The genes of cattle can be altered to omit a protein that causes the mad cow disease without any adverse effect on the cattle. Scientists at Hematech Inc., a unit of Japanese company Kirin Brewery Co., and the U.S. department of agriculture found that cows bred without the prion protein were healthy at age 20 months and their tissue showed signs of resistance to the brain-destroying disease called bovine spongiform encephalopathy.

The disease is fatal to cows and has also lead to some 200 human deaths in the last 10 years.

The scientists' findings, published in the journal Nature Biotechnology, say that the alteration can offer protection to the cattle from the disease, which in turn can completely wipe out the disease. They said the cattle produced with the genetic modification did not have the prions, which is a protein in the nervous system, which when becomes damaged and spreads to an animal's brain tissue causes the collapse of the cow's central nervous system. It leads to the mad cow disease and other related diseases like scrapie in sheep and Creutzfeldt-Jakob disease, or CJD, in humans, the researchers added.

The man, whose case was reported to the CDC by the Virginia Department of Health, has variant Creutzfeldt Jakob Disease, or vCJD, the CDC said on its Web site.

This is a carefully diagnosed, brain-destroying illness that scientists believe is caused by eating beef products from cattle infected with bovine spongiform encephalopathy, also known as BSE, or mad cow disease.

"The current patient has no history of donating blood and the public health investigation has identified no risk of transmission to U.S. residents from this patient."

The current case-patient has no history of receipt of blood, a past neurosurgical procedure, or residing in or visiting countries of Europe. Based on the patient's history, the occurrence of a previously reported Saudi case of vCJD attributed to likely consumption of BSE-contaminated cattle products in Saudi Arabia, and the expected greater than 7 year incubation period for food-related vCJD, this U.S. case-patient was most likely infected from contaminated cattle products consumed as a child when living in Saudi Arabia (1). The current patient has no history of donating blood and the public health investigation has identified no risk of transmission to U.S. residents from this patient.

An examination of the Alabama cow identified as the third U.S. case of mad cow disease showed the animal was at least 10 years old, meaning it was born before the 1997 feed ban was implemented, U.S. officials said Thursday.

The U.S. Agriculture Department also said federal officials located a six-week-old calf that belonged to the infected animal. The calf has been quarantined and moved to USDA's lab in Ames, Iowa, for further observation.

The animal was exhumed and its teeth examined to confirm that it was at least 10 years old.

Separately, USDA officials said the department was drawing plans to scale down its mad cow surveillance program, which found two of the three U.S. cases of the disease.

Japanese consumers, already wary of eating U.S. beef due to mad cow fears, will become even more concerned if the United States goes ahead with plans to cut back on its mad cow testing, Japanese Vice Agriculture Minister Mamoru Ishihara said at a news conference on Thursday.

The mystery has deepened in recent weeks. Only at the end of May did local health officials see a second elderly woman die of the incurable disease involving a malformed protein, or prion, that kills brain cells. After that, they learned of three other suspected cases, including a CJD death in February that was reported only last month.

vIs what is happening in Idaho an anomaly, a statistical fluke? That is possible," said Ermias Belay, a top CJD expert with the Centers for Disease Control and Prevention in Atlanta who is helping advise officials in Idaho. "But once it exceeds 1.5 or 2 per million, you start asking questions."

"If they are all confirmed, it could be odd."

In a year, the United States typically sees fewer than 300 CJD cases, which mete out rapid death to the elderly, according to the Centers for Disease Control.

The infected 12-year-old beef cow was born, raised and used for breeding at the same ranch and had never left the property, authorities said Thursday. They would not identify the ranch or the size of the herd.

Agriculture officials announced Wednesday the latest confirmed case of mad cow disease in the United States had been traced to the animal, which was a "downer" that could not walk. The cow arrived dead at a pet-food plant in Waco, Texas, in November and never entered the nation's human food supply.