OSTEOPOROSIS, OR BIGHEAD. 



By John R. Mohler, V. M. D., 

 Chief of Pathological Division, Bureau of Animal Industry. 



NATURE OF THE DLSEASE. 



Osteoporosis is a general disease of the bones which develops slowly 

 and progressively and is characterized by the absorption of the cal- 

 careous or compact bony substance and the formation of enlarged, soft- 

 ened, and porous bone. It is particularly manifest in the bones of the 

 head, causing enlargement and bulging of the face and jaws, thereby 

 giving rise to the terms '' bighead" and ''swelled head," which are 

 applied to it. The disease affects horses, mules, and asses of all ages, 

 classes, and breeds, and of both sexes, and is found under all soil, 

 dietetic, and climatic conditions. It may occur in sporadic form, but 

 in certain regions, such as South Africa, Australia, Madagascar, India, 

 Hawaii, and in this country it seems to be enzootic, several cases 

 usuall}^ appearing in the same stable or on the same farm, and numer- 

 ous animals being affected in the same district. In the United States 

 the disease has been found in all the States bordering the Delaware 

 River and Chesapeake Bay, in some of the New England States, and 

 in many of the Southern States, especially along the coast in regions 

 of low altitude. In Europe the disease appears to be quite rare, and 

 is usually described as a form of osteomalacia, a disease which is not 

 uncommon among cattle of that continent. However, the opinion 

 that bighead is only a form of osteomalacia can not be accepted, nor can 

 the infrequency of the former among European horses and the fre- 

 quency of the latter among other live stock be conceded on the argu- 

 ment which has been presented, namely, that the better care which 

 horses receive prevents them from becoming affected. In the South- 

 west, where osteomalacia, or creeps, has not infrequent!}^ been 

 observed by the writer among range cattle, no case of osteoporosis of 

 the horses using the same range has been noted, although the latter 

 animals are given no more attention than the cattle. 



The appropriate treatment of osteomalacia in cattle is so effective that 



if osteoporosis were a similar manifestation of disease a similar line of 



treatment should prove equally efficacious. However, this is not the 



fact. On the other hand, the occurrence of osteomalacia on old, 



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