Fever associated with cardiac disease

Cardiac infection should be considered as a possibility when presented with a horse with fever of unknown origin, particularly when tachycardia is also present. Early clinical signs of cardiac infection are fairly nonspecific but jugular distension, ventral oedema and abnormal sounds on auscultation should raise suspicion.

Infective endocarditis

Infective endocarditis (IE) is uncommon but unfortunately often fatal in horses. No single organism has emerged as the most common cause, both bacterial and fungal species have the potential to cause IE. Pasteurella and Actinobacillus species represent around 20% of cases and Pseudomonas spp. were isolated from around 10%. In horses the structures of the left side of the heart are most likely to be affected. Reports of a link between dental problems and equine IE are rare [1]. Septic jugular thrombophlebitis is considered a risk factor for tricuspid IE in horse.
Equine IE is usually vegetative and these tend to form at the line of valve closure and on the forward side of the valve but may occur on an endocardial surface. More than one site can be involved and IE can extend to involve adjacent structures such as the chordae tendineae [2–4] and papillary muscles [5] or form myocardial abscesses. The haemodynamic consequences of IE involve an inter-play of the effects of regurgitation and the systemic inflammatory response syndrome (SIRS). Embolic pneumonia occurs secondary to tricuspid IE [6,7] and renal infarcts are common [4,8–10]. The kidney can be further compromised by immunological processes, pre-renal azotaemia and disseminated intravascular coagulation [6,7,11].  […]