T^NIASIS 183 



Diagnosis. — The presence of tapeworms maj^ in most cases be recog- 

 nized by the passing of segments, or fragments of the chain, with the 

 feces; occasionally these may also be expelled with vomited matter. 

 Often the fragments may be arrested near or partly protrude from the 

 anus, causing a pruritus in this region which the animal endeavors to 

 reheve by rubbing the parts upon the ground. 



Diagnosis may be assisted in doubtful cases bj' the administration 

 of a laxative, in the operation of which detached portions of the chain 

 will be expelled if present. Echinococcus, however, on account of its 

 small size, is likely to escape observation in the ordinary means of 

 examining fecal matter. 



Dog Tapeworms in Relation to Human Infection. — Two species of 

 tapeworms harbored by dogs — Echinoccocus granulosus and Dipylidium 

 caninum — are especially of medical interest in that they may also 

 infect man. The first mentioned produces in its larval development a 

 condition known as hydatid disease, or echinococcosis, in man as well 

 as in numerous lower animals. 



The larval or, as it is called, the hydatid form of this tapeworm occurs 

 usually in the liver, lungs and kidneys of these animals, and may pro- 

 duce from the original cyst numerous daughter cysts, the growth going 

 on indefinitely and evolving bladders as large or even much larger than 

 an orange (Fig. 117). Due to its pressure, necrotic degeneration of 

 tissue, and also to secondary infection by bacteria, this growth gives 

 rise to serious distm^bances in the organ in which it is lodged. In man 

 the condition is often fatal, less so in the lower animals, probably owing 

 to the fact that their term of life is shorter, or they are likely to be 

 slaughtered before sufiicient time has elapsed for the full development 

 of the slow-growing hydatid. 



A more detailed reference to the echinococcus cyst is given further 

 on in the special consideration of the cestode larvae (p. 210). 



The common tapeworm of the dog, Dipylidium caninum, may find 

 adult hostage in the human intestine. According to Hall (Bull. 260, 

 U. S. Dept. of Agriculture, 1915), seventy-six cases of this tapeworm 

 in man, mostly children, have been reported, a number of these from 

 the United States. It has been found in an adult thirty-eight years old, 

 and it is stated that as many as two hundred and fifty-eight of these 

 worms have been found in a single person. 



Considering the privileges which are allowed dogs, it is quite apparent 

 that a flea or louse containing the Cryptocystis might pass from the dog 

 to the human mouth by the dog licking the face, or through the inter- 

 mediation of food, especially sticky candy to which the insect readily 

 adheres. Children give little attention to incidental contamination 

 of their food, which is frequently partaken of in intimate proximity to 

 their canine companions, the dog often sharing in the feast — perhaps 



