Clinical findings, treatment and resolution of Simplex® toxicity in three horses

Abstract

Three horses were presented two hours after accidental ingestion of plants contaminated with Simplex®. Simplex®, containing aminopyralid (30g/l) and fluroxypyr (100g/l), is an herbicide used against common ragwort. The toxic effect of both ingredients is probably induced by free acid, but an effect of dissociated fluoride ions of fluroxypyr is conceivable, too. At presentation, all horses showed a moderate impairment of their general condition, appeared sedated with intestinal hypomotility and showed symptoms of marked conjunctival irritation. A mild ataxia and cardiac arrhythmia were observed in one horse. Within one day, all horses revealed a slight decrease in plasma calcium concentration, two horses developed a mild oral ulceration and one horse a mild skin irritation in the area of the mouth. The initial treatment consisted of minimising absorption from the gastrointestinal tract and increasing urinary excretion. To counteract any damage induced by dissociated fluoride ions, calcium gluconate was administered as a continuous rate infusion. Initially, an irrigation of the stomach with 1% calcium gluconate was performed, and the horses received a resuscitative intravenous fluid therapy with Ringer's solution and 23% calcium gluconate. Subsequently, a lavage of the eyes was performed. Over 36 hours Ringer s solution was administered, and sucralfate (40mg/kg bwt/tid p.o.) was given over three days. On day five and day six two horses and one horse, respectively were discharged without abnormal clinical or laboratory findings. Follow-up enquiries after 3 months with the owners indicated that the horses were healthy, sound and had returned to their previous level of work. To our knowledge, these are the first documented clinical cases of Simplex® toxicity in horses.