578 DISEASES OF THE HOBSE. 



OSTEOPOROSIS OR BIGHEAD. 



By John R. Mohlee, V. M. D., Assistant Chief, Bureau of Animal Industry. 



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, 

 softened, 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, Mada- 

 gascar, India, Hawaii, and in this coimtry it seems to be enzootic, 

 several cases usually appearing in the same stable or on the same 

 farm, and numerous animals being affected in the same district. In 

 the United States the disease has been found in all the States border- 

 ing the Delaware Eiver and Chesapeake Bay, in some of the New 

 England States, and in many of the Southern States, especially in 

 low regions along the coast. In Europe the disease appears to be 

 quite rare, and is usually described as a form of osteomalacia, a dis- 

 ease which is not uncommon among cattle of that continent. The 

 opinion that bighead is only a form of osteomalacia, however, can not 

 be accepted, nor can the infrequency of the former among European 

 horses and the frequency of the latter among other live stock be con- 

 ceded on the argument which has been presented, namely, that the bet- 

 ter care which horses receive prevents them from becoming affected. 

 In the Southwest, where osteomalacia, or creeps, has not infrequently 

 been observed among range cattle by the writer, no case of osteo- 

 porosis 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, worn-out soil, or on land deficient in lime salts, or from eating 

 feed lacking in these bone-forming substances, or drinking water 

 with a lime deficiency, is in perfect accord with our knowledge of the 

 disease. But osteoporosis may occur on rich, fertile soil, in the most 

 hygienic stables, and in animals receiving the best of care and of 

 bone- forming feeds with a proper amount of mineral salts in the 

 drinking water. 



Cause. — The cause of this disease still remains obscure, although 

 various theories have been advanced, some entirely erroneous, others 



