PAEASITES AXD PARASITIC DISEASES OF HORSES 



27 



legion in the form of yellow crusts. In either case, the eggs develop 

 outside of the body, as do those of the large intestinal roundworm, 

 and in a few days they reach the infective stage. Each egg which 

 develops normally contains a small worm within the shell. Ordi- 

 narily the eggs do not hatch outside the horse's body. Horses become 

 infested with pinworms as a result of swallowing the infective eggs 

 in feed or water. 



Symptoms and lesions. — The most evident injury produced by 

 pinworms is the irritation of the anus, which causes a horse to rub 

 its tail and buttocks against any convenient object. This irritation 

 may result from the passage of the worms out of the anus, from the 

 crushing of the female worms as they pass out. or from some irritant 

 property of the eggs. It is also reported that aside from causing 

 this irritation, pinworms are responsible for digestive disturbances, 

 and that, when present in large numbers, they produce anemia. 



Treatment. — Oil of chenopodium. administered as for large stron- 

 gyles, is effective for the removal of pinworms from the horse. Oil 

 of turpentine is also 

 an effective treatment 

 and should be given 

 in a dose of 2 fluid 

 ounces (60 cubic cen- 

 timeters) for a 1,000- 

 pound animal, imme- 

 diately preceded or 

 followed by 1 quart 

 of raw linseed oil or 

 by the proper dose of 

 the mixture of castor 

 oil and neutral oil, as 

 given under the treat- 

 in e n t for large 

 strongyles. 



Prevention. — Pre- 



,■ •,■! Figure 20. — Pinworms. Oxi/uris equi (females), of the 



ventive measures with hors ,.. ffaturai size 



reference to the con- 

 trol of pinworms are similar to those recommended for the large 

 intestinal roundworms and for blood strongyles. 



LUN'GWOKMS 



Lungworms. DictyoeauJus arnfehli. are long, slender, whitish 

 worms and range from about 1 inch to a little over 2 inches in length. 

 They occur in the bronchi and in the bronchioles (branches of the 

 bronchi). 



Life history. — The egg contains an embryo at the time it is depos- 

 ited by the female. The eggs hatch in the lungs, and presumably 

 the larva? are coughed up. swallowed, and eliminated from the body 

 with the manure. It is also likely that larvae are expelled with 

 mucus during coughing or sneezing. In either event, the larvae 

 undergo their development on the ground and attain the infective 

 stage in a few days. On the basis of what is known regarding the 

 method of infestation with closely related species of lungworms 



