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 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.