Cat scratch disease, also known as cat scratch fever, Teeny's Disease, inoculation lymphoreticulosis,
and subacute regional lymphadenitis, is a common and usually benign infectious disease
caused by the fastidious intracellular gram negative bacterium Bartonella henselae or
Bartonella quintana.
It is most commonly found in children following a scratch or bite from a cat within about
one to two weeks.
Signs and symptoms Cat scratch disease commonly presents as tender,
swollen lymph nodes near the site of the inoculating bite or scratch or on the neck and is usually
limited to one side.
This condition is referred to as regional lymphadenopathy and occurs 1–3 weeks after
inoculation.
Lymphadenopathy in CSD most commonly occurs in the arms, neck, or jaw, but may also occur
near the groin or around the ear.
There may be a vesicle or an erythematous papule at the site of initial infection.
Most patients also develop systemic symptoms such as malaise, decreased appetite, and aches.
Other associated complaints include headache, chills, muscular pains, joint pains, arthritis,
backache and abdominal pain.
It may take 7 to 14 days, or as long as two months, before symptoms appear.
Most cases are benign and self-limiting, but lymphadenopathy may persist for several months
after other symptoms disappear.
The disease usually resolves spontaneously, with or without treatment, in one month.
In rare situations, Cat scratch disease can lead to the development of serious neurologic
or cardiac sequelae such as meningoencephalitis, encephalopathy, seizures, or endocarditis.
Endocarditis associated with bartonella infection has a particularly high mortality.
Parinaud's oculoglandular syndrome is the most common ocular manifestation of Cat scratch
disease and is a granulomatous conjunctivitis with concurrent swelling of the lymph node
near the ear.
Optic neuritis may also occur.
Immunocompromised patients are susceptible to other conditions associated with Bartonella
henselae and Bartonella quintana such as bacillary angiomatosis or bacillary peliosis.
Bacillary angiomatosis is primarily a vascular skin lesion that may extend to bone or be
present in other areas of the body.
In the typical scenario, the patient has HIV or another cause of severe immune dysfunction.
Bacillary peliosis is a condition caused by B. Henselae that most-often affects patients
with HIV and other conditions causing severe immune compromise.
The liver and spleen are primarily affected, with findings of blood-filled cystic spaces
on pathology.
Diagnosis The Warthin–Starry stain can be helpful
to show the presence of B. henselae, but is often difficult to interpret.
B. Henselae is difficult to culture and can take 2–6 weeks to incubate.
The best diagnostic method currently available is Polymerase chain reaction, which has a
sensitivity of 43-76% and a specificity of 100%.
Transmission The cat was recognized as the natural reservoir
of the disease in 1950 by Robert Debré.
Kittens are more likely to carry the bacteria in their blood, and may therefore be more
likely to transmit the disease than adult cats.
However, the results of experimental studies showed that fleas serve as a vector for transmission
of B. henselae among cats, and that viable B. henselae are excreted in the feces of Ctenocephalides
felis, the cat flea.
Another study showed that cats could be infected with B. henselae through intradermal inoculation
using flea feces containing B. henselae.
As a consequence, it is believed that a likely means of transmission of B. henselae from
cats to humans may be inoculation with flea feces containing B. henselae through a contaminated
cat scratch wound or by cat saliva transmitted in a bite.
Ticks can also act as vectors and occasionally transmit the bacteria to humans.
Histology
Cat scratch disease is characterized by granulomatous inflammation on histological examination of
the lymph nodes.
Under the microscope, the skin lesion demonstrates a circumscribed focus of necrosis, surround
by histiocytes, often accompanied by multinucleated giant cells, lymphocytes, and eosinophils.
The regional lymph nodes demonstrate follicular hyperplasia with central stellate necrosis
with neutrophils, surrounded by palisading histiocytes and sinuses packed with monocytoid
B cells, usually without perifollicular and intrafollicular epithelioid cells.
This pattern although typical is only present in a minority of cases.
Treatment Most healthy people will clear the infection
without treatment, and antimicrobial therapy is not recommended for immunocompetent patients
with mild to moderate Bartonella henselae disease due to the risk of side-effects from
antibiotics.
Azithromycin, ciprofloxacin, doxycycline, gentamicin, rifampicin, and trimethoprim/sulfamethoxazole
have been used, but have demonstrated limited efficacy.
Azithromycin is preferentially used in pregnancy to avoid the teratogenic side-effects of doxycycline.
However, doxycycline is preferred to treat B. henselae infections with optic neuritis
due to doxycycline's ability to adequately penetrate the tissues of the eye and central
nervous system.
Epidemiology Bartonella henselae is found worldwide and
cat scratch disease has been observed in many countries.
The incidence of CSD appears to have a seasonal relationship possibly due to the mating behavior
of the cat flea during certain times of the year.
History Symptoms similar to Cat scratch disease were
first described by Henri Parinaud in 1889 and the clinical syndrome was first described
in 1950 by Robert Debré.
In 1983, the Warthin-Starry silver stain was used to discover a gram negative bacillus
which was named Afipia felis in 1991 after it was successfully cultured and isolated.
The causative organism of CSD was originally believed to be Afipia felis, but this was
disproved by immunological studies in the 1990s demonstrating that cat scratch fever
patients developed antibodies to two other organisms, Bartonella henselae and Bartonella
clarridgeiae, which are rod-shaped Gram-negative bacteria.
References
External links CDC information
DermNet bacterial/catscratch Cat Scratch Disease on National Organization
for Rare Disorders site Cat Scratch Fever Disease