THE RESPIRATORY SYSTEM 83 



animal body in the food or water, infestation of swine 

 being easily accomplished. Young pigs are most sus- 

 ceptible; however, the parasites have been identified in 

 swine of all ages. After the parasites gain entrance to 

 the animal body they begin to migrate, some of them 

 ultimately reaching the bronchial tubes. The exact 

 route of migration is still a disputed question, but they 

 pass either by way of the pharynx through the larynx 

 to the bronchial tubes, by way of the blood stream, or 

 directly through the tissues. 



Lesions. The principal lesions in swine are found 

 in the posterior lobes and in the superior part of those 

 lobes. At first the lesions are confined to centers, or 

 foci, which are cone-shaped and usually atelectatic, 

 though they may protrude and be of a doughy con- 

 sistency. In a later stage these foci are found to contain 

 mucopurulent, purulent, or even caseous substances in 

 varying quantities in addition to from one to many 

 Strongyli and their ova. Similar discharges will be 

 found in the bronchial tubes and even in the trachea, 

 and occasionally disintegrated vermes and their ova will 

 be found in the expectorate. There may be bronchiec- 

 tasis, but this condition is not common. The visceral 

 pleura may show evidence of chronic inflammation. 



Symptoms. The period of incubation varies from 

 four to eight weeks. Although this condition is very 

 prevalent, the infestation is usually limited and fatalities 

 from this disease are exceptional. The primary symptom 

 is a cough, which usually involves several animals at once 

 and becomes more frequent as the disease progresses. 

 In fatal or severe cases the cough is paroxysmal, the 

 animals sometimes falling to the ground from exhaustion 

 and lack of air. A sticky, adhesive discharge prevails 

 and accumulates upon the nostrils, respiration becomes 

 difficult, and a distinct wheezing sound can be heard. 

 The temperature may be increased from one to three 

 degrees Fahrenheit. Emaciation is rapid. Edema of 

 the dependent parts occurs, and the animals become 

 weak and finally die of exhaustion. The course of the 



