Clostridium botulinum type-C intoxication associated with consumption of processed alfalfa hay cubes in horses

Abstract

Sept 26, 1989, a 9-year-old Thoroughbred mare suddenly became weak and recumbent and died within 13 hours of the onset of signs.About 4 weeks later, a 4-year-old pony gelding died at a different location after manifesting similar signs of disease.Between Oct 31,1989 and Dec 8, 1989, 36 other horses were affected with similar signs of disease at 17 premises in 4 counties in southern California (Los Angeles, San Bernardino, Orange, and Ventura).These equids manifested signs of paresis.Initially, an asymmetric decrease in palpebral tone was clinically detectable up to 24 hours before onset of overt clinical signs of disease.As the condition progressed, horses began to stand with slight carpal flexion , resulting in periodic "unlocking" of the carpi.At this stage, muscular fasciculations in the triceps area were often palpable, but not visible.Initial carpal flexion and fasciculations were intermittent and/or of short duration.As the syndrome progressed, usually within 24 hours, severe muscular tremors of the fore -and, to a lesser degree, hind limbs became obvious.Affected horses would often strike the ground and appear restless before lying down.During rest, clinical signs of disease subsided, and horses, misleadingly, appeared to be recovering.In many of the horses, fecal balls became notably smaller and firm.In the most advanced stages, hypoglossal tone was decreased slightly, but difficulty in swallowing was not observed.Slight mydriasis and slow pupillary light reflexes were observed in some horses.Over the ensuing 36 to 48 hours , horses became sternally recumbent and lay with the neck extended and muzzle resting on the ground.Terminally, horses became laterally recumbent and paddled their limbs rhythmically without any success or ability in rising.