Selenium Deficiency in Hovsgol Livestock: An Example of the Potential Impace of Climate Change on the Burden of Disease in Mongolian Livestock?
Amanda Fine, Justin Zyskowski, and Shiirev-Adiya Saruul
White Muscle Disease is caused by a deficiency of selenium and/or vitamin E. It is a degenerative muscle disease that has been reported in all species of livestock. Clinical signs of the disease include obvious stiffness, stumbling and difficulty walking as well as respiratory signs (increased respiratory effort and rate) related to the effects on cardiac muscle. Animals that have died of white muscle disease often have white streaks visible in their muscle tissue. The disease is generally seen in newborn livestock though adults can be affected.
A series of interviews, conducted in 2004 with livestock owners residing in the valleys along the Eastern shore of Lake Hovsgol, Mongolia, revealed anecdotal evidence of the occurrence of white muscle disease in livestock of the region. In 2005 an effort was made to collect blood samples from sheep, goats and cattle in region for vitamin E and selenium analysis. Vitamin E levels in livestock were within the normal range but the level of selenium in whole blood of many of the animals was at or below the levels considered consistent with disease (less than 0.04 ppm of selenium). Selenium deficiency is generally associated with selenium deficient soils and/or the inadequate uptake of selenium by forages grown on these soils. Selenium deficiency occurs when the soil contains less than 0.5 mg Se/kg of soil and locally harvested feeds or pasture contain less than 0.1 mg Se/kg of feed.
Whether or not climate change in the Hovsgol region has affected the levels of selenium in the soil or the rates of selenium uptake in the forages on which livestock of the region feed is yet to be determined. Generally, concerns regarding the implication of climate change on disease prevalence have been focused on the changing patterns of disease vector distribution; mosquitoes, ticks and other parasites. In the Hovsgol region the increased reports of white muscle disease in livestock may be due to changes in the soil and forage composition and/or increased grazing pressure and other factors related to increases in livestock density in the region.