1931 ANNUAL REPORT, 1930 11 



Notes ox Breeding 



Breeding operations have been carried out along strictly practical lines. 

 Selective mating and the continued concentration of the descendants of superior 

 foxes has resulted in a steady improvement in the pups and pelts. 



Foxes which are not producing a satisfactory quality of pups are being 

 rapidly eliminated. 



Cross foxes are attracting considerable attention and many enquiries have 

 been received regarding possible results from given matings. Before definite 

 statements can be made, thorough investigation of the subject is required. 



So far, reds mated to silver blacks have produced a predominance of red 

 pups. A majority of these pups have bluish-black markings on the chest and 

 throat. They produce pups with a distinct cross marking, and produce cross 

 pups when mated to silvers and black foxes. 



Those engaged in cross fox-breeding are advised to carry on to the second 

 generation at least. Particularly is this the case if the pups have the markings 

 referred to. 



Distemper of Foxes 



During the past year we had the opportunity of investigating a number of 

 outbreaks of infectious diseases among silver foxes. Several of these resembled 

 distemper of the dog and were later found to be transmissible from dogs to foxes. 



The foxes were observed on the ranches where the disease occurred and every 

 assistance was given the staff in making observations and securing laboratory 

 material. 



Cause 



Distemper is a highly contagious disease affecting animals and is due to a 

 filtrable virus. The susceptibility of the fox to canine distemper has been a 

 subject of considerable controversy among fox ranchers and veterinarians. In 

 one particular outbreak, two dogs, obviously suffering from distemper, were 

 at liberty in the ranch cook-house. We were of the opinion that it was necessary 

 to eliminate or confirm the possibility of the foxes having contracted the disease 

 from these dogs. 



With this objective in view, two healthy scrub foxes were shipped to the 

 \'eterinary Hospital conducted by Dr. J. A. Campbell, Toronto. They were 

 placed in the isolation distemper ward in pens adjacent to dogs manifesting 

 all stages of virulent distemper. Both foxes were dead within a month and 

 showed similar post-mortem lesions observed later in our investigations. 



Course and Characteristics 



In the epidemics observed, the disease originated in one or two pens, and 

 did not break out simultaneously from all quarters of the ranches. Where it 

 was not checked, however, in a few weeks a general epidemic was in force. 



The heaviest mortality was among the pups. This is to be expected consider- 

 ing the general practice of running the litters in the same pens for the greater 

 part of the summer. One infected pup will quickly give the contagion to his 

 litter mates. Where pups are housed in sheds a rapid spread can be looked for. 



The thermometer offers little assistance in diagnosing the disease in the 

 incubation period, the period when the fox may be sickening but does not show 

 any definite symptoms. Even with normal foxes, the excitement of catching 

 and handling will elevate the temperature. Once the temperature drops to 

 subnormal, i.e. below 100 degrees, death can be expected in a short time. 



3— G & F 



