Most people know the term cat scratch fever, but few actually know what the name is derived from.  This is an infection caused by a bacterium called Bartonella henselae.  The bacteria live in fleas, and the cats can harbor these bacteria under their claws when scratching to get rid of their fleas.  When the cat scratches a person, the bacteria are transmitted through the scratch marks. 

Following a cat scratch where a person becomes infected with Bartonella, the area that was scratched will develop a small red bump, and then the lymph nodes around the cat scratch area will become enlarged and painful.  Fever develops, and usually this disease resolves on its own over the course of a week or two.  Sometimes antibiotics are needed to shorten the course of the disease.  In immunocompromised people, however, this bacteria can cause damage to the spleen, heart infections, and encephalitis.

Cats without flea prevention in warm climates are most at risk for being infected with Bartonella.  Up to 40% of cats are infected at any given time.  The question is - does infection cause disease?  There are several conditions that have been theorized to be caused by Bartonella in cats, and research is still being done to prove that certain conditions are linked to this bacteria.  These include:

• Fever
• Eye inflammation (squinting, ocular discharge, pawing at eyes)
• Chronic stomatitis (inflammation in the mouth) and gingivitis
  
• Lymph node enlargement
• Muscle pain
• Heart infections

Just as with people, this disease condition seems to be worse in cats that are immunosuppressed, especially those with concurrent Feline Immunodeficiency Virus infections. 

There are several tests available for Bartonella henselae.  However, most of these tests are not 100% accurate.  Tests to detect circulating antibodies do not tell us if this is a current or prior infection.  Also, some cats with active infection will not produce antibodies at all.   Tests to detect organisms in the blood stream are not very accurate either because the bacteria does not circulate in the bloodstream continually.  So we must interpret these tests along with the patient's symptoms and likelihood of infection, and treat when we think that antibiotics will be beneficial.

Antibiotics targeted at Bartonella generally clear about 80% of infections in cats.  Proper flea control is imperative so infection does not continue to re-occur.  In Texas, we recommend that cats be on a flea preventative monthly for the entire year as we can still see parasites such as fleas even in December and January.