The use of chimpanzees in medical research, already seriously waning in recent years, would decline even further under new rules proposed Tuesday by the National Institutes of Health (NIH). The United States and Gabon are currently the only nations that allow medical research to be conducted on chimpanzees.

The NIH is already in the process of retiring many of its 400-plus research chimps — in fact, nine apes moved to a new sanctuary in Louisiana just this week — but the new rules would retire even more animals and place strict limits on further research.

Although all chimpanzee species and subspecies are listed as endangered and face declining populations, the apes have long held a special distinction under the Endangered Species Act, which allowed them to be bred in captivity and used for science or exhibition as long as new apes were not imported into the country. Some scientists predict that wild chimpanzees could go extinct in the next few decades.

Current research projects will be allowed to continue under the proposed NIH rules, but new research projects would be restricted to studies that could not be conducted on humans, rats, monkeys or other animal species. Any of the animals kept for research — the NIH is recommending keeping what could be called an emergency backup population of 50 apes — will need to be housed under new conditions designed to improve their physical and social health, including letting them live in social groups and using open habitats of at least 1,000 square feet per chimp. Any proposals for new research projects would need to be approved by a designated review committee.

The NIH has been mulling these new rules since late 2011, when a panel of scientific and medical advisors concluded that further use of chimps in medical research could be considered inhumane and costly and was unlikely to produce any further dramatic results. Chimpanzees have had some value in medical research, most notably for the development of vaccines for hepatitis A and B decades ago, but more recent research into HIV treatments has been fruitless.

Animal rights groups praised the proposed rules. "These recommendations reinforce what the public has been asking for, which is a move away from invasive research and getting chimps to sanctuaries," Kathleen Conlee, vice president of the Humane Society of the United States (HSUS), told The Washington Post. HSUS has been pushing to remove chimps from research studies for several years.

Housing retired medical chimps will not be cheap and could cost $20,000 per animal per year. Those funds have not yet been allocated in the federal budget.

As with all federal policy changes, the public may comment on these proposed rules for the next 60 days, after which NIH Director Francis Collins will have the opportunity to accept or reject the rules.

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