APHIS’ cattle health surveillance system provides protection to the U.S. cattle and bison herd from incursions of foreign, emerging, and certain endemic diseases that can cost billions of dollars in lost domestic and international market trade by quickly locating these diseases and limiting their spread. This minimizes production losses and helps to maintain market viability. Additionally, by conducting surveillance to find animal diseases, the system also verifies and documents for our international trading partners that certain diseases do not exist in the U.S. animal population.
Brucellosis Testing of Cattle
States in blue include brucellosis (B. abortus) in their lab testing panels used when cattle abort. This may be through the in-state laboratory or through a partnership with an out-of-state laboratory.
Each Yellowstone-area State conducts surveillance in partnership with APHIS. Testing is completed on animals leaving the Designated Surveillance Area as well as at slaughter.
Bovine Spongiform Encephalopathy (BSE) surveillance has been conducted in the U.S. since 1990. After the initial case of BSE was detected in the U.S. in late 2003, APHIS conducted a BSE Enhanced Surveillance Program from 2004 to 2006. This was a one-time intensive effort to detect BSE if present at a very low level and to provide information about prevalence. More than 830,000 animals were tested. Subsequent data analysis indicated that the prevalence of BSE in the U.S. was very low—less than one infected animal per million based on a population of 42 million adult cattle.
Beginning in 2006, the BSE Ongoing Surveillance Program was implemented. This program follows a stringent U.S. standard of detecting one case of BSE per one million adult cattle with 95% confidence. This standard far exceeds the current surveillance standards provided by the OIE for the U.S. under BSE negligible risk or Type B surveillance which is to detect one case of BSE per 50,000 adult cattle with 95% confidence. Both standards are based on a point system that reflects the likelihood of finding BSE. The BSE Ongoing Surveillance Program focuses on populations of cattle at higher risk for BSE, including those animals that are 12 months of age and older that display CNS signs and those over 30 months of age that are condemned on ante-mortem inspection at slaughter and thus are excluded from slaughter due to poor health status (non-ambulatory, unhealthy, or dead). From 2006 to 2015, the BSE Ongoing Surveillance Program tested approximately 40,000 samples per year. On 2015, the BSE sample collections were reduced to 25,000 per year. In the last 11 years the U.S. BSE sample collection resulted in point totals that far exceed both the OIE and U.S. requirements.
Currently, there is no validated test to detect the disease in a live animal. BSE testing is done by examining the obex portion of the brain stem for the accumulation of abnormally folded prion protein. BSE screening is generally done by enzyme-linked immunosorbent assay (ELISA) on fresh tissue. BSE can be confirmed by immunohistochemistry or Western Blot. Histopathology may also be utilized to look for spongiform changes in brain stem tissue that are characteristic of the TSEs. The accumulation of abnormal prion protein material and other changes in brain stem tissue that are diagnostic for BSE are not apparent in the early stages of the disease. Thus, the failure to detect BSE is not equivalent to a negative test or the absence of infectivity. Current testing methods are surveillance tools only. They are not intended to protect human health or animal health nor can they guarantee food safety.