What causes catscratch disease and who gets it?
Bartonella henselae is a common infection in young cats. IT is also known as Rochalimaea henselae. It is passed from cat to cat via fleas. In the absence of fleas, an infected cat cannot pass the infection to uninfected cats. Currently there are no reports of fleas infecting humans directly, but this may explain cases where there has been no history of exposure to cats.
People at risk of getting catscratch fever include those:
- owning a cat younger than 12 months
- licked, bitten or scratched by an infected kitten
- petting an infected cat
- owning at least one kitten or cat with fleas.
The bacteria are present in saliva deposited in cat's fur and claws. It can occur in people of all ages but is most common in children and adolescents. 80% of patients with catscratch disease are less than 21 years old.
What are the clinical features of catscratch disease?
A small red raised spot develops at the site of contact with an infected cat's saliva. This changes into a fluid-filled blister that later forms a crusty sore. This usually heals without scarring in several days or months. It is often mistaken for an insect bite. Most are found on the hands, arms, face or neck as people often hold kittens close to their chest and face.
The nearest lymph glands then become swollen and tender, most often those on the head, neck and armpit. This is known as regional lymphadenopathy. The lymph glands may swell to 10-12 cm in the first two weeks of the disease. On questioning, patients often recall being licked, bitten or scratched by a cat in the previous one to eight weeks.
About 50% of patients will experience additional signs and symptoms including:
- nausea and vomiting
- sore throat
- stomach pains
Less common problems occur in about 10% of patients. These include:
- Parinaud's oculoglandular syndrome (POS), characterised by an inflamed lump in the eye and swollen lymph glands in front of the nearby ear
- bacillary angiomatosis (infection of the blood vessels)
- bacillary hepatitis and splenitis (infection of the liver and spleen)
- erythema nodosum (red lumps on the shins)
- sepsis (infection disseminated through the blood stream)
- encephalopathy (brain infection)
- bacterial endocarditis (heart valve infection)
Encephalopathy is an uncommon complication of catscratch disease that occurs one to six weeks after the lymph glands swell up. The abrupt symptoms of fever, seizures and coma can be frightening. With hospitalisation and high doses of antibiotics most patients recover completely.
Diagnosis of catscratch disease
Diagnosis is based on the presence of three of the four following criteria:
- contact with a cat and the presence of a scratch or lesion on the skin, eye or mucous membranes
- regional lymphadenopathy, after excluding all other possible causes
- positive skin test for catscratch disease
- suggestive biopsy of skin or lymph node
What is the treatment of catscratch disease?
Treatment of uncomplicated catscratch disease remains controversial. Because it is a benign and self-limiting condition, with most cases of regional lymphadenopathy resolving spontaneously in two to four months, no specific treatment is usually necessary. However, some studies suggest that certain antibiotics including doxycycline, erythromycin, gentamicin, rifampicin, cotrimoxazole and ciprofloxacin may significantly shorten the duration of lymphadenopathy. Antibiotics are warranted in patients with severe or persistent symptoms of catscratch disease. In rare cases, large pus-filled lymph nodes may persist for one to three years.
The pus may need to be repeatedly drained through a needle. Pain and fever can be managed by increasing fluid intake and paracetamol. Warm moist compresses to affected lymph glands may decrease swelling and tenderness.
Textbook of Dermatology. Ed Rook A, Wilkinson DS, Ebling FJB, Champion RH, Burton JL. Fourth edition. Blackwell Scientific Publications.
On DermNet NZ:
- Catscratch diseae – Medscape Reference
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