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Cat-Scratch Disease

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(Editor's note: this page was written with help from Sniff and Cat Scan. They also told me to make sure I told you that cat-scratch disease is not their fault.)

Cat-scratch disease is an infection with the bacteria Bartonella henselae. This bug is commonly found in cats, thus the term "cat-scratch". However, the bacteria is spread between cats by fleas and ticks, and researchers have recently suggested that ticks may be able to transmit B. henselae to humans. There are several other bacteria in the Bartonella family, some of which behave very much like B. henselae if they infect people.

(Note from Cat Scan: So that's why you give us that stuff every month!
(Editor's note: She's talking about their flea and tick medicine.)
  I still don't like it, though. Hmph!)
(Note from Sniff: But we like the treats Daddy gives us afterwards...)
Although cats can carry Bartonella -- in fact, 2 out of 5 cats carry the bacteria at some time during their lives -- and may have the bacteria in their blood for weeks to months (sometimes for more than a year) they don't often have symptoms. This means that we can't tell if a cat is carrying Bartonella just by examining her. Kittens (less than a year old) are more likely than older cats to have Bartonella in their blood. Stray cats carry the bacteria more often than do pet cats. Indoor cats are less likely to be carriers than outdoor cats, but they can be carriers if they are exposed to Bartonella.
(Editor's note to Cat Scan and Sniff: Now do you see why I don't let you out of the house?)
(Note from Cat Scan: You mean it's not because you don't want Sniff and me to visit all the birdies outside?)
(Editor's note to Cat Scan and Sniff: Visit them? Or chase them? And besides, every time Grandma or Granddad or I open the door you and Sniff run and hide!)

When we need to test for cat-scratch disease, we look for antibodies to Bartonella rather than for the bacteria themselves. About 6% of healthy people have antibodies to Bartonella. Most people who have signs of infection are 20 years old or younger. Dogs can also be infected with Bartonella, as can deer, dogs, cattle, rabbits, rodents, lions, and even porpoises. Unlike cats, infected dogs often develop medical problems very like those seen in infected people.

(Note from Cat Scan: That's because we're better than dogs.)
(Editor's note to Cat Scan: Aren't you being a little speciesist?)
(Note from Sniff: What's "speciesist", Daddy?)
(Editor's note to Sniff: It's a term that probably would be used by proponents of political correctitude.)
(Note from Cat Scan: And what's political correctitude?)
(Editor's note to Cat Scan: It's... oh, forget it.)

In most people, the only sign of cat-scratch disease is a papule (a bump) at the site of the scratch, appearing about 1 to 1-1/2 weeks after the scratch. This papule eventually turns into a pustule (a bump full of pus). About 1-3 weeks after the initial bump appears, we see swollen glands near the bump (in the armpit if the arm was scratched, in the groin if the leg was scratched). We can also see low-grade fever, malaise (feeling lousy), and myalgia (aches and pains); sometimes we also see headaches, loss of appetite, and enlagement of the spleen. Occasionally an abscess develops in an enlarged lymph node. Sometimes (in less than 9% of patients) a patient develops encephalitis (inflammation of the brain, as opposed to meningitis, which is inflammation of the membranes covering the brain and spinal cord), endocarditis (inflammation of the heart walls), pneumonia, or other problems. Although patients with encephalitis can have seizures while they are sick, they tend to recover without long-term problems, and there has been only one report of a death from cat-scratch related encephalitis. Usually, people severely ill with cat-scratch disease have problems with immunity to begin with; these include very young children, the elderly, and people who are being treated for cancer.

People with cat-scratch disease usually recover in 2 to 4 months even without treatment. Several antibiotics, including amoxicillin, trimethoprim/sulfamethoxazole, rifampin, azithromycin, ciprofloxacin, and tetracycline, will kill Bartonella and can be used to treat cat-scratch disease; sometimes, an abscess needs to be opened up and the pus inside drained.

As always, the best treatment is prevention. I do not recommend avoiding cats entirely,

(Note from Cat Scan: We certainly hope not!)
although you might want to think twice about cats that do a lot of scratching or biting if you know you have immune-system problems. Some authorities recommend that immunocompromised people should not get a new cat who's less than one year old, as they are more prone to scratching and biting.
(Note from Sniff: Well, when we were less than 1 year old we didn't scratch people who treated us properly (like Daddy and Grandma and Granddad), and we still don't -- especially when they're giving us treats.)
You should also be diligent about flea treatment for your cat (they'll thank you for it, too, no matter what Cat Scan says).
(Note from Cat Scan: did Daddy just say that it doesn't matter what we say? I think a little reeducation's in order.)
(Note from Sniff: Hmmm... maybe we ought to reconsider not scratching him.)
(Editor's note to Cat Scan and Sniff: And were you expecting your bedtime treats tonight?)
(Note from Sniff: Uh-oh... )

You should also wash your hand thoroughly with soap and running water after handling your cats, or taking care of their litter boxes.

(Note from Sniff: And before and after you feed us, too -- don't forget that.)
(Editor's note to Cat Scan and Sniff: Don't forget what? Feeding you? You never forget to remind me -- even when it isn't time!)
(Note from Sniff: I meant washing your hands before and after you feed us.)
(Editor's note to Cat Scan and Sniff: I always do -- even when you and your sister are trying to drink from the faucet... and, apropos, if your cats drink from the faucet you should let the water run for a bit before washing your hands in it -- just on general principles of hygiene.)

If your cat does scratch you, wash the scratched area thoroughly with soap and running water. Let your doctor know about the scratch if any papules, pustules, or swollen glands appear, especially if you have immune-system problems.

(Note from Cat Scan: And if your cats scratched you because you made them mad at you, make sure you tell them you're sorry -- that's very important, too.)

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PLEASE NOTE: As with all of this Web site, I try to give general answers to common questions my patients and their parents ask me in my (real) office. If you have specific questions about your child you must ask your child's regular doctor. No doctor can give completely accurate advice about a particular child without knowing and examining that child. I will be happy to try and answer general questions about children's health, but unless your child is a regular patient of mine I cannot give you specific advice. (And Cat Scan and Sniff don't let me try to give advice on cat health.)

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Copyright © 2006, 2007, 2008, 2011 Cat Scan, Sniff, and Vinay N. Reddy, M.D. All rights reserved.
Written 03/29/06; major revision (mostly by Cat Scan) 01/21/07; last revised 07/05/11 counter