Texas Bovine TB Testing
Finds Infected Dairy Cattle

From Patricia Doyle, PhD
Texas Animal Health Commission (TAHC) News Release
An ambitious cattle herd tuberculosis (TB) testing program, launched statewide in November 2003, 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 2400 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.
"Of the 57 purebred herds and 82 dairies tested since November 2003, the Hamilton County dairy is the first found to be infected," said Dr Hillman. He assured consumers that milk from this herd is safe to drink, because the required, routine pasteurization kills TB bacteria.
Dr Hillman explained that, in late December 2003, 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 2004 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. Dr Hillman noted that a complete epidemiological investigation will be conducted to determine how infection was introduced into the dairy, and whether it has spread to other herds.
"By detecting the infected dairy in Hamilton County, we're one step closer to reclaiming our cattle TB-free status," he said. Texas initially earned the US Department of Agriculture's (USDA) coveted TB-free ranking in 2000, but lost it in 2002, after 2 infected cattle herds were detected in Texas 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," he said. "Since l983, cattle TB has been detected in 14 Texas dairies and 5 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 2400 seedstock herds either will detect infection or provide assurance that Texas cattle are free of the disease."
Dr Hillman said similar testing is underway in California, New Mexico, and Michigan -- other states that have lost their TB-free ranking. "An infected herd also was confirmed in Arizona in mid-January 2004. That state could lose its 'free' status, if a second infected herd is found within the next 48 months," he said.
"Most often, the first case of cattle TB in a state is detected at slaughter, when meat inspectors examine carcasses and collect tissues for laboratory testing from potentially infected animals," said Dr Hillman. "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."
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