cat-scratch disease in that database. Of those, only 538 people had symptoms severe enough to be hospitalized. The other 12,735 were seen by a doctor and sent home.
From those numbers, the CDC researchers estimated that 4.5 of every 100,000 Americans under the age of 65 are diagnosed with cat-scratch disease each year, but fewer than 1 in 500,000 Americans need to be hospitalized as a result of the infection.
In the West North Central region of the United States, which includes Minnesota, the incidence rate was 3.3 per 100,000 residents.
The report also found that the national number of reported cases of cat-scratch disease fell by about 1 per 100,000 between 2005 and 2013, but that the number of people being admitted to hospitals with the disease stayed about the same.
The CDC researchers estimate that the annual direct medical cost to the U.S. for treating cases of cat-scratch disease is $9.7 million.
Here are some other findings from the report:
- Children aged 5 to 9 were more likely to get the disease, as were women aged 60 to 64.
- Women and girls accounted for 62 percent of outpatient cases of the disease and 56 percent of hospitalized cases.
- The highest rates for the disease were in the South, while the lowest rates were in the arid West, where cat fleas are less common.
- The largest proportion of reported cases occurred in January and in August through November. Interestingly, the January spike was most pronounced in the North Central region (which does, of course, include Minnesota).
The CDC researchers say it’s unclear why such an unusually high number of cat-scratch disease cases occur in January. It could be because cats are indoors more in winter, and thus have greater chances to interact with humans. Also, the fleas that spread cat-scratch disease tend to be around more in the fall and winter.
“Another hypothesis is that teenagers and middle-aged adults, who typically spend a great deal of time at school or work, spend more time during the holidays at home in contact with their cats or traveling to other house with cats,” the CDC researchers add.
What cat-owners can do
To prevent cat-scratch disease, the CDC recommends the following:
Things to do
Wash cat bites and scratches right away with soap and running water.
Wash your hands with soap and running water after playing with your cat, especially if you live with young children or people with weakened immune systems.
Since cats less than one year of age are more likely to have CSD and spread it to people, persons with a weakened immune system should adopt cats older than one year of age.
Keep your cat’s nails trimmed.
Keep your cat indoors.
Apply a flea product (topical or oral medication) approved by your veterinarian once a month. (BEWARE: Over-the-counter flea products may not be safe for cats. Check with your veterinarian before applying ANY flea product to make sure it is safe for your cat and your family.)
Check for fleas by using a flea comb on your cat to inspect for flea dirt.
Control fleas in your home by vacuuming frequently and contacting a pest-control agent if necessary
Things not to do
Don’t play rough with your pets because they may scratch and bite.
Don’t allow cats to lick your open wounds.
Don’t pet or touch stray or feral cats.
Oh, and all you dog owners out there, don’t get too smug. Species of Bartonella linked to cat-scratch disease have been found on other mammals — including dogs.