Prevention of BSE in the US.

To prevent BSE from entering the United States, APHIS has restricted the importation of live ruminants and ruminant products from countries where BSE is known to exist. Other products derived from ruminants, such as fetal bovine serum, bonemeal, meat and bonemeal, bloodmeal, offal, fats, and glands, also cannot be imported into the United States from these countries, except under a special permit for scientific research purposes. As part of increased surveillance for BSE, APHIS veterinarians traced 499 head of cattle imported from Great Britain between 1981 and 1989 (before the ban on imports went into effect) to check their health status. No signs of BSE have been found.

APHIS leads the US interagency effort to coordinate surveillance for BSE. Officials of USDA's Food Safety and Inspection Service notify APHIS of cattle having neurological signs at slaughter. State diagnostic laboratories and public health officials also submit the brains of rabies-negative cattle to NVSL for testing. In addition to international importation restrictions, APHIS has increased surveillance efforts to detect BSE if it is accidentally introduced into the United States. More than 250 APHIS and State veterinarians specially trained to diagnose foreign animal diseases regularly conduct field investigations of suspicious disease conditions.

More than 60 veterinary diagnostic laboratories throughout the United States are participating in the BSE Surveillance Program along with the National Veterinary Services Laboratories in Ames, IA. Over 2,600 specimens from 42 states have been received, and no evidence of BSE has been seen. APHIS veterinary pathologists and field investigators also have received training from their British counterparts for diagnosing BSE. These pathologists examine brain tissue from cattle over 2 years of age that show signs of neurological disease.

Based on USDA sampling, BSE appears to be absent from US cattle or has an incidence so low that current surveillance methods have failed to detect it (2/million to 1/100,000 cattle is the detection threshold) (AAPB, 1996). If the hypothesis that the origin of BSE is related to feeding rendered sheep infected with scrapie is true, the US should be at low risk of a "spontaneous" BSE epidemic. There are 40 million sheep and 1.2 million cattle in Great Britain (a 3 to 1 ratio) in a total land area similar to the state of Oregon. In the US there are 10 million sheep and 100 million cattle (a 1 to 10 ratio).

In October, 1996, the federal Centers for Disease Control and Prevention (CDC) released a report on the incidence of CJD in the US from 1979 to 1994. The CDC found no cases of vCJD in the US and the incidence of CJD overall was slightly less than 1/1,000,000 population annually (CDC, Anonymous, 1996; Anonymous, 1996, Surveillance for Creutzfeld-Jakob disease - United States. MMWR 45(31):665-668).

Proposed rules to limit the use of ruminant derived meat and bone meal in ruminant feeds (similar to the British SBO) were first published in the January 3, 1997 (Federal Register, Volume 62, Number 2, Page 551-583) and updated in 2000. The FDAs: Center for Veterinary Medicine provides a list of common questions and answers related to prevention as does APHIS. Such rules would limit potential spread of prion disease in US cattle from any spontaneous cases or from species in the US which are known to have prion diseases (deer, elk, mink).