224 SWINE PRACTICE 



years, and in many instances it is found that the breeding stock on 

 such premises is of the same origin and that the affected aninuus 

 are inbred. As a rule, wlien the disease first appears on a farui 

 only a few swine become affected but each succeeding year tlie per- 

 centage of affected animals increases, and by the fourth or fifth year 

 after the disease first appeared from one-fourth to one-third of the pig 

 crop becomes affected. It is not uncommon to find the disease affect- 

 ing swine that have been recently introduced onto the premises 

 where the disease had previously existed. This fact indicates that 

 the infection persists on a premise or that swine on an infected 

 farm may be carriers of the infection. 



Etiology. — Filthy pens, impropei'ly ventilated hog houses, the con- 

 tinuous use of the same quarters and inbreeding are factors that 

 predispose to infectious rhinitis. The Bacillus pyocyaneus has been 

 suggested by Dimock as the probable cause of this disease. This 

 micro-organism is usually distributed in soil and manure heaps, and 

 could, therefore, readily gain access to the nasal mucosa. It can 

 be demonstrated in the discharges and lesions of a large percentage 

 of affected animals. 



Lesions. — In the beginning there will be noted an acute catarrhal 

 inflammation of the nasal mucosa manifested by congestion and tume- 

 faction. As the disease progresses the inflammatory process becomes 

 purulent and there is usually a deposit of a dirty gray, sticky exu- 

 date upon the mucosa. The infection may destroy variable sized 

 areas of the mucous membranes. Soon after the necrosis of the 

 mucosa there will be noted a bulging of the facial bones resulting 

 in more or less deformity. In some cases the hard palate is forced 

 downward, diminishing the oral cavity. The bulging of the. facial 

 bones is due to an increased volume, the result of hyperplasia. The 

 inflammatory and necrotic processes extend from the nasal mucosa 

 and involve the mucous membrane of the various facial sinuses and 

 the conjunctiva is usually similarly affected. Affected animals are 

 usually unthrifty, emaciated and small for their age. In extreme 

 cases, suppurative centers may occur in the various lymph-glands. 



Symptoms. — Sneezing is usually an early symptom of infectious 

 rhinitis. There will be a watery discharge in the beginning which 

 later becomes purulent or mucopurulent. The affected swine have 

 a tendency to root in their food but they eat little, consequently 

 they do not gain in weight. There will also be a mucous or muco- 

 purulent discharge from the conjunctiva, and the eyes may be closed 



