A brief report in the latest edition of the Canadian Medical Association Journal describes a child with lymphadenopathy (swollen lymph nodes) due to cat scratch disease.
I was a bit surprised to see a straightforward case like this published in such a journal, but it’s a good reminder of a few issues.
Cat scratch disease is caused by the bacterium Bartonella henselae, and it’s a common (and probably commonly missed or misdiagnosed) disease. The bacterium can live in the bloodstream of cats, where it usually doesn’t cause a problem. People typically get exposed through fleas that feed off the cat, ingest the bacterium from the cat’s blood, and then pass the bacterium in their feces (“flea dirt”) which then comes in contact with people. Cat scratches are often linked to human infections, not because the bacterium is living on the cat’s claws, but because claws create an opening for the bacterium to get into the body through this exposure to flea dirt, or if there are flea feces on the cat’s claws from grooming or scratching itself. Contact with flea-infested cats, especially young stray kittens, is a big risk factor for infection in people.
The story in this case report is pretty straightforward:
- A 10-year-old boy was presented with a 10-day history of worsening elbow pain and intermittent fever, and no response to empirical antibiotics.
- He had been bitten by a stray kitten 4 weeks earlier. The bite likely wasn’t the issue in this case, but was an indicator that he had close contact with the cat, and presumably was exposed to flea feces. The bite could have inoculated flea feces from his skin into his body.
- Swollen lymph nodes were identified, and extensive testing revealed only Bartonella henselae in his blood, in terms of a potential cause.
- He responded quickly to appropriate antibiotics for Bartonella henselae.
That’s a pretty typical presentation of this disease – low grade fever, enlarged lymph nodes and a bump at the scratch site are most common. However, more serious infections can occur rarely.
The authors concluded: “Physicians should consider cat-scratch disease in their differential diagnosis of regional or unilateral lymphadenopathy.”
True. However, the bigger statement to me should have been “Physicians should routinely query animal contact.” Zoonotic infections are often missed or diagnosed late because of failure to ask a simple question about animal contact.
Interestingly, there’s no mention about the child being given rabies post-exposure prophylaxis, which is surprising after a bite with a stray cat. Maybe it was done and they didn’t report it. Or perhaps the stray cat was captured and they were able to keep it under observation for 10 days to rule out rabies shedding at the time of the bite. If not, rabies would also be a concern.