234 PARASITES OF THE DOMESTIC ANIMALS 



Young animals, as a result of aggravated ascariasis, lose condition 

 and there is arrest in their development. Due largely to the accumula- 

 tion of gas, they are likel}^ to become more or less pot-bellied, the activity 

 of the skin is reduced, and the coat takes on a dry, harsh, and erect 

 appearance. The alertness and inclination to play, natural to foals and 

 young horses, is lost, and the animals maj' stand about looking more or 

 less dejected. 



Nervous disturbances are occasionally exhibited by vertigo or, 

 rarely, by epileptiform or tetanic symptoms. They may be due to reflex 

 irritation or to toxic products from the bodies of living worms, to which 

 is added toxins from the bodies of worms which are dead and decompos- 

 ing. 



Etiology. — Infection occurs by the introduction of eggs and embryos 

 into the alimentary canal with food and water. Development takes 

 place after the eggs have left the body of the host and is favored by 

 factors of warmth and moisture, such as is suppHed by moist earth and 

 a temperature of about 37° C. (98° F.). AVhile segmentation will not 

 proceed under low temperature conditions, the eggs will retain their 

 fertility in unfavorable surroundings for a comparatively long period 

 and will develop upon reaching a favorable environment. Embryos 

 within the eggs appear to possess considerable resistance, since they 

 have been observed to retain their vitality in dried horse manure for 

 six months. It is probable that infection is by eggs, and that few em- 

 br3^os are released until the intestinal contents of the equine host is 

 reached. 



Control. — Considering the persistent vitality of the eggs and em- 

 bryos, it is especially important as a prophylactic measure that as man}^ 

 as possible of the expelled worms be collected and burned. If they are 

 permitted to find their way to the manure pile or to be scattered about, 

 some of the myriads of eggs contained in their bodies will meet with 

 conditions favorable to their development and infect other horses. 

 Precaution should be taken that the drinking water for horses does not 

 receive contamination from collected manure, and that it be as pure and 

 free from surface drainage as possible. 



Treatment. — Treatment should be preceded by the withholding of 

 all bulk}^ food for twenty-four to fortj'-eight hours. During this time 

 the animal should be at rest and may be given bran mashes, to which a 

 moderate amount of grain may be added during the first twenty-four 

 hours if the preparation is to be for the longer period. 



While the preliminary fasting of the host for a daj^ or two probably 

 will not sufficiently "starve" the parasites to be of any value as an aid 

 in their expulsion, it permits the removal of the bulky portion of the 

 intestinal contents and prepares for a diffuse action of the anthelmintic 

 which otherwise would not be possible. 



