Mice have become the world’s most used mammal in research.

Mice have become the world’s most used mammal in research.

Armin Rodler/Flickr (CC BY-NC 2.0)

PETA study finds 'dramatic' rise in use of lab animals in United States

The number of animals used by the top federally funded U.S. biomedical research institutions has risen 73% over 15 years, a “dramatic increase” driven mostly by more mice, concludes an animal rights group. They say researchers are not doing enough to reduce their use of mice, which are exempt from some federal animal protection laws.

The National Institutes of Health (NIH), which collected the data, says the analysis by People for the Ethical Treatment of Animals (PETA) is “inappropriate.” The analysis was published online today in the Journal of Medical Ethics.

Although the Animal Welfare Act requires that the U.S. Department of Agriculture track research labs’ use of cats, dogs, and nonhuman primates, smaller vertebrates—including mice, rats, fish, and birds bred for research—are exempt. To get a sense of the trends, PETA filed Freedom of Information Act requests for data from inventories that NIH-funded institutions must submit to NIH every 4 years to receive an “assurance” allowing them to do animal research.

Looking at the 25 top NIH-funded institutions, PETA found these institutions housed a daily average of about 74,600 animals between 1997 and 2003; that leaped to an average of about 128,900 a day by 2008 to 2012, a 73% increase. (Because institutions don’t report at the same time, PETA combined figures over three time periods.)

Most of the increase resulted from more mice, which made up more than three-quarters of the animals counted. This parallels a rise in the use of transgenic mice internationally, PETA says. Only the number of cats went down significantly (from 17 to seven animals on average).

In a written response to the study, NIH’s Office of Extramural Research cautioned that using the inventory data to track animal numbers is “inappropriate” because the data don’t show usage, but are only a “snapshot” that NIH uses to make sure institutions have adequate veterinary care. Moreover, more than 1000 institutions have assurances to use animals and including only the 25 largest could be misleading, especially because some provide mice to other institutions.

Even if the uptick is real, “The direction of the research is exactly the way the public and scientists want it to go—i.e., using species lower on the phylogenetic scales,” NIH says. Furthermore, NIH funds more research grants today than it did in 1997, so the rise “may reflect the overall increase in research” the agency says. (Indeed, most of the rise coincided with the doubling of NIH’s budget from 1999 to 2003.)

PETA’s Alka Chandna, a co-author of the paper, agrees that “in some sense it’s not surprising” that the number of animals used in biomedical labs has gone up. The point of the study, she says, is “that we need transparency” to understand whether federal policies that encourage research labs to reduce their use of animals are working. NIH should make the inventory numbers public, she says: “This is just a very fundamental, basic piece of information for the public to have.”

The National Association for Biomedical Research, which advocates for the use of animals in research, says it cannot comment on the study's design without seeing the underlying data. But the fact that the use of genetically modified rodents has increased in the United States is "unsurprising" given advances in biomedical research that use these animals, says Matthew Bailey, executive vice president  for NABR. He adds that it is "flawed" to suggest that knowing how many are used would lead to a reduction in their numbers. That has not happened in the United Kingdom, where numbers of research mice are reported publicly, Bailey points out.