From the Guidelines
Cat scratch disease should be treated with azithromycin 500mg on day 1, followed by 250mg daily for 4 additional days for patients weighing ≥45.5 kg, as it has been shown to reduce lymph node size by 80% at 30 days in a double-blind placebo-controlled study 1. The disease is caused by Bartonella henselae and typically presents as a papule or pustule at the scratch site, followed by regional lymphadenopathy 1-3 weeks later, often accompanied by fever, fatigue, and headache. Some key points to consider in the management of cat scratch disease include:
- The disease course varies, but lymphadenopathy generally resolves within 1–6 months without treatment 1.
- Extranodal disease, such as central nervous system, liver, spleen, bone, and lung involvement, develops in ≤2% of cases 1.
- Diagnosis may be difficult due to the fastidious nature of the organism, but serological testing, PCR, and Warthin-Starry silver stain of infected lymph node tissue can support the diagnosis 1.
- Prevention involves proper hand washing after handling cats, avoiding rough play that might lead to scratches, and keeping cats free of fleas which can transmit the bacteria between cats.
- Immunocompromised individuals should be particularly cautious around cats, especially kittens and strays, as they're at higher risk for developing serious complications, such as bacillary angiomatosis 1.
From the Research
Causes and Transmission of Cat Scratch Disease
- Cat scratch disease (CSD) is caused by the bacterium Bartonella henselae, which is transmitted to humans through cat scratches or bites, particularly from infected kittens or cats 2, 3, 4, 5.
- The cat flea is thought to play a role in amplifying the reservoir of B. henselae among cats, but it is unlikely to be directly involved in human infection 2.
- Asymptomatic, bacteremic cats with B. henselae in their saliva can serve as vectors by biting and clawing the skin 5.
Clinical Manifestations and Diagnosis
- CSD typically presents as tender lymphadenopathy, and may also manifest as fever of unknown origin or any lymphadenopathy syndrome 5.
- Atypical forms of infection can include Parinaud oculoglandular syndrome, stellate neuroretinitis, persistent fever without localizing signs, hepatosplenic infection, encephalopathy, osteomyelitis, and endocarditis 2, 3, 4.
- Diagnosis is often based on a history of exposure to cats and serologic tests with high titers of immunoglobulin G antibody to B. henselae 5.
Treatment and Management
- Most cases of CSD are self-limited and do not require antibiotic treatment 2, 3, 4, 5.
- Antibiotics such as azithromycin, ciprofloxacin, gentamicin, trimethoprim and sulfamethoxazole, and rifampin may be effective in treating CSD, particularly in severe or complicated cases 2, 3, 4.
- In immunocompromised patients, antibiotics are dramatically effective against CSD, and may be necessary to prevent serious complications 4, 6.