The moratorium has been extended annually since 2001. National Geographic News has learned that the NIH-affiliated National Center for Research Resources (NCRR), which oversees federally funded primate research, has recommended that the breeding ban be extended for at least one more year.
"Chimps are very expensive animals to keep they need good-sized facilities, and live for a long time," said John Harding, the director of primate resources at NCRR, which is based in Bethesda, Maryland.
Scientists on both sides of the issue agree that there is little doubt that chimpanzees can be of great biomedical research value.
Researchers are now using chimps to test special antibodies known as monoclonal antibodies, which are genetically engineered to be almost identical to human antibodies, in the hope of finding cancer treatments.
"Other species will try to reject these monoclonals, but chimps won't because their system is very much like ours," said Stuart Zola, director of the Yerkes National Primate Research Laboratory at Emory University in Atlanta, Georgia.
He says the recent sequencing of the chimp genome will help scientists better understand human-specific diseases, as well as human evolution and traits such as language.
Yerkes is one of two NIH-funded facilities that use chimps for biomedical research. The other is the Southwest National Primate Center in San Antonio, Texas.
Zola and John VandeBerg, who directs the Southwest National Primate Center, warned in another Nature article that the number of chimpanzees available for research is declining. The pair argued that the breeding moratorium should be lifted.
Scientists' understanding of the physiology of chimps is still limited. Some researchers say that despite the genetic and biological similarities, humans and chimps differ greatly in their susceptibility to some diseases.
"Chimps are surprisingly bad models for human disease," Gagneux, the UC San Diego scientist, said. "Diseases don't progress in chimpanzees like they do in humans."
Gagneux calls for stricter guidelines for the ethical and humane treatment of research chimpanzees. While NIH rules stipulate that chimps can only be used for invasive experiments when no other animal model can be used, Gagneux would like to see a ban on all research that harms chimps.
"I'm not against animal experiments in principle, but I believe we can study chimpanzees without doing irreparable harm to them," he said.
"But if a completely new Hanta virus is discovered tomorrow that threatens to take over the world, and it turns out that doing something harmful to chimpanzees could immensely increase our knowledge of the virus, we would have to weigh that option."
Gagneux says biomedical researchers have special ethical responsibilities toward great apes. Among all the animals used in labs, chimps seem to be the only ones that are self-aware, and that puts them in a special category, he says.
Zola, the Yerkes director, disagrees.
"I don't think we should make a distinction between our obligation to treat humanely any species, whether it's a rat or a monkey or a chimpanzee," he said. "No matter how much we may wish it, chimps are not human."
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