August 1997
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SAN DIEGO — Physicians trying to determine the cause of a child's infectious disease need to remember the four Ws of epidemiology — who, what, when and where — said William J. Barson, MD, associate professor of pediatrics at The Ohio State University College of Medicine, here at the the American Academy of Pediatrics meeting.
This will help the physician determine when, in terms of the season, the infection took place; where the child had been; with whom the child had been in contact; and what the child had been doing.
Barson presented the case of a 9-year-old Caucasian girl who was in good health until three weeks prior to admission, when she developed a fever. Initially the fever reached a maximum of 102°, but during the week prior to admission it reached 105°. The child was also increasingly tired and anorectic and had lost 5 lbs. Her only complaint was some mild right upper-quadrant discomfort.
The physical examination revealed a chronically ill child with dark circles under her eyes. Her vital signs were unremarkable. Examination of her head, ears, eyes, nose and throat were normal, and she had no cervical adenopathy. The lungs and heart were normal. An abdominal examination revealed an enlarged and tender liver, but no splenomegaly. She had no rash and her extremities and neurological examination were within normal limits. However, there was a 1.5 cm non-tender right axillary lymph node.
The blood count was unremarkable, and her urinalysis was within normal limits. Liver function tests were normal, however a CT scan of the abdomen revealed low-density areas in both the liver and spleen. These tests together with the physical examination led to the diagnosis of cat scratch disease (CSD), which was subsequently confirmed serologically.
There are about 24,000 cases of cat scratch disease in the United States annually, causing about 2,000 hospitalizations. Eighty percent of patients are younger than 21 years of age. Peak incidences are between the ages of 2 and 14 years. Disease occurrence is between September and February in temperate climates and include July and August in warmer climates.
Patients are more likely to contract the disease from kittens rather than cats because most kittens have asymptomatic bacteremia with Bartonella henselae, the organism that causes CSD. Older cats are not bacteremic, but are usually seropositive.
Studies are being done to determine if fleas might be carriers of the disease. There are a number of people who have cat scratch disease and contact with cats, but no history of scratches. "One study took fleas that had been on infected kittens and placed them on uninfected kittens and those kittens became bacteremic," Barson said.
A person with CSD will typically present with chronic lymphangitis. Three to 10 days following the initial scratch, up to 90% of patients will develop a 3-mm to 5-mm inoculation lesion. The lesion can be a vesicle or pustule. About two weeks after the scratch the individual will develop an enlarged lymph node, maximum size about 5 cm. This usually regresses over two to four months, with 1% to 2% lasting up to three years. About 15% of lesions will need to be aspirated.
Although the typical presentation of CSD is lymphangitis, 2.3% of patients will present with a fever of unknown origin. Additional presentations include Parinaud's ocularglandular syndrome, encephalopathy, neroretinitis, erythema nodosum, pneumonia or osteomyelitis. In addition to a prolonged high-grade fever, nonspecific manifestations include malaise, fatigue, myalgia, arthralgia, rashes, generalized lymphadenopathy and weight loss. The finding that's noted on the abdominal imaging studies is consistent with granulomatous hepatitis, and a biopsy of the lesions would confirm the presence of granulomas, Barson said.
To confirm the diagnosis of cat scratch disease, B. henselae needs to be isolated from the blood and biopsy material, or DNA sequences may be detected in clinical specimens. These studies are performed in specialized laboratories; hospital laboratories do not routinely do these tests. However, hospital labs can do serology, which is a very sensitive indicator of cat scratch disease. Labs can get the protocol for the serology and also the reagents needed to perform the procedure from the Centers for Disease Control and Prevention (CDC), Barson said.
Once B. henselae has been confirmed and the patient is diagnosed with CSD, supportive treatment is in order. Antibiotic treatment, however, is still controversial. "We don't know if any drugs have a beneficial effect on cat scratch disease," he said.
A retrospective study published in Pediatric Infectious Disease Journal indicated that rifampin was the most effective drug. However, when the study is reviewed it shows that only 15 patients received rifampin, of whom 87% improved. "I've treated some patients with rifampin, and they did get better," Barson said. "I've treated others with other antibiotics, and they got better too. I also recall contemplating the start of antibiotics first before patients defervesced and they remained fine. The bottom line is we don't know for sure what the best treatment is for cat scratch disease, other than supportive care."
For more information:
- Barson WJ, Prober CG. Infectious disease mini-course: informative cases. Presented at the American Academy of Pediatrics. May 10-13. San Diego.
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