_Cause._ A fungoid growth in the windpipe and bronchial tubes, sometimes extending to the lungs and liver. Fig. 8 shows the spores and filaments of the species of aspergillosis most commonly responsible for this disease. Infection may be due to musty grain or dirty straw. [Illustration: FIG. 8.—ASPERGILLOSIS On left—Windpipe cut open. On right—A fungus that causes aspergillosis] _Treatment._ No medicines are of any avail. Protection lies in not using musty grain or moldy litter. Burn dead birds. BLACKHEAD OF TURKEYS _A very serious disease, making the successful rearing of turkeys difficult and in some cases impossible_. _Symptoms._ Young turkeys, or poults, are most commonly attacked; there is loss of weight and loss of appetite; the bird appears listless and stands by itself with drooping wings and tail. Diarrhea is generally one of the symptoms. The comb often turns a dark purple—a symptom that has given rise to the name blackhead. Death generally follows an attack fairly rapidly, but in some cases the disease may take a chronic form, while it is believed that recovery is occasionally effected. _Post-mortem symptoms._ The cæca (see Fig. 32) are enlarged, are diseased in parts, and are more or less plugged with cheesy matter and pus. The liver is diseased, being sometimes very much enlarged and covered with yellowish necrotic areas, generally depressed in the centre (see Fig. 24_d_). In cases of an acute attack, especially in young birds, one of the cæca only may be affected and the liver may not be invaded. The extent of the necrotic areas and the degree of the enlargement of the infected organs may vary greatly in different cases. _Cause._ The cause of blackhead has been shown by Drs. Cole and Hadley to be a coccidium. A full account of their work is published in Bulletin 141 of the Rhode Island Experiment Station. Coccidia enter the digestive tract of the healthy turkey by means of food or water infected by the excrement of a sick bird. The organisms pass along the alimentary canal until they reach the cæca, the lining of which they attack, giving rise to the conditions mentioned under post-mortem symptoms. How the infection spreads from the cæca to the liver is not clear. It has been conclusively proved that fowls, as well as pigeons, sparrows, etc., act as hosts for these parasites. Although adult fowls have a great degree of resistance themselves, they are a means of carrying infection to turkeys. Eggs may be one of the means of spreading the disease, as they may become contaminated in the oviduct or the cloaca of birds affected with blackhead. _Treatment._ No remedy or satisfactory method of prevention has been discovered. The difficulty of effecting a cure is obvious when the nature of the disease is considered. Drs. Cole and Hadley summarize measures of prevention as follows: