If there are chickens nearby, there is a good chance that it is blackhead (histomoniasis). You can contact a local vet who deals with either birds or farm animals for medication. Diagnosis is typically made on necropsy. If you live in the states, most states have low cost to free necropsy testing on poultry. The lesions are distinctive (liver) & cecum. You need to control cecal worms in the flock with regular deworming- this will help control the carrier worm. The protozoal organism needs to be treated separately. Many turkeys get a yellowish diarrhea, but not all. They don't usually get a black head. You cannot cure them long term if they stay on your property, you can treat them, and try to prevent reinfection.... Keeping the soil dry and moving waterers and feeders can help prevent buildup of the organism in the soil.
