The first clinical signs include uneasiness, restlessness, anxiety, muscle twitching and stiffness of the neck. The animal is in severe pain and the pupils are dilated. These signs can resemble tetanus, with an increase in spinal reflexes leading to tonic convulsions characterized by sudden contractions of all striated muscles followed by complete relaxation. The animal becomes hypersensitive to external stimuli and the slightest noise or touch can trigger convulsions. Birds affected by strychnine poisoning exhibit feathers fluffed or held tightly against the body, ataxia, wing droop, salivation, tremors, muscle tenseness, and convulsions.
Death occurs as a result of respiratory arrest.
No postmortem lesions are observed with the exception of small pinpoint hemorrhages in the lungs resulting from death due to asphyxia. Rigor mortis occurs shortly after death and persists for days. Strychnine poisoning in birds is generally accompanied by the presence of cracked corn in the digestive tract. A tentative diagnosis can be made based on clinical signs and history. However, a positive diagnosis can only be made by identifying strychnine in the stomach contents and viscera.