Bovine Tuberculosis Eradication Efforts
Q. How long does it take to eradicate TB from a herd?
A. The amount of time needed to eradicate TB varies depending on the outbreak. It can depend on factors such as herd size, the number of animals bought or sold, and the potential need to retest animals. It also depends greatly on the availability of herd records, the animal identification system used by the herd owner, and the overall traceability of the herd’s animals.
Q. What is the government doing to eradicate TB?
A. The most efficient way for animal health officials to find the disease is through nationwide slaughter plant surveillance activities. If a case of TB is found and confirmed through laboratory testing, animal health officials conduct an exhaustive search and attempt to trace the infected animal back to its herd of origin. Officials test the herd of origin and depopulate it if it is diagnosed with TB. Animal health officials also carry out additional animal tracing activities and attempt to locate where the disease came from and prevent its potential spread.
Q. Why are some affected herds quarantined rather than depopulated?
A. Depopulation of an entire herd is voluntary. The U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) encourages producers to depopulate entire herds and offers indemnity payments at fair-market value (up to $3,000 per animal). Due to the biological limitations of TB tests, total herd depopulation is the only method guaranteed to remove 100 percent of the infected animals; it is the preferred method of TB control for the eradication program.
Q. Why are whole herds depopulated when only a few animals are positive for the disease?
A. The disease is difficult to detect, and false negative test results do occur. If an entire herd is not depopulated, there is a chance that an animal with a false negative test result may be missed. Also, signs and symptoms of TB can take time to become apparent in an animal.
If such an animal remains in a herd, the TB infection can continue to spread. By depopulating the entire herd, animal health officials can ensure that the disease is not spread by an undetected TB-positive animal.
Q. Who depopulates infected herds?
A. Regulatory animal health officials lead depopulation efforts. Other participants typically include State or Federal animal health officials. While not required, producers also sometimes assist in the handling and loading of animals.
Q. Who pays for the depopulation?
A. The salaries for participating regulatory personnel are paid by their respective employing agencies. APHIS pays the haulage costs and fees. Producers and their employees who choose to participate in the depopulation are not compensated for their time.
APHIS is authorized to pay owners of TB-affected herds indemnity in an amount that, together with net salvage paid to the herd owner, does not exceed the appraised fair-market value of the individual animal (up to $3,000 per animal).
Q. How do you find the source of an outbreak?
A. Veterinary epidemiologists attempt to determine when a herd was likely infected. Then, they attempt to trace all cattle moved in and out of the herd, looking for where the disease may have originated and where it may have spread. If producers participate in an animal identification program like USDA’s National Animal Identification System (NAIS), it takes animal health officials much less time to determine where affected animals may have moved. NAIS means that officials eradicate the disease more quickly and stop its spread.
Q. Why is it difficult to determine the source of infection?
A. It is often difficult to tell which animals moved into and out of a herd and when. Animals may lose identification or have it changed in the case of management identifications. It is also a challenge to determine whether or not wildlife could have spread the disease to cattle in those areas known to have TB in wildlife.
Q. How are TB positive animals disposed of?
A. After a herd is identified as affected with TB, all animals that have exhibited a response to a TB test in the past are taken for diagnostic necropsy. They do not enter the food chain.
September 10, 2008