DISEASE IN HAND-REARED GROUSE 441 



When the disease occurs in young pouhry, during the brooding period, it has an acute 

 course for death commonly occurs within a few days after exposure. This rapidly fatal form 

 of the malady is extremely rare in grouse. Most cases which have been observed at the Center 

 have been chronic and confined to adult birds. Aspergillosis is a decidedly infrequent finding 

 in grouse autopsies. 



Dissemination. Dark and damp conditions either in the bird's quarters or in places of 

 grain storage are conducive to the development and maintenance of the mold. 



Control. Procedures which foster dry, clean, uncrowded housing of birds and feed should 

 be employed. 



Air Sac Mites i Cytoleichus nudus) 



Cause. The air sac mites are very small spider-like animals, found in the air sacs and less 

 often in the bronchioles, lungs, trachea and even in the hollow bones of grouse and other 

 game birds, chickens and |)igeons. The parasites appear as tiny yellowish-white spots. The 

 males measure 450 x 300 microns and the females 300-600 x 400 microns. 



Nature of the Disease. Light infections of these mites produced no gross pathologic 

 changes. If the birds had just been killed or had just died, the tiny mites could be detected by 

 their slow movement over the air sac membranes. In heavier infections the membranes became 

 much thicker than normal and leiided to become nicire opaque. In a few severe cases, pneumonic 

 areas in the lungs with catarrhal exudate in the bidtichi and lower trachea were found. Large 

 numbers of eggs and adult mites were seen in wcl prc-paraliotis of mucus takcti from these 

 places. 



Very few hand-reared grouse succumbed In tliis infection. 



Dissemination. Little is known about its life c\(le or natural method of transmission from 

 one host to the next. The females lay eggs which contain larval mites ready to hatch. 



In the cases encoutitt'rcd in artificiallv reared grouse, infection was believed to have been 

 acquired from chickens which, in the early days of the Investigation, were used for hatching 

 grouse eggs. 



Control. Discontinuance of the use of chickens as foster mothers and prompt isolation of 

 all grouse that appeared dumpy served to eliminate this infection. 



Slipped Tendon. Hock Disease or Perosis 



Cause. Work by Wilgus and co-workers™' in 19.S7 and confirmed since then by many 

 others, indicates that the basic cause for this nutritional disease is a lack of manganese in the 

 ration. 



Nature of the Disease. This disease, fairly common in domestic poultry, is characterized 

 by the shifting either to one side or the other of the large Achilles tendon as it passes over the 

 hock joint. There resuhs a curving of the shanks and a twisting of the leg out of the normal 

 position. The birds not only become lame but in many instances are obliged to hobble along 

 with the hock dragging along the ground. Only a small number of grouse chicks succumbed 

 to this condition although it always seemed that the largest and fastest growing chicks were 

 most likely to come down with perosis. The disease has not been observed among adults. 



Control. Prevention of this condition is effective when sufficient manganese is present in 

 the ration. Domestic poultry require 50 parts of manganese per million. 



