18-5 |
USDA surveillance of livestock and animals for TSE |
L. A. DETWILER, Veterinary Services, USDA-Animal & Plant Health Inspection Service, 320 Corporate Blvd., Robbinsville, NJ 07726 Bovine Spongiform Encephalopathy (BSE) has NOT been detected in the United States, and USDA has worked since 1989 to keep it that way. The measures APHIS has taken include prohibitions and/or restrictions on certain animal and product imports; ongoing surveillance; preparation of an emergency response plan in the event an introduction were to occur; and ongoing educational efforts. APHIS has had a comprehensive surveillance program in place in the United States since 1990. This surveillance program incorporates both the location of imports from countries known to have detected BSE and those populations where the disease would most likely be found. Samples for BSE surveillance are obtained from: 1) Field cases of adult cattle exhibiting signs of neurological disease, 2) Adult cattle condemned at slaughter for neurological reasons, 3) Rabies-negative adult cattle submitted to public health laboratories, 4) Neurological cases submitted to veterinary diagnostic laboratories and teaching hospitals and 5) Sampling of aged cattle which are non-ambulatory (ie. fallen stock). As of November 30, 2001, over 19,100 cattle brains had been examined for BSE or another form of a transmissible spongiform encephalopathy (TSE). The use of immunohistochemistry for the detection of the abnormal form of the prion protein was introduced in 1994. As of 1997, all samples submitted to the National Veterinary Services Laboratory (NVSL) are tested by immunohistochemistry. No evidence of BSE or another TSE has been found. Three other TSEs which affect animals have been diagnosed in the United States. There has been speculation of interrelationships between these diseases. Scrapie which affects sheep and goats was first confirmed in the US in 1947. There has been eradication or control measures in place since 1952. Chronic Wasting Disease of deer and elk has been detected primarily in Colorado and Wyoming. Wide-scale surveillance for CWD has been conducted since 1998. In addition several outbreaks of Transmissible Mink Encephalopathy have occurred. The last of these was in 1985 on a ranch in Wisconsin.
Session 18, The prion diseases: Human health and food safety
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