Natural Inrec-tioii. Pathogenesis. (j]^X 



Water contaminated with nitrogenous materials and all 

 food coming into contact Avitli it are equally dangerous in this 

 connection. Ostertag & Profe have been "able to isolate the 

 Borna streptococcus from Avater containing anmionia and nitrous 

 acid obtained from the drains of infecte'd stables. According 

 to Liebener the organism may exist in the ground and its dis- 

 semination depends largely upon the nature of the flooring. 

 Where the subsoil is loamy the infective material may l)e washed 

 down by heavy rains and finally be carried into streams. 



It is not certainly known how the infective material reached 

 the ground or water, but, although its presence in urine is the 

 exception, yet it is possible that it is by means of the urine of 

 diseased animals. It is probable that under suitable conditions 

 the organism can maintain a saprophytic existence, and that un- 

 der certain circumstances that are not as yet known it becomes 

 pathogenic. 



No observations have been made in veterinary medicine as to whether the 

 organism may be present in the upper air passages of otherwise healthy animals 

 and under certain conditions develop pathogenic characters. 



The disease is not transmitted directly from animal to ani- 

 mal. Some observations appear to suggest at first sight that 

 this does occur, but it is far more probable in such cases 

 that the infection is carried by food or water which has at some 

 time been in contact with diseased or infected animals. 



Susceptibility. Naturally the horse is the most susceptible 

 animal, followed in order by the sheep, ox and goat, while the 

 pig and dog are only very exceptionally infected. In certain 

 outbreaks several species of animals have been affected at the 

 same time. 



Breed and sex exercise no influence on the susceptibility, 

 while intensive feeding, especially with clover hay, appears to 

 increase the susceptibility. Young animals appear to be more 

 susceptible than old ones, but this is not always the case. 



Recovery from one attack leaves the animal with no im- 

 munity. 



Pathogenesis. When the causal organisms reach the mem- 

 branes or the neighboring part of the cortex toxic materials, 

 either secreted by them or set free by their disintegration, injure 

 the vessel walls and the adjacent tissues. As a result there is 

 set up an inflammatory process associated with cellular infiltra- 

 tion and sometimes hemorrhage. This holds good both for the 

 socalled Borna disease and for other forms of cerebro-spinal 

 meningitis. In certain cases there is only the escape of a liquid 

 that is poor in albumen and the formation of small, scattered 

 centers of cellular infiltration, and even these may in some cases 

 be absent. The final result appears to he influenced not only 

 by the virulence of the infective material, but also by the species 

 of animal affected. 



