Dark warts and sores on chickens' faces, wattles, and combs may indicate fowl pox. Fowl pox is a slow-spreading viral disease characterized in the cutaneous form by the development of discrete lesions on the nonfeathered parts of the body and in the diphtheritic form by the development of lesions in the upper respiratory tract, mouth, and esophagus.
There is no treatment for chickens infected with fowl pox. Mortality in flocks exhibiting the mild cutaneous form of the disease is usually low. Birds can be vaccinated for fowl pox, and vaccination is recommended in areas where there are large numbers of mosquitoes. Chickens must be vaccinated before they are four months old or before they start to lay.
See the article on Fowl Pox for more information about this disease.