Endemic Diseases of Animals

diseases that develop in specific biogeochemical provinces as a result of a deficiency or absence of vital chemical elements in the soil, water, and feed. The deficiency or lack of one or several trace elements in an animal—or the depletion of these trace elements while there is an excess of others—results in a disturbance in metabolism (including mineral metabolism), in the dysfunction of organs or systems, and in a change in tissue structure. For example, a deficiency of phosphorus, cobalt, and copper or a deficiency of calcium and an excess of phosphorus salts leads to an imbalance in phosphorus-calcium exchange and the destruction of bone tissue (endemic osteodystrophy). A deficiency of iodine causes an imbalance in the function of the thyroid gland (endemic goiter), resulting in the slowed growth and development of young animals. Adult females abort, or their young are underdeveloped in utero. A deficiency of copper or an excess of molybdenum and lead when there is a sufficient quantity of copper causes fusion of brain tissue in lambs (enzootic ataxia). Motor functions are disturbed, and spasms and paralysis follow. Blindness and hearing loss also occur. During the lambing period there is high mortality of newborns. In some endemic diseases chronic poisoning is possible (for example, with an excessive fluorine content in agricultural feeds).

The clinical symptoms of endemic diseases depend on the absolute quantity of trace elements entering the body and on the quantitative relationships between the elements. Treatment and prophylaxis include developing rations with a balanced mineral content. The necessary administrative measures are currently being taken to improve meadows and pastures (for example, application of inorganic fertilizers); these measures are based on data obtained from chemical analyses of the soil, water, and plants in each specific biochemical region.