Black locust (Robinia pseudoacacia) intoxication as a suspected cause of transient hyperammonaemia and enteral encephalopathy in a pony

Two ponies presented with mild abdominal pain and mild diarrhoea one hour after ingestion of roots of a black locust tree. On admission, symptoms had progressed to depression, weakness and the passing of dark, firm faeces. Treatment was symptomatic and supportive, aiming at the evacuation of the toxin from the gastrointestinal tract. One pony developed severe, reversible neurological signs associated with transient hyperammonaemia in the absence of liver disease. After 24 h the ammonia level returned to normal and central nervous signs disappeared. Both ponies recovered completely. This report describes the ingestion of black locust closely followed by the development of central nervous signs and hyperammonaemia. Increased ammonia absorption due to the intestinal wall inflammation caused by the toxins of the black locust tree, as well as increased ammonia production by enteric bacteria is therefore considered a plausible pathophysiological mechanism of the neurological signs displayed in black locust intoxication.