230 DISEASES OF THE BRAIN 



Natural History. — Coenurus cerebralis is the cyst form of 

 the tapeworm Taenia ccenurus. The adult worm is harbored 

 by dogs, principally shepherd and butcher's dogs. Occasion- 

 ally wolves and foxes are hosts. The infestation of sheep and 

 cattle takes place by their ingesting the eggs or proglottides 

 which are voided with the feces. The shell of the egg is 

 dissolved in the abomasum allowing the six-hooked embryo to 

 escape. The embryos perforate the bowel wall and probably 

 through the bloodvessels reach the brain and spinal cord 

 where they produce a hemorrhagic leptomeningitis and in 

 some instances a purulent infection. They ultimately develop 

 into cysts from the size of a pigeon 's to a hen's egg. The 

 cyst produces atrophy of the brain tissue surrounding it and 

 also of the overlying skull. 



Occurrence. — While gid is common in some districts abroad 

 it is a comparatively rare disease in the United States, 

 although isolated outbreaks have occurred in various parts of 

 this country. Sheep are much more commonly infested than 

 cattle, in which it is a very rare disease. Young sheep are 

 more susceptible than aged ones. 



Symptoms in Sheep. — From a clinical standpoint, and due 

 to the development of the parasite in the brain, three stages 

 of the disorder may be determined: (a) The stage of acute 

 cerebral inflammation, (b) the stage of latency due to the 

 gradual growth of the cyst, and (c) the stage of gid, the cyst 

 being completely developed. 



The stage of brain irritation sets in from one to two weeks 

 after infestation, and, as a rule, lasts about one week. Usu- 

 ally this stage is overlooked by the shepherd, as most com- 

 monly the symptoms are not marked. Otherwise the sheep 

 present symptoms of excitement, fright, forced movements, 

 and even convulsions; or, on the other hand, may show lan- 

 guor, stupor, irregular gait, and more rarely maniacal symp- 

 toms. 



In the stage of latency, which lasts from three to six 

 months, the patient appears normal. 



The gid stage usually develops in winter or early spring, 

 and lasts about one month. In this stage the patient shows 

 mental or motor disturbance and often topical symptoms. 



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