206 PARASITES IN THE INTESTINES 



the kennel or flock should be examined and treated before 

 being allowed with the other animals or birds. 



Pregnant animals should be entirely freed of all parasites, 

 and thoroughly washed to remove all ova or embryos that 

 may be on the hair or skin. Afterward remove to a clean 

 place that has not been used for animals for some time where 

 the mother and young should be kept for several weeks. 

 The feed and water, and all receptacles must not be per- 

 mitted to be soiled by other animals which harbor parasites. 

 In this way it is possible to rear puppies, kittens or birds 

 without experiencing the trouble with parasites. 



Strongylidae. — Hookworm. — This species of the nematodes 

 inhabits the small intestines, preferring the anterior half, 

 and occasionally is found in the stomach. They attach 

 themselves to the intestinal walls, wound the mucosa, eat 

 the epithelium, and suck the blood. According to present 

 evidence they produce a poisonous substance which inhibits 

 the coagulation of blood and possibly also injures the host. 

 Inasmuch as these parasites frequently move from place 

 to place, wounding the mucous membrane in many different 

 places, from which hemorrhage continues for some time, a 

 severe anemia is soon produced. These continued injuries 

 to the mucosa soon result in a severe enteritis with all of 

 the symptoms of inanition. 



The adult parasite in the intestine lays numerous eggs 

 which are passed out with the fecal material. After a short 

 time (eight hours to several days), the period varying accord- 

 ing to conditions of heat and moisture, an embryo develops 

 in each egg. The embryo soon breaks through the shell. In 

 the soil it undergoes a change in two or three days, and 

 another in about a week, during which time it also becomes 

 larger. This stage is known as the infesting stage. The 

 parasite may live in this condition for five months or longer. 

 Infestation may occur via the mouth, the embryo being 

 taken with the food or drink; also by burrowing through 

 the skin or mucous membrane and by following the blood 

 stream finally reaching the intestines. In experimental 

 cases the worm has been found in the intestines in eight to 

 fourteen days after skin infestation. 



