The USDA "needs to start to take some sort of corrective action in the low states," Lurie says.
But Linda Detwiler, DVM, counters Public Citizen's charges by saying that the variability between states is deliberate because the USDA targets its testing on animals that are most likely to have mad cow disease. Detwiler is a senior staff veterinarian with the USDA.
These include older cattle and dairy cattle, and these types of animals are not distributed evenly across the country, Detwiler tells WebMD. So variability from state to state is to be expected.
Shu Chen, PhD, director of protein analysis at the National Prion Disease Pathology Surveillance Center, which monitors the possible occurrence of a case of vCJD in the U.S., concurs with Public Citizen's view that the USDA's surveillance is inadequate and needs to be strengthened.
"More rigorous surveillance is needed ... so we won't regret it later on," Chen tells WebMD, referring to the potential for mad cow disease to make its way into the food supply and infect humans.
Chen points out that "Germany and Italy claimed that they didn't have BSE but when they looked hard and did more rigorous testing," they found that they did have cases of mad cow disease.
But he notes that even if mad cow disease is detected, it does not necessarily mean that cases of vCJD will be found. This is because it depends on whether the disease made it into the food supply and the extent of human exposure.
The USDA plans to increase its rate of surveillance from about 2,500 to 5,000 animals per year, Detwiler says. At this rate, the agency could detect an outbreak of mad cow disease that involved as few as 59 cattle among the 99 to 100 million cattle in the U.S.
She concedes that the agency could be doing more surveillance and that "we have requested funds for additional surveillance."
But Detwiler says the surveillance system, along with the ban on the importation of cattle, goats, and sheep from countries known to have cases of mad cow disease and the FDA's ban on ingredients in cattle feed that may cause mad cow disease, combine to provide a reasonable assurance that an outbreak in the U.S. will be prevented -- or at least detected early on.