Chickens are frequently infected without showing signs of the disease. These chickens may shed enormous numbers of blackhead organisms, many of which are protected by cecal worm eggs. Outbreaks in turkeys can often be traced to direct or indirect contact with ranges, houses or equipment previously used by chickens. Free-flying birds may also contribute to an infection. Among the symptoms are loss of appetite, increased thirst, droopiness, drowsiness, darkening of the facial regions and diarrhea.
Losses are usually low in chickens.
Lesions of uncomplicated blackhead are confined to the cecae and liver, thus the reason for the synonymous term, enterohepatitis. The cecae are ballooned and walls may be thickened, necrotic and ulcerated. Peritonitis may be present if ulcers have perforated the ceca walls. Livers are swollen and display circular depressed areas of necrosis about one-half inch in diameter. Smaller lesions coalesce to form larger ones.