CHAPTER VIII. 



A FEW DISEASES CAUSED BY ANIMAL PARASITES. 



THE NODULAR DISEASE OF THE INTESTINES OF SHEEP. 



§277. Characterization. The intestinal, nodular disease 

 •of sheep is characterized by the presence of nodules in the 

 upper part of the large intestine, although they are sometimes 

 found in the walls of the ileum and jejunum, varj-ing in size 

 from that of a pin head to that of a bean. They are caused by a 

 nematode and because of their tubercle-like appearance the 

 ■disease is often mistaken for tuberculosis. It is often called 

 " knotty " viscera by butchers. 



§ 278. History. This disease has been observed in the 

 eastern part of this country for a number of years. Just when 

 it was introduced does not seem to be known. In 18S8-9 Dr. 

 Cooper Curtice, then in the Bureau of Animal Industry, inves- 

 tigated this affection which up to that time was quite gener- 

 ally thought to be tuberculosis. The nodules had frequently 

 been examined for tubercle bacilli, but with negative results. 

 By means of serial sections and the microscopic examination 

 of the fresh, small nodules, Curtice discovered the embryo of a 

 nematode. The adult was found in the intestine in large 

 numbers. It was readily referred to the genus Oesophagos- 

 toma and Curtice gave to this species the name of Colum- 

 bianum because the worm was first found in the District of 

 Columbia. 



§ 279. Geographical distribution. When first investi- 

 _gated, this disease seemed to be east of the Mississippi river. 

 It was known to exist south of the Potomac river, but it had 

 not been identified in the north. It is now known to be more 

 ■or less prevalent in the middle and New England states. 



