TB strikes cattle in southwestern states

Washington-As the United States Department of Agriculture (USDA)strips Texas of its tuberculosis (TB)-free status, TB spreads to a Californiadairy farm and has researchers looking to Mexico for the source.

At presstime, TB, a bacterial infection causing lesions in the lungs,lymph nodes or other internal organs, was limited to just one dairy herdin a state ranking first among the country's producers with more than 1.5million cattle, officials say. With that in mind, the possibility Californiacould lose its TB-free status has state leaders and producers on the "highestalert."

"As we understand it, taking away our status would require an outbreakat more than one dairy," says Steve Lyle, spokesman for the CaliforniaDepartment of Food and Agriculture. "But the ultimate problem wouldbe a huge economic one. Losing our TB-free status means any cow moving inor out of here would require additional testing, costing producers big andcausing lengthy delays."

Crossing the border

Texas, a state exporting 150,000 cattle a year, lost its tuberculosis-freestanding in June with the identification of two infected herds in less than48 months. The worst case occurred at a West Texas dairy where 67 animalstesting positive out of 160 on the milking line.

It had been more than a decade since the last outbreak.

"We strongly suspect without any proof that much of this tuberculosisinfection is originating out of Mexico," says Texas State EpidemiologistTerry Conger, DVM. "It likely circulates over here from the rodeo circuit.

"Mexican roping steers are acquired around here for backyard arenas.Even if they test negative at the border, that doesn't ensure they haven'tbeen exposed."

By contrast, Lyle refuses to confirm any Mexican-related suspicions.

"All we're willing to say is we know bovine tuberculosis has beenfound in Texas, Michigan and Mexico," he says. "We're really inthe formative states of tracing back the outbreak."

Michigan, currently reapplying for a form of TB-free status, lost itsranking in 1995 when wild whitetail deer were found with the disease.

"We're in a little different situation than Texas and California,"State Veterinarian Nancy Frank says. "We have a case where TB spilledover into wildlife and re-infected our cattle. Nobody really knows how."

USDA takes action

Despite doubt in California, USDA has raised health standards for importingMexican feeder cattle to protect U.S. livestock, conducting in-depth TBstatus reviews in 16 Mexican states.

Cattle movement across any TB-infected border, whether it is a stateor country line, must be tested 60 days ahead of time.

Texas and California can reapply for TB-free status once two years havepassed with no new outbreaks.