It's possible the latest and fourth case of BSE in the United States is a natural but extremely rare occurrence.
Guy Longeragan, an epidemiologist and food safety expert at Texas Tech University, said Tuesday afternoon that the "atypical" form of BSE with which this California dairy cow was diagnosed "could be a spontaneous and extremely rare event, usually in older animals."
The case was diagnosed with what he called a protein fingerprint, similar to a DNA analysis.
Of the four BSE cases in this country, only the first one in 2003 was "classical" or typical BSE, which Longeragan said is known to be spread only through feed. The next two cases, discovered in 2005 and 2006, were both atypical cases and both were in beef cattle.
So little is known about the atypical form of BSE that its origin is a mystery and there appears to be no scientific trail to follow, he said. BSE has never shown to be contagious to other animals in either form.
Worldwide there have been 180,000 cases of classical BSE but only just over 60 atypical cases.
The U.S. Centers for Disease Control confirms this in its explanation of typical and atypical BSE. CDC reports that scientists in the UK in 2007 first suggested atypical BSE may be a distinct strain of prion disease, which is a protein. Unlike typical BSE, cases of atypical BSE may have risen spontaneously (although transmission through feed or the environment cannot be ruled out). The agency says French data support that theory about it being a sporadic disease.
Longeragan explained USDA will trace the latest infected cow to its origin and then investigate herd mates and related cattle going forward to the present, as has been done with all other cases.
He repeatedly stressed this event shows how effective are the monitoring systems USDA and other agencies have put in place.
"This is really an animal health issue and not a human health issue," added Colin Woodall, vice president for governmental affairs for the National Cattlemen's Beef Association.
Longeragan said, "This is an isolated event."
Woodall said NCBA and USDA have already been talking to U.S. trading partners and so far there has been no negative response from those export markets.
Longeragan outlined the many forms of protection the food system and human health system have put in place to protect the public from BSE:
- USDA import prohibition of infected cattle.
- Food and Drug Administration's ruminant meat and bone meal feeding ban.
- USDA's Food Safety Inspection Service requires the removal of "specified risk materials" such as spinal cord from carcasses.
- FDA and the Centers for Disease Control ban people who were residents of the UK during the time of the BSE outbreak from donating blood.
- USDA inspects all carcasses multiple times.
- USDA surveillance program tracks and tests 700,000 at risk animals, ongoing.
- International export restrictions agree to control and destroy all such diseased cattle and parts from such cattle.