40 DISEASES OF THE BRONCHI 



asses are rarely affected. The lung worm plague is most 

 ■ apt to follow after wet summers and among animals kept 

 in swampy pastm-es or lands subject to overflow. Outbreaks 

 have occurred, however, among stabled sheep. 



Etiology. — From a clinical standpoint the following varie- 

 ties of the nematode worm are important. 



1. Strongylus filaria of sheep. (Dictyocaulus filaria.) 



2. Strongylus micrurus of cattle. (Dictyocaulus viva- 



parus.) 



3. Strongylus paradoxus of swine. (Metastrongylus apri.) 

 The life history is not entirely known. These parasites, 



which are long, slender, filiform worms, in the adult stage 

 inhabit the bronchi and trachea. Their eggs and embryos 

 are eliminated from the body by coughing and with the feces. 

 Outside of the body they probably undergo changes. Sheep, 

 cattle and swine take them up with food and water of infested 

 pastures, feed boxes, stable floors, etc. The parasites pass 

 first to the stomach; probably during rumination they reach 

 the pharynx, trachea, and bronchi. It is also probable that 

 the embryos are carried to the lungs by the blood, as nodules 

 containing them are not infrequently found in the lungs. 

 In about two months after ingestion the strongylus becomes 

 sexually ripe. The worm brood is usually taken into the 

 body diu-ing the spring and the clinical symptoms of the 

 disorder produced develop two to three months later. 

 Infestation, however, is possible during the summer or fall. 

 Young animals (lambs and calves) are more susceptible than 

 adults. Suckling lambs and calves may be infected from the 

 udders of their dams. 



Necropsy. — On necropsy the lungs of affected sheep show 

 chronic bronchitis with bronchiectasis and usually catarrhal 

 pneumonia and nodular parabronchitis. The cadaver in 

 the later stages of the disease is anemic and hydremic, 

 transudates occurring in the body cavities and the connective 

 tissue. There is obviously evidence of bronchitis, the 

 bronchial tubes being partially filled with mucopurulent 

 exudate. Numbers of sexually mature worms are present 

 and under the microscope ova and embryos can be seen. 



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