Cat-scratch disease is an infectious self-limited disease caused by Bartonella henselae.
Cat-scratch disease (CSD) is an infectious disease caused by the Bartonella henselae. The characteristic feature of the disease is the long-lasting enlargement of the regional lymph nodes, which resolves spontaneously (so-called typical CSD), although this illness may also have a much more severe course when bacteria disseminate all over the body and affect various organs causing different symptoms and decreasing person’s quality of life. The disease name refers to the route of bacterial transmission via the cat scratches. Usually, all the symptoms disappear during a few months with no treatment. Severe course of the disease and extra-nodal involvement require antimicrobial therapy.
Cat-scratch disease is considered the most common cause of enlarged regional lymph nodes in children and adolescents. Bacteria thrive in the warm and humid climate. The disease occurs in the tropics all year-round, in the other regions fall and winter incidence peaks are observed.
Gram-negative bacterium Bartonella henselae causes the disease. Cats are the host for Bartonella spp., whereas the cat flea (Ctenocephalides felis) transmits the bacteria from cat to cat. A person becomes infected when he/she is scratched, bitten or licked by an infected cat, rarely dogs. Afterward, the bacteria travel from the lesion via the lymphatic vessels and get to the lymph nodes where they induce granulomatous inflammation and, as a result, enlargement of the lymph nodes.
Afipia felis and other Bartonella species were also reported to cause the cat-scratch disease.
- Typical manifestation of the cat-scratch disease is observed in about 85-90% of cases.
The incubation period lasts approximately from 5 to 7 days – it means that the symptoms of the disease appear 5-7 days after a person was scratched or bitten by an infected cat. At the site of the scratch or a bite appears a painless nodule, papule or vesicle from 0,5 to 1 cm in diameter which remains for 1-3 weeks. 2-3 weeks later one or several lymph nodes (typically the lymph nodes close to the site of the initial lesion are affected) become large, tender or even painful and firm – the phenomenon known as a lymphadenopathy with axillary and epitrochlear nodes most commonly affected, less frequently head and neck nodes are involved followed by the inguinal and femoral lymph nodes. Skin over the lymph nodes may be erythematous (somewhat red). Usually, lymphadenopathy disappears by itself within 3 months. Other possible symptoms of the disease include various nonspecific complaints such as low-grade fever (not higher than 39ºC), anorexia (loss of appetite), headache, muscle pain, general malaise, and abdominal pain which resolves for several weeks. Rarely ill person may experience night sweating and lose weight.
- Atypical cat-scratch disease occurs in about 10-15% of infected individuals. Bacteria may spread all over the body and affect almost any organ and organ systems causing a variety of symptoms and complaints.
Atypical presentation of the disease may be accompanied by lymphadenopathy. However, lymph nodes may not be involved (especially in individuals over 60 years). Parinaud’s oculoglandular syndrome is one of the possible atypical manifestations of the CSD. This syndrome includes conjunctivitis (inflammation of the conjunctiva – the eyes appear blood-shot with watery discharge and itching) and unilateral periauricular lymphadenitis (enlargement of the lymph node in front of the ear on one side). Other ophthalmologic impairment may be seen as well.
Bacteria may affect the liver causing hepatitis and the spleen leading to the splenitis. Involvement of the nervous system may lead to encephalopathy (disorder of the brain), seizures, myelitis (inflammation of the spinal cord), radiculitis (inflammation of the spinal nerve roots), cerebellitis (inflammation of the cerebellum), facial and other cranial or peripheral palsies (weakness of the muscles innervated by the cranial or spinal nerve). Joints and musculoskeletal system can be affected (myalgia, arthritis, arthralgia, osteomyelitis, tendinitis). Pneumonitis (inflammation of the part of the lung), pleural effusions (accumulation of the fluid in the pleural cavity) and erythema nodosum (red nodules or lumps may be seen on the extremities) may also develop due to CSD.
The diagnosis is made based on the characteristic symptoms and serologic testing via immunofluorescence or enzyme immunoassay. Biopsy of the affected lymph nodes reveals lymphoid hyperplasia with necrosis and microabscesses.
In mild disease, no treatment is needed as the symptoms resolve spontaneously up to 3 months whereas in severe cases with systemic involvement antibiotics are necessary. The purulent lesions may require drainage via needle aspiration.
Different antibiotics are administered depending on the course of the disease.
Antimicrobial therapy is unnecessary in case mild to moderate typical cat-scratch disease. A severe course of the disease requires treatment with azithromycin (500 mg should be taken on the first day of treatment and then 250 mg on day 2-5).
Doxycyline, rifampin, gentamicin, and ceftriaxone may also be administered in severe cases of CSD with multiple organ involvement.