The facilities at Johns Hopkins University house nearly 200,000 mice.
The government shutdown is likely to mean an early death for thousands of mice used in research on diseases such as diabetes, cancer and Alzheimer's.
Federal research centers including the National Institutes of Health will have to kill some mice to avoid overcrowding, researchers say. Others will die because it is impossible to maintain certain lines of genetically altered mice without constant monitoring by scientists. And most federal scientists have been banned from their own labs since Oct. 1.
"I'm sure it's chaos at the NIH for anyone doing mouse experiments," says Roger Reeves, a researcher at Johns Hopkins University in Baltimore who uses hundreds of so-called transgenic mice in his work on Down syndrome.
NIH officials say they aren't doing media interviews. So Reeves and other scientists at Johns Hopkins agreed to talk about what a shutdown would mean for their lab animals and the research these animals make possible.
The loss of so-called transgenic mice, many of which have genes that cause them to develop versions of human diseases, is especially troubling, scientists say. A single animal can cost thousands of dollars to replace, they say. And some cannot be replaced at any cost.
To maintain a colony of transgenic mice, every new pup must have its DNA tested by a highly trained researcher, Reeves says. The animal care staff now in charge of NIH mice would not be able to do the testing, he says. So, once federal scientists knew a shutdown was going to happen, they probably had to choose certain mice to eliminate.
"If I thought we were going to be down for two weeks we certainly would reduce the colony," Reeves says. "If I thought it was going to be a month then I would take a little harder look. And if I thought it would be longer than that then we really would have to take things off the shelf."
By "off the shelf," Reeves means freezing some embryos and killing an entire line of mice. Reviving a line that has been "frozen down" can take months and cost thousands of dollars, he says.
Bob Adams is a lab animal veterinarian at Johns Hopkins University.
Bob Adams is a lab animal veterinarian at Johns Hopkins University. Maggie Starbard/NPR
Reeves has seen what a government shutdown can do to research. He was at a government lab in the 1980s when a shutdown forced him to walk away from his experiments with cell cultures. The experiments were ruined, he says. "It was a complete waste."
Shutdowns in the 1980s typically lasted no more than a few days. The current one promises to go on for weeks. And that could be disastrous for researchers, says Carol Greider, a researcher at Hopkins, and a 2009 Nobel Prize winner. "Not being able to breed mice for several weeks could really shut down years' worth of experiments," she says.
The NIH will face another problem with its mice, researchers say: overcrowding. Ordinarily, the NIH keeps more than 300,000 mice on hand. But that number has almost certainly been growing quickly since the shutdown, says Bob Adams, who is in charge of research animals at Johns Hopkins.
"Every 21 days a female mouse can have a litter," which can mean 10 or more pups, he says. "So you can see it's a geometric progression of how many mice you would have to deal with."
A female mouse can have a litter of six to 10 pups every 21 days.
A female mouse can have a litter of six to 10 pups every 21 days. Maggie Starbard/NPR
The mouse facilities at most research institutions run near capacity, Adams says. And national guidelines for research animals prohibit crowding more mice into the same space, he says.
"We might start moving animals around to facilities where we have some room," Adams says. "But at some point we would probably have to start euthanizing animals."
It's not clear how much of that has already occurred at NIH. One reason is that federal researchers had been keeping fewer mice than usual because of budget cuts from sequestration.
In response to questions about mice at the NIH, a spokesperson provided a written statement saying that institute directors are "developing approaches to manage the population of animals so as not to delay experiments further after the shutdown has ended and taking into consideration facility constraints during the shutdown."
Managing the population of NIH mice won't be easy, Adams says. The first thing he would do if Hopkins faced a shutdown would be to separate male and female mice, he says. That would require a lot of extra cages. And pregnant females would still be producing new litters for weeks, he says, which would require many more cages.
Within a couple of weeks of a shutdown, Hopkins would run out of room, Adams says. Then he would have to start bringing animals to a machine that includes a stack of airtight chambers.
Mice cages would be placed in the cages and the machine turned on, he says. "It slowly brings up the carbon dioxide levels so they essentially get anesthetized and then they eventually suffocate," he says
Biomedical research often involves killing animals, Adams says. But usually there is a compelling scientific reason.
Ginny Miller, an animal care specialist, places mice into a machine that will first anesthetize, then euthanize the mice by slowly increasing the level of carbon dioxide in the air.