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 and stray cats
5. There have been rare cases after exposure to infected dogs

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

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.
2. Suppurative nodes that are painful may be needle aspirated and rarely need to be surgically excised.
3. Oral antibiotics may be useful in immunocompromised patients, toxic appearing patients, and individuals with hepatosplenomegaly.
4. Some studies have demonstrated the effectiveness of Azithromycin in decreasing the size of nodes compared to placebo after one month.  Other antibiotics include Bactrim, Rifampin, and Ciproflaxacin.