The US Food and Drug Administration (FDA) has a message for researchers working on transgenic animals, but first it has to find them. The agency sent a letter this month to land grant universities, warning that it takes an interest in research involving genetically engineered animals — an interest that could include site inspections — but the agency is still unsure of the true size of the field it is attempting to regulate. The May 13 letters went to 70 schools involved in agricultural research.

"We know there's more than that, but we don't know how many investigators there are or how many species," said John Matheson, the FDA toxicologist in charge of explaining the rules to scientists.

To date, FDA has concerned itself largely with transgenic animals intended for human consumption. But following a recent incident in which pigs involved in bioengineering research were sent to a slaughterhouse, the agency is extending its scrutiny to scientists trying to design animals to be living pharmaceutical factories or models for human disease if their research subjects are cows, pigs, sheep or other species that could end up in a grocery case. The FDA is not interested in rats, mice or other animals that do not usually have a place in the human food chain.

The FDA rests its right to regulate the transgenic animals on the premise that the genetic material scientists insert in the process of bioengineering animals is the equivalent of an experimental drug. The agency says it wants to make sure genetically engineered animals are kept out of the food supply, and that concern extends to creatures not specifically created for consumption.

"We're not trying to load on the bureaucratic issues. We're trying to get a grip on the size of this problem," said Matheson.

FDA is planning an educational campaign to make sure universities are aware of their responsibilities as sponsors of genetic research, he said.

"We were not aware of the FDA's position on this," said Candice Yekel, director of the office for research protection at Pennsylvania State University. "That was news to us," she told The Scientist, referring to the FDA's "reminder" letters. Penn State genetic researchers are not working with food animals, she said.

FDA's interest in transgenic lab animals was provoked earlier this year when it was discovered that between April 2001 and January 2003, researchers at the University of Illinois, Urbana-Champaign (UIUC) sold 386 pigs produced in bioengineering efforts to a livestock dealer, who in turn sent them to a slaughterhouse.

The pigs were normal offspring of normal and bioengineered parents, and all the animals were tested before being sold to make sure they did not carry the trans gene, according to Melanie Loots, associate vice chancellor for research at UIUC. The school is cooperating with FDA's continuing investigation to verify that the pigs were free of trans genes.

Matheson said the agency has entertained requests from some institutions to approve the sale for consumption of normal animals produced during bioengineering. "It's a legitimate question," he said. "It costs a lot to burn animals." But FDA wants to be consulted in advance, in writing, about the disposal of normal or engineered livestock, he added. Investigational site visits to verify research records on genetically modified animals are also a distinct possibility, he said.

Both the FDA and the University of Illinois agree that the trouble there involved bad communication rather than wrongdoing.

"We're not out to punish anyone. We're out to correct and address this one issue," Matheson said.