226 DISEASES OF THE BRAIN 



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the infection is acquired through the respiratory organs. 

 However, Borna disease is more common in the winter and 

 early spring months than in summer, the dusty period of the 

 year. It is possible that the virus is voided with the urine. 

 The disease is not communicable. It is much more common 

 among farm than city horses. 



Necropsy. — Macroscopically the brain appears normal, but 

 under the microscope a marked cellular infiltration is noted in 

 the meninges, brain, and spinal cord. Especially typical 

 changes have been noted in the ganglionic cells in the olfac- 

 tory lobes a'nd horns of Ammon which contain peculiar, - 

 intensively stained bodies within the cell nucleus ("nuclear 

 inclusions"). 



Symptoms. — The symptoms are varied, but in general are : 

 early fatigue, icterus of the mucous membranes and digestive 

 disturbances, sometimes amounting to colic attacks. These 

 are followed by symptoms of cerebral excitement; twitching 

 of the muscles of the face ; spasms of the muscles of the neck, 

 sometimes producing torticollis; occasionally trismus, nystag- 

 mus, unequal dilatation of the pupils, skin hyperesthesia, 

 exaggerated reflexes, occasionally increased sexual desire, and 

 psychic phenomena. In some instances the patients are 

 vicious, aggressive; in others they show epileptiform spasms. 

 Later the patients appear depressed, stupid, even soporous, 

 and may show forced movements. Motor paralysis is recog- 

 nized by a weak, staggering gait, paralysis of the pharynx 

 and general paralysis. The pulse, respirations, and tempera- 

 tures are usually little affected. In a few cases an eczema of 

 the skin appears. 



Course and Prognosis. — The course is usually from eight to 

 fourteen days. The mortality is over 90 per cent. Those 

 which recover are often left infirm through blindness, epilepsy, 

 permanent loin lameness or they remain "dummies." 



Treatment. — Treatment is of no avail. As a preventive it is 

 recommended to change the food and drinking water and to 

 keep the animals from infested pastures. Water from wells 

 and cisterns which are contaminated with stable seepage 

 should be'especially ayoided, 



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