THE MORE COMMON AILMENTS OF SHEEP 4OI 



severe cases, diarrhoea. Nevertheless, sheep may in some 

 instances be infected in a considerable degree and still re- 

 tain a fair degree of thrift, but usually the indications of 

 debility are present, and increasingly so as time advances. 

 Unlike the stomach worm afifection, it does more harm to 

 mature sheep than to lambs. This may be partly the out- 

 come of the gradual rate of the infection and the slow 

 rate of development within the tumors. The parasites 

 affect the digestion adversely. 



The life history of the parasite is only known during 

 the period of its development in the intestinal canal. 

 When the eggs escape, as doubtless they do, in the ex- 

 crement, they in some way reach the sheep, probably 

 in the food or water. In the intestines they become sur- 

 rounded by a cyst and later by the products of the inflam- 

 mation which they produce in the surrounding tissues. 

 When about 1-16 of an inch long they break from the 

 tumors and begin life in the intestine, where they grow 

 to maturity. 



The preventive measures are about the same as for 

 stomach worms (see page 393). Frequent changing of 

 the pastures, the avoidance of all grazing grounds and the 

 breaking up of the same are greatly important. Nodular 

 disease is most in evidence in the early spring season. 

 There is no sure remedy for the disease. 



While preventive measures should receive every at- 

 tention when combating internal parasites, and while 

 treatment should be most faithfully and persistently ad- 

 ministered where it is probable that it will do some good, 

 it is true, nevertheless, that in many instances it would be 

 better in every way to sell the entire flock and begin 

 again with other sheep after an interval of several 

 months. This will apply in many instances to the inva- 

 sion of flocks by stomach worms, tapeworms, lung worms 

 and the worms that cause nodular disease. One season 

 should suffice to leave the farm free from sheep, that the 

 germs may perish. When restocking the farm every pre 



