Texas Initiates Testing Program to Help Regain Cattle Tuberculosis (TB) Status
September 10, 2003
Texas Animal Health Commission - Beginning November 1, Texas will begin implementing the cattle tuberculosis (TB) plan developed by an industry and agency task force in late 2002. The strategy includes testing dairy and purebred cattle herds, work that may be conducted by certified private veterinary practitioners, without cost to Texas ranchers, reports Dr. Bob Hillman, Texas' state veterinarian and executive director for the Texas Animal Health Commission (TAHC), the state's livestock health regulatory agency.
The surveillance testing, being funded by the U.S. Department of Agriculture, is one element of the plan for regaining Texas' cattle TB-free status, which was granted in 2000, but revoked in 2002. In 2001, two of Texas 153,000 cattle herds were found to have cattle TB and were depopulated. As a result, the USDA, in 2002, downgraded Texas' TB status to 'TB modified accredited advanced,' the second-highest level in the five-tiered disease program. Today, all states, except Texas, California, New Mexico and Michigan are classified free of cattle TB, a bacterial infection that causes internal lesions or tumors to develop on the animal's lungs, lymph nodes or other internal organs.
Texas' TB problems surfaced in summer 2001, when infection was detected in a purebred beef herd in Fayette County. In fall 2001, infection also was found in a Pecos County dairy and a beef operation in Irion County; these operations were counted as one herd, because they had a single owner. In August 2003, a third herd-an infected purebred beef herd--was detected and depopulated in Zavala County.
Dr. Hillman said the infected herds in Texas were detected through routine examination of carcasses at slaughter. Federal and state meat inspectors check all carcasses for wholesomeness and submit suspicious tissue samples for laboratory testing. If lesions are TB-positive, the carcass is handled according to accepted health regulations, and the remaining animals in the herd of origin are subjected to TB skin tests. Test-positive animals are destroyed and carefully examined, and if additional infection is detected and confirmed, the herd is depopulated and ranchers are reimbursed with federal funds.
In the effort to locate the source of TB infection, or to determine if it has spread, possibly exposed herds also are tested, as are operations from which cattle were bought, sold or moved. In Texas, TAHC and USDA veterinarians have TB tested more than 14,000 head of cattle that had an epidemiological link to the state's three infected herds. So far, no additional infection has been found.
"Texas is the country's leading cattle state and number six for dairy production. We must do everything possible to regain our cattle TB-free status, so animals can move across state lines without restrictions," explained Dr. Hillman.
Under current USDA regulations, Texas breeding cattle not originating from a TB-accredited free herd may not be exported out of state until they've tested negative for cattle TB, a process that takes 72 hours. Additionally, some states penalize Texas cattle by requiring additional testing or identification procedures for dairy calves or feeder cattle. TB tests or tagging requirements can be costly for Texas ranchers, who, each year, export more than 150,000 breeding cattle and nearly a million head of feeder animals.
"To regain our TB-free status, we must prove to the USDA and to other states that we've conducted surveillance herd testing sufficient to identify and eliminate all cattle TB infection," said Dr. Hillman. "If testing reveals no additional infection, we could reapply for TB-free status in August 2005."
"California and New Mexico, two other states that also recently lost TB-free status, are conducting similar disease surveillance," commented Dr. Hillman. In California, where three infected dairies have been detected since May 2002, animal health officials have tested more than a half million animals in about 300 of the 700 dairies slated for disease surveillance. Another 100,000 beef animals being moved from one state to another for grazing also are being tested.
"New Mexico lost its TB-free status in August 2003, after two infected dairies were detected. Since then, well over 50,000 head of cattle have been tested," reported Dr. Hillman.
He reported that in both California and New Mexico, to date, no additional infected herds have been found.
"Michigan's TB ranking is modified accredited, the lowest TB classification of all U.S. states. In this northern state, more than 20 infected cattle herds have been detected and destroyed, but their disease situation is complicated, because of infected free-ranging white-tailed deer. When disease transmission occurs between wildlife and livestock, disease eradication is extremely difficult," commented Dr. Hillman.
"USDA funding recently was approved for the Texas TB plan, so we can enlist and pay private practitioners to help with the TB testing program, which will begin November 1. We need the extra manpower for this effort, and some cattle producers just prefer to have their own practitioner conduct any tests."
"In September and October, we're offering the certification training seminars that are required for accredited private veterinary practitioners who want to participate," he explained. "We expect that at least 250 private practitioners will be certified by November 1 and will be ready to conduct herd tests under a 'fee-basis' contract agreement with the TAHC. Ranchers will have no out-of-pocket expenses, other than gathering the herd, presenting the cattle for testing, and holding the animals in a pen during the 72-hour test period."
Dr. Hillman explained that veterinarians test cattle by injecting tuberculin into skin of the animal's caudal fold, under the tail. Seventy-two hours later, the veterinarian examines the injection site for any swelling, lumps or thickening of the skin, which indicates a positive response to the test.
"Some 'suspect' animals will react to the tuberculin skin test, and these animals may have a blood sample drawn for a blood test, but a USDA or TAHC veterinarian also will follow up with another skin test on the animal's neck," he explained. "Animals positive on this test, called a 'comparative cervical' test must be slaughtered and carefully examined for internal lesions."
"When we start testing, we'll first focus on the state's nearly 850 dairies," commented Dr. Hillman. "This surveillance testing is no reflection whatsoever on the wholesomeness or safety of milk from Texas dairies or our meat supply. Commercially sold milk products are pasteurized, or heat-treated, which kills bacteria that may be present in the raw milk. These TB herd tests, instead, are one more way to assure that dairy and beef herds are not infected."
"While the Texas TB strategy begins with testing dairy herds, we'll also need TB tests on 2,000 to 2,500 purebred cattle herds, to ensure adequate surveillance," he said. "If we find TB infection in any Texas herd, federal funds are available to pay ranchers for the animals, so the herd may be depopulated, to prevent the spread of disease."
"The Texas TB plan calls for surveillance through herd testing of dairies and purebred beef herds, because, during the past 20 years in Texas, TB infection has been detected in these classes of cattle. Infected animals may not exhibit clinical evidence of illness until they are in the latter stages of the disease, so conducting live-animal surveillance is an important tool in determining the status of these important herds," said Dr. Hillman.
Dr. Hillman said another major aspect of Texas' TB plan involves enhanced slaughter surveillance. The USDA has hired and stationed additional animal health technicians in federally inspected slaughter plants around the country. "Because this is our ongoing, first line of TB detection, slaughter inspection services must be fully supported," he said.
Other key components of the TB plan include controlling feeder cattle and rodeo stock imported from Mexico, a country that is known to have greater rates of TB infection than the U.S. "Mexican states have improved their TB control and eradication programs. The USDA has instituted additional import requirements on Mexican feeder cattle, and TAHC regulations require annual TB tests for Mexican-origin imported rodeo stock," said Dr. Hillman.
"In early 2003, the 12 TAHC commissioners adopted regulations that would require Mexican-origin imported feeder cattle to be completely separated from Texas animals," he said. "However, this regulation was 'on hold' indefinitely, as TAHC staff shortages and budgetary restrictions make it impossible for us to enforce this regulation. Furthermore, the number of TB-infected Mexican-imported feeders detected at slaughter has dropped to 13 so far this year. Instead, the commissioners have passed a resolution, urging the Texas cattle industry to voluntarily maintain Mexican-origin feeder cattle separate from native cattle."
"I believe we can regain our TB-free status," said Dr. Hillman. "The alternative is tantamount to throwing away nearly a century of disease eradication work. TB can damage our ability to market cattle freely, and if not addressed effectively, could destroy Texas' credibility as the country's leading cattle production state."
Texas Animal Health Commission
Box 12966 * Austin, Texas 78711 * (800) 550-8242 * FAX (512) 719-0719
Bob Hillman, DVM * Executive Director
For info, contact Carla Everett, information officer, at 1-800-550-8242, ext. 710, or ceverett@tahc.state.tx.us