670 DISEASES OF SWINE 



produce quite severe symptoms and often cause such unthriftiness 

 as to permanently stunt the animal. 



Description. — Strongylus paradoxus, or the lung worm, is a 

 thread-like parasite, white or brownish-white in color. The length 

 of the worm is from f inch to 1 ^ inches. The male parasite is smaller 

 than the female. On its anterior end the worm has a small mouth, 

 and surrounding this mouth, when examined with a powerful lens, 

 six small papillae can be made out. 



Mode of Infestation. — The mode of infestation with these 

 parasites has never been clearly worked out, but it would seem most 

 likely that the female worm lays a large number of eggs in the 

 bronchi, and these are carried out with the abundant mucous secre- 

 tion that is produced as a result of the irritation caused by the 

 parasite. This egg-bearing mucus may be discharged through the 

 nose or it may be swallowed and pass out through the intestines 

 with the feces. In either case the result is the same. The eggs in 

 this manner reach the ground, where they are hatched and the 

 minute larval form of the worm is set free. These larvae again 

 enter the respiratory tract of healthy animals by being taken in 

 with the inspired air through the nostrils. As soon as they reach 

 the bronchi and trachea they find conditions suitable for their 

 growth and development, and they rapidly increase in size until 

 they are fully developed. 



Symptoms. — The sjrmptoms produced by lung worms will vary 

 with the number of parasites present. If only a few of them are 

 in the air-passages they may not cause any trouble which would be 

 especially worthy of notice. In old animals the mucous membrane 

 of the bronchial tubes is much less irritable than in the case of 

 young pigs, and, as a result, we find that symptoms of this form of 

 parasitic infestation are much more commonly met with in pigs 

 than in older animals. 



Even in pigs the symptoms are often quite mild. The main 

 symptom noticed is a frequent spasmodic cough. The condition is 

 properly classed as a verminous bronchitis — that is, a bronchitis 

 produced as a result of irritation by worms, and all the prominent 

 disturbances noted are those of a bronchitis. The coughing spells 

 which characterize this disease are most frequently brought on 

 when the animal gets up and starts to move around after lying 



