The U.S. Agriculture Department’s blunder in failing to test a condemned Texas cow for mad cow disease may reflect wider problems in the government’s surveillance program, a Democratic lawmaker said on Thursday.

The USDA last week acknowledged it erred in failing to test a 12-year-old cow for the brain-wasting disease when the animal arrived at a Texas slaughterhouse exhibiting a possible central nervous system disorder.

A USDA supervisor in Austin, Texas refused to test the animal despite requests from federal animal health inspectors, said California Rep. Henry Waxman.

“This sequence of events is troubling, and it raises the question of whether this is an isolated incident,” Waxman said in a letter to Agriculture Secretary Ann Veneman.

Under USDA standards, all animals suspected of a central nervous system problem must be tested for mad cow disease as a precaution.

The USDA is expected this week to wrap up its investigation into the Texas cow incident.

Waxman questioned the effectiveness of USDA’s surveillance program, saying the department apparently does not track how many condemned cows are actually tested for the disease.

The USDA condemns about 250 cows each year because of signs of central nervous system damage, Waxman said.

“We look forward to having the opportunity to review and respond to the Congressman’s letter,” USDA spokesman Ed Loyd said.

The USDA is trying to put into place by June 1 a system that would test nearly all suspicious cattle, more than 200,000 during an 18-month period, for mad cow disease.

However, that level of testing is not enough to satisfy Japan, which has refused to resume U.S. beef shipments unless the United States tests all cattle bound for the Japanese market. Last year, Japan was the biggest buyer of American beef, with $1.4 billion in purchases.

American and Japanese officials will meet Tuesday in Tokyo to discuss the trade ban.

“We’re trying to set a precedent here to guide trade with Korea and with Mexico and with every other country of the world,” said U.S. Agriculture Undersecretary J.B. Penn. “We think we’ve got a process in motion that’s got an endpoint to it.”

With more cases of mad cow disease likely to emerge around the world, countries need to follow scientific guidelines set by an international animal health group known as the OIE, Penn said. “A lot of countries aren’t following the guidelines,” he added.