Phalaris toxicoses is caused by ingestion of Phalaris
genus, most frequently bulbous canarygrass (Phalaris aquatica
, reed canarygrass (P. arundinacea)
, paradoxa grass (P. paradoxa
), and sunolgrass (P. coerulescens
). It generally presents in one of two forms---as 'staggers' or as a 'sudden death' syndrome in horses.
are drought-tolerant grasses that are found most commonly growing in pastures during the spring and autumn months. The plants contain a number of different secondary metabolites implicated to cause phalaris toxicoses, including indole alkaloids (N-methyltyramine (NMT), N-dimethyltryptamine (DMT), 5-methoxy-N,N-dimethyltryptamine (5-MeO-DMT)) and tryptamine alkaloids (Gramine) which can affect both cardiac and neurological function in horses.
Although outbreaks of poisonings have occurred worldwide, Australia has a higher prevalence of phalaris toxicity. Horses are at a greater risk of toxicoses when Phalaris
plants are young and undergoing rapid growth. Soil cobalt levels have been associated with outbreaks.