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. 2011 Oct 20;79(4):523–530. doi: 10.4065/79.4.523
World Health Organization www.who.int/en/
Centers for Disease Control and Prevention www.cdc.gov/
World Organization for Animal Health www.oie.int/eng/en_index.htm
Animal and Plant Health Inspection Service, US Department of Agriculture www.aphis.usda.gov/
Food and Agriculture Organization of the United Nations www.fao.org/