With the retirement of 110 government-owned chimpanzees, the end of medical research on man's closest living relative may be near.

Today, the National Institutes of Health announced that all of its chimps now living at the New Iberia Research Center would be permanently removed from the research population.

Long criticized by animal advocates for mistreating animals and illegally breeding chimps, New Iberia operates the largest research chimp colony in the United States and is a bastion of a practice abandoned in every other country.

"This is a major message from the NIH: that this era is coming to an end," said John Pippin of the Physicians Committee for Responsible Medicine, an animal advocacy group. "This is huge."

In December of last year, an expert panel convened by the Institute of Medicine, the nation's medical science advisers, declared that medical research on chimpanzees was ethically problematic and, in most cases, scientifically unnecessary. The NIH announced a moratorium on new chimp research funding and agreed to review the status of its own animals. After years of fighting for an end to medical research on chimps, whose ability to think, feel and suffer is not far removed from our own, animal advocates greeted that news with cautious relief. The NIH's intentions sounded good, but what they'd actually do remained to be seen.

With the decision to retire 110 chimps at New Iberia, the NIH leaves little doubt of its plans. “This is a significant step in winding down NIH’s investment in chimpanzee research based on the way science has evolved and our great sensitivity to the special nature of these remarkable animals, our closest relatives,” said NIH director Francis Collins to the Washington Post.

Excluding the retired chimpanzees, the NIH still owns an estimated 475 chimps eligible for research. Another 500 or so are owned by pharmaceutical companies. The NIH's decisions influence their fate as well, said Pippin.

"With this indication that the NIH is going to get out of chimp research, that's going to drop the bottom out of the whole chimpanzee research enterprise," Pippin said. "How are you going to justify your research in light of what the IOM and NIH have said? Even those not directly affected by this prohibition are going to give up. They do not have scientific or ethical justification to continue."

Kathleen Conlee, animal research director with the Humane Society of the United States, was more measured in her response.

"They're taking a step in the right direction by deeming these chimps ineligible for research," she said. "But we'd rather see them go to sanctuary." She noted that while 10 of the New Iberia retirees will be sent to the Chimp Haven sanctuary, the rest will go to the Texas Biomedical Institute's Southwest National Primate Research Center.

Though the newly retired chimps won't be used again in medical research, that type of research still occurs at Southwest. Indeed, it was an attempt to send retired chimps back into research at Southwest that sparked the controversy that led to the IOM report and NIH review.

"Places like Southwest were built to be research labs. We'd urge the chimps to be sent somewhere where the mission is the well-being of chimps," Conlee said. According to Conlee, housing animals at Chimp Haven costs the government $40 per day, compared to $60 per day at research laboratories.

Conlee said that some companies, including Abbott Labs and Idenix, have agreed to follow the IOM guidelines for chimp research or abandon it altogether. Others, including GlaxoSmithKline, have already given up.

Rather than relying on corporate goodwill, however, both Conlee and Pippin urged people to support the Great Ape Protection Act and Cost Savings Act. Now under Congressional consideration, the bill would end on medical research on chimps.