10 



A suggestive sign of blackhead usually occurs after a few 

 days in the appearance of opaque yellow or sulphur colored 

 material in the droppings. No importance is to be attached 

 to loose foamy or creamy droppings, varying in color from 

 amber to greenish. These are often mistaken for evidence of 

 diarrhoea, but represent material which is discharged normally 

 at intervals, possibly once or twice a day, from the caeca, and 

 appear quite different from more frequently passed, formed 

 droppings from the intestine proper. 



Incubation Period of the Disease. — ■ From ten days to two 

 weeks elapse from the actual invasion of the tissues by the 

 parasite until the appearance of symptoms. Nothing is at 

 present knowai of how long the parasite may live in the caeca 

 without penetrating the tissues. 



Course of the Disease. — Blackhead kills such a large pro- 

 portion of turkeys which it attacks that any instance of recov- 

 ery is questioned by some authorities. Such cases, however, 

 do occur which show typical symptoms and later apparently 

 return to normal health without any special treatment. On 

 killing such birds one finds scars where healing has taken 

 place in the caecum and liver. It is also quite probable that 

 mild unrecognized cases occur in birds that are approaching 

 maturity. 



Age of Birds attacked. — The opinion is frequently expressed 

 that blackhead affects only young turkeys, and that after they 

 have reached a certain age, popularly known as "throwing the 

 red," they are quite safe. This is not true. While resistance 

 to the infection evidently increases with age so that fewer birds 

 are affected, and often in a less acute form, the disease may 

 appear at any time during the growth of the turkey. We have 

 noted blackliead in December, during the last three seasons, 

 in turkeys which weighed from 5 to 12 pounds. 



Death appears to be due to the involvement of a vital organ, 

 usually the liver, to such an extent as to prevent it function- 

 ing. Apparently no definite poison is produced in this disease. 

 The temperature of a considerable number of infected birds 

 showed no fever or variation from the normal. 



