Palicourea marcgravii is a perennial shrub that has been associated with numerous deaths in cattle and horses that live in Brazil.
Toxic components P. marcgravii contains monofluoroacetate (MFA), which is a highly toxic chemical compound and indole alkaloid. N-methyltyramine and 2-methyltetrahydro-beta-carboline (2-Me THBC) may also influence the monoamine oxidase type A (MAO-A): N-methyltyramine acts as a competitive substrate, and 2-Me THBC is one of the most effective MAO-A-inhibitors.
P. marcgravii is reported to be highly palatable to livestock, and is responsible for over 500,000 annual deaths of livestock in Brazil.
In most cases clinical signs presented in the animal are hyperacute and appear when the horse is exercising. Affected animals rarely recover, and many instances occur where the horse is found dead in the pasture.