Great Ape Diseases
Aside from their help in investigating and treating human diseases, chimpanzees have played a significant role in the development of prophylactic vaccines against diseases that kill African great apes. Each species of African great apes including chimpanzees, gorillas, and bonobos remain endangered, according to the Jane Goodall Institute. African apes are largely confined to the relatively intact forests of Equatorial Africa, and Chimpanzees are extinct in 4 of their 25 range countries (Gambia, Burkina Faso, Togo, and Benin). While these animals numbered about 1 million at the turn of the 20th century, today’s estimates put their numbers at between 172,000–300,000.
The causes for the demise of these animals include habitat loss as a result of conversion of land for agriculture, armed conflict among local human populations, and the commercial bush meat and illegal exotic pet trades. Infectious diseases also pose a serious threat. Pathogens that threaten wild gorillas and chimpanzees may be those that circulate in other forest animals (sylvatic pathogens), pathogens that spill over from humans (reverse zoonotic pathogens), and pathogens that circulate persistently within wild ape populations (enzootic pathogens).
Perhaps the best known pathogen to recently threaten African apes was (and is) the Ebola virus. Over the last two decades the Zaire strain of Ebola killed about one third of the world’s gorilla population and only a slightly smaller proportion of the world’s chimpanzees. Although these large Ebola Zaire outbreaks in great apes have been documented only in Gabon and the Republic of Congo, chimpanzees in Ivory Coast have been killed by another strain, Ebola Cote d’Ivoire.
Since many of the diseases are spilling over from humans, concern about the great ape’s vulnerability is increasing, with some advocating vaccination against common human childhood diseases.
FASEB noted in its presentation “Chimpanzee Research Helps Chimpanzees and Other Great Apes” that thousands of wild chimpanzees and gorillas have died from Ebola, which kills 95% and 77% of affected gorillas and chimpanzees, respectively. The disease alone led to a 32% decline in world populations.
Chimpanzee studies have proven invaluable in developing vaccines aimed at protecting wild apes. An ebola vaccine trial conducted in chimps in 2011 led to the development of a potential vaccine for wild gorillas, whose populations had already been reduced by a third due to the virus. The project was conducted at the New Iberia Research Center, a branch of the University of Louisiana, Lafayette with a vaccine manufactured by Integrated Biotherapeutics. The vaccine consists of a virus-like particle containing viral proteins but not the viral genome and therefore can neither be infectious nor reproduce in vivo. The vaccine was tested to determine its safety and whether it could trigger a potentially protective immune response.
Primatologist Peter Walsh, the driving force behind the experiment, ultimately wants to vaccinate wild chimpanzees and gorillas against Ebola, and he hopes this test will help get past some hurdles. “The objective is to show the conservation community that the vaccine won’t kill chimpanzees or gorillas,” he said to Science last February.
And the problem is reaching critical proportions: Apes are indeed passing the virus to each other within social groups, between social groups, and even between species. Scientists believe that control measures should be “initiated as soon as possible” to avoid the reduction of once widely distributed ape species to “tiny remnant populations.”
IOM’s 190-page report entitled “Chimpanzees in Biomedical and Behavioral Research: Assessing the Necessity” was described by NIH director Francis Collins, Ph.D., as a “thoughtful and careful analysis.” He added that “NIH will not issue any new awards for research involving chimpanzees until processes for implementing the recommendations are in place.” As those guidelines get defined, it is hoped that besides advancing drugs for human diseases, chimpanzees and other similar animals will also benefit from findings, including helping preserve wild great ape populations. Additionally, should the new guidelines restrict the use of chimps in biomedical research, well-defined rules about the ethical use of these animals should accompany them.