Toxicoinfectious botulism in foals and adult horses.

Toxicoinfectious botulism was proved to be the cause of a neuromuscular paralytic syndrome in foals and adult horses. In eight successive cases, Clostridium botulinum type B was isolated at necropsy. Foals were either found dead without premonitory signs of illness or, most often, they had signs of progressive and symmetric motor paralysis. Stilted gait, muscular tremors, and the inability to stand longer than 4 to 5 minutes were the salient clinical signs. Other clinical manifestations included dysphagia, constipation, mydriasis, and frequent urination. As the disease progressed, dyspnea with extension of the head and neck, tachycardia, and respiratory arrest occurred. Death occurred most often 24 to 72 hours after the onset of clinical signs. The most consistent postmortem findings were congestion and edema of the lungs and excessive pericardial fluid, which contained free-floating strands of fibrin. Gastric ulcers, foci of necrosis in the liver, abscesses in the navel and lungs, and wounds of the skin and muscle were predisposing sites for development of toxicoinfectious botulism.