154 ANIMAL PARASITES IN THE STOMACH 



(d) Sunondsia Paradoxa: The female, 45 mm. long, is 

 found in cysts which it forms in the wall of the stomach. 

 The male occurs free in: the stomach contents. 



ANIMAL PARASITES IN THE INTESTINES. 



Animal parasites in the intestines may injure their hosts 

 in several different ways. They may produce lesions in 

 the mucous membrane to which they attach themselves, 

 especially worms provided with hooks with which they 

 may perforate the deeper layers or the entire wall of the 

 intestine. Perforative peritonitis may thus result. Where 

 large numbers of parasites are accumulated in balls or 

 bundles they may block the lumen of the bowel. Quite 

 commonly a parasite strays into a duct such as the hepatic 

 duct or may even enter the stomach, esophagus or pharynx. 

 Parasites abstract from the host nutritive material, which 

 leads to an impoverishment of the blood, anemia and emaci- 

 ation. Probably the greatest injury to the host is wrought 

 through toxic substances eliminated by the parasite. Toxins 

 have been isolated from several worm parasites. When 

 introduced into the body they produce destruction of the 

 red blood corpuscles, loss of hemoglobin, anemia, poikilo- 

 cytosis and eosinophils. 



In some instances a secondary infection with bacteria or 

 an intoxication with the toxins of the parasites may occur. 

 Therefore helminthiasis may have associated with it pro- 

 nounced nervous symptoms such as hyperesthesia, spasms, 

 or on the other hand, paralysis. 



As a general proposition intestinal parasitism becomes 

 serious only when the host has become run down through 

 neglect of proper care and feeding. In well-fed, well-cared- 

 for animals parasites only do harm in case the number is 

 very great or from the fact that the parasite is armed with 

 hooks which may lesion the mucous membrane. Further- 

 more certain individuals seem to suffer more from the 

 parasites they contain than do others. 



Tapeworms (Cestodes). — Life Cycle. — In its development 

 the tapeworm passes through two stages, viz.: The cyst or 



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