Like humans, gorillas and chimpanzees can get infected by Ebola. To protect our closest relatives from this dreaded disease, and to prevent the virus from spilling over into human populations, scientists have now developed an oral vaccine to combat Ebola in the wild. It sounds very promising, but the researchers have run into legal, political, and ethical obstacles that could make it difficult to push the research further.
Ingestible vaccines are nothing new, but this marks the first time that scientists have developed one specifically for the purpose of protecting and preserving wild apes. This new vaccine, should it ever be put to use, would indirectly help humans by reducing Ebola’s opportunity to take root in wild animal populations, from where it could spread to humans. But in order for this to happen, and to allow scientists the opportunity to push this work further, we may have to rethink animal experimentation—particularly when the animals themselves stand to benefit.
In addition to having a shared ancestry, humans and apes both have to contend with the Ebola virus. Over the past three decades, the disease has killed about a third of the world’s gorillas and countless chimpanzees. Ebola threatens wild primates that are already at risk, be it from habitat loss or rampant poaching.
The virus, like so many other diseases, can jump from species to species—in this case, fruit bats (perhaps the most prolific spreader of the disease), monkeys, forest antelope, porcupines, and various apes. Suffice to say, the fewer wild animals infected by the virus, the better.
Thankfully, Ebola can be curbed with vaccines, and there have been several recent developments on that front. The challenge, however, is delivering the vaccine to vulnerable populations in the wild. Conservationists have experimented with hypodermic darts, but it has proven difficult to to target animals who live in thick tropical forests and fear humans, like so many primates do.
A potential solution to this problem comes in the form of ingestible vaccines. And in fact, conservationists have had great success with oral vaccines in the fight against rabies. Since 1983, more than 250 million baits containing a rabies vaccine have been distributed in Europe, resulting a 75 percent decrease of the disease in wild animal populations. Similar effects have been seen in North America.
With this idea in mind, researchers from the University of Cambridge and Thomas Jefferson University embarked on a project to see if a similar oral vaccine could be developed to protect wild apes from Ebola. Using a promising Ebola vaccine called filorab1, and combining it with an inactive version of the rabies virus, the researchers were able to create an oral version of the vaccine. The disabled rabies virus allows the Ebola vaccine to pass more easily into the bloodstream when ingested, triggering a robust immune response.
This oral vaccine was tested on ten captive chimps who were being studied at the New Iberia Research Center in Louisiana. The researchers monitored the chimps for nearly a month, assessing the animals for any side effects and measuring the amounts of anti-Ebola antibodies in their blood. During the 28-day trial, the researchers watched as the antibodies increased in volume, indicating that the primates had developed an immunity to the virus. No serious side effects were recorded.
The scientists say this represents a new potential strategy for combatting Ebola, one that could protect both apes and ourselves from the disease. The oral vaccine could eventually be injected into tasty baits that would be scattered throughout ape habitats, inoculating the population over time. The researchers say a similar oral vaccine could be developed for other diseases that plague wild apes, such as anthrax. This research now appears in Scientific Reports.
It’s important to note, however, that the chimps were never exposed to the Ebola virus after being immunized, so the researchers aren’t actually certain that it works.