Abstract
BackgroundBacterial endocarditis is a recognised disease in humans and animals. In humans, infection with Coxiella burnetii can cause endocarditis, but this has not been investigated thoroughly in animals. Endocarditis in cattle is a common post-mortem finding in abattoirs and studies have identified Trueperella pyogenes as a major cause. Despite exposure of cattle to C. burnetii, the significance of this particular bacterium for development and progression of endocarditis has not been studied in detail. Cardiac valves of cattle affected with endocarditis (n = 100) were examined by histology, fluorescence in situ hybridization (FISH) and real time quantitative polymerase chain reaction (PCR). Serum was examined for anti-C. burnetii antibodies by enzyme-linked immunosorbent assay (ELISA).ResultsSerology revealed that 70% of the cattle were positive for antibodies to C. burnetii, while PCR analysis identified 25% of endocarditis valve samples as being positive. C. burnetii was not detected by FISH, probably due to the low infection levels. Most cattle had chronic valvular vegetative endocarditis with lesions being characterised by a core of fibrous tissue covered by significant amounts of fibrin, sometimes with areas of liquefaction, and with a coagulum covering the surface. In a few cases, including the case with the highest infection level, lesions were characterized by extensive fibrosis and calcification. Histologically, bacteria other than C. burnetii were observed in most cases.ConclusionsThe presence of C. burnetii DNA is relatively common in cattle affected with valvular endocarditis. The role of C. burnetii remains however unknown as lesions did not differ between C. burnetii infected and non-infected cattle and because T. pyogenes–like bacteria were present in the inflamed valves; a bacterium able to induce the observed lesions. Heart valves of normal cattle should be investigated to assess if C. burnetii may be present without preexisting lesions.
Highlights
Bacterial endocarditis is a recognised disease in humans and animals
The findings indicate the presence of C. burnetii DNA in a proportion of heart valve lesions in cattle
The exact role of C. burnetii in the development and progression of lesions remains unknown as most cases were infected by huge numbers of T. pyogenes; a bacterium known to be associated with severe endocarditis in cattle
Summary
Bacterial endocarditis is a recognised disease in humans and animals. In humans, infection with Coxiella burnetii can cause endocarditis, but this has not been investigated thoroughly in animals. Despite exposure of cattle to C. burnetii, the significance of this particular bacterium for development and progression of endocarditis has not been studied in detail. The infection may become chronic and lead to development of endocarditis in those individuals with predisposing conditions, such as valvulopathy, The diagnosis of Q fever in animals is typically associated with abortion or delivery of weak or stillborn offspring. Such reproductive consequences occur sporadically in cattle, while flock outbreaks have been reported in goats and sheep [6, 7]. Based on the comparative aspects in humans, where C. burnetii is a well-known cause of endocarditis, it could be suspected that C. burnetii may be implicated in the development
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