Mad cow disease investigation complete


One of many Holstein cows in the Yakima Valley

Monday, Dr. Ron DeHaven, Deputy Administrator of Veterinary Services for USDA's Animal and Plant Health Inspection Service, announced that the field investigation of the case of BSE, or mad cow disease, in a cow that once was being milked at a Mabton dairy is complete.

DeHaven said the epidemiological tracing and DNA evidence proves that the BSE positive cow slaughtered in Washington on Dec. 9, 2003 was born on a dairy farm in Calmar, Alberta, Canada, on April 9, 1997. The Holstein was moved to the United States in September 2001 along with 80 other cattle from that dairy. A brain sample collected from the cow at slaughter tested positive for BSE on Dec. 23.

The epidemiological investigation to find additional animals from the source herd led to a total of 189 investigations. That led to complete herd inventories on 51 premises in three states: Washington, Oregon and Idaho. The inventories involved the examination of the identification on more than 75,000 animals. All herd inventories have now been completed and appropriate analysis of those inventories performed, said DeHaven. There are no premises remaining under hold order.

A total of 255 "Animals of Interest" were identified on 10 premises in the three states. "Animals of Interest" are defined as animals that were - or could have been -from the source herd in Alberta, Canada. All 255 animals were destroyed and BSE testing was negative on all of them. The carcasses from all of the euthanized animals were disposed of in landfills in accordance with all federal, state and local regulations, said DeHaven.

Included in the 255 animals of interest were 28 positively identified back to the group of 80 cattle that entered the U.S. with the index cow, as well as seven heifers out of a group of 17 heifers which were also known to be from the source herd. It is not believed that all of these 17 entered the U.S., but all of them would be considered minimal risk and not significant to the investigation, DeHaven said.

Guidelines on bovine spongiform encephalopathy (BSE) issued by the World Organization for Animal Health (OIE), the international animal heath standard setting organization, state that animals born on a premises within one year (before or after) of a BSE-affected animal should be considered of greater risk to the country reporting the BSE detection. As such, USDA focused on 25 of the 81 animals also born into the birth herd of the index animal. Based on normal culling practices of local dairies, APHIS estimated that the Agency would be able to locate approximately 11 of these animals. APHIS definitively located 13 of these animals, plus the index cow, for a total of 14.

DeHaven said USDA feels confident that the remaining animals represent very little risk. Even in countries like the United Kingdom where the prevalence of BSE has been very high, it is very uncommon to find more than one or maybe two positive animals within a herd, he said. Any of these animals showing nervous system disorder - or any that are nonambulatory at the time of slaughter - will be condemned and not allowed into the human food chain. USDA officials said animals slaughtered after Jan. 12 would have the specified risk materials removed and not allowed into the human food chain. Specified risk materials are those tissues or portions of the carcass likely to contain the infectious agent in an infected animal.

Over 2,000 tons of meat and bone meal being held due to potential contamination with protein from the positive cow is on hold and will soon be disposed of in a landfill in accordance with all federal, state and local regulations.

Of the 255 animals that were destroyed, 28 were part of the 81-cow herd that entered the U.S. with the infected Holstein. A total of 220 of the destroyed cows could have been part of the original herd.

Of the 81 that came in from Canada, 29 of which have definitively been accounted for, one is the BSE-positive cow that was located in the index herd in Mabton, nine were located in theMabton herd, three were located at a facility in Tenino, six were located at a facility in Connell, one was located at a facility in Quincy, three were located at a facility in Mattawa, one was located at a facility in Moxee, three were located at a facility in Burley, Idaho, one was located at a facility in Othello and another cow was located at a different facility in Mabton.

The USDA destroyed more than 700 cows, including 449 bull calves at a Sunnyside area feeding operation, a total of 134 animals in Mabton, 39 cows in Mattawa, 15 in Connell, 20 in Boardman, Ore., 18 in Quincy, four in Tenino, 15 in Moxee, three cows in Othello and seven in Burley.

All adult animals that were killed were sampled and tested for BSE. The bull calves depopulated at Sunnyside were not sampled because they were too young for the BSE agent to be detected. There have been a total of 255 samples taken from the animals depopulated in the Mabton index herd, the herds in Mattawa, Connell, Quincy, Tenino, Moxee, Othello, and the second Mabton facility, as well as facilities in Boardman and Burley. All samples have tested negative for BSE.

The report from the International Review Subcommittee was delivered to the Secretary of Agriculture's Advisory Committee for Foreign Animal and Poultry Diseases last Wednesday. That same afternoon, the co-chairs of the Advisory Committee and members of the Subcommittee provided the Secretary a copy of the report and briefed her on its content.

The report identified several positive findings and actions taken by the U.S. since finding this BSE positive cow, including:

• They commended the Department on the comprehensive and thorough epidemiological investigation, and suggested all relevant information had been obtained at this point. Their recommendation was to conclude the investigation.

• They stated that the tracing and recall of the rendered meat and bone meal that may have been contaminated with specified risk materials from the index case was effective and appropriate.

• They indicated that the U.S. ban on specified risk materials from cattle over 30 months of age removes the highest risk tissues from the human food supply and is in accordance with international standards.

• The Subcommittee confirmed the action taken by the Secretary in her Dec. 30 announcement to prohibit air injection stunning for slaughter animals.

• In addition, the Subcommittee confirmed the validity of the Secretary's announcement to prohibit Advanced Meat Recovery and mechanically separated meat from cattle over 30 months of age.

• The Subcommittee recognized the food safety merit of prohibiting nonambulatory cattle from entering the human food supply.

• They confirmed that the testing of all normal cattle slaughtered for human consumption to be scientifically unjustified, both in terms of protecting human and animal health.

• They recommended the adoption of rapid screening tests, which is consistent with the USDA's announcement to accept applications for licensure of such tests.

• The Subcommittee acknowledged the importance of effective animal identification and traceability systems.

• The subcommittee acknowledged the efforts of the US government to follow a science-based approach to policy formulation.

The Subcommittee also made several recommendations, all of which are being fully analyzed by USDA and the Food and Drug Administration colleagues.

These include a recommendation for a very aggressive surveillance program that tests all high-risk animals. The results from that intensive surveillance could then be considered in an evaluation of the overall BSE program. The Subcommittee also suggested that consideration be given to random sampling of animals greater than 30 months of age at slaughter, to encourage disease reporting at the farm level.

The Subcommittee also recommended that a number of laboratories throughout the United States should be approved by USDA's National Veterinary Services Laboratories to conduct screening tests as part of the national surveillance program.

The subcommittee, too, urged the United States to collaborate with the global community in the evaluation and validation of new BSE diagnostic tests.


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