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Lab loses trio of plague mice

September 16, 2005 By Roxanne Khamsi This article courtesy of Nature News.

Risk to public is thought negligible.

Three mice infected with the bacteria that cause bubonic plague have gone missing from a laboratory in Newark, New Jersey. Authorities have launched a search for the animals and an investigation into how they might have escaped. But researchers are quick to add that the mice, even if they are on the loose, pose little risk to the public.

"At this point we are satisfied that there is no public-safety risk, but the investigation is ongoing," says Steve Siegel of the US Federal Bureau of Investigation (FBI) Newark office.

The mice, which carried Yersinia pestis bacteria, were being studied at the Public Health Research Institute as part of a vaccine experiment. The institute, which handles about 10,000 mice a year, had a total of 24 plague mice in this experiment. Eight of these had not been vaccinated, 8 had been given the best current vaccine, and 8 had an experimental version: each group is missing a mouse, and has been for the past two-and-a-half weeks.

There are many potential explanations. The rodents could have been stolen or accidentally incinerated along with bedding from the cages. It is even possible that they ate each other, as mice are known to do this when they have plague. The institute's director, David Perlin, acknowledges the possibility of theft, but says he thinks it is more likely to be "an honest mistake".

Terror research

Some estimate that research into plague and plague vaccines has tripled in the United States following fears of bioterrorism sparked by the 11 September 2001 attacks. This trend means there are more infected animals scattered about the country that could, potentially, go missing.

But experts have expressed surprise that such mice could actually escape. Research on plague takes place under tight security, in labs categorized as biosafety level 3 (out of a possible 4). Perlin adds there is some video surveillance in the institute.

"I've never heard of such an incident before in my life," says Brendan Wren, a scientist at the London School of Hygiene and Tropical Medicine who helped to sequence the DNA of the plague bacterium.

"The CDC is working with the FBI and local officials to see what happened," says Von Roebuck, a spokesman for the Centers for Disease Control and Prevention in Atlanta, Georgia.

Safe enough

If the mice did actually escape from the lab, they would have quickly died from the disease. And the animals' bodies wouldn't be expected to pose a risk after decomposing for several days.

Wren notes that having plague running wild is not as unusual as some might think. The Y. pestis bacterium can be found in many parts of the United States, and squirrels sometimes carry the disease in the southwest of the country.

According to the World Health Organization, between 1,000 and 3,000 people around the globe contract plague each year. The disease can be treated effectively with antibiotics.

The infection usually passes from mice to humans through fleas, but it can also be transmitted by breathing the infected breath of another animal.

Wren says this is an unlikely risk from escaped lab animals: “I can’t see the mice sneezing on a human.”


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