LECTURE XLVIII. 

 NODULE DISEASE OF SHEEP. 



General history. — The history of outbreaks is often as fol- 

 lows : Sheep have access during the summer and fall to pond or 

 well w^ater that receives drainage from a sheep yard or pasture. 

 Perhaps the grass was short and the flock was compelled to graze 

 very close. 



During the winter the flock becomes unthrifty; some indi- 

 viduals grow gradually thinner and weaker until a number die 

 during the late winter and early spring. As soon as the grass 

 comes and the sheep are turned out they begin to do better and 

 the disease seems to disappear. A dead sheep is opened and the 

 intestines show a large number of nodules, about the size of gar- 

 den peas. 



Cause. — The disease is caused by a minute round worm 

 {Oesophagostoma columhianuiii). The adult worms are about 

 half an inch in length and may be found in the intestines. The 

 immature forms vary from i-ioo to i-6 of an inch in length, de- 

 pending on the age and stage of development, and are found in- 

 side of the little nodules which constitute the most prominent feat- 

 ure of the disease seen on examination post mortem. 



The eggs are laid by the adult female in the intestine. The 

 eggs soon hatch, and the embryo worms pass through the internal 

 lining of the intestine, and become mibedded, giving rise as for- 

 eign bodies to the little tumors or nodules which nature throws 

 around them, evidently in an attempt to fence them off. They 

 cause some irritation as foreign bodies, and this irritation will ac- 

 count for the little tumors which are found on the side of the in- 

 testine. 



Some of the adult worms pass out witli the manure, and thus 

 infect the ])astures and feed yards, ponds or sluggish streams 

 which receive tlnir drainage. 



Injury done. — The extent of injury to the individual sheep 

 depends mainly upon the number of worms present, and the con- 



