Cat scratch fever (cat scratch disease, inoculation lymphoreticulosis, subacute regional lymphadenitis) is an infectious disease of children and adolescents, caused by the bacterium Bartonella henselae.
The signs and symptoms of the disease are mild to moderate and are usually self-limiting. They develop after an incubatory period of 1 to 2 weeks or even longer after the initial bite. The onset of the symptoms is gradual. The salient clinical features are swollen and painful lymph nodes (lymphadenopathy), in particular the axillary, cervical and inguinal lymph nodes . There may be formation of erythematous vesicles or pustules at the initial site of infection (bite or scratch). The patient has low grade fever of about 101 F which may be associated with chills. Other non-specific symptoms such as malaise, loss of appetite and weight loss occur. The patient also feels pain in various regions of the body. These include abdominal pain, back ache, muscle aches, sore throat and headache.
In rare cases, the patient may have other severe symptoms. Encephalopathy along with seizures may develop in these patients . They may also have involvement of the heart in the form of endocarditis. Involvement of the liver (granulomatous hepatitis) and spleen may also be seen  . Occasionally, there may be osteomyelitis and osteolytic lesions of the bone  . Joints may also be affected.
Involvement of the eyes and ears can also occur, including visual disorders, neuroretinitis and otic neuralgia. Other serious complications include involvement of the lungs, Parinaud’s syndrome and thrombocytopenic purpura.
The following tests are also helpful:
The symptoms are usually self-limiting and resolve spontaneously. The following medicines may be used:
Complete cure is possible within 2 to 6 months after therapeutic measures are taken. In immunocompromised patients, it may take longer but the prognosis is generally good.
Infection with Bartonella henselae bacterium is responsible for the disease . Afipia felis and Bartonella clarridgeiea have also been found in association with cat scratch fever. Cats are the vectors for this agent. Fleas are responsible for transmission of this agent to cats. Biting, scratching and even licking can transfer the bacterium to humans as saliva of the cats has also been found to contain the organism.
The transfer of the bacterium from cats’ bloodstream to the saliva has, however, not been explained as yet. The transfer of this disease from one human to another has not been proved as yet.
The disease is common in children and in people under 21 years of age. Almost 25,000 cases of cat scratch disease surface every year. There is a seasonal tendency of the disease, with more cases emerging during the early summers and mid-winters.
Bartonella henselae is a gram-negative organism. The infection by this organism evokes a suppurative granulomatous response in the infected patients. In immunocompromised states, it can trigger a vascular reaction followed by recruitment and proliferation of lymphocytes. The bacteria cause angiogenesis in the infected area via adhesin A involvement.
The host’s immune system is activated. Following phagocytosis by macrophages, the internalized bacteria are circulated to the regional lymph nodes. The lymph nodes proximal to the site of infection show granuloma formation, suppuration and hyperplasia on biopsy. Biopsy findings also include stellate abscesses and leucocyte infiltrates. The macrophages release several inflammatory cytokines including interleukin-1 (IL-1) and tumor necrosis factor α (TNFα). These cause recruitment of neutrophils and more macrophages to the site of infection.
Helper T cells are activated by presentation of the invading bacterial antigens by macrophages and dendritic cells. TNF-gamma is produced by the activated helper T cells which triggers the release of NO locally. NO produced cytotoxic elements kill the bacteria. The inflammation and suppurative granulomation ultimately resolves.
Bartonella henselae is the bacterium responsible for this condition. The cats are asymptomatic carriers of the agent. The bacterium is transferred to cats by fleas, Ctenocephalides fells. The fleas may also be responsible for direct transference of the bacteria to man. Typical feature of the disease is persistent low grade fever, hence the name cat scratch fever.
The infected persons develop pustules at the site of scratch or bite. Low grade fever, generalized fatigue, muscle pain. Lower back pain, abdominal pain, loss of appetite and weight commonly develop in the patients.
With proper treatment, the symptoms completely regress and patients can be completely cured. Proper preventive measures should also be taken to avoid getting infected. Cats should be looked after and their hygiene should be maintained. They should be regularly checked for flea infestation. Hands should be washed with antibacterial soap and plenty of water immediately after playing with cats especially in children as their bodies have weaker defense mechanisms and are more susceptible to the disease. If open wounds are present on the skin, one should avoid going near the cats. With proper care, the disease can be prevented altogether.