AN ATTEMPT TO REPRODUCE MAL SECO IN HORSES BY FEEDING THEM FESTUCA-ARGENTINA

'Mal seco' is an almost invariably fatal disease of horses in Argentin a and Chile, which resembles grass sickness, a dysautonomia of horses in Europe, The aetiology of mal seco remains unknown, An attempt to re produce the disease was made by feeding horses,vith Festuca argentina, a plant considered to be toxic to animals and which was consistently found in the diet of nine horses suffering from mal seco, Three horses were fed with F argentina ad libitum for 28 days, The plant was infec ted with an endophytic fungus, whose morphological characteristics wer e in agreement with descriptions of Acremonium chlamydosporioides. No clinical abnormalities were observed in two of the horses, but one die d on the fifth day of the trial after becoming incoordinated, unsteady and ataxic in the fore- and hindlimbs, No gross changes were observed post mortem in any of the horses, with the exception of a small numbe r of Fasciola hepatica in the liver of the horse which died, and a mod erate number of Gasterophilus species in the stomach of all three hors es, No histopathological changes were observed in any of the organs ex amined, including several autonomic ganglia, brain including most brai n stem nuclei, spinal cord, liver, kidney, stomach and small and large intestine, The results of this study suggest that F argentina is eith er not implicated in the aetiology of mal seco or produces its effects only when they are triggered by other unknown factors.