What is cat scratch disease?

Also known as "cat scratch fever", cat scratch disease is a condition mainly of people, not cats and as the name suggests, cat scratch disease is most often associated with cat scratches (although cat bites & licks can often lead to CSD too). It  is caused by a recently discovered gram negative bacterium called Bartonella henselae & is found worldwide. It is seen more commonly in children (under 17 years) than adults. Most cases come from kittens, although adults can also pass on the disease.

Cats are the main reservoir of CSD although puncture wounds & scratches from dogs, thorns, splinters & even fish bones have been implicated in a few cases too.  Although the bacterium is relatively common in cats, it is quite uncommon to catch CSD, which indicates that it's quite difficult to catch.

What are the symptoms of cat scratch disease in humans?

Typical CSD

In between 25 & 60% of cases, a small papule (tiny skin nodule) often develops several days after the scratch or bite and may be mistaken for an insect bite. This blister or bump is called an "inoculation lesion" (a wound at the site where the bacteria enter the body). Lymphadenopathy (swollen lymph nodes, especially those in the armpits, head & neck)  appear approximately 1-3 weeks after the scratch, headache, joint pain, lethargy, loss of appetite & flu like symptoms lasting several weeks.  In healthy people, CSD usually resolves itself, treatment is not necessary.

Atypical CSD

Bacillary angiomatosis is a "syndrome" that is most often seen in immunocompromised people.  Serious skin lesions develop, patients may develop high fever, sweats, chills, poor appetite, vomiting, weight loss, bone lesions & occasionally seizures.  If not treated, it can lead to death. Antibiotic treatment has been shown to cure the infection.

12-29%* of veterinarians have shown positive skin tests & 5% of healthy people in other jobs, which indicates that while they have had the infection, symptoms have been mild it not apparent at all.

How do cats become infected?

Fleas pass Bartonella from one cat to another via flea bites. It is not possible to pass on the disease from human to human.

What are they symptoms in cats?

Generally cats don't display symptoms.

How is cat scratch disease diagnosed?

Diagnosis may be based on a history of patient contact with a cat, a blood test of in some cases a biopsy of the affected lymph node.

How is cat scratch disease treated?

In most cases the disease is self limiting & will resolve itself in time. It can take several months for lymph nodes to go down. Warm, damp compresses may be used to reduce the pain of swollen lymph nodes, along with non prescription pain medication. Your doctor will be able to advise which form of pain relief is recommended, if necessary.

Occasionally your doctor will aspirate pus from the lymph node to reduce pressure & pain.

In severe cases antibiotics may be prescribed.

How can I reduce my risk of getting cat scratch disease from my cat?