182 PARASITES OF THE DOMESTIC ANIMALS 



their accumulation may bring about obstruction with attendant dis- 

 placement and degenerative changes in the intestinal walls; and, again, 

 there may be a serious and even fatal result from their unusual location. 

 Such consequences of tseniasis are, however, exceptional in dogs. In 

 general, the symptoms are those of chronic gastro-intestinal catarrh. 

 The capricious appetite varies between extreme voraciousness and com- 

 plete anorexia. Regardless of the amount of food consumed, there is a 

 noticeable emaciation which may become well marked, young dogs 

 especially becoming pot-bellied and stunted in growth. More char- 

 acteristic is restlessness, straining, and itching about the anus, the latter 

 manifested by agitation of the tail and a peculiar squatting and dragging 

 of the hind parts, sometimes referred to in the expressive, but highly 

 untechnical term, "rough-locking." 



With increasing uneasiness, the development of intestinal pains, 

 howhng, and an inclination to bite, which is perhaps conjoined with a 

 dull or wild expression, there are presented sjmiptoms somewhat similar 

 to those of rabies. In such cases convulsions may set in and the animal 

 may die during an attack, or it may gradually succumb after sinking 

 into a cataleptic condition. 



Pathogenesis. — Necropsies upon dogs which have suffered from 

 tseniasis generally show the worms lodged in the small intestine only. 

 Probably as a result of post-mortem wandering, they may also be found 

 in small numbers in the large intestine or stomach. The inflammation of 

 the mucosa is especially extensive and of aggravated character in in- 

 festation with Echinococcus. This is a tapeworm of the dog which, 

 though relatively very small, sets up the greatest irritation by reason 

 of the vast number of individuals present, which, firmly implanted by 

 their hooks, may completely cover the intestinal lining over large areas. 

 Where obstruction occurs in tseniasis, it is generally brought about by 

 the presence of the larger tapeworms massed in coils. Dipylidium 

 caninum, though smaller than some other species inhabiting the dog, is 

 most likely to be found the offending agent in such conditions because 

 of its prevalence and the presence of numerous individuals in the 

 same host. The projecting rostellum of this species, sinking deep 

 into the mucosa, is also a factor increasing its capabilities for dam- 

 age. Tcenia hydatigena and T. fisiforjnis are much larger, but less 

 common, while MuUiceps muUiceps and M. serialis have thus far 

 been found more commonly in European countries than in the 

 United States. 



Contributing to the systemic effects of tapeworm invasion, there is, 

 as in other helminthiases, the operation of toxins elaborated by the 

 worms. In cases of heavy infestation this factor must be a considerable 

 one, especially when combined with that of poisons derived from the 

 dead and decomposing bodies of the parasites. 



