Page 195 - Feline Cardiology

198 Section E: Other Forms of Structural Heart Disease

reported to cause mitral endocarditis in the cat (Yamaguchi eling and calcification of infected valves in some affected
1983). Gram-positive bacteria are most often implicated cats (Noakes 1988; Malik et al. 1992), which suggests the
in the development of IE (Streptococcus spp. and disease is sufficiently chronic to allow time for remodel-
Staphylococcus spp.) (Peddle and Sleeper 2007). Valvular ing to occur. Chronicity is supported by a case series of
infection with gram-negative organisms is less common 6 cats with IE, in which 4 of the cases were presented
but is possible (Peddle and Sleeper 2007). Clusters of primarily due to signs of congestive heart failure and
microorganisms in vegetations are protected by layers of had normal leukograms and body temperatures. The
fibrin from the circulating blood pool. Moreover, the aortic vegetation was documented to have mineralized
valves are minimally vascularized, which limits the access by the time of examination in one of the cats in this
of the host immune response as well as antibiotics. series. The other 2 cats presented with a more typical
In a large feline pathology study which included acute pattern of sepsis and multisystemic disease follow-
results from 4933 necropsied cats between 1962 and ing recent histories of abscessation, and gram-positive
Misc. Heart Diseases cases were always associated with focal or systemic bac- was most frequently involved (5/6), followed by the
cocci were documented postmortem. The aortic valve
1976, 13 cases of IE were identified (Liu 1977). These
mitral valve (4/6); the tricuspid valve was involved in 1
terial infections, and the mitral valve, aortic valve, or
case. Streptococcus species were detected via gram-stain
both were most commonly involved. In severe cases,
of valve lesions in 1 case and gram-positive cocci were
valve perforation was noted and concurrent arterial
thromboembolism occurred in 3 of the 13 cats (Liu
had positive blood cultures for a Bartonella species, sug-
1977). None of the cats had evidence of concurrent con-
gesting a possible link to Bartonella (Malik et al. 1999).
genital heart disease (nor have any studies since), sug- demonstrated in valve vegetations of another cat; 2 cats
gesting that there is not likely an association with Bartonella are fastidious, hemotropic gram-negative
subaortic stenosis, which has been recognized in dogs bacteria that are primarily transmitted by arthropod
and humans. However, since both diseases are rare in vectors and possibly fleas. Domestic cats are the primary
cats, it is possible that a relationship has simply not been reservoir for B. henselae and infected cats can have bacte-
recognized due to the low number of reported cases. In remia for more than a year (Chomel et al. 2006). In recent
a retrospective study that included cats diagnosed ante- years, Bartonellae have been implicated as an important
mortem with sepsis (and confirmed by postmortem his- cause of endocarditis in humans and dogs. Cats had previ-
topathologic evidence of multiorgan bacterial infection) ously been believed to be healthy carriers of the pathogen;
over a 12-year period, 4 of 29 cats were found to have however, since Malik’s report in 1999, several Bartonella
infective endocarditis (Brady et al. 2000). Therefore, IE endocarditis cases, including B. henselae have been
is a rare but significant disease in the cat. reported in cats (Malik et al. 1999, Chomel et al. 2009).
In dogs, the definitive diagnosis of IE is often compli- Four types of B. vinsonii subsp. berkhoffi, B. clarridgeiae, B.
cated, although most affected patients show signs con- washoensis, B quintana, and B. rochalimae have all been
sistent with sepsis (fever, malaise, inflammatory associated with endocarditis in the dog. In Malik’s case
leukogram), evidence of systemic embolization (septic series from Australia, although Bartonella sp. were iso-
arthritis, uveitis, myocarditis), and signs of severe valve lated from 2 cats with endocarditis of the aortic valve, no
insufficiency (murmurs, arrhythmias, bounding pulses, direct causality was proven (Malik et al. 1999). However,
congestive heart failure). Moreover, the disease course in 1 feline B. henselae endocarditis case was reported in
dogs tends to be acute to subacute (Peddle and Sleeper California several years later with PCR evidence of the
2007). Cats presenting with IE can present with similar organism in the aortic valve (Chomel et al. 2003), and the
signs to those described for dogs. Because the mitral and same group reported another feline case from New York
aortic valves are most commonly involved, a left para- (Chomel et al. 2009). The pattern of disease in these feline
sternal systolic murmur or a left basilar diastolic murmur cases was similar to human and canine Bartonella endo-
is often present. However, diastolic murmurs in cats can carditis, with large vegetative lesions involving the aortic
be challenging to identify, particularly in the presence of valve. The mitral valve was also involved but less severely
sinus tachycardia. There have been sporadic case reports affected. Seropositive cats are also more likely to have
of IE in cats causing unusual sequelae such as a dissect- kidney disease and urinary tract infections, stomatitis,
ing aortic aneurysm (Laurenço et al. 2002) and cerebel- and lymphadenopathy (Chomel et al. 2006). In humans
lar infarction (Cherubini et al. 2007). Systemic arterial (and cats), the disease follows a northern to southern
embolization and CHF appear to be particularly gradient with the highest prevalence in southern latitudes
common findings in cats affected with IE. However, (Chomel et al. 2006, 2009). Antibody titers for Bartonella
most case reports suggest disease progression may be spp. have also been detected in numerous wild felid popu-
slower than what is seen in dogs, with extensive remod- lations (Chomel et al. 2006).