February 6, 2004
Targeted TB test
An ambitious cattle herd tuberculosis (TB) testing program, launched statewide in November, is being credited with detecting cattle TB in a Texas dairy in Hamilton County.
The Texas Animal Health Commission (TAHC) is working with nearly 450 TB-certified private veterinary practitioners to provide TB herd tests for about 2,400 of the state's seedstock beef herds and all of Texas' 831 dairy herds before September 2004.
"Targeted, intensive herd testing is a major component of Texas' plan for regaining our cattle TB-free ranking, which was downgraded in 2002. Finding an infected herd this early in the testing effort indicates we are on the right track," said Dr. Bob Hillman, Texas' state veterinarian and executive director for the TAHC, the state's livestock and poultry health regulatory agency.
"While we never enjoy finding TB infection in our cattle herds, the identification of this dairy herd validates the necessity for testing our dairy and seedstock herds, and it also confirms that our herd surveillance program is working," he said. "The U.S. Department of Agriculture (USDA) is underwriting the TB testing program, so that we can train, certify and contract with accredited private veterinary practitioners to test herds for this bacterial infection. There is no cost to producers for the TB herd test. The USDA also will pay owners an indemnity for depopulating any infected herds that are found."
Of the 57 purebred herds and 82 dairies tested since November, the Hamilton County dairy is the first found to be infected, Hillman said. He explained that, in late December, the Hamilton County dairy was quarantined by the TAHC after a number of animals reacted to TB skin tests. TAHC veterinarians collected tissue from several of the dairy animals and forwarded the samples for confirmation testing to the National Veterinary Services Laboratory (NVSL) in Ames, Iowa.
"Lab results in mid-January confirmed the preliminary diagnosis, and we are working with the dairy owner to determine the most appropriate way to deal with the infected herd. The owner will have the option of depopulating the herd with fair market indemnity paid by the USDA, or he may retain the herd under quarantine for repeated testing, until all infected animals have been identified and removed," he said.
Hillman noted that a complete epidemiological investigation will be conducted to determine how infection was introduced into the dairy, and if it has spread to other herds.
He noted that by detecting the infected dairy, Texas is one step closer to reclaiming its cattle TB-free status. Texas initially earned the U.S. Department of Agriculture's (USDA) coveted TB-free ranking in 2000, but lost it in 2002, after two infected cattle herds were detected in 2001. In August 2003, a third infected cattle herd was detected and depopulated in Zavala County.
"Texas must prove to the USDA, and to other states, that we are conducting thorough TB disease surveillance in our state's domestic herds," Hillman said. "Since l983, cattle TB has been detected in 14 Texas dairies and five beef seedstock herds, identifying these classes of cattle as most likely to be infected with TB. Epidemiological reviews have shown that testing all of the state's dairies and at least 2,400 seedstock herds either will detect infection or provide assurance that Texas cattle are free of the disease."
Hillman said similar testing is underway in California, New Mexico and Michiganother states that have lost their TB-free ranking. An infected herd also was confirmed in Arizona in mid-January. That state that could lose its 'free' status, if a second infected herd is found within the next 48 months.
"Most often, the first case of cattle TB in a state is detected at slaughter, where meat inspectors examine carcasses and collect tissues for laboratory testing from potentially infected animals," Hillman said. "This is an effective method for routine surveillance. However, because of the resurgence of TB in Texas dairy and seedstock herds during the past few years, a more aggressive surveillance program was needed to supplement the slaughter surveillance program and identify infected herds quickly."
"I urge dairy and seedstock producers to contact the TAHC or their accredited veterinary practitioner about getting their herds tested," Hillman continued. "The herd test program targets adult cattle 24 months of age and older for TB skin tests, but owners may elect to have their younger, purchased heifers tested, also at no cost. Current USDA funding for herd surveillance testing is available another eight months. We have made a good start, but there is much more work to do to complete the program."
Producers can contact the TAHC Austin office at 1-800-550-8242, or their TAHC Area Office for more information and a list of accredited private veterinary practitioners certified to conduct the TB testing.