4 October 2006

6 minute read

North America

This valuable status was lost in 2002 after two TB infected cattle herds were detected in Texas. Since September 2003, more than 335,000 cows in Texas’ 818 dairies, and nearly 129,000 beef cattle in 2,014 of the state’s seed stock or purebred herds have been tested for cattle TB, in a bid to ensure that all TB infection had been detected and eliminated, and that effective disease surveillance has been implemented.

“For cattle owners involved in regional and statewide stock shows and fairs, the benefit of TB-free status is immediate,” explained Dr. Bob Hillman, Texas’ state veterinarian. “Achieving free status enables Texas-origin cattle to be transported to events in the state without a TB test. Always check with show or fair officials, however, as they may establish more stringent requirements.”

USDA regulations also allow the 150,000 or so breeding and dairy cattle moved from Texas to other states each year to be shipped without a TB test. Dr. Hillman, who heads the Texas Animal Health Commission (TAHC), the state’s livestock and regulatory health agency, cautioned ranchers and accredited veterinary practitioners to check with states of destination prior to shipping cattle, as it will take time for animal health officials to update regulations recognizing Texas’ TB-free status. Also, because states are at liberty to impose rules beyond USDA standards, he said some states will keep TB testing requirements “on the books.” Cattle moved interstate from TB-free states for feeding purposes have not been required to have a TB test.

“We have reason to celebrate TB-free status, but we always must remain on guard against the re-introduction of TB infection into our state’s 14 million cattle. We know this ranking is fragile, having initially attained TB-free status in 2000, only to lose it in 2002, after two infected herds were detected. Two more infected herds were detected in 2003. These infected herds were depopulated,” said Dr. Hillman. He elaborated that TB-free status in 2000 extended to all of Texas, except the El Paso Milk Shed, where low levels of infection persisted or reoccurred for years, despite repeated quarantines, testing and removal of infected cows. The affected herds were depopulated with indemnity funds provided by USDA, and agreements specified that dairies could not be re-established in the
El Paso Milk Shed. Thus, TB-free status now applies to the entire state.

Cattle TB is caused by the bacterium Mycobacterim bovis, while human TB is attributed to M. tuberculosis. TBinfected cattle can develop tubercles, or encapsulated lesions in the lungs, lymph nodes, or in other internal organs.
Most often, cattle TB infection is first detected at slaughter plants, where inspectors examine carcasses for tubercles, which they collect and submit for laboratory confirmation. While awaiting lab results, the carcasses are held, or allowed to be used only in cooked products. Cooking meat, or pasteurizing milk (also a heat treatment process) kills TB bacteria.

“The effort to regain TB-free status has been a true partnership of ranchers, private veterinary practitioners, and state and federal animal health personnel,” said Hillman. “Everyone who has played a role deserves hearty congratulations for their diligence to ensure that Texas is again free of this dangerous disease that has been a concern to the livestock industry for nearly a century.”

Dr. Hillman said a TB Task Force, comprised of Texas cattle industry representatives and called by TAHC Chairman Richard Traylor in 2002, developed the winning strategy for regaining free status. He credited Dr. Dan Baca, a former TAHC TB epidemiologist, who is now in the USDA ranks, with advising the task force and helping to write the five-point plan that included:
• testing dairy and breeding cattle being moved from Texas (about 150,000 per year)
• TB surveillance of Texas dairies and statistically determined percentage of the state’s beef seed stock and
purebred herds
• improved inspection of carcasses by the USDA’s Food Safety Inspection Service (FSIS)
• yearly TB testing requirements for roping and rodeo steers imported from Mexico
• reducing the risk posed by Mexican origin feeder cattle, while continuing work with Mexican states to
control and eradicate TB in Mexico

“We could not have completed the five strategies and tested as many Texas herds without the funding support of the USDA and the cooperation of producers and accredited private veterinary practitioners,” Dr. Hillman explained. He noted that commercial beef herds and stocker cattle were not tested, as historically in Texas, these animals have not been found to be infected with TB. Dairy cattle, however, are procured from multiple sources and are in confinement conditions more conducive to disease transmission. Purebred and seed stock beef animals also are held in more confined areas and may remain in a herd for years and could spread TB, if they are infected.

“More than 500 accredited private veterinary practitioners licensed in Texas gained certification through a TB training refresher course and tested the dairy and beef herds through a ‘fee-basis’ arrangement. While all Texas dairies were tested, the more than 2,000 beef purebred and seed stock herds were drawn by random lottery. Nearly all herd owners involved were very cooperative, realizing the necessity to accomplish the disease surveillance. Herd owners had had to cover the expense of rounding up and holding cattle during the 72-hour testing period, but the fee-basis payment to the veterinarians covered the veterinary expenses.”

Keeping herds free of cattle TB is now the key, said Dr. Hillman, and he urged cattle producers to take precautions.
“Keep Mexican feeder cattle away from breeding herds,” he admonished. “Although we work with Mexico to help Mexican states control and eradicate cattle TB -- through sharing of disease information, TB testing and eradication protocols, and establishment of regulations aimed at elimination of the disease -- infection still exists in that country. Do not commingle Mexican feeder cattle with Texas cattle on pastures or in grower lots, and ensure that Mexican roping cattle or rodeo steers are held separately from Texas cattle. Also, dairy producers who purchase replacement heifers should assure that the animals originate from reliable sources and have a negative TB test prior to purchase.”

“If you purchase breeding cattle from other states, it is your prerogative, as a condition of sale, to request a TB test prior to accepting shipment of the animals. If breeding animals originate from states not TB-free – Minnesota, and parts of New Mexico and Michigan—a test is required. Sexually intact dairy cattle from any state must be tested prior to entering Texas, unless they originate from a TB accredited-free herd. You also may want to consider buying beef breeding stock only from herds that are accredited TB-free, which means the herd is tested annually under a voluntary program, certified by that state’s animal health officials,” said Dr. Hillman.

“Keeping our cattle TB-free status now is a matter of reducing risk and disease exposure,” said Dr. Hillman. “Our ranchers’ ability to move cattle interstate and the credibility of Texas’ cattle industry depends on achieving and maintaining freedom from diseases, such as cattle TB. For anyone who owns cattle, it means business.”

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