BOSTON – New England could lose thousands of blood donors, under new regulations adopted by the Red Cross aimed at protecting the blood supply from mad cow disease.

Under the Red Cross plan, scheduled to go into effect in September, donors who have a cumulative time in Europe of six months from 1980 to the present, or three months in Britain, would be rejected.

The restrictions would disqualify about 14,000 of the approximately 175,000 donors who give blood in New England every year, a Red Cross official told The Boston Globe.

There have been no identified cases of mad cow disease in American cattle. A human form of the disease, called new variant Creutzfeldt-Jakob disease, has claimed victims in Britain and other European countries, but has not been reported in the United States.

There is no evidence that the human variety can be spread through blood transfusions.

But while the risk to Americans remains “theoretical,” it is likely the disease will expand to the United States “at some point,” said Stephanie Millian, spokeswoman for the New England Region of Red Cross Blood Services.

“Our number one concern is the safety and availability of blood,” Millian said.