Cat scratch disease (CSD) is a relatively common infection that usually presents as a tender lymphadenopathy which follows a bite wound or scratch from an infected cat. Bartonella henselae is the microorganism responsible for CSD. It is found in feline erythrocytes and fleas, which can contaminate saliva and be introduced into humans through biting and clawing by cats. The cat flea, Ctenocephalides felis, is the vector responsible for transmission of the disease from cat to cat, and its bite can also infect humans. For this reason, it is certainly prudent to use appropriate flea control at all times. Approximately 50% of cats harbor Bartonella and are entirely asymptomatic.
After contact with an infected cat, patients can develop a primary skin lesion that starts as a vesicle at the bite wound or clawing site. Lymphadenopathy develops within one to two weeks in about 10-45% of patients. In these patients, the lymph nodes are swollen and tender and may eventually suppurate. Many patients will also develop aching, general malaise and/or a low grade fever. A diagnosis of CSD is most often arrived at by obtaining a history of exposure to cats and a serologic test with high titers (greater than 1:256) of immunoglobulin G antibody to Bartonella. Most cases of CSD are self limiting and do not require antibiotic treatment. Infrequently, CSD may present or progress to a more disseminated form which can result in serious consequences for the patient. Most if not all of those patients in whom a more disseminated form occurs are severely immuno-compromised. If an antibiotic is chosen for treatment, azithromycin (Zithromax) has been demonstrated to achieve a rapid resolution of the clinical signs of disease. Obviously, immuno-compromised patients will require much more extensive medical support to alleviate the clinical signs of infection.
In conclusion, CSD is a somewhat common condition which can result in pain and discomfort at the bite wound or clawing site and progress in some people to painful lymph node enlargement. Most cases do not require treatment. At most, a course of antibiotics results in rapid resolution of clinical signs in the majority of affected people, unless the patient is immuno-compromised. Consistent flea control is an effective way of preventing exposure to the causative organism.