Three mice infected with bubonic plague have been reported missing from a New Jersey bioterrorism research lab, but authorities say they most likely were eaten by their fellow test subjects - a possibility apparently overlooked by employees.
Their disappearance triggered a federal investigation. Although what happened to the mice is not definitely known, officials said yesterday there was no reason for the public to worry about a spread of the disease that killed millions of people during the Middle Ages.
The genetically engineered mice were among 24 being used in a trial of an experimental plague vaccine at the Public Health Research Institute on the campus of the University of Medicine & Dentistry of New Jersey in Newark.
When a lab scientist working on the experiment learned about two weeks ago that three mice could not be accounted for, the institute followed protocol and contacted federal authorities.
The investigation by the FBI so far has found no evidence of terrorism or even a crime at the lab, said Special Agent Steve Siegel of the FBI's Newark office. Lie-detector tests were given to several lab employees, he said.
"The FBI has expended a tremendous amount of manpower and resources on this matter," Siegel said.
The lab incident was first reported by the Star Ledger in Newark yesterday. It is unusual for the FBI to comment on an ongoing investigation, but Siegel said the agency decided to discuss the case "since there was a perceived risk to the public."
There were three sets of eight mice being used for the experiment - one set injected with a proven vaccine, one with the trial vaccine, and one receiving no vaccine. About three weeks ago, all were injected with the plague. The mice then typically die within three days, according to lab officials.
A scientist working on the trial could not get a satisfactory answer from the animal handlers who monitor and care for the animals as to why only 21 mice remained at the end the testing. Following lab protocol, the federal Centers for Disease Control and Prevention was called, and then the FBI, said David Perlin, president and scientific director of the institute.
Perlin said in a telephone interview that he is confident there is no way any of the mice could have escaped the lab and the building, or have been removed by a staff member. The best theory, Perlin said, is the mice were eaten by their cagemates and the lab staff didn't see the remains in the sawdust the animals live in when the cages were cleaned and sterilized.
"We believe it was inadvertent and the animal-care staff made a mistake," Perlin said. "That doesn't excuse it."
Perlin said workers would be retrained in proper handling of lab animals in such sensitive experiments.
The facility deals with about 10,000 animals a year, he said, and all need to be accounted for. Law enforcement would not have been notified, Perlin said, except that the plague is on a list of agents that could possibly be used by terrorists. Tuberculosis-infected mice, for instance, would not have rated the FBI investigation.
Security at the facility is tight. Of more than 100 employees, only eight have access to the lab working with the plague, Perlin said.
The employees must go through five separate electronic and manual security checkpoints before entering that lab while cameras capture their moves, he said. All those who worked on the experiment had clearance from the Department of Justice and were interviewed by the FBI after the mice couldn't be found, Perlin said.
Experts said there would be virtually no threat to the public even if the mice had somehow escaped.
The infected mice would have to be bitten by fleas, which would then have to bite humans to spread the disease. "And the odds of that occurring are ridiculous. It's hard to even imagine such a scenario," said Laurie Garrett, head of the global health program for the Council on Foreign Relations in New York, a think tank studying bioterrorism and other issues.