Over the last two decades the Ebola virus has killed about one third of the world gorilla population and large numbers of chimpanzees. If this continues, the death toll may rise to one half of the world gorilla population. Human respiratory viruses are also a growing threat to wild apes. However, this need not happen. There now are at least six different vaccines that have successfully protected laboratory monkeys against the Ebola challenge and none have shown serious side effects. This is the rare case in which vaccine testing on non-human primates could actually help the conservation of critically endangered non-human primates, as the Ebola vaccines intended for human use would likely protect gorillas and chimpanzees.

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VaccinApe

Since 2003, We have been agitating for one of the Ebola vaccines in development for humans to be used to protect wild apes. These efforts have gradually evolved into VaccinApe, a loose consortium of individuals and institutions. Because of concerns about the safety of vaccinating wild apes we have gone to great lengths to solicit input from a wide range of primatologists, virologists, vaccine labs, and conservationists, including large expert workshops in 2004 and 2008. The consensus of the experts is that if the process is approached in a rigorous, scientific manner, wild ape vaccination would be safe, effective, and affordable. They also recommend that, for reasons of safety, technical complexity, and cost, a darted vaccine should first be used to vaccinate the relatively small number of gorillas and chimpanzees in research and tourism programs. However, in the long term the most effective way to protect larger numbers of wild apes against Ebola and other disease threats such as human respiratory viruses would be vaccines delivered in oral baits.

To meet this high standard of safety and scientific rigor, VaccinApe is now embarked on an incremental program that will lead eventually to the vaccination of wild apes against the Ebola virus. The first step of the process is to test a vaccine on captive chimpanzees. This testing will not involve exposure of chimpanzees to Ebola virus, but simply evaluate whether: 1) the vaccine produces negative side-effects or 2), the vaccine evokes serum antibodies correlated with immunity to Ebola, and 3) antibody correlates of immunity can also be assayed from non-invasively sampled dung . The vaccine used in these trials has been chosen specifically because it has low potential for serious side-effects and no potential for spread between animals (the vaccine is not “alive”). In parallel, a pilot measles vaccination study will be used to validate that wild gorillas can be safely darted and that non-invasively collected dung sampling can be used to assay for immune response to vaccination. Measles vaccine has been chosen both because of its high safety level (it has been safely given to hundreds of millions of human children) and because measles is a known threat to apes in tourist programs (it is the suspected cause of death in an outbreak that killed numerous mountain gorillas).

Results from these captive and field studies will be included, with extensive results from the human vaccine development program, in an application for veterinary licensing of the Ebola vaccine by the US Department of Agriculture. Once this license has been obtained, a field pilot study will then be used to deliver the vaccine using a hypodermic dart to wild gorillas habituated to human presence. After the pilot study is completed and vaccination success is evaluated, the next step will be a larger program in which gorillas and chimpanzees in multiple research and tourism programs are dart vaccinated. In parallel to these darted vaccination programs, research on oral vaccine delivery will be conducted, with the long term objective of vaccinating large numbers of gorillas and chimpanzees against Ebola and other pathogens; particularly human respiratory viruses transmitted to habituated apes in tourism and research programs. A working group at the National Center for Ecological Analysis and Synthesis is also examining efficient strategies for vaccinating apes and comparing the cost-effectiveness of Ebola vaccination to that of other ape conservation strategies.