Cat scratch disease, also known as cat scratch fever, is an infectious disease that is caused by a bacterium called Bartonella henselae. Cats are considered a natural reservoir for this particular type of Bartonella, which means that they can act as a long-term host for the bacteria and then transmit it to humans. An infected cat can cause cat scratch disease in humans through bites or scratches. A human also might get the infection if the cat’s saliva enters the body through broken skin or membrane.
Cats that carry the bacteria show no signs, and as many as half of all cats could carry it at some point in their lives. Kittens are more likely to be infected than adult cats. Ticks also can transmit the bacteria, but the vast majority of cat scratch disease cases are caused by felines.
When an individual has cat scratch disease, there usually is skin irritation, such as a bump or blister at the injury site. Some people might experience fever, fatigue, headache, or swelling of the lymph nodes. A smaller number of people with the disease experience symptoms that include chills, abdominal pain, enlarged spleen, backache, sore throat, loss of appetite and weight loss. Symptoms can manifest anytime from one week to several months after the individual first becomes infected.
Cat scratch disease is not contagious from human to human, and most cases are mild and without complications. People who have suppressed immune systems because of HIV or certain cancer treatments are more likely to have complications with an infection. If an individual has contracted the disease once, he or she most likely will not get it again.
A doctor typically will diagnose cat scratch disease with a physical examination and after asking questions regarding the patient’s recent interactions with cats. The doctor probably will want to rule out other possible causes of swollen lymph nodes and might run some skin, blood or culture tests to do so. There also is a specific blood test to determine the presence of the Bartonella hensalae bacteria.
Prognosis for individuals with the disease typically is excellent, particularly for those with healthy immune systems. For many people, infection goes away on its own without treatment. In the case of more severe infection, a doctor most likely will prescribe antibiotics.
People who are concerned about contracting cat scratch disease can take steps to prevent it. Some tips include avoiding rough play with kittens and cats, washing hands thoroughly after play and taking care to clean any bites or scratches immediately. There is some evidence that cats might get Bartonella hensalae from flea feces, so keeping a cat and home free of fleas also could help prevent infection.