THE INCUBATOR-BROODER METHOD OF RAISING GROUSE 495 



burned. During the rearing season, flies, which may carry ulcerative enteritis, can be dis- 

 couraged by the prompt removal of waste feed and the covering of the ground under each 

 pen with a thin coat of hydrated lime once every two weeks. 



The price of freedom from most diseases is the maintenance of clean conditions within as 

 well as about each pen. All feeding and watering equipment should, therefore, be disinfected 

 at least twice a week and any accumulation of droppings either on the wire floor or on the 

 conifers used as shelter should be promptly removed. As a precautionary measure it is wise 

 to continue limitations on visitors and to place a folded feed bag in a pan of disinfectant 

 so that all who enter the rearing field may step on it. It is, of course, hazardous to allow 

 poultry or those caring for it, access to the immediate vicinity of the rearing field. 



In spite of every precaution, the two most serious epizootic diseases known to afiFect grouse 

 in captivity, ulcerative enteritis and blackhead, occasionally may appear at this time. Until 

 Dr. P. P. Levine, working for the Investigation, demonstrated in 1933 that the former might 

 be carried by flies, even the most exacting precautions failed to check its spread. In 1932, 

 96 out of 196 birds were lost during September from such an outbreak. Each day, after this 

 disease appeared all pens were disinfected, all feed dishes boiled and all feeding done by 

 attendants wearing rubber gloves. These were dipped in disinfectant after servicing each 

 individual pen. Yet the disease spread. During a similar epizootic the following year, all 

 birds occupying supposedly uninfected pens were moved to a hastily fenced rearing field a 

 quarter of a mile away where carefully disinfected pens were placed 100 feet apart. Even 

 though a new attendant, who kept scrupulously clear of the old rearing field, was assigned 

 to care for these birds, many subsequently were infected and died of this highly contagious 

 disease. 



In 1934, however, it was demonstrated at the Research Center that by fly-proofing each pen 

 with cheesecloth or muslin at the outset of the epizootic and by carrying out all the precau- 

 tions normally associated with the control of an extraordinarily infectious organism, the dis- 

 ease usually could be confined to the unit in which it originated. To make certain of control, 

 uninfected pens may likewise be screened, although this practice was discontinued as unnec- 

 essary at the Research Center. 



The key to effective control of ulcerative enteritis* is the prompt recognition of its presence. 

 The very swiftness of the onset provides one of the best indications. Infected birds seldom 

 appear sick more than 24 hours before death occurs. The unexpected loss of several young 

 grouse from the same pen in a single night without apparent cause should always be a dan- 

 ger signal to be followed by the immediate screening of the pen against flies. At this time a 

 prompt examination of dead birds by an experienced pathologist may not always reveal 

 ulcerative enteritis, for the characteristic lesions in the small intestine often do not appear in 

 excessive numbers until the epizootic is well under way. Dead birds should never be kept 

 within the rearing field. 



The only other serious disease likely to be encountered is blackhead. Birds reared in cap- 

 tivity on the ground are most apt to acquire it, although even on wire a few are mysteriously 

 affected each year. In the latter situation, isolating the birds from the infected pen into 

 groups of two or three is usually sufficient to check it from spreading'''. Grouse thus infected 

 may appear to be sick for several days since its progress in birds of eight to twelve weeks of 

 age is not usually as rapid as is that of ulcerative enteritis. 



* See Chapter X, p. 437 for description and full control measures. 

 A See Chapter X, p. 438. 



