Scientists develop vaccine to protect young elephants from potentially lethal herpesvirus

Scientists have produced a novel vaccine which protects young elephants from EEHV, a potentially lethal herpesvirus which can kill the animal within 24 hours. A young calf is protected by its mothers immunity but as it weans and grows it becomes a target of the virus which is especially prevalent in Asian elephants.

Adult Asian elephants, like those that roam the jungles of Thailand, are not at particular danger from elephant endotheliotropic herpesvirus, or EEHV.

But young elephants which haven't had a chance to fully develop their immune systems are at serious risk which is why scientists from the UK's Chester Zoo, the University of Surrey and the Animal and Plant Health Agency have spent years developing a vaccine which can protect young elephants.

The IUCN group of international conservationists describes the Asian elephant as endangered with fewer that 40,000 animals remaining.

Scientists say cases of the virus causing deaths has been documented in India, Nepal, Myanmar and Thailand.

But it's not just in the wild, the virus is striking elephant conservation and breeding programmes in zoos around the world.

The scientists say they've focused on producing a vaccine for the Asian species for this reason, although the virus has been detected in African elephants.

Proof of concept vaccine

Elderly male elephant Aung Bo is a much loved presence at Chester Zoo in the north of England.

He was one of three elephants who took part in a proof of concept vaccine aimed at protecting young elephants who fall into the gap between having their mother's immunity and developing their own.

Dr Falko Steinbach, the Professor of Veterinary Immunology at the University of Surrey co-authored the study which has been published in the journal Nature Communications.

He says the vaccine isn't aimed at preventing the elephants catching the infection, but ensuring that they can survive it, bolstering their immune system's ability to fight it.

"The elephant herpesvirus is in a certain way in its biology, quite comparable to herpesviruses in other species in that like we also carry some herpesviruses latently in the end at an adult stage, almost every elephant will also carry some herpesviruses. But if the young animals become infected for the first time their immune system is perhaps not fully matured and it may not react appropriately to this challenge. And when this happens it may turn into a really bad disease with a high likelihood of a lethal outcome. And to prevent this the vaccine was designed specifically to prevent death and severe disease you cannot effectively generate a vaccine against herpesviruses that prevent infection," says Steinbach.

Dr Katie Edwards, Lead Conservation Scientist at Chester Zoo and co-author of the study, says when the symptoms of the virus appear in a young elephant, it's already too late to save them.

Edwards says: "It very quickly turns into this haemorrhagic form of the disease, where there's essentially lots of, kind of internal bleeding. So the symptoms outwardly are kind of swelling of the head, we see lesions to the tongue where the tongue swells and there can be some stiffness, general lethargy. So it can progress very quickly from that stage. By the time we see clinical signs in a young elephant it's very it difficult to kind of get through the disease."

Genotyping the virus

Traditionally many vaccines are created by injecting the animal - or human - with a weakened strain of the virus, just enough to prime the immune system.

But Edwards says this was not possible with the elephant herpesvirus.

This is because it's not possible to culture the virus outside of an elephant's body.

She explains: "So instead what we did it is we looked to the genetic sequence of the the virus, so we genotyped the virus that had caused death in one of the elephant calves previously at Chester Zoos and we started to look for pieces of that virus that were candidates for stimulating the immune system. So there is a really great global community that are working on EHV and lots of people looking at this from different angles. But the approach that we took was to essentially identify two different parts of the virus that were very good candidates for a vaccine and we actually used an approach called a heterologous vaccine approach, what that basically means is we have two types of vaccine, so kind of two delivery methods almost, but both contain those key pieces of EHV."

The team says the vaccine is given via injection with booster doses, making it ideal for use in zoos and sanctuaries.

Edwards says the new vaccine allows scientists to strategically target a very specific part of the elephant's immune system using technology which hasn't been used for these animals before.

She says the way it works means it can be adapted to other animals and treat other viruses.

"Some of the technology that we use has not been used in wildlife before. And so it was very informative to help us really pin down whether we were able to stimulate the right part of the immune system for the virus we were attempting to tackle. Certainly that type of technology could be really informative for lots of other species and with elephants with lots of other diseases as well," says Edwards.

The team is aiming to develop the vaccine so that it can be made suitable for animals in wild populations.