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

Abstract

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 intoxicatio

Plants poisonous to horses in Europe

“…Horses are the animals most susceptible to the effects of black locust (Vanschandevijl et al . ). Poisoning may result from the ingestion of roots, bark, sprouts, seeds and pods (Anadón et al .…”

“…; Vanschandevijl et al . ). The following clinical signs have been reported: anorexia, lethargy, abdominal pain, diarrhoea (which may be bloody) or dark and firm faeces, laminitis, weakness to posterior paralysis, head pressing and absence of menace response and pupil reflexes (Botha and Naudé ; Uhlig et al .…”

“…Abnormalities in heart rate and/or rhythm have also been described (Vanschandevijl et al . ). Although death is not frequent (Anadón et al .…”

“…Ponies seem very susceptible, showing severe, reversible CNS signs attributable to hyperammonaemia caused by gastrointestinal disease (Vanschandevijl et al . ).…”

Intestinal hyperammonaemia in horses

“…1997). In this issue, Vanschandevijl et al. (2010) describe 2 cases of HA due to ingestion of Black Locust ( Robinia pseudoacacia ) and suggest that the neurological signs reported in horses with Black Locust intoxication could, at least partially, be caused by HA arising from toxin‐induced bacterial overgrowth leading to an increase in NH 4 + production and subsequent increased absorption facilitated by toxin‐induced irritation of the intestinal wall.…”