The Blackhead organism can penetrate and live inside the cecal worm egg. Birds picking up the infected egg also infect themselves with Blackhead. As with many parasite eggs, the cecal worm egg is highly resistant to heat, cold, and most disinfectants. Therefore, a contaminated premise remains contaminated for a long time. The signs associated with this illness are not specific.
Affected birds develop droppings which often have a yellow color.
This, however, is not specific for Blackhead since it may be seen with a wide variety of diseases in birds. The disease develops slowly, with birds often losing much of their breast muscle because they are too sick to eat. The organism causes much damage to the bird's lower intestine and the liver. Sometimes the disease can be diagnosed during processing or slaughter by a trained individual, but frequently, a necropsy by a veterinarian trained in bird diseases is needed. Getting the correct diagnosis is extremely important because several diseases can mimic Blackhead and treatments and prevention of each disease are different.