28 CIRCULAR 148, U. S. DEPARTMENT OF AGRICULTURE 
which occur in cattle and sheep, one may assume that horses be- 
come infested with lungworms as a result of swallowing the infective 
larvee 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 uncontaminated 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 Jarve. 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. 
THH 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 
trom 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 OF THE ABDOMINAL CAVITY 
Threadworms, Setaria eqguina, 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 alimentary canal of the 
