Autumn poisoning hazards

Abstract

The main poisoning hazard of autumn is the abundance of fruits and seeds following summer growth, but if the summer has seen extreme weather conditions, then pasture may be poor and horses may eat plants they would normally avoid. Usually the most significant hazard for horses in the autumn is atypical myopathy from repeated ingestion of sycamore seeds. Dried or wilted leaves of a related species, red maple, can cause haemolysis and methaemoglobinaemia in equines. Other potential risks in the autumn include yew; autumn crocus; oak (acorns); horse chestnut (conkers); plants containing cyanogenic glycosides, such as Prunus species; and ragwort. The fruit bodies of fungi (that is, mushrooms) are also abundant in warm, wet weather and although rarely reported (and possibly underreported), mushroom poisoning is a potential risk in horses. Depending on the type of mushroom there is risk of gastrointestinal, neurological, renal and liver effects. Treatment of plant and mushroom poisoning in horses will depend on the clinical signs and the plant or mushroom involved, but should include identification and removal of the plant or mushroom, and symptomatic care.