TAPEWORMS OF CHICKENS 191 



According to Grassi and Rovelli the intermediate host is a lepidop- 

 terous or coleopterous insect. 



5. Davainea echinobothrida {Tcenia echinobothrida) . — The small 

 head (Fig. 105) presents an infundibulum provided with a double crown 

 of about 200 hooks. The suckers are armed with 8-10 circlets. There 

 is no neck. The segments gradually increase in width, the largest being 

 1-4 mm. The genital pores are irregularly alternate. 



Length, 5-25 cm. (2-9 J^ inches). 



Nothing is known of its larval development. 



This species has a characteristic pathological effect in that the scolex, 

 with its accessory armature about the suckers, bores through the in- 

 testinal mucosa, producing large nodules or ulcers. The condition in 

 fowls is termed "nodular tzeniasis" and is described by Moore (Bureau 

 of Animal Industry, Cir. No. 3, 1895). The nodules are often mistaken 

 for other diseases showing similar features. 



6. Davainea proglottina {Tcenia proglottina) . — The head is quad- 

 rangular, slightly rounded. The rostellmn is armed at its base with 

 80-95 hooks. The chain is composed of 2-5 segments. The terminal 

 and largest segments have a tendency to detach and develop separately 

 in the intestine. These free segments may acquire a length exceeding 

 that of the entire chain. The genital pores are irregularly alternate. 



Length, 0.5-1.55 mm. 



Grassi and Rovelli have demonstrated that the larva of this species 

 is a cysticercoid which inhabits several species of snail — Limax cinereus, 

 L. agrestis, L. variegatus. 



The species has not as yet been reported in this country. 



Occurrence. — Guberlet, in a report of his investigations carried on 

 in Nebraska (Journal of the American Veterinary Medical Association, 

 May, 1916), sets forth some significant data as to the prevalence, in 

 parts of the United States at least, of chicken cestode infection. During 

 1912-13 he examined sixty-eight birds collected mostly from Nebraska 

 and Illinois. From this material he obtained 1,561 tapeworms, specif- 

 ically distributed as follows: Davainea tetragona, 598; D. cesticillus, 582; 

 Choanotcenia infundibuliformis, 176; Hymenolepsis carioca, 154; Davainea 

 echinobothrida, 51. The worms were present in mmabers per host varying 

 from 1-35. (The author is informed by Dr. Guberlet that he has since 

 found as many as 115 in a single animal.) Most of the birds examined 

 ranged in age from four to six months. 



Symptoms. — As a rule it is only in moderate to heavy infection that 

 tapeworms bring about morbid conditions in fowl. In any case the 

 symptoms are not well defined. They may vary in different individuals 

 having an equal degree of infestation, age especially having an influence, 

 young birds being much more affected than adults and exhibiting the 

 symptoms more definitely. The following are among the more usual : 



