BUREAU OF ANIMAL INDUSTRY. 125 



MISCELLANEOUS INVESTIGATIONS OF ANIMAL PARASITES. 



In further investigations on the hfe history of the common round- 

 worm of liogs (Ascnris suum) it has been conclusively proved that 

 the parasite requires no intermediate host. The eggs of the worm 

 pass out of the body of infested hogs in the feces. When swallowed 

 by a pig the eggs liatch m the small intestine and the embryos, aided 

 by the circulation, migrate to various organs of the body, including 

 the liver and lungs. Those which reach the lungs crawl u]) the 

 trachea and down the esophagus and enter the intestine again. 

 During these migrations the worms undergo considerable growth 

 and development, and at the time they leave the lungs are several 

 times their original size. Wlien they finally return to the small 

 intestine they settle down and develop slowly to maturity. In 

 young pigs as well as in small laboratory animals a heavy invasion 

 of the lungs by the young worms may cause pneumonia, with fatal 

 results. It is not unlikely that obscure lung trouble in pigs, children, 

 and other young animals may sometimes be the result of infection 

 with Ascaris or closely related worms. Lambs and young goats 

 have been found to be susceptible to infection with the pig Ascaris. 



Evidence indicates that young pigs are more susceptil)le than 

 older animals to infection with Ascans, as well as being more liable 

 to serious injury from the parasite. It therefore appears particularly 

 important to protect young pigs from infection. The teats of the sow 

 when soiled with the dirt of the pigpen are liable to carry numerous 

 Ascaris eggs, so thnt pigs are exposed to infection during the act of 

 suckling. It is, therefore, likely that greater care with respect to 

 cleanliness of the sow and the places occupied by her during the 

 farrowing and suckling periods will help to reduce the damage done 

 to pigs by Ascaris infection. 



A preliniinarv note on the life history of Ascaris has been published 

 in the Journal of Agricultural Research (vol. 1 1 , No. 8). 



In cooperation witb the Health of Animals Branch, Canadian 

 Department of Agriculture, investigations have been made of the 

 nematodes parasitic in the intestines of horses. Over 20 different 

 species of these parasites have been found to occur among horses in 

 the middle western regions of Canada and the United States. One 

 species {Tnodontophonis lenuicolUs) has been discovered to be asso- 

 ciated with ulcers of the colon, and is the apparent cause of these 

 ulcers. Tliese investigations, in connection with which are l^eing 

 conducted investigations concerning swamp fever, an important 

 disease of horses of unknown cause, have not yet been completed. 



Further work has been done relating to the gapeworm of chickens, 

 with results thus far indicating that as chickens grow older they 

 becom.e less susceptible to infection as well as less liable to be killed 

 by the parasite; that adult chickens are of little importance as car- 

 riers of the y)arasite, but that turkeys of all ages are highly important 

 as a source of infection of young chickens. 



The Zoological Division has cooperated with the War Department 

 in various ways, such as supplying information to the Surgeon Gen- 

 eral's Office relating to parasites, identifying specimens of parasites, 

 examining scrapings from the skin of horses susjiected of mange, 

 providing material for use in instructing medical and veterinary offi- 

 cers, furnishing plans of dip])ing vats for horses, and supplying 



