This paper represents a case report of aortic bacterial endocarditis with discussion of infective endocarditis in horses. Fyre is a 6 year old Arabian Gelding who presented to the Cornell University Equine and Farm Animal Hospital on July 17, 2008 for fever of unknown origin and ataxia. On presentation, Fyre was bright, alert and responsive. His problem list included pyrexia, tachycardia, endotoxemia, petechiation, a grade 3/6 diastolic murmur, and ataxia. Initial diagnostics revealed hyperproteinemia, neutrophilia, thrombocytopenia, hypoalbuminemia, elevated D-dimer and hyperfibrinogenemia. Fyre was treated for suspected Potomac Horse Fever and Equine Protozoal Myeloencephalitis. 5 days after presentation, Fyre developed a sudden grade 6/6 left sided diastolic murmur. Diagnosis of aortic infective endocarditis was made based on echocardiography. Blood culture revealed growth of Actinobacillus equuli ssp. equuli. Fyre was treated with intravenous antimicrobial and anti-inflammatory medications. Recheck appointments revealed healing of Fyre's vegetative lesions and the inevitable progression of his aortic insufficiency, causing mitral regurgitation and left sided heart enlargement.