Jul 14, 2004 (CIDRAP News) A draft report by the inspector general of the US Department of Agriculture (USDA) says the department's expanded surveillance program for bovine spongiform encephalopathy (BSE) has several flaws that could lead to unreliable estimates of the prevalence of BSE in American cattle.
The report says the plan is based on some questionable assumptions, does not accurately reflect the geographic distribution of cattle, and does not ensure the testing of all high-risk cattle. In addition, the report says that in the past 2 to 3 years, more than 500 cattle that had possible symptoms of neurologic disease were not tested for BSE.
"The problems disclosed during our review, if not corrected, may negatively impact the effectiveness of USDA's overall BSE surveillance program . . . and reduce the credibility of any assertions regarding the prevalence of BSE in the United States," the 54-page report states.
At a news briefing yesterday, Ron DeHaven, administrator of USDA's Animal and Plant Health Inspection Service (APHIS), said that the report largely reflects the surveillance program as it existed in March and that USDA is already addressing many of the problems cited in the document. The USDA posted a transcript of the briefing on its Web site.
The draft report was released a day early by Rep. Henry Waxman, D-Calif., who has been a critic of the USDA. It was scheduled to be released today at a hearing of the House Committee on Government Reform.
DeHaven said inspector general's reports ordinarily are not released until the agencies involved have had a chance to review and comment on them.
Before the nation's first BSE case was found in Washington last December, the USDA had been testing about 20,000 cattle per year for BSE, focusing on disabled cattle and those showing possible signs of central nervous system (CNS) disease. After the first case turned up, the department moved to increase testing. The expanded surveillance was launched in June with the aim of testing more than 200,000 cattle over the next 12 to 18 months.
The testing effort focuses on cattle that can't walk (downers), those showing CNS signs or other possible signs of BSE, and those that die on farms. Plans also call for testing about 20,000 apparently healthy older cattle, chosen at random. If 268,000 cattle are tested, the program should make it possible to identify the disease at a level of 1 case in 10 million cattle with 99% confidence, the USDA has said.
The inspector general's report cites several alleged flaws in the expanded surveillance program:
- The plan assumes that BSE is confined to high-risk cattle, but studies show that healthy-looking animals can have the disease.
- Testing only 20,000 apparently healthy older cattle may not give an accurate measure of the prevalence of BSE in the 45 million adult cattle in the nation.
- APHIS cannot easily identify and test all the cattle in the high-risk population, especially those that die on farms, which make up the largest share of high-risk cattle.
- The current plan will not permit APHIS to obtain "a statistically appropriate geographical representation of the US cattle population."
The report says the surveillance as it has operated in recent months illustrate the problems with the USDA approach. In particular, of 680 cattle that were condemned at slaughter facilities because of possible CNS signs from fiscal years 2002 to 2004, it appears that only 162 were tested for BSE. The report blamed this on confusion over testing requirements and lack of coordination between APHIS and the USDA Food Safety and Inspection Service (FSIS).
In addition, USDA has not "adequately pursued" BSE testing for cattle that showed signs of rabies but tested negative for that disease, according to the inspector general. Laboratories that handle rabies testing have not consistently submitted rabies-negative samples for BSE testing, because there has been no formal mechanism for that.
At the news briefing, as recorded in the transcript, DeHaven insisted that USDA is "testing precisely the population of animals that we should be testing," including those with possible signs of CNS disease, downer cattle, and those that die before reaching a slaughter plant.
He said that in June, the first month of the expanded testing program, APHIS succeeded in testing samples from many cattle that died on farms: about 70% of the 11,000 cattle tested were in that category. He said officials had previously estimated that "dead animals" would constitute about 56% of all high-risk cattle.
Some of the dead cattle were collected directly from farms, while others were collected at rendering plants and salvage plants, DeHaven said. But regardless of where samples were collected, "for the most part those are animals off the farm," he added.
Keith Collins, the USDA's chief economist, acknowledged there is room for debate about the USDA's assumption that BSE is found only in cattle classified as high-risk. He said it "is not an assumption that is right or wrong," but one that makes it possible to estimate the sensitivity of the testing program. Following the report's recommendation, he said, "We are going to look at alternative approaches to that and see if we can provide a fuller context of the sampling program."
Concerning the charge that many cattle with signs of CNS disease have not been tested, DeHaven said, "We're not focusing on the past but ensuring that in this program and in the future we do collect those samples. So we have, for example, instructed our field staff, when in doubt take a sample."
DeHaven also asserted, "Nothing in the report would suggest there has been any compromise to public health." He said the USDA continues to take the most important precaution for protecting the public from BSE-tainted meat products: removing high-risk cattle parts, or specified-risk materials, from carcasses destined for the food supply.
Also at the news briefing, Barbara Masters, acting APHIS administrator, said a separate inspector general's investigation has turned up no evidence of wrongdoing in the USDA's assessment of the cow in Washington that was found to have BSE. A USDA veterinarian at the slaughter plant had examined the cow and determined that it was unable to walk, but others at the plant have alleged they saw the cow walking.
Masters said the inspector general's office has found "no evidence of any records falsification by FSIS or USDA employees related to the downer cow." DeHaven said it is not unusual for a cow with neurologic disease to go down and appear disabled but later get up again.
Transcript of Jul 13 USDA news briefing