Valvular Endocarditis due to Enterococcus casseliflavus in a 4-Month-Old Female Foal

Endocarditis is uncommon in adult horses and rarer still in very young horses. The present report describes a case of endocarditis due to Enterococcus casseliflavus in a 4-month-old foal. Chronic-active, fibrotic, and fibrinous endocarditis of the mitral valve was detected at necropsy. A pure growth of Enterococcus spp. was isolated from the lesion, and the isolate initially identified as Enterococcus faecium using standard biochemical methods. However, after subsequent sequencing of the 16S ribosomal RNA gene, the isolate was classified as E. casseliflavus. Septicemia was suggested by the presence of additional lesions including renal and cardiac infarcts and neutrophilic meningitis. This report constitutes the first description of endocarditis caused by an enterococcal species in a horse and suggests that genetic studies may be necessary for definitive identification at the species level.