Cat scratch fever or disease (CSD) is a bacterial infection caused by Bartonella henselae.   Bartonella are a group of gram-negative bacteria that parasitize erythrocytes   (red blood cells or RBCs) of the host and are transmitted by arthropods. Most people infected with cat scratch fever have been previously bitten or scratched by a cat. Cat bites are less frequently implemented in transmission than are scratches.  CSD transmission requires only a broken mucous membrane or dermal barrier; therefore a scratch is no t necessary for infection to occur, even an old wound or injury will suffice.
 
Typically an individual will develop a mild infection at the point of entry (bite wound or scratch).  Clinical signs in people include swollen lymph nodes, especially around the head, neck, and upper limbs.  Immunocompetent (people with a normal acting immune system) individuals will typically contain the infection to the local or regional lymph nodes.  Additional symptoms may include fever, headache, fatigue, and anorexia (poor appetite).  In rare instances bacillary angiomatosis (diseased state of the blood vessels) and Parinaud’s oculolandular syndrome (involves paralysis of the eye muscles secondary to infection) may occur.
 
Cats that carry B. henselae typically do not show any physical sign of disease, but the infection has been seen as a contributing factor to some cases of rhinitis, conjunctivitis, stomatitis (infection of the mouth), hepatitis, and possibly even pancreatitis and diabetes. 
 
Direct (cat to cat transmission) and vertical (from mother to offspring) transmission between cats has not been documented.  The cat flea or Ctenocephalides felis is necessary for transmission to occur between cats. The cat flea is the most common type of flea seen in the United States. 
 
Kittens are more likely to be infected and capable of transmitting the bacterium to people. Approximately 5% of human cases of CSD do not have a history of exposure to cats.  In cases void of any contact with cats, transmission of CDS is believed to occur through direct exposure to the flea.
 
People that are immunocompromised with conditions such as HIV/AIDS, cancer, or transplant patients are more likely to develop cat scratch fever and to develop complications from it. The CDC currently estimates that about 1 in every 10,000 Americans will develop CSD yearly. 
 
Fleas have been found to contain B. henselae.  To date there is no evidence that a bite from=2 0an infected flea can transmit the bacterium.   “Dr Michael Lapin states that of every 10 cats that have fleas, up to eight of them will carry B. henselae or Rickettsia felis in the flea dirt produced from fleas housed upon them.”3
 
To prevent cat scratch fever avoid “rough play” with cats, especially kittens.  Wash cat bites and scratches immediately and thoroughly with soap and water.  Cats should not be allowed to lick any open wounds an individual may have.  Flea populations should be controlled.  In flea endemic areas, year-round flea control is recommended.  According to the Centers for Disease Control or CDC, any person developing an infection following a cat bite or scratch should contact their physician.
 
In flea endemic areas the incidence of Bartonella seroprevalence is high.  In parts of the United States up to 93% of the cat population may test positive for Bartonella.  In general, serology and PCR testing are both recommended in suspected clinical cases of Bartonella in cats.  PCR testing is available from Colorado State University and the University of California at the Davis campus. 
 
According to the American Association of Feline Practitioners cats suspected of having clinical bartonellosis should be treated with doxycycline.  Those cats not responding to initial treatment with doxycycline may be treated with azithromycin or fluoroquinolone.  It is not recommended that healthy cats be tested or treated for Bartonella infections unless they are exhibiting clinical signs of illness or are responsible for zoonotic disease transmission.
  
References:
 
1.  http://www.cdc.gov/healthypets/diseases/catscratch.htm
 
2.  Norsworthy, Gary. The Feline Patient.  3rd Ed.  2006.  Blackwell Publishing.  Pp. 27-28.
 
3.  Rosenthal, Marie, Ed.  “What does it mean if a Cat has Bartonella?  It Depends.”  Veterinary Forum.  June 2008. P. 17.