For more than three years, consumer groups, members of Congress and scientists have warned of the inadequacy or insufficiency of government efforts to prevent the spread of mad cow disease into the United States.

The General Accounting Office, Congress's investigative arm, in 2000 criticized poor enforcement by federal inspectors of a ban on certain types of cattle feed believed to cause the spread of the disease. Sixteen months later it issued a second report making similar criticisms.

This year the Senate passed legislation banning the slaughter of disabled "downer" cattle, only to have the provision eliminated in a joint Senate-House version of the measure. The 41/2-year-old Washington state dairy cow -- the country's first known case of mad cow disease -- was slaughtered Dec. 9 as a downer animal.

Also this year, neurologist Stanley B. Prusiner, who won a Nobel Prize in 1997 for his work on prions, the cell proteins that cause mad cow disease, warned Agriculture Secretary Ann M. Veneman that the frequency and methods of testing cattle were inadequate to prevent the disease's spread to the United States.

Lisa A. Ferguson, senior staff veterinarian at the Agriculture Department's Animal and Plant Health Inspection Service, defended the agency's testing program, saying statistical studies showed that it was best to focus on animals with obvious health problems.

"We are testing animals for surveillance for animal health reasons to try to identify if the disease is present in the U.S.," Ferguson said in an interview. "The best way to do that is to focus on where we are most likely to find the disease if it is here."

W. Ron DeHaven, chief veterinarian at the Agriculture Department, said yesterday that federal officials are "looking at any necessary modifications" to the feed ban and had already planned to nearly double -- from 20,526 cattle in 2003 to 38,000 in 2004 -- the number of animals to be tested before slaughter. DeHaven also said the USDA is "well on the road" to developing a system to trace cattle from the slaughterhouse back to their birth farms.

"I hope this is a wake-up call," said Nancy Donley, president of the consumer advocacy group Safe Tables Our Priority. "The government has to plan and enforce preventive measures to make sure that these problems don't recur."

Bovine spongiform encephalopathy, or BSE, the brain malady known as mad cow disease, usually afflicts cattle that have eaten contaminated bone and protein meal made from the remains of other infected ruminants. {Cows are vegetarians!  Having them eat meat can make them sick.  Don't mess with Mother Nature.  CT} Health authorities have linked a similar human disorder to the consumption of contaminated beef.