UNITED STATES DEPARTMENT OF AGRICULTURE 



lift BULLETIN No. 817 ^^m 



<5klk>-<if>?? Contribution from the Bureau of Animal Industry <5 



JOHN R. MOHLER, Chief 



Washington, D. C. 



PROFESSIONAL PAPER 



May 12, 1920 



OBSERVATIONS ON THE LIFE HISTORY OF 

 ASCARIS LUMBRICOIDES. 



By B. H. Ransom, Chief, and W. D. Fostetj,^ Junior ZooJoffUt, Zoologi.al 



D hnsion. 



CONTENTS. 



Page. 



Historical summary 1 



I'rohalile identity of Ascuris lumbri- 



coidrn and Asraris suuiu 4 



Egg stagp of Ascaris 4 



Incubation 4 



Incul)atiug Ascaris eggs for ex- 

 perimental use a 



Longevity of Aaccn-is eggs 6 



Resistance of Ascaris eggs to 



chemical agents 6 



Avenue of infection with As- 

 caris 7 



Hatching of Ascaris eggs 8 



Larval stages of Ascaris 10 



Migrations of larvae in hody of 



the host 10 



Development in the intestine. _ 15 



Description of lai-val stages 18 



Page. 



r.arval stages of Ascaris — Continued. 

 Relation of host to size of de- 

 veloping iarvff 19 



Lesions associated witli migrat- 

 ing larvae 21 



Death of migrating larvae 23 



Relation of age to Ascaris infes- 

 tation 24 



Ascaris pneumonia 27 



Longevity of larvie outside tlic 



host 29 



Natural occurrence of Ascaris in 



sheep 29 



Life liistory of related nematodes-.. 30 



Details of experiments' with Ascact-s - 31 



General summary 43 



Bibliograpliy 45 



HISTORICAL SUMMARY. 



The results of experiments by Liitz (1888), Epstein (1892), and 

 other investigators, together with A^arious considerations of general 

 and special nature, liaAe led to the acceptance of the belief to the 

 extent that it has been taken as an established fact that Ascaris lum- 

 hiicoides and Ascaris smun, parasites of man and the pig, respec- 

 tively, have a direct life history and require no intermediate hosts in 

 their cycle of development. Recent work by Stewart (1916-1918), 

 however, has shown that the life history of Ascaris is not so simple 

 as commonly supposed, and he has made the highly interesting and 



"^ This paper was written after the death of Mr. Foster, which occurred October 6, 

 1918, but in view of liis participation in the investigations upon which the paper is l>ased 

 his name appears as .ioint author. 



1375.50°— 20— Bull. SIT 2 



