Parasites and Parasitic Diseases of Sheep. 43 
of the sheep are passed in the manure. The subsequent develop- 
ment of the worm up to the time it is again found in the sheep has 
not been determined. When the young worms are first found in 
the sheep they are encysted in the wall of the intestine. These cysts 
commonly reach a considerable size and contain a necrotic material, 
usually yellowish or greenish in color, cheesy in consistence or often 
hard and almost stonelike (fig. 27). After a time the larve leave 
these nodules and become adults in the lumen of the large intestine. 
Usually larvee can be found only in the smaller and more recent 
nodules. Those larvee which get to the mesenteric lymph glands, 
the omentum, and the liver probably die in these places and never 
get back to the intestine to complete their development. 
Distribution.—This parasite was originally present in this country 
only in the Southern and Eastern States, but it has been spreading 
westward, probably with 
infested sheep introduced 
into western localities for 
breeding purposes, and : 
there is reason to fear that \ ss 
it will become generally : 
distributed over the coun- Fic. 26.—Nodular worm (Proteracrum columbianum). 
try. Tithwerhdatare vether ee figure, male; lower, female. Magnified five 
common in the Middle 
West, and is a serious pest in the Northeastern States. It is still un- 
common in the Rocky Mountain States, and as yet has not been 
reported from a number of these States. 
Symptoms and lesions.—According to one investigator (Curtice) 
the symptoms of this disease may be only those of general debility— 
a pale mucous lining of the eyelids and mouth, emaciation, dry wool, 
etc. In severe cases diarrhea and emaciation may be excessive. In 
some places sheep raising has been abandoned on account of the 
damage done by this worm. It is evident that the injury due to 
numerous intestinal nodules, which prevent large areas of the intes- 
tine from functioning properly in the work of secretion and absorp- 
tion, which act as persistent irritants to the sensitive nervous system 
of the digestive tract, and which serve to supply poisonous material 
from worms, bacteria, and dead tissue to the adjacent absorbing 
tissues of the intestines, can not fail to have a bad effect on the host 
animal. The resultant loss can not be accurately stated, but it occurs 
in terms of meat, wool, decreased growth, and poorer quality of 
animals and from the fact that nodular intestines, or so-called 
“knotty guts,” are unfit for sausage casings. 
The post-mortem lesions are easily seen, the principal ones being 
the nodules, which may be larger than a good-sized pea, on the walls 
of the large and small intestines, or in the mesenteric lymph glands, 
