CHAPTER XXIV 



DISEASES DUE TO ANIMAL PARASITES 

 DISEASES DUE TO PROTOZOA 



AMEBIC DYSENTERY 



Definition. An acute or chronic colitis due to the 

 Amoeba dysenteriae. 



Etiology. The disease usually occurs in tropical 

 climates. Nothing is known of the life-history of the 

 ameba outside the body, but infection probably occurs 

 through drinking-water or raw foods. Amebae are 

 found in the stools of healthy individuals, but whether 

 there exists an immunity in some persons or whether 

 there are pathogenic and non-pathogenic varieties of 

 the parasite is not at present known. 



Morbid Anatomy. Ulcerations of the walls of the 

 large bowel are always present in this disease. Abscess 

 of the liver frequently accompanies the intestinal pro- 

 cess. The disease progresses by a gradual infiltration 

 of the connective- tissue layers of the intestines. The 

 infiltration is composed of proliferative connective- 

 tissue cells. Amebae are found in the ulcers and the 

 surrounding lymphatic spaces. 



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