Cat-scratch disease is an infection caused by Bartonella henselae that is most commonly acquired by exposure to infected kittens and cats.

Etiology
1. B. henselae is a low growing gram negative bacillus
2. Cats are the most common reservoir
3. There may be cat-cat transmission by fleas
4. There is a higher incidence in kittens ( especially< 1 year old) and stray cats
5. There have been rare cases after exposure to infected dog
6. Increasinglyprevalent in cat populations in warmer climates:0% in Norway vs. 68% in Phillipines.
7. 22,00-24,00 cases anually in the US requiring 2000 admissions to hospital

Epidemiology
1. 90% of infected individuals have been exposed to cats
2. 7-12 days after scratch the primary cutaneous lesion appears
3. 5-50 days from the appearance of the primary lesion, there is lymph node enlargement.

Clinical Manifestations
1. Typical presentation in immunocompetent host
     a. papular or nodular lesion at the site of the scratch
     b. nodal enlargement over course of 1 month
     c. 10-30% will suppurate
     d. Enlargement of node for 2-3 month and then regresses
2. Signs and symptoms
     a. 100% have lymphadenopathy. In 50% of cases, it is the sole manifestation.  Usually the node is mildly or not tender
     b. 30% have fever and malaise
     c. 15% have headache, anorexia, and emesis
     d. Other symptoms include rash, pharyngitis, conjunctivitis, joint pains, seizures, and blindness. 
3. Atypical presentation
     a. prolonged fever and generalized symptoms with malaise, fatigue, diffuse adenopathy, and hepatosplenomegaly.
     b. Hepatosplenomegaly with lesions within the liver
     c. ocularglandular syndrome
4. Immunocompromised patients- can show 2 distinct manifestations:
    a. baciallary angiomatosis- vascular proliferative lesion of the skin and subcutaneous tissue
    b. bacillary peliosis- reticuloendothelial lesions in visceral organs, primarily the liver.

Diagnosis
1. History of exposure to cats and primary site of inoculation and enlarged regional lymph nodes. 
2. Serological evidence of B henselae infection can be done by indirect fluorescent antibodies and enzyme-linked immunosorbent assay.
3. Acute and convalescent titers
4. B. henselae is difficult to culture
5. PCR is expensive and not readily available
6. Biopsy material may demonstrate silver staining of the organism by the Warthin Starry stain and the presence of granulomas.  This may help differentiate cat -scratch from other etiologies of lymphadenopathy.
7. Skin test is not utilized presently

Treatment
1. The majority of cases in immunocompetent individuals are self limited infections that will resolve in 2-4 months and no treatment is necessary. Many patients will relapse within 6 months with or without treatment.
2. No antimicrobial regimen has been shown to cure B. henselae but antimicrobials may shorten the disease course in patients with severe symptoms and/or immunodeficiency.  No antimicrobial therapy has shown to be effective in treating infections in cats.
3. Doxycycline, erythromycin, rifampin, penicillin, gentamicin, ceftriaxone, ciprofloxacin, and azithromyci have been shown to be helpful.  The optimal duration of therapy has not been determined; one source recommends a two week course in immunocompetent patients and a six week course in immunodeficient patients.
4. Patients with bacillary angiomatosis and bacillary peliosis have shown benefit tfrom treatment with azithromycin, etythromycin, and doxycylcine for several months.
5.Suppurative nodes that are painful may be needle aspirated and rarely need to be surgically excised.

Prevention
1. Flea control in cats and avoid contact with stray cats.
2. Rapid cleansing of areas of scratch or bite
3. Testing cats for B. henselae is not recommended