Cat Scratch Disease

Overview, Causes, & Risk Factors

Cat-scratch disease is an infection caused by the bacteria Bartonella henselae.

What is going on in the body?

The Bartonella henselae bacteria causes a local infection at the site where it entered the body. Lymph nodes near the area become swollen 1 to 7 weeks after exposure to the bacteria. Sometimes, a small, solid skin lesion will develop at the site. Most cases of cat- scratch disease are self-limited, which means they go away on their own.

In rare cases, cat-scratch disease can cause infections in other body areas, such as the following:

  • conjunctivitis, which involves the eyes
  • encephalitis, which involves the brain
  • meningitis, which involves the brain and spinal cord
  • osteomyelitis, which involves bone
  • pneumonia, which affects the lungs
  • People with impaired immune systems are more likely to suffer severe and complicated infections. This includes people with immunodeficiency disorders, such as HIV. People who are being treated with chemotherapy or radiation therapy for cancer are also at higher risk.

    What are the causes and risks of the infection?

    Bartonella henselae bacteria cause cat-scratch disease. They are transmitted by contact with the saliva of a cat. An individual can become infected from a cat bite or scratch, or even from petting the cat. The saliva is found on the cat’s fur and paws after the cat grooms itself. The cat itself is usually healthy. Young cats are the most common source of infection for humans.

    Cat-scratch disease is most common in children and adolescents. It is seen most often in late summer, fall, and early winter.

    Symptoms & Signs

    What are the signs and symptoms of the infection?

    Following are some of the common symptoms of cat-scratch disease:

  • fever
  • headache
  • loss of appetite
  • malaise, or a vague feeling of illness
  • swollen lymph nodes that can be tender, warm, and red
  • If the infection spreads to other body organs, symptoms will reflect that involvement.

    Diagnosis & Tests

    How is the infection diagnosed?

    Diagnosis of cat-scratch disease begins with a medical history and physical exam. An antibody titer test may be ordered to see if the person is producing antibodies to Bartonella henselae. A polymerase chain reaction test can be ordered to identify the genes of the bacteria. Using special techniques, the bacteria can sometimes be seen in a biopsy specimen from the affected body part.

    Prevention & Expectations

    What are the long-term effects of the infection?

    Most healthy people recover without long-term effects. People with impaired immune systems can have permanent organ damage or can die as a result of cat-scratch fever.

    What are the risks to others?

    Cat-scratch disease is not passed from person to person.

    Treatment & Monitoring

    What are the treatments for the infection?

    In healthy people, the infection usually goes away in 2 to 4 months without treatment. In complicated cases, antibiotics, such as erythromycin or doxycycline, can be used.

    Lymph nodes that are large and painful can be drained with a needle. Powerful antibiotics, such as azithromycin, can be given to people with impaired immune systems or severe infections.

    What are the side effects of the treatments?

    Antibiotics may cause rash, stomach upset, or allergic reactions.

    What happens after treatment for the infection?

    Most people recover from cat-scratch disease and need no further treatment. If the person has an impaired immune system or permanent organ damage, further treatment may be required.

    How is the infection monitored?

    Any new or worsening symptoms should be reported to the healthcare provider.

    Article type: xmedgeneral