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Monday, November 21, 2011

Bacterial or infective endocarditis in a Pointer (endocardite infectieuse chez un Pointer)

A relatively rare diagnosis in veterinary medicine is one of infective or bacterial endocarditis. This occurs when bacteria enter the blood from either a wound or other focus of infection and attach to the inside of the heart, often on a valve. This causes lesions called "vegetations" as they appear to be plant- or moss-like growths made up of a colony of bacteria. Bacteria in the blood are more susceptible to "sticking" to a damaged or leaky valve.
My case involved a 7 year-old male, intact (not neutered) male Pointer. Now "Max" is not your typical family pet. Oh no, Max is truly his owner's sidekick. Max is a working dog, spending most of his time outdoors with his old-fashioned, old school, European, owner. They both spend time exercising outdoors, in the woods, especially during winter hunting season. The septuagenerian brought his dog in to see me when the dog starting slowing down and essentially stopped eating: two things this pet owner had never experienced with his uber-fit canine.
Examination findings included a fever, a 7% drop in weight over one to two months, lethargy, and a grade 4 heart murmur that I had not heard on previous examinations. His prostate was normal (this is important to note as a common cause for fever in an older intact male dog is prostatitis). The (acquired) heart murmur and fever were highly suspicious for endocarditis. Bloodwork on this dog showed a very high white blood cell count of about 37 thousand, and many young neutrophils, called band cells or bands, were seen on his blood smear (called a left shift). A left shift occurs when the bone marrow releases young white blood cells in an effort to stave off an infection. A cardiac ultrasound, called an echocardiogram, showed moderate mitral valve insufficiency and some "clubbing" of one of the mitral valves. These sonographic findings support the diagnosis of, but are not specific for, bacterial endocarditis.
Blood was collected in a special blood culture medium and sent to the lab for microbiology and a culture and sensitivity. This was an effort to isolate the offending bacteria in the blood, which, if positive, would allow me to choose the most appropriate antibiotic for his treatment. These results would take a little less than a week to return. Pending these results, I started the dog on a few injectable antibiotics and iv fluids. The following morning, his fever was gone, he had started eating, and his owner reported the dog pulling him on his leash, as was normal for this dog! The blood culture grew E. coli, a common bacterium, which was sensitive to all antibiotics on the antibiogram. This positive blood culture had been the real clincher in the diagnosis. It's not often we have to do blood cultures but it makes for an interesting case.
Max is now receiving medication for his heart and a two-month course of antibiotics. He continues to improve day after day and his owner (and I) couldn't be happier.
What's interesting in this case is that the owner reported that about one month prior to Max's illness, he had suffered a laceration or rash on his skin (likely from running in the bush). This just might have been the source of the dog's bacterial endocarditis.

Vegetative bacterial lesions on the inside of a cow's heart. Gross.