Distemper in the silver fox (Culpes vulpes).

Abstract

An epidemic of very large proportions has occurred on a number of fox ranches in Minnesota. The specific disease under consideration had been diagnosed as “fox distemper” because of its similarity, from the clinical aspect, to the disease in dogs which is known as “canine distemper.” The varied features of canine distemper, which is described as appearing in several forms—the upper respiratory, the central nervous system, and the intestinal types—were all present in the foxes afflicted with this disease on each individual ranch. Most foxes exhibited a very marked infection of the conjunctiva and nasal cavity, from which issued a purulent discharge. A large number of foxes exhibited nervous symptoms before death, ranging from muscular twitching to violent convulsions. A diarrhea appeared to be always present.

Many foxes were not recognized as being sick but were found dead in their pens, although visited daily. Autopsies on a hundred foxes showed a great preponderance of pneumonia, usually extensive. The liver was usually congested; the spleen congested and enlarged. The intestinal mucosa was usually inflamed in the lower portion. Ulcerations were present in the intestine in some cases.

Bacteriological studies of foxes dying on the ranches yielded a great variety of organisms. Streptococci and various diplococci predominated in the pneumonias. Bacillus bronchosepticus could be isolated from the nasal secretions. Blood cultures yielded a great variety of organisms. Usually a mixed culture was obtained. Because of the large numbers of organisms encountered, it was believed that these were secondary invaders, and that much of the pathology observed was due to these secondary invaders. It was noted that some few foxes) dying on the ranch did not exhibit pneumonia. Some did not exhibit a very marked discharge from the eyes and nose.