The last batch of chimpanzees to be used in medical research in America have been retired. The National Institutes of Health (NIH) declared in November that the last 50 animals kept for testing would no longer be used for the research.

Dr Francis Collins, director of NIH, said, "A lot of the things that we used to depend on chimpanzees or other animals, we can now actually do in other ways that are probably more reliable in terms of their predictability about what would happen in a human being. That's both good science and it also means we can be even more good stewards of our responsibility to these special animals".

"I want to be first to say, those chimps who participated in research, whether it was on AIDS or hepatitis C, they gave us all a gift by the things that we learned. Animal research is critical for many of the advances that have made it possible for people to live long and healthy lives, and that includes other non-human primates," he added.

The announcement was made after researchers said that no new proposals had come forward requesting the use of the animals. Chimpanzees have also recently been declared an endangered species.

The move from the NIH has been widely praised by animal rights groups. They are now aiming to move as many chimps as possible to Chimp Haven in Keithville, Lousiana.