612 Epizootic Cerebro-spinal Meningitis. 



Borna disease was recognized by Siedamgrotzky as a 

 serous leptomeningitis and by Kitt as an inflammatory process. 

 Dexler was able to demonstrate evident signs of inflammation, 

 namely, centers of small-celled infiltration in the membranes of 

 the brain and cord, the adjacent layers of the nervous tissue and 

 in the venous plexuses (see Figs. 84 and 85). The last named 

 author considered Borna disease to be a meningo-encephalitis 

 and myelitis. He admits that there is bacterial intoxication as 

 in the case of other inflammatory diseases of the In-ain, such as 

 rabies. In some cases the toxic effects and in others the in- 

 flammatorj'- processes gain the upper hand, depending upon 

 the intensity of the infection. Dexler 's view was further sup- 

 ported by the results of the histological investigations of Wil- 

 son and Brimhall. These authors pointed out at the same time 

 the discrepancy between the lesions and the disturl^ance of 

 health, a point already remarked by Dexler. More recently 

 Oppenheim has proved the presence of diffuse meningitis in- 

 volving also the superficial layers of the nervous tissue in a 

 typical case of Borna disease. 



How difficult the discovery of the inflammatory lesions is, is shown by Dex- 

 ler 's case mentioned above. In this case preliminary microscopic examinations of 

 the various parts of the central nervous system proved absolutely negative, and the 

 lesions were only found by systematic examination of a number of pieces of the 

 brain. 



According to Schmorl and Johne, Borna disease is a pure intox- 

 ication of the central nervous system which leads to dropsy of the men- 

 inges and ventricles, owing to injury to the endothelial lining of the 

 vessels caused by venous stagnation. In view of the fact that both in 

 natural and in experimental cases the streptococcus of Borna disease 

 occurs but sparingly in the cerebro-spinal fluid, Ostertag believes that 

 the organism is destroyed in the blood of the animal, and that the 

 toxin thus liberated is able to exert its effects upon the nervous tis- 

 sues. 



Apart from the toxic effects the nervous tissues are injured 

 more or less severely by the products of the inflammation. Tlie 

 escape of liquid raises the intracranial pressure and pro- 

 nounced disturbances of function are caused by the cellular in- 

 filtrations. 



Anatomical Changes. In susceptible animals the only 

 lesions that are found are, as a rule, dilatation of the veins in 

 the pia mater of the brain and cord and an increased quantity 

 of clear yellowish liquid in the sub-arachnoid space and the 

 ventricles. Endothelial cells are sparingly present in the liquid 

 and a few red and white corpuscles. In five cases investigated 

 by Johne the percentage of albumen in the liquid varied from 

 0.035-0.17 per cent. 



Occasionally there is localized gelatinous infiltration around 

 the vessels. The brain substance appears more or less moist. 



