Law makers from the last major industrialized country to still use apes for experiments, the United States, proposed bills on Wednesday banning medical research on chimpanzees in the US.
"Scientists worldwide have halted chimpanzee experiments, because these intelligent creatures suffer immensely and are poor models for researching human diseases," said Elizabeth Kucinich, director of government affairs for the Physicians Committee for Responsible Medecine.
Her research ethics group has campaigned for the bills now being sponsored in the Senate and the House of Representatives.
Democratic Senator Maria Cantwell of Washington, Independent Senator Bernie Sanders of Vermont and Susan Collins, a Republican senator, are sponsoring the Great Ape Protection and Cost Savings Act, which would put an end to experiments on chimpanzees.
It would also mandate the release to sanctuaries of chimps owned by the government and bar the breeding of chimpanzees for experiments.
Representative Roscoe Bartlett, a Republican who worked with some of the first chimpanzees in space as a research scientist in the 1950s and 1960s, is introducing a companion bill in the House with fellow Republican congressman Dave Reichert and Democrats Edolphus Towns, Steve Israel and Jim Langevin.
Last year, the European Union banned the use of chimpanzees, gorillas and orangutans in experiments and set restrictions on using other primates, after similar measures passed in Japan, Australia and other wealthy nations.
About 1,000 chimpanzees remain in labs in the United States, including half that belong to the government-run National Institutes of Health.
Their numbers are dropping due to a ban on reproduction in captivity and because importing them is against the law.
Some researchers continue to mount a vigorous defense of using animals like mice and chimpanzees in labs to advance medical research.
"We've made a lot of progress in research on hepatitis using chimpanzees," Southwest National Primate Research Center director John VandeBerg told The Washington Post in an interview published last month.
He said the experiments led to the development of "many drugs for treating both hepatitis B and C."
For his experiments, chimps infected with hepatitis underwent two medical examinations where blood was drawn to gauge the levels of the virus, while two needle biopsies extracted tissue from their livers for examination.
"The animal rights people make it seem like it's a horrible thing to do," VandeBerg said. "It's a very simple clinical procedure. It's not painful."