262 PARASITIC DISEASES 



Verminous Bronchitis in Calves. — The lung worms of cattle, 

 Slrongijlus micnirus and Slrongijlus pidmonaris, may cause 

 heavy losses in calves and yearlings. Older cattle may harbor 

 these parasites, but they do not seem to be inconvenienced by 

 them. The >S'. micrurus is from 1 to 3 inches (25 to 75 mm.) 

 long. The S. j)ulmonaris is smaller. It is from 0.4 to 1.3 inches 

 (10 to 35 mm.) long. They are found in the trachea and small 

 bronchial tubes, where they are mixed with mucous secretions 

 from the inflamed lining membrane of the bronchial tubes. 



Wet seasons and low, wet pastures are said to favor the 

 development of lung worms. Their life history is not fully 

 understood. They do not persist generation after generation 

 in the air passages of an animal, but the eggs and embryos are 

 expelled and live for a time outside of the animal, when they 

 may again become parasites of another or the same host. 



The symptoms are the same as occur in bronchitis and pneu- 

 monia. Calves and yearlings are the only animals in the herd 

 that may show symptoms of the disease. The air passages be- 

 come irritated and inflamed, and the calf shows a slight cough. 

 As the inflammation increases and the worms and mucous secre- 

 tions plug up the small bronchial tubes, the coughing spells 

 become more severe and rattling, wheezing sounds may be heard 

 on auscultating the lungs. The calf finally loses its appetite, 

 ])cconios emaciated and weak, and wanders off alone. It is 

 usually found lying down and shows labored breathing that is 

 occasionally interrupted by paroxysmal coughing. The death 

 rate in poorly-cared-for herds is heavy. 



Verminous Bronchitis and Pneumonia of Sheep. — The two 

 lung worms of sheep are the Strongyhis filaria and Strongylus 

 rufescens. The former is from 1.3 to 3 inches (33 to 80 mm.) 

 long, and the latter from O.G to 1 inch (1 G to 25 mm.) long. The 

 S. filaria is thread-like and the S. refuscens hair-like in appear- 

 ance. For this reason they are termed thread and hair lung- 

 worms. The thread-worm is found in the trachea and the larger 



