Cat Scratch Fever in Cats

Bartonellosis is zoonotic, meaning that it can be transferred to humans via a bite or scratch from the cat. Though the disease is typically mild in humans, over 25,000 people are hospitalized from it each year.

Cat scratch fever, also known as cat scratch disease or bartonellosis, is an infectious disease caused by the bacteria Bartonella henselae. The bacteria originate in the feces of fleas that gets deposited onto the cat's skin. The cat contracts the bacteria during normal grooming or by scratching the fleas. Ticks may also spread the bacteria to cats.

Symptoms are typically mild and may be present for only a short period of time.

• Fever
• Lethargy
• History of fleas or tick infestation
• Swollen lymph nodes or glands
• Lack of appetite
• Stiff, sore muscles
• Vomiting
• Reproductive difficulty
• Eye redness

Both fleas and ticks are known to spread the Bartonella henselae bacteria. Cats contract the disease through the feces of the fleas. When scratching the fleas or when grooming, the bacteria from the feces catches in the cat's nails. The cat then passes on the bacteria when playing with humans or when protecting itself by scratching or biting a human.

The veterinarian will ask for a complete health history of the cat and whether the cat has had any recent exposure to ticks or flea infestations. There are several tests available to diagnose cat scratch fever in cats. Because the Bartonella bacteria isn't always present in the bloodstream, the veterinarian may need to run more than one of the tests to get a definitive diagnosis. These possible tests include:

• Western blot, which tests for antibodies against the Bartonella bacteria. The cat's immune system will make the antibodies once exposed to the bacteria. The presence of these specific antibodies indicates bartonellosis. The blood used for the Western blot test must be sent to an outside lab for the proper diagnosis and takes some time to get the results back.
• Immunofluorescence is used to illuminate antibodies in the blood or tissue using fluorescent dye. The veterinarian will take a sample of the cat's blood and expose it to a specific antibody for Bartonella. The antibody will attach to any bacteria in the sample and glow bright green on the slide under a microscope.
• ELISA testing, which works similarly to the Western blot but takes a shorter period of time to get results. ELISA stands for "enzyme-linked immunosorbent assay" and is used to detect cat bartonellosis by seeing if the cat's body has made antibodies against the Bartonella bacteria.
• Polymerase chain reaction (PCR) is an advanced method that tests the cat's blood or a lesion on the affected human for the bacterial DNA of Bartonella.

Antibiotics: The Bartonella bacteria is gram-negative, which makes it a more difficult type of bacteria to treat due to its complex outer membrane that is difficult to penetrate. Because of this, more intensive antibiotics are used. Most often, veterinarians put cats on an antibiotic called azithromycin and require that they remain on it for three weeks in order to ensure the bacteria have been eliminated. Other antibiotics may be used if azithromycin isn't effective.

Wait and See Approach: Many cats are able to develop the antibodies to protect themselves from the bacteria. If the cat has only mild symptoms and no one in the household is extremely young, elderly or has a compromised immune system, the veterinarian may opt for no treatment in order to allow the cat's immune system to fight it on its own.

Humans: Many people only become aware that their cat has bartonellosis when they contract cat scratch fever and become ill. Humans may be placed on antimicrobial therapy, placed on bed rest and have the option of draining painful, swollen lymph nodes to ensure their comfort while their body fights the illness. 

Most cases of bartonellosis resolve within a few weeks. Care should be taken to prevent the cat from coming into contact with the bacteria again by placing the cat on a flea preventative and keeping them out of areas that contain ticks, such as the woods. The cat's nails should be neatly trimmed by a veterinarian to prevent scratching.

Humans who have contracted the bacteria should take care to stay away from kittens until they no longer have the illness as the bacteria could possibly be transferred to the kitten. Humans who get scratched or bit by a cat should immediately wash the wound with soap and water to prevent the bacteria from entering their body. Those who have a compromised immune system should regularly get their cat tested for bartonellosis in order to be proactive in treating the bacteria.