Toxemia is a condition in which toxins — produced by bacteria, released from dying tissue, or generated by abnormal metabolic processes — circulate in the bloodstream at levels sufficient to cause systemic pathology. In horses, toxemia most commonly arises as a complication of severe gastrointestinal disease, infected wounds, or conditions involving extensive tissue necrosis. The distinction from bacteremia (bacteria in the blood) and septicemia (bacteria actively multiplying in the blood) is sometimes collapsed in clinical usage, though technically toxemia refers specifically to the presence of toxins rather than organisms.
Gram-negative bacterial endotoxemia — the release of lipopolysaccharide (LPS) from the cell walls of intestinal bacteria — is the most clinically significant form in equine medicine. It occurs when the mucosal barrier of the gut is compromised, as happens in severe strangulating intestinal lesions, strangulating intestinal lesions, or grain overload. Endotoxin triggers a cascade of inflammatory mediators that can cause laminitis, cardiovascular collapse, and multi-organ failure.
Clinical signs of toxemia include an elevated heart rate, injected or congested mucous membranes, a toxic line at the gum margin, depressed mentation, and reduced gut sounds. The lamellar vulnerability to endotoxin laminae are particularly vulnerable to the vascular effects of endotoxin, which is why early aggressive anti-inflammatory treatment and digital cryotherapy are standard in cases with suspected endotoxemia.
Treatment is directed at removing or controlling the source of toxin, supporting circulation with intravenous fluids, and blocking the inflammatory cascade with NSAIDs such as flunixin meglumine. Prognosis depends on the underlying cause and how rapidly intervention is initiated.