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112 Bartonellosis

• Bacillary angiomatosis (rare subdermal disease ○ Uveitis, infertility, abortion, and stillbirth • Organisms are passed from one animal to
consequence of human infection with B. are described in experimentally infected another by hematophagous insects such as
VetBooks.ir • Peliosis hepatis (rare vascular condition of ○ Fever, endocarditis, and myocarditis are • Pathogens may be passed in the excrement
fleas, ticks, lice, keds, biting flies, and perhaps
cats.
henselae or Bartonella quintana)
others.
described in naturally infected cats.
the liver with several causes, including B.
○ Osteomyelitis, stomatitis suggested to be
henselae infection)
B. henselae, and potentially through saliva
caused by bartonellosis of the vectors, as appears to be the case for
Epidemiology • B. vinsonii subsp berkhoffii is best understood by ticks or sand flies.
SPECIES, AGE, SEX as a cause of blood culture–negative endo- • In the adapted reservoir host, the organisms
• Dogs and cats of either sex and any age, carditis in dogs. Other possible manifesta- exist in red blood cells (RBCs) and vascular
although bacteremia with some Bartonella tions include endothelial cells for long periods. The organ-
spp seems to be more common in young ○ Endocarditis, myocarditis, arrhythmia isms also gain access to mononuclear and
and old animals ○ Bacillary angiomatosis other cell types. Because the bacteria escape
• Cats are the reservoir host for B. henselae, ○ Granulomatous hepatitis, splenitis, and immune control, they are often described
Bartonella clarridgeiae, and Bartonella lymphadenitis as stealth pathogens. The location of the
koehlerae. ○ Panniculitis pathogen in RBCs is ideal for transmitting
• Wild canids and dogs are the reservoir hosts ○ Polyarthritis the bacterium to naïve vector insects.
for Bartonella vinsonii subsp berkhoffii, ○ Rhinitis • Because the bacteria are well adapted to the
Bartonella rochalimae, and Candidatus ○ Meningoencephalitis reservoir host, diseases may not occur at all
Bartonella merieuxii. ○ Vasculitis (cutaneous) or may be delayed in onset. Chronic bacte-
• Numerous other Bartonella spp exist in other ○ Uveitis and chorioretinitis remia is often detected by polymerase chain
reservoir hosts, and accidental infection can ○ Immune-mediated blood disorders (e.g., reaction (PCR) assays or blood culture in
occur in dogs or cats. immune-mediated hemolytic anemia) seemingly healthy reservoir hosts. Although
○ Thromboembolism overt illness is not common in the infected
RISK FACTORS reservoir host, long-term infection may exact
• Exposure to and lack of protection from HISTORY, CHIEF COMPLAINT a biological toll on the host that predisposes
hematophagous insects such as fleas, ticks, • Because the types of illness caused by infec- to disease at some point in life. Immune
and biting flies increase risk of infection. tion are diverse and not well characterized, suppression or other stressors make illness
• Immunosuppression or co-infection increase the history of infected animals is also quite in the reservoir more likely.
risk of illness associated with Bartonella varied. ○ Endocarditis, myocarditis, and vascular
infection. • B. henselae in cats: most often, no clinical signs. pathology may be consequences of
Occasionally, nonspecific signs of anorexia, infection.
CONTAGION AND ZOONOSIS lethargy, weakness, or ocular abnormalities ○ Immune-mediated (e.g., glomerulonephri-
• These pathogens are transmitted primarily noticed. Abortion or stillbirths may occur. tis) and autoimmune (e.g., immune-
through exposure to insect vectors or their • B. vinsonii subspecies berkhoffii in dogs: mediated hemolytic anemia) disease may
waste (e.g., flea frass). infection is often subclinical. Illness is usually be manifestations of infection.
• Each Bartonella species is associated with accompanied by nonspecific signs that can • When nonadapted animals become infected,
one or more adapted reservoir host. Although include lethargy, exercise intolerance, weight disease is more likely to occur than in adapted
easily transmitted from one such adapted loss, collapse, sudden death (p. 294). hosts. Nevertheless, subclinical infections are
host to another, overt disease in the adapted also well documented in nonadapted hosts.
species is uncommon. PHYSICAL EXAM FINDINGS
• Disease is more likely when Bartonella infect • B. henselae in cats: usually unremarkable. DIAGNOSIS
a nonadapted or accidental host. Although Possible abnormalities include
many Bartonella spp can cause zoonotic ○ Fever Diagnostic Overview
infection, the best known infections associ- ○ Ocular abnormalities suggestive of uveitis Bartonellosis should be considered in the
ated with dogs and cats are listed in the (p. 1023) differential diagnosis for a number of disorders,
table. ○ Heart murmur especially when another cause is not identified;
○ Cardiac arrhythmia if there has been a history of exposure to insect
GEOGRAPHY AND SEASONALITY ○ Lymphadenomegaly vectors; if an underlying immunodeficiency or
Worldwide; especially common where vectors ○ Stomatitis (usually in cats co-infected with immunosuppression is recognized; or if the
are likely (often warm climates) feline immunodeficiency virus) animal fails to improve with standard care.
• B. vinsonii subsp berkhoffii in dogs: possible It can be challenging to prove that bartonel-
ASSOCIATED DISORDERS abnormalities include losis is the cause of clinical disease. There are
Numerous manifestations of acute or chronic ○ Heart murmur no specific suggestive findings on routine labora-
infection are possible. ○ Fever tory testing or imaging studies. The bacterium
○ Arrhythmia is too small to see on microscopic evaluation
Clinical Presentation ○ Evidence of congestive heart failure (CHF) of the blood smear or in most instances tissue
DISEASE FORMS/SUBTYPES (p. 408) histopathology. Culture of the organisms from
• The complete spectrum of illness associ- ○ Lymphadenomegaly blood is possible in the reservoir host, but
ated with bartonellosis is not understood. ○ Splenomegaly/hepatomegaly infection in the reservoir does not prove disease
Although some disease manifestations are ○ Lameness causation and may be common in a given
clearly associated with infection (e.g., endo- ○ Uveitis population and therefore incidental to an illness.
carditis), other illnesses have been recognized Culture from the nonadapted host, on the other
in infected animals, but a causal relationship Etiology and Pathophysiology hand, is extremely challenging. Serologic testing
has not been established. • Bartonella spp are relatively newly recognized is often positive in a predisposed population
• B. henselae in cats is most often a subclinical pathogens, with new species and new disease (i.e., those exposed to insect vectors) and is
infection of primary importance as a zoonotic manifestations still being described on a sometimes negative despite infection in animals
pathogen (i.e., cat-scratch disease). frequent basis. with bartonellosis. Specialized PCR performed

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