ergotism

The plant disease caused by ergot.

The effect of long-term ergot poisoning, traditionally due to the ingestion of the alkaloids produced by the fungus Claviceps purpurea which infects rye and other cereals, and more recently by the action of a number of ergoline-based drugs, consisting of convulsive and gangrenous symptoms.

The use of ergot-infested grain to poison animals.

A logical deduction.