In April and May 2011 VaccinApe is conducting the first ever controlled vaccination trial on wild apes. Gorillas from two social groups visited by tourists at the Dzanga National Park in Central African Republic are being vaccinated against measles virus. The aim of the project is to scientifically evaluate whether vaccination can be a safe and effective tool for ape conversation.

Measles vaccine was chosen for the study because it extraordinarily safe; given with little or no adverse effects to hundreds of zoo gorillas as well as hundreds of millions of human children over the last decade. Measles is also a known threat to gorillas in tourism programs, killing mountain gorillas in a 1988 outbreak in Rwanda. During that outbreak, the Mountain Gorilla Veterinary Project conducted the only vaccination campaign ever attempted on wild gorillas, eventually dart vaccinating about 65 gorillas.

Since the 1988 measles outbreak in Rwanda further efforts to vaccinate wild apes have been thwarted by a combination of fears about the safety of dart vaccination to both apes and darting teams, concerns about potential negative impacts of darting on ape behavior towards humans, doubts on whether apes could be effectively immunized under primitive field conditions, and a visceral antipathy of some towards any intervention that decreases the “wildness” of gorillas and chimpanzees. However, the death toll from infectious disease has gradually mounted and modern diagnostic methods have made it increasingly clear that disease spillover from humans is often the culprit. It is now evident that more aggressive medical intervention is essential if ape tourism is to be sustainable.

VaccinApe’s measles campaign at Dzanga has been carefully designed to address the concerns of vaccination critics. Darting protocols that maximize safety to gorillas and the darting team have been developed through extensive negotiation with the Dzanga-Sangha Protected Areas, which manages the Gorilla Habituation Program at Dzanga National Park and is providing expertise and logistical support for the vaccination project. Behavioral observations are being used to evaluate whether gorillas become more wary of or aggressive towards people as a consequence of darting. Fecal assays will assess whether darting elevates gorilla stress hormone levels. Extensive efforts have been made to maintain vaccine “cold chain” under remote field conditions. And non-invasive fecal assays of measles antibodies and shed RNA are being custom-developed and validated to evaluate whether vaccination results in a robust, protective immune response. This is the first time any vaccination program has used non-invasive fecal antibodies or RNA to assay immune response.

Darting team members bring a deep well of experience to the project. Darting wild mountain gorillas in Rwanda, Uganda, and Democratic Republic of Congo 75-100 times, lead veterinarian Christopher Whittier of the Smithsonian Institution’s National Zoological Park may be the most experienced gorilla darter in the world. Assisting veterinarian Sonja Metzger of the Robert Koch Institute in Germany has darted chimpanzees in Ivory Coast as well as hyenas and jackals in Namibia. Working with the Dzanga-Sangha Protected Areas since 1998, the World Wildlife Fund’s Angelique Todd has contributed to, led, or supervised over half of the western gorilla habituations ever successfully completed. Principle gorilla guide Paolo Bopalanzognako of the Dzanga-Sangha Project is the first Central African to successfully habituate western gorillas for tourism and has worked with wild gorillas at Dzanga since 1998. Kathryn Shutt, a graduate student at the University of Durham, has worked with wild gorillas since 2006 and will collect fecal samples for hormone analyses. Team leader and VaccinApe President Peter Walsh has conducted fieldwork in the Dzanga-Ndoki ecosystem since 1996, with studies at Dzanga National Park dating back to 1998.

The project also has impressive laboratory backup. Antibody and RNA assays are being developed by postdoctoral fellow Martin Ludlow in the laboratories of measles vaccine experts Paul Duprex of Boston University and the U.S. National Emerging Infectious Disease Laboratory and Rik de Swart of Erasmus MC in the Netherlands. Assays are being validated using fecal samples from vaccine trials on captive monkeys and ferrets at Erasmus MC as well as from a gorilla vaccinated as part of the animal health program at the Smithsonian’s National Zoo. Ludlow will assay field samples at Duprex’s lab in Boston. Duprex and de Swart were also instrumental in negotiating donation and shipment of measles vaccine by the manufacturer, the Serum Institute of India. Hormone analyses will be conducted in the laboratory of Michael Heistermann of the German Primate Center.

VaccinApe Phase 1

We are now in a “proof of concept” phase which will demonstrate that wild apes can be vaccinated safely, economically, and with rigorous assays of vaccination effectiveness. This phase will include screening of adjuvants to enhance immune response to vaccination, safety testing of an Ebola vaccine on captive chimpanzees (without Ebola exposure), development of non-invasive (fecal) assays for estimating immunization rate in the field, a measles vaccination field pilot to fine tune safe vaccine delivery methods and validate field assays, conditional veterinary licensing of an Ebola vaccine with the US Department of Agriculture, modeling of vaccination cost-effectiveness relative to other conservation efforts, and finally, a pilot study in which gorillas will be vaccinated against Ebola using a hypodermic dart. Most of the funding has already been secured for the first phase, which will take place over the next two years.

VaccinApe Phase 2

We have chosen to start with a darted vaccine because it entails fewer technical, safety, and cost problems than a promising alternate method of vaccine delivery, oral baiting. However, darting limits the number of apes that can be vaccinated. Consequently, Phase II will focus on dart vaccination of hundreds of gorillas and chimpanzees that have been habituated to human presence against both Ebola and human respiratory viruses. Habituated apes have disproportionate conservation value because of the revenue and local support generated by ape tourism as well as the international exposure provide by films about ape research and the conservation efforts of researchers. The vaccination program will include epidemiological and demographic studies to quantify immunization rate and population impact. In parallel to the dart vaccination program, field and laboratory work will be used to develop effective oral baiting systems and oral vaccine formulations.

VaccinApe Phase 3

In the third and final phase of the project we will vaccinate large numbers (thousands) of unhabituated apes against Ebola and respiratory viruses with the objective of maintaining the viability of entire ape populations.

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.

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.