Page 1568 - Small Animal Internal Medicine, 6th Edition

1540 PART XIV Infectious Diseases

Mycoplasma spp. infections of humans resulting from cat
bites, one with cellulitis and one with septic arthritis, have
VetBooks.ir been reported. L-form bacteria are cell wall–deficient organ-
isms associated with chronic draining skin wounds in cats
commonly resistant to cell wall–inhibiting antibiotics such
as penicillins and cephalosporins. Infection of a human
being after a cat bite has been documented. Diagnosis can
be confirmed only by histologic examination of tissue. Doxy-
cycline has been used to treat cats and people successfully.
Gloves should be worn when attending cats with draining
tracts, and hands should be cleansed thoroughly.
Bartonella henselae can infect both dogs and cats, and
is the most common cause of cat scratch disease, as well
as bacillary angiomatosis and bacillary peliosis—common
disorders in humans with AIDS (Breitschwerdt et al., 2010).
Dogs and cats can also be infected with several other Bar- FIG 99.2
tonella spp., including Bartonella clarridgeiae, Bartonella Ctenocephalides felis frass and eggs that can contain live
koehlerae, Bartonella vinsonii (dogs), and Bartonella quin- Bartonella spp. or Rickettsia felis. (Courtesy the HESKA
tana (see Chapter 94). Bartonella henselae has been isolated Corporation.)
from the blood of subclinically ill, seropositive cats and also
from some cats with a variety of clinical manifestations such
as fever, lethargy, lymphadenopathy, uveitis, gingivitis, and this differential and should be informed if a patient is exhib-
neurologic diseases. Infection of dogs has also been associ- iting these problems.
ated with clinical illness. Seroprevalence in cats varies by Blood culture, blood PCR, and serologic testing can be
region, but up to 93% of cats in some geographic areas of used to determine the risk of individual cats, dogs, or people
the United States are Bartonella spp. seropositive. Bartonella (see Chapter 94). The use of Bartonella alpha proteobacteria
spp. have also been detected in dog saliva, and dogs have growth medium (BAPGM) culture media with PCR assay
been associated with bartonellosis in people (see Chapter has been shown to be one of the most sensitive ways to prove
94). Bartonella henselae, B. clarridgeiae, and B. koehlerae Bartonella spp. bacteremia in dogs and people. This assay is
are transmitted between cats by fleas, so the prevalence is available at a commercial laboratory (www.galaxydx.com).
greatest in cats from states where fleas are common (Bre- In dogs and cats, although serologic testing can be used to
itschwerdt et al., 2010). Transmission to humans commonly determine whether an individual has been exposed, both
occurs after cat bites or scratches; the disease appears to seropositive and seronegative cats can be bacteremic, limit-
be transmitted most commonly from kittens. B. henselae ing the diagnostic utility of serologic testing. Thus testing
survives in flea frass for at least 9 days, so the cat’s claws healthy cats or dogs for Bartonella spp. infection is not cur-
and teeth are likely contaminated with B. henselae during rently recommended by the Centers for Disease Control and
grooming, which emphasizes the maintenance of flea control Prevention (Kaplan et al., 2009) or the American Association
on dogs and cats (Fig. 99.2). In one study of cats with C. felis of Feline Practitioners (Brunt et al., 2006). Testing should be
infestation, Bartonella spp. DNA could be amplified from reserved for cats with suspected clinical bartonellosis.
the skin (31%) and claw beds (18%) of the cats (Lappin and In experimental studies, administration of doxycycline,
Hawley, 2009). tetracycline, erythromycin, amoxicillin-clavulanate, or enro-
Humans with cat scratch disease develop a variety of floxacin can limit bacteremia but does not cure infection in
clinical signs, such as lymphadenopathy, fever, malaise, all cats and has not been shown to lessen the risk of cat
weight loss, myalgia, headache, conjunctivitis, skin erup- scratch disease. Azithromycin was commonly administered
tions, and arthralgia (Breitschwerdt et al., 2007; Breitschw- to cats with suspected clinical bartonellosis but is now con-
erdt et al., 2010). Bacillary angiomatosis is a diffuse disease sidered contraindicated for feline bartonellosis due to rapid
resulting in vascular cutaneous eruptions. Bacillary peliosis induction of antimicrobial resistance (Biswas et al., 2010).
is a diffuse systemic vasculitis of parenchymal organs, par- Thus antibiotic treatment of healthy bacteremic cats is con-
ticularly the liver. The incubation period for cat scratch troversial and not currently recommended by the Centers for
disease is approximately 3 weeks. Most cases of cat scratch Disease Control (Kaplan et al., 2009) and Prevention or the
disease are self-limiting but may take several months to com- American Association of Feline Practitioners (Brunt et al.,
pletely resolve. Recently, B. henselae has been documented 2006). Treatment should be reserved for cats with suspected
as a cause of chronic disease syndromes like fever, headaches, clinical bartonellosis. Strict flea control should be main-
polyarthritis, and chronic fatigue; immunocompetent veteri- tained because the administration of monthly imidacloprid
nary healthcare providers or Bartonella researchers may be topically or in an 8-month collar has been shown to block
overrepresented from increased risk of exposure (Breitschw- transmission of B. henselae among cats (Bradbury and
erdt et al., 2007). Most medical doctors may not recognize Lappin, 2010; Lappin et al., 2013). Immunodeficient people