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CIRCULAR 14 8, U. S. DEPARTMENT OF AGRICULTURE 



Symptoms and lesions. — The blood strongyles injure the wall of 

 the gut to which they are attached. These worms suck a tuft of 

 the inner wall of the gut into their mouth cups (fig. 15) and abstract 

 blood from this delicate lining. As the worms move from one place 

 to another within the gut they expose its injured wall to the entrance 

 of disease-producing bacteria. Bloodworms abstract blood from the 

 finer blood vessels in the lining of the gut, and when many worms 

 are present in a horse at the same time the loss of blood may be 

 considerable and may lead to anemia with the usual consequences 

 of weakness and of watery swellings (edema) in various parts of 

 the body. These worms also produce injuries of various sorts in 

 the parts of the body to which they wander, such as the liver. 



pancreas, and other 

 organs. 



One species, the 

 single-toothed 

 strongyle, is espe- 

 cially injurious be- 

 cause as an imma- 

 ture form it settles 

 in certain arteries, 

 especially in the an- 

 t e r i o r mesenteric 

 artery which sup- 

 plies blood to the 

 large gut. As a re- 

 sult of the presence 

 of the worms in this 

 blood vessel, the 

 wall of the artery, 

 where the worms 

 accumulate, becomes 

 thickened and 

 stretches consider- 

 ably to form what 

 is known as an 

 aneurism. An 

 aneurism is a spindle-shaped, cylindrical, or globular dilation of a 

 blood vessel and often contains a heavy deposit of fibrin inside. In 

 the horse it may attain the size of a child's head. (Fig. 16.) 



An aneurism interferes to a considerable extent with the circula- 

 tion of blood through the affected artery, because the heavy deposits 

 of fibrin inside may almost obliterate the lumen of the blood vessel. 

 This condition results in a diminished blood supply to the large 

 intestine; when the intestine becomes anemic as a result of this it 

 becomes predisposed to colic, twist, and intussusception, the last 

 being a condition in which part of the gut slips into an adjoining 

 part. When a piece of fibrin deposit in the aneurism breaks loose, 

 it may be carried in the circulation to a terminal portion of an artery 

 and may lodge there as a plug. As a consequence, the circulation 

 to a part of the large gut may be completely shut off. Such a con- 

 dition interferes with the functions of the large gut, produces an 

 anemic condition with the consequences noted above, and in extreme 



Figure 15. — Section through the wall of the large gut, 

 showing the head end of an attached blood strongyle. 

 8. equinus, with a tuft of the inner lining of gut drawn 

 into the mouth cup of the worm. Greatly enlarged. 

 From Wetzel, 1928 



