Cat-Scratch Disease

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Cat-Scratch Disease
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Cat-scratch diseases (CSD) is a bacterial disease
caused by Bartonella henselae and is spread
through cat bites or scratches. The clinical
syndrome of CSD was first documented by the
Parisian physician, Robert Debre in the 1930s,
but the etiologic agent has only recently been
confirmed.
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Causative Agent Bacteria short slightly
curved gram-negative aerobic
rod The bacteria usually required a long
incubation period. Currently there are 6
Bartonella species that infect humans.
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CSD occurs only in humans and is not a disease of
animals. CSD can be seen worldwide with Ba.
Henselae being endemic in Europe, Africa,
Australia and Japan. In the United States
about 25,000 cases of CSD occur annually with
80 of those occurring in children and
adolescents.
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TRANSMISSION The reservoir of Ba. Henselae is
domestic cats, which do not show clinical signs
of disease but are bacteremic for extended
periods of time. Transmission among cats is
believed to be via the cat flea. It is
unlikely that the cat flea is involved directly
in human infection. Transmission to humans is
believed to be via dried infected flea feces via
the claws of cats by scratching
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PATHOGENESIS Typically, CSD causes regional
lymphadenopathy in those lymph nodes that drain
the inoculation site ( area of the scratch in
which bacteria are introduced). The most
common lymph nodes involved are found in the
upper extremities. Low-grade fever and
lethargy occurs in up to 50 of patients with
lymphadenopathy. Skin lesions typically develop
in 3 10 days after injury and progress to
lymphadenopahty in one to two weeks. As the
patient becomes bacteremic many organ systems
become infected including the central nervous
system, eyes, lungs and bones.
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CLINICAL SIGNS IN ANIMALS Infected cats do not
show signs of disease, but are bacteremic. Ba.
vinsonii may cause endocarditis, lameness, and
granulomatous lymphadenitis in dogs. CLINICAL
SIGNS IN HUMANS A cat scratch is typically the
primary lesion with CSD and this lesion serves as
the portal of entry for the bacteria. The skin
lesion usually appears as an erythematous (red)
papule. Following an incubation of 1 -2 weeks,
CSD usually presents as a self-limiting
lymphadenopahty associated with a cat scratch or
bite.
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The most common initial finding is subactue
regional lymph node enlargement that may develop
purulent discharge in 10 to 15 of cases. In
up to 25 of cases systemic involvement may occur
which includes ocular involvement,
encephalopathy, hepatitis, and hepatosplenic
infection. DIAGNOSIS IN ANIMALS Diagnosis in
cats is not done because the bacterium does not
cause disease in cats.
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DIAGNOSIS IN HUMANS The tissues infection with
Bartonella bacteria vary in people and biopsies
are typically not used in people to diagnose CSD.
There are skin tests that can be
performed. TREATMENT IN HUMANS The majority of
CSD cases resolve spontaneously and do not
require antibiotic treatment. Antipyretics and
analgesics may be needed to reduce fever and
pain. Aspiration of enlarged fluid-filled
lymph nodes may be recommended to relieve pain
however incision and drainage leaves a scar and
my spread the bacterium from one location to
another.
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MANGEMENT AND CONTROL IN ANIMALS There is no
current management of bacteremic cats to control
CSD. Flea control may help limit transmission
between cats and reduce bacterial load in the
reservoir host. MANGEMENT AND CONTROL IN
HUMANS Prevention of CSD includes teaching
people, especially children, how to handle pets
gently to avoid scratches. Any scratch or
bite, especially from cats, should be thoroughly
washed immediately and monitored to make sure it
resolves and that lymphadenopathy does not
occur.
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Cats should not be allowed to lick open wounds.
People who are immunocomprised, especially
people with AIDS, have an increased risk of
developing CSD and any skin lesion should be
examined by medical professionals.
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