THE MORE COMMON AILMENTS OF SHEEP 399 



The symptoms in the early stages of the disease may 

 be mistaken for those caused by some other ailments. 

 Sheep that are seriously affected with either disease have 

 pale mucous membranes, a coat harsh and dry, more or 

 less difficulty in breathing, and in many instances a deep 

 cough. Both ailments are of rather slow development, 

 especially in the case of the hair lung worm; hence the 

 losses that occur are in old rather than in young sheep. 

 Such ailments as bronchitis and pneumonia are much 

 more rapid in their action. The losses occur to a greater 

 extent from lack of thrift than from deaths in the flock. 



The life history of the hair and thread lung worms 

 respectively is not far different. The young of both es- 

 cape from the lungs of the sheep oftentimes while in the 

 act of coughing. They are scattered over the yards and 

 pastures where sheep take their food and drink, and prob- 

 ably through the medium of these they reach the lungs of 

 the sheep. When the former reaches the extreme end of 

 the bronchial tube they become encysted. In the cyst 

 they grow to adult size. Escaping from the cyst, they 

 make their way into the small air tubes, mate and repro- 

 duce. The eggs are laid in the surrounding cavities. The 

 young worms hatched from these make their way into 

 the neighboring air chambers, and some of them are 

 caught up at a later period. These may aid in the spread- 

 ing of the disease. The thread lung worm deposits eggs 

 in the surrounding mucus within the bronchial tubes. 

 Each egg contains within it a young worm. When these 

 are hatched many of them are expelled through coughing, 

 and these in turn may aid in spreading the disease. The 

 symptoms are more pronounced than in the case of the 

 hair worms. The young parasites have great vitality. 

 They can live for months in stagnant water. 



The preventive measures that may be adopted may 

 not always be eiiFective in all instances in staying the 

 progress of the disease. The expulsion of the parasites 

 through coughing makes it difficult to keep hitherto un- 



