If you take another look they are now saying the poisoning came from wheat glutton tainted with a plastic additive called melamine in concentrations as high as 6.6%. If it was the rodenticide as first reported, not sure it would still be accurate to compare to the commonly found rodenticides used by the public here. With aminopterin not being registered to be used in the US I can't say if it is an acute acting toxin or not.
Lar