Should a Vaccine for Wild Chimps Be Tested on Captive Ones?

Gorillas could be protected against Ebola too—but at a price.

Photo: Guenter Guni/Getty Images

May 27, 2014· 4 MIN READ
Richard Conniff is the author of House of Lost Worlds: Dinosaurs, Dynasties, and the Story of Life on Earth and other books.

Let’s say you have a technology that could save chimpanzee and gorilla species, our closest primate kin, from the almost certain prospect of extinction in the wild. But to make it work, you must first do biomedical testing on captive chimpanzees, a practice that has been denounced as cruel and largely unnecessary by the revered primatologist Jane Goodall and many others.

That’s the ethical dilemma posed by a study appearing today in the journal Proceedings of the National Academy of Sciences. It notes that outbreaks of the Ebola virus “have killed roughly one-third of the world gorilla population,” leading in 2007 to the listing of western gorillas as critically endangered. It reports the results of the first experiment to vaccinate captive chimpanzees against this notorious disease.

While the immediate focus is on Ebola, the coauthors, led by University of Cambridge population biologist Peter D. Walsh, suggest that the study sets a precedent. Effective human vaccines often languish because drug companies cannot justify the huge expense of doing proper trials to bring them to market, especially when they treat conditions found only in impoverished regions. Hence the Ebola vaccine in the study remains unavailable for human use. But “our study demonstrates that it is feasible,” the coauthors write, “even for modestly funded ape conservationists to adapt such orphan vaccines as conservation tools by confirming their safety and immunogenicity using trials on captive chimpanzees.”

Orphan vaccines could protect chimpanzee and gorilla populations not just from Ebola, they suggest, but also from the respiratory viruses that commonly spill over from field researchers and tourists, as well as from SIV (simian HIV), malaria, and other deadly afflictions. But only, Walsh argued in an interview, if they can be properly tested first in captive chimpanzees.

Walsh worked for many years in West Africa, at a time when Ebola was killing many of the chimpanzees and gorillas he and other researchers were studying. Eradicating the disease isn’t possible, because it has a natural “reservoir host” in fruit bats. But Walsh noticed “the wavelike spread of infection” moving predictably across populations and realized that it might be possible to contain an epidemic. “You figure out where it’s going to show up,” he theorized, “and you go ahead of it” with one of the Ebola vaccines that have already been tested in captive macaque monkeys. Vaccinating apes has the advantage of being relatively easy compared with ending logging or the commercial bush meat trade. Vaccinate chimps and gorillas—as Goodall famously did when polio spread to the population she was studying in the 1960s—and “you knock off one big part of the extinction equation with this one fix,” Walsh maintains.

Yet even as ape populations were being decimated, Wash was unable to convince major conservation groups to act. “Invasive medical management is like the third rail of wildlife conservation,” he explained. He argued that this scruple was out of date when epidemic disease was piling onto bush meat hunting and habitat destruction to drive great apes toward extinction in the wild. Finally, representatives of Seattle billionaire Paul G. Allen “heard my ranting” and put up the money to test the idea.

Because park managers, veterinarians, and others expressed concerns about using live vaccines in the wild, the study team chose to work with a novel vaccine technology, a virus-like particle, or VLP. It’s basically a fragment from the exterior of the virus, just enough to elicit an immune system response but not to cause an infection. The researchers tested the vaccine in two different formulations on a half-dozen captive chimps at the New Iberia Research Center in Louisiana. Following vaccination, the chimps all developed a robust immune response without apparent side effects.

For obvious reasons, the researchers did not go on to test the effectiveness of the vaccine by exposing the chimps to Ebola. Instead, they transferred immune properties from the chimps to experimental mice. All unprotected mice died on being exposed to Ebola. But of those receiving immune products from the more successful vaccine formulation, 60 percent survived. The research team has gone on to test the vaccine in a field study on gorillas in Africa; those results have not yet been published.

The coauthors of the current study go out of their way to make a political statement about biomedical testing. “To our knowledge, our study was the first conservation-related vaccine trial on captive chimpanzees,” they write. “It may be the last. U.S. government policy is now headed toward an end to biomedical testing on captive chimpanzees in the United States, the only developed country to allow such research.” If that happens, they warn, “there will be nowhere left to do conservation-related trials on chimpanzees. Thus in an effort to pay back an ethical debt to captive chimpanzees, the U.S. Government is poised to renege on an even larger debt to wild chimpanzees,” including the ones “that will die from viruses transmitted by American tourists and researchers.”

They argue for establishment of “a humanely housed captive chimpanzee population specifically dedicated to conservation research, with funding at a level comparable to the tens of millions of dollars the U.S. Congress has already allocated to house ‘retired’ research chimpanzees.” There’s precedent for such an effort: Four decades ago, Goodall was closely involved with the development, design, and operation of the Stanford Outdoor Primate Facility, a research enclosure dedicated to chimp conservation.

Asked to comment, Kathleen Conlee, vice president for animal research issues at the Humane Society of the United States, cited government reports that chimpanzees are largely unnecessary for biomedical research. When the Humane Society ran a 2009 undercover investigation of the New Iberia facility, she said, it found that only about 20 of 240 captive chimpanzees were involved in research studies. The rest “were simply being warehoused. We would argue,” she added, “that you don't need captive chimpanzees in U.S. laboratories” for the kind of experiments in the new study. “We have said that there could be the possibility of doing this study in the wild, or in sanctuaries in Africa that have chimpanzees that need protection from Ebola because they have exposure.”

Walsh countered that government officials in Africa would never allow experimentation with untested drugs on animals in the wild.

“I will never be able to test these vaccines,” he added, “if they shut down the labs.” Without that kind of direct attack on disease, he asserts, apes and gorillas cease to exist as they experience life today. “They’ll exist in zoos and wild populations that are effectively zoos, but they won’t be out there operating as part of the wildlife community.”

It comes down to a choice between individual rights and species survival, he said. Do we accept the ethical compromise of requiring a few individual chimpanzees to pass their lives in captivity to save entire species? Or do we stand on ethical purity and risk letting gorillas and chimpanzees vanish forever from the wild?