28 CIRCULAR 14 8. U. S. DEPARTMENT OF AGBICTJI/TTTKE 



which occur in cattle and sheep, one may assume that horses be- 

 come infested with lungworms as a result of swallowing the infective 

 larva? with feed or water. 



Symptoms. — When few lungworms are present in a horse, definite 

 symptoms are not produced. In heavy infestations the parasites 

 produce bronchitis, and the most outstanding symptom of this con- 

 dition is a cough. Excessive coughing weakens an animal, and in 

 severe cases it may result in death. So far as is known, lungworms 

 are not very common in horses in the United States, and as a rule 

 the infestations when present are not very severe. 



Treatment. — Medicinal treatment for lungworm infestation is un- 

 satisfactory. Many drugs have been advocated for injection into the 

 trachea or windpipe but there is little evidence to indicate that such 

 drugs actually kill the lungworms. On the other hand, considerable 

 damage to the delicate lining of the air passages may result. 



Nursing treatment usually gives better results and is without harm 

 to the animal. Nursing treatment consists in providing nourishing 

 food, pure and uncont animated drinking water, salt, clean, sanitary 

 quarters, and adequate shelter. The affected animals should be re- 

 moved from contaminated pastures and placed in lots or pastures 

 which are not infested with parasite eggs and larva?. This plan of 

 treatment is designed to remove the animal from areas in which it 

 is subject to gross reinfestation, to improve its condition, and to tide 

 it over the more critical period of the disease while it builds up its 

 resistance to the lungworms. 



Prevention. — Preventive measures are similar to those recom- 

 mended for the control of blood strongyles and the large intestinal 

 roundworm. The manure must be disposed of in a manner that 

 keeps the infective material away from the horse. 



THE NECK THREADWORM 



The large ligament of the horse's neck, known to veterinarians as 

 the ligamentum nuchae. is frequently parasitized by a long, slender 

 threadworm, Onchocerca cervicalis. The exact length of these worms 

 has not been determined owing to the difficulty of extracting them 

 from the ligament without breaking them. 



Life history. — The life history of this parasite has not been as- 

 certained. 



Symptoms and lesions. — These worms apparently act as irritants 

 to the tissues and thus weaken their resistance to the attacks of dis- 

 ease germs. There is reason to believe that this may lead to the de- 

 velopment of poll evil and fistulous withers. 



Treatment. — Surgical and medicinal treatment may be employed 

 where poll evil or fistulous withers is present, but there is no treat- 

 ment for the destruction of the worms. 



Prevention. — In the absence of information concerning the life his- 

 tory of these parasites no definite measures can be recommended. 



THREADWORMS OE THE ABDOMINAL CAVITY 



Threadworms, Setaria equina, of the body cavity of the horse, also 

 known as filarids or setarids, are relatively long and slender (fig. 21) 

 and occur in various locations outside the alimentarv canal of the 



