18 DEPARTMENT OF GAME AND FISHERIES No. 9 



Conclusion. — An outbreak of infectious pneumonia in silver foxes has been 

 studied and found to be caused by a hemolytic streptococcus. It would appear 

 to be a virulent organism causing the death of fox pups with a severe lobar 

 pneumonia. Age immunity is marked in adult foxes. Although several adult 

 females were equally exposed to the infection none developed the disease. The 

 outbreak was checked after a mortality of 10 per cent, in the pups before treat- 

 ment was commenced. Immediate isolation of sick and contact animals and 

 rigid sanitation was advised and an autogenous bacterin prepared. The bacterin 

 appeared to be of great benefit and gave an immediate positive immunity. 

 Injected control fox pups placed with sick animals were 100 per cent, protected. 

 As with all outbreaks of infectious disease, this one may have been self-limiting 

 but the controls favour good results from the bacterin. The above outbreak 

 appears to be similar to that of one studied by Dr. F. W. Schofield and recorded 

 in the Ontario \ eterinary College Report, 1929. 



Broncho- Pneumonia 



The outbreak occurred on a modern, well-kept ranch causing a total loss 

 of 67 foxes which included all the pups, some 45 in number, and 22 adults of all 

 ages. Two visits v/ere paid to the ranch but no error in management could be 

 detected. The pens were almost all completely board-floored and no serious 

 trouble had occurred from lung-worm infection. Several adults had died from 

 time to time and the losses were increasing when the pups arrived. The pups 

 all died within a short period. The remaining adults were then affected in 

 epidemic proportions. Cases had occurred in all parts of the ranch showing that 

 the infection was widespread. 



Bacteriological Findings. — Stained smears of the cut lung tissue oozing with 

 pus from the tiny bronchioles showed several organisms. When plated out on 

 blood agar, streptococci, staphylococci, and colon bacilli were isolated. 



Injections of the pus from the lungs intravenously into the ear veins of 

 rabbits caused death in 48 hours. Both streptococcus and staphylococcus 

 organisms were present in stained smears of the heart's blood of the injected 

 rabbits. Ferrets injected subcutaneously with pus from the fox lungs came 

 down with a typical broncho-pneumonia similar to that of the foxes and died 

 in ten days. The same organisms were isolated from the ferret lungs as were 

 found present in the fox-lung lesions. 



An autogenous bacterin containing all three organisms was prepared and 

 all the remaining foxes injected with 3^ c.c. doses two days apart. Three more 

 animals died while the bacterin was being prepared, but no further losses occurred 

 after ten days from the first injections. Apparently the three foxes died before 

 they had time to work up sufficient immunity. One of these foxes was given 

 3^ c.c. injections of bacterin every two days, but although it lasted some three 

 weeks and appeared well on the way to recovery it finally succumbed. 



Summary. — An outbreak of infectious disease in silver foxes has been 

 studied and would appear to be a severe broncho-pneumonia caused by a mixed 

 infection with streptococci, staphylococci, and colon. Cultures of the intestines 

 failed to show any paratyphoid organisms, which have been recorded as causing 

 somewhat similar outbreaks. The infection had been well established before 

 it was brought to our attention and the mortality was high with a loss of 67 foxes 

 out of 89 on the ranch. An autogenous bacterin was prepared and its injection 

 appeared to stop further losses. Broncho-pneumonia is the predominant 

 symptom and post-mortem lesion. 



