A COMPARATIVE STUDY OF DARLING PEA (SWAINSONA SPP.) POISONING IN AUSTRALIA WITH LOCOWEED (ASTRAGALUS AND OXYTROPIS SPP.) POISONING IN NORTH AMERICA

I. ABSTRACT Swainsona spp. poisoning is a chronic progressive neurologic disorder seen in extensively grazed cattle, sheep, and horses in Australia. There are no macroscopic lesions but microscopically the entity is characterized by widespread neurovisceral ‘watery’ cytoplasmic vacuolation, and in more protracted cases also neuroaxonal dystrophy and pigment deposition. The stored substance is thought to be contained in lysosomes, but its nature is not known. The lesions in this entity are closely similar to those caused by locoweeds in the U.S.A., except that congenitally deformed lambs and calves have not been seen in Australia. The effects of experimental A. lentiginosus intoxication in the pregnant ewe are summarized.