Pearls of Wisdom: Cat Scratch Fever
A 10-year-old otherwise healthy boy presents to the emergency department with a 2-day history of sore throat and substantial fever (100.2°F to 102.4°F). On physical exam, “hen egg-sized” prominent bilateral cervical adenopathy is noted, but no exudate is reported.
Laboratory tests found an erythrocyte sedimentation rate of 48 mm/hr, lactate dehydrogenase at 445 mg/dL, and C-reactive protein at 2.1 mg/L. A test for mononucleosis was negative. No strep tests are indicated in the case report; whether this reflects an omission or whether it was not done because the clinician was going to treat the young man with antibiotics regardless is not stated. After 4 days of cefdinir, the patient showed no improvement.
The patient reports no contact with cats.
How would you treat him?
- Consider that the boy is being untruthful, and test for Bartonella on that basis.
- Test for Bartonella because of exposure to other animals.
- Test for human papilloma virus.
- Omit Bartonella testing: no cat = no Bartonella.
What is the correct answer?
(Answer and discussion on next page)
Louis Kuritzky, MD, has been involved in medical education since the 1970s. Drawing upon years of clinical experience, he has crafted each year for almost 3 decades a collection of items that are often underappreciated by clinicians, yet important for patients. His “Pearls of Wisdom” as we like to call them, have been shared with primary care physicians annually in an educational presentation entitled 5TIWIKLY (“5 Things I Wish I Knew Last Year”…. or the grammatically correct, “5 Things I Wish I’d Known Last Year”).
Now, for the first time, Dr Kuritzky is sharing with the Consultant360 audience. Sign up today to receive new advice each week.
Answer: Test for Bartonella because of exposure to other animals.
Since the patient was not improving, he was switched to minocycline on day 6. One of the practitioners was obviously thinking cat scratch disease (CSD), even though the youngster had experienced no known contacts with cats.
Accordingly, the astute clinician had ordered both immunoglobulin G (IgG) and immunoglobulin M (IgM) antibodies to Bartonella henselae—the causative organism of CSD.
On day 8, an IgG antibody level against Bartonella was 1:256. This could represent old infection, but that is unlikely since the level is so high; rather, it is more supportive of an acute infection. A confirmatory IgG level 10 days later showed a 4-fold rise in anti-Bartonella IgG, confirming recent infection. The minocycline was appropriate therapy for CSD.
Cat Dog Scratch Fever Case Report1
Discussion
It must have been the degree of adenopathy, perhaps coupled with absence of signs of strep that motivated the clinician to think of so unusual a diagnosis. I have only seen CSD confirmed twice in my 40-year career. Both times, young adults were involved and cats were implicated.
The tip-off was the prominent adenopathy in both cases: one with unilateral cervical adenopathy (hen egg-sized? Maybe anemic hens) and one with epitrochlear adenopathy (robin egg-sized).
Cat Dog Scratch Fever Outcome1
This Case
The authors of this case report went on to confirm that the young patient’s dog was the culprit; culturing the new puppy’s gingiva was found to be Bartonella henselae positive. Subsequently, other dogs were tested and again Bartonella was confirmed.
Bartonella henselae can live on the cornified epithelium of any keratinized structure (eg, the claws of a dog or cat, or even the horns of a deer), which provides a risk for taxidermists and hunters. Because cats and kittens are the most common reservoir, and it is commonplace for pet owners to experience incidental minor claw injuries when their pet squirms to get away, cats become the usual cause of CSD.
What’s the “Take Home”?
You can get tennis elbow without playing tennis. You can get nursemaid’s knee without being a nursemaid. You can get cat scratch disease in the absence of contact with cats.
1. Tsukahara M, Tsuneoka H, Iino H, et al. Bartonella henselae infection from a dog. Lancet. 1998;352(9141):1682.