Feline Health
Caring for Cats
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A Winn Feline Foundation Health Article On ...
Cat Scratch Disease
by Susan Little, DVM
For almost 100 years, cat scratches have been associated with illness in
people. Cat Scratch Disease (CSD) is also called Cat Scratch Fever and
benign lymphoreticulosis. While CSD is found all over the world, it is an
uncommon disease. One estimate by the
Centers for Disease Control found
that there were 2.5 cases of CSD per 100,000 people per year in the United
States. While multiple cases of CSD in one household can occur, this
situation is rare. A study in Florida found that more than one member of a
family contracted CSD only 3.5% of the time. The majority of individuals who
contract CSD are under the age of 17, and are usually under the age of 12.
Typically, a small skin lesion (resembling an insect bite) develops at the
site of a cat scratch or (less commonly) a bite, followed within two weeks
by swollen lymph nodes and sometimes a fever. The illness is mild and
self-limiting in the majority of patients, although it may take some months
for the swollen lymph nodes to return to normal. Treatment is usually not
required. Reports over the last few years, however, have extended the
spectrum of problems associated with CSD to include such things as
tonsillitis, encephalitis, hepatitis, pneumonia and other serious illnesses
in a very small number of cases. People with compromised immune systems,
such as AIDS and cancer patients, are most at risk and can become most
seriously ill.
Diagnosis of CSD may not be easy. There is no simple diagnostic test. Most
physicians rely on history of exposure to a cat , the presence of typical
clinical signs, failure to find another cause, and examination of tissues,
such as biopsy of a swollen lymph node. Other diseases, such as
tuberculosis, brucellosis, and lymphoma, can cause similar symptoms.
Over the years, the cause of CSD had remained elusive, although bacteria
were commonly suspected to be the culprit. In 1988, a bacterium called
Afipia felis was cultured from the lymph nodes of patients with CSD. In
recent years, many studies have implicated the gram negative bacterium
Bartonella henselae as the primary (but not the sole) cause of CSD. B.
henselae is related to the agent of Trench Fever, B. quintana, a disease
common in the trenches of World War I. Other Bartonella species may also be
involved in CSD.
Cats are the main reservoir for B. henselae. Surveys for B. henselae
antibodies in cats in
the United States have found average infection rates to be from 25% to 41%
in clinically healthy cats. The lowest rates were in the midwest and great
plains regions (4-7%) and the highest were in the southeast (60%). Warmer,
more humid climates are most supportive of fleas, which have been shown to
transmit B. henselae from cat to cat. It appears that the majority of cats
do not become ill when they are infected with this bacterium and kittens are
more commonly infected than adults. Experimental infections in cats,
however, have caused a mild illness with fever, anemia, and transient
neurological dysfunction. Once infected, cats carry bacteria in their blood
for many months. It is important to note, however, that despite widespread
presence of B. henselae in cats, CSD itself is uncommon. It appears that CSD
is not easily acquired.
While most patients with CSD have a history of a cat scratch or bite, not
all do. Some patients have had no contact with cats at all. This makes the
exact modes of transmission unclear. It is likely that CSD can also be
contracted from environmental sources of the bacteria or from other animals.
For this reason, the term “bartonellosis” is a better way to describe the
variety of illnesses that are caused by B. henselae. Recently, it has been
found that dogs can become ill with a related Bartonella species and the
role of dogs as a possible reservoir for human infection is undergoing
study.
CSD is primarily a concern in homes with immunocompromised people. Since
kittens are more likely to carry B. henselae than adult cats, it is
recommended that people with compromised immune systems adopt cats older
than 1 year of age as pets to reduce the risk of contracting CSD. Any cat
suspected of carrying B. henselae should be isolated from sick or
immunocompromised individuals. However, there is no reliable and available
diagnostic test to determine if a cat is a carrier of B. henselae. Since
carrier cats are always healthy and multiple cases of CSD within a household
are rare, euthanasia of a suspected carrier is not warranted. Onychectomy
(declawing) is also not recommended, since infection can occur without a cat
scratch. As is always the case, any cut or scratch should be promptly washed
with soap and water. In addition, children should be taught not to tease or
annoy cats and rough play should be discouraged. A common sense approach is
the best way to safeguard against CSD.
Further reading:
- Abbott RC, Chomel BB, et al. Experimental and natural infection with
Bartonella henselae
in domestic cats. Comparative Immunology, Microbiology, and Infectious
Disease, Vol
20(1), 1997, p. 41.
- Breitschwerdt EB. Bartonellosis: of cats, dogs, mice and me. Proceedings of
the 15th American College of Veterinary Internal Medicine Forum, 1997, p.
505.
- Chomel BB, Kasten RW, et al. Experimental transmission of Bartonella
henselae by the
cat flea. Journal of Clinical Microbiology, Vol 34(8), August 1996, p.
1952.
- Groves MG, Hoskins JD, Harrington KS. Cat Scratch Disease: an update.
Compendium
on Continuing Education for the Practicing Veterinarian Vol 15(3), March
1993, p. 441.
Please Note: The Winn Feline Foundation provides the feline health
information on this site as a service to the public. Diagnosis and
treatment of specific conditions should always be in consultation with
one's own veterinarian. The Winn Feline Foundation disclaims
all warranties and liability related to the veterinary advice and
information provided on this site.
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