Cat scratch disease

CSD is a bacterial infection caused by Bartonella henselae, an aerobic Gram-negative bacillus.

CSD is caused by Bartonella henselae, an aerobic Gram-negative bacillus. Bartonella henselae can infect feline erythrocytes and fleas, which can contaminate saliva and then be introduced into humans through biting and clawing by cats. The cat flea, Ctenocephalides felis, is the vector responsible for horizontal transmission of the disease from cat to cat, and its bite can also infect humans. In addition, tick bites may transmit the bacterium to humans.

In the US, the annual incidence of CSD is estimated at 4.5 cases per 100,000 person-years, while the incidence of CSD requiring hospitalization is estimated at 0.19 cases per 100,000 person-years.

In the classic disease course, a papule or pustule develops 3-30 days following a scratch or a bite, and regional lymphadenopathy develops about 3 weeks after inoculation. Suppurative lymphadenopathy may develop in 10% of cases. Less than 2% of patients develop extranodal disease (for example CNS, liver, spleen, bone, and lung involvement).

In most patients, especially children, the disease is self-limited, and resolves without specific treatment. In immunosuppressed patients, Bartonella henselae can lead to bacillary angiomatosis and bacillary peliosis, which have high rates of relapse and require prolonged antibiotics.