Droves of Britons gave up meat during England’s mad cow outbreak in the 1980s, but since the discovery of an infected cow in Washington state, American vegetarians mostly have trod carefully, trying not to take advantage of a situation that could cost lives and cripple a $40 billion industry.

“I caution vegetarians from using mad cow disease as a recruiting tool,” said Joseph Connelly, editor of San Francisco-based VegNews magazine. “Mad cow disease is not a good thing no matter how you look at it.”

Vegetarians generally eat no meat, fish or poultry. Vegans eat no animal products at all, including dairy and honey.

Though vegetarian headcounts are imprecise, Britain’s meat-free population surged following its bout with mad cow, which killed 143 people, according to Tina Fox, spokeswoman for the Vegetarian Society of the United Kingdom.

She estimates up to 10 percent of the population is vegetarian, and up to 40 percent has reduced its meat consumption.

Vegetarian businesses and advocacy groups mostly say the discovery of mad cow in the United States still is too isolated to prompt people to change their diets.

“We’re not really at that stage,” said Charles Stahler, co-director of the Baltimore-based Vegetarian Resource Group. “They haven’t shown that anyone is sick, so it’s really very different here.”

For now, the discovery of one sick cow mostly will steel the minds of existing vegetarians.

“It’s giving them another good reason to stay firm in their beliefs,” said Carla Davis, managing editor of Glen Allen, Va.-based Vegetarian Times magazine, which has a monthly circulation of 300,000.

Ginger Riege-Blackman stocks food at the Concord Food Co-Op in Concord, N.H. Since the discovery of a mad cow case in Washington state, American vegetarians mostly have been careful not to take advantage of the situation.

Vegetarianism has been on an upswing in the United States. Vegetarian Resource Group estimates there are roughly 5.7 million adult vegetarians, up from about 2 million a decade ago.

Johanna Dwyer, a nutrition professor at Tufts University in Medford, Mass., attributes that to a growing awareness of healthy eating styles, and wider availability of vegetarian foods.

But she doesn’t think mad cow will spur more converts on its own, since many vegetarians have philosophical reasons, such as animal rights, that influence their food choices.

“That means buying into a whole bunch of things more than a health concern,” she said. “Some people may want to go meatless because of that, but I don’t think it will be many.”

One group that doesn’t seem concerned about appearing political is People for the Ethical Treatment of Animals. The Norfolk, Va.-based animal rights group has activists around the country distributing information about vegetarianism outside restaurants. Its new ad campaign: “You would have to be MAD to eat meat.”