Kashin-Beck disease in rural Tibet: an agri-environmental disorder | La maladie de Kashin-Beck et le milieu rural au Tibet: un probleme agri-environnemental

Kashin-Beck disease (KBD) is an endemic osteochondropathy that primarily affects children in Asia. More than 30 million people are living in endemic areas at direct risk of developing KBD, with approximately 2 million people affected in China alone. Its unknown etiology is an ongoing challenge to agro-environmental and medical sciences. Three major environmental causes of this disease have been proposed: (1) severe cereal contamination by mycotoxin-producing fungi; (2) selenium deficiency, and (3) high organic matter concentrations in drinking water. Several agricultural and traditional practices influence KBD development, with selenium deficiency widely considered to the author a major factor. In China, analyses of soil and grain samples in the main types of environment have shown that low selenium concentrations coincide with most regions where people are affected by the disease, including the autonomous region of Tibet. KBD villages always seem to be located in semiarid steppe valleys near humid vegetation zones with dark-red earth and water. Organic acids are probably responsible for colouring water used by Tibetan women for drinking and humidifying barley grain before processing into "tchang" (local alcoholic beverage). High elevation and very severe climatic conditions affect land and naturel resource use. In urbanized areas, Tibetan farmers rely on a wide variety of foods from different regions. In agricultural areas, people depend heavily on local barley, which is the main staple food in all villages with grains and "tsampa" (roasted flour) being stored in 97% of the families surveyed. Barley crops are grown during the humid summer season (June-August) and harvested in August, September or October, when there are marked gaps between daily minimum and maximum temperatures. Ears are beaten with flails and the grain is stored in yak-skin and yak-hair bags. Under these climatic conditions, the grain moisture content and contamination by mycotoxin-producing fungi are very high. Fungal plant pathogens affect cereal grain quality and fungus-induced symptoms are often observed in Tibetan grain. Saprophytic (Alternaria sp., Cladosporium sp.) and pathogenic (Drechslera sp.) fungi cause kernel discoloration and black points. To maintain the quality of barley grain, cereal crop management should include seed decontamination, crop-residue destruction, fungicide treatment, and grain drying before storage. The overall environmental conditions in the concerned areas of Tibet are unfavourable for agriculture, thus making it difficult to meet basic food needs