5<»G ACUTE GENERAL INFECTIOUS DISEASES 



produces the marked initial symptoms of the disease. (6) 

 Secondary organisms which produce many varied and serious 

 complicating conditions. A large number of organisms have 

 been isolated from animals affected with distemper, but so 

 far they have proved to be simply secondary invaders. 



Natural Infection. —Natural infection takes place in 

 several ways. It may be either direct or indirect, the 

 animals coming into immediate contact with each other, 

 or through intermediary agents, the virus being taken into 

 the digestive tract with the food or drink. There are a 

 number of factors which tend to favor the development of 

 the virus, such as influence of any kind which reduces the 

 general resistance of the animal, in the way of poor food, 

 insufficient food, colds, etc., or various diseased conditions 

 interfering with the assimilation of food. Puppies with 

 weak constitutions are especially susceptible. The develop- 

 ment of the disease is ordinarily in animals from three 

 months to one year of age. Older animals are very seldom 

 affected and if so take the disease in a mild form. This 

 may be explained by the immunity the dog possesses or by 

 its having had the disease in a mild form. House dogs 

 which have been pampered and petted, or those of the finer 

 breeds are more susceptible, and usually take distemper in 

 a more severe form. 



It has been determined quite conclusively that the specific 

 virus produces an acute or peracute condition with a high 

 temperature followed in a few days by secondary changes 

 due to other bacteria resulting in various complications, 

 such as occur in the skin (pustules), respiratory passages, 

 digestive tract, nervous system, etc. 



Necropsy.— Owing to the variety of forms of distemper 

 in dogs the lesions found on examination are of many kinds, 

 varying with the complications due to secondary infection. 

 In peracute and acute cases there will be effusions of fluid 

 from the serous membranes particularly in the pericardial 

 sac, the thoracic and abdominal cavities. Small hemor- 

 rhages are observed in some of the organs (heart, liver 

 and kidneys). In most cases of distemper the lungs will be 

 affected, either as a capillary bronchitis, congestion or 



