Inside the Australian zoo saving baby elephants from a killer virus

Sitting in her office, surrounded by elephant pictures, zookeeper Lucy Truelson's voice cracks when she talks about Man Jai.

She watched the Asian elephant's birth in 2013 to mum Kulab. She was there when he had an operation to remove his tusks — broken during rough play — in 2021.

And she was with the cheeky nine-year-old who loved to eat dates when he got unexpectedly sick with elephant endotheliotropic herpesvirus (EEHV).

The virus, which has no cure, usually affects Asian elephants younger than Man Jai.

"The team worked day and night with him, and he was super brave," she says.

"We were all extremely devastated when we lost the fight."

It's been three years since Man Jai died.

But Ms Truelson hopes a new vaccine trial happening today can prevent the same fate for the other young elephants at Werribee Open Range Zoo, and around the world.

With nearly 30 years in the job, Ms Truelson's seen plenty of life and death.

"Any elephant death is devastating. They're all so precious, each individual," she says.

But EEHV can progress rapidly, with massive internal bleeding leading to death within just 24 hours.

In the past 25 years, there have been more than 90 deadly cases of the virus in elephant calves under human care. The virus is one of the largest killers of young Asian elephants in zoos around the world.

And all the new calves at Werribee, with their own personalities and favourite snacks, are at risk.

A common, but deadly disease

Tabitha Hoornweg, a veterinary scientist at Utrecht University in the Netherlands, has been researching how EEHV works and how to stop it since 2019.

Her team is one of three groups around the world, along with teams in the US and the UK, that are developing and trialling vaccines.

"All elephants have this virus or get this virus somewhere during their lives," she says.

"However, for some younger elephants, when they first get in contact with this virus, they get very, very ill."

This is well documented in elephants under human care, but there is also evidence it occurs in the wild.

"It's been estimated that at least 100 to 150 wild calves have also died from this disease," Dr Hoornweg says.

The vaccine developed by Dr Hoornweg's team, which trains the elephant's immune system to recognise the virus, was tested on six older elephants in Dutch zoos about three years ago.

While the elephants didn't have any dangerous side effects, the research only showed the vaccine was safe.

"Now we also want to know whether it's effective to protect the young ones," Dr Hoornweg says.

So far 11 elephant calves have been vaccinated across Europe.

Three young elephants from Werribee Zoo are the first from Australia to join a vaccine trial.

Since Man Jai died, elephants at the zoo have undergone weekly PCR and blood tests for EEHV so zookeepers can immediately detect if one of the animals is ill.

"Not all elephants that have participated in Europe are monitored in the same way," Dr Hoornweg says.

Copping a faceful of 'trunk wash'

Taking a PCR test for elephants isn't as simple as with humans where you shove a swab up a nose.

Werribee keepers have to teach an elephant how to work with them.

Ms Truelson says they take it in stages with plenty of "behaviour reinforcers", aka fruit treats.

The first step is to insert a large syringe full of saline into one trunk nostril.

The elephants are trained to then immediately raise their trunk up and let it all drain down for 20 seconds to get all "that beautiful goodness" in there.

"Trunk wash", saline mixed with dirt and whatever else the elephant has been up to that day, is then blown into a plastic bag and tested for a variety of viruses including EEHV.

"[When they're first learning] it's very cute. They might get saline in, and they want to blow it out really quick because they know that's the next step, and they're excited."

This has also led to the occasional faceful of trunk wash, Ms Truelson says.

But it's all part of the learning process and building trust between elephant and keeper.

Preparing to vaccinate an elephant

In the barn where the calves will be vaccinated there's an unmistakeable waft of farm in the air.

"It's a beautiful blend isn't it?" Werribee Zoo veterinarian Natalie Rourke says.

"Smells like horses and hay and poo … it's good for the soul."

Dr Rourke is one of two veterinarians doing the vaccinating, but she's mostly here to listen to the keepers.

"They train me as much as they train the calves … and they often have to retrain me, so I very much appreciate the guidance."

The nine zookeepers follow a well-practised routine.

Tiny magnets tell each person what their job is, there's a check in for how they're feeling, and there's even a few jokes.

But behind the laughs, there's a bit of nervousness as they get ready to vaccinate the three young calves with the experimental jab.

Adult elephants are easily heavier than 2,000 kilograms, and even the calves are about 1,400kg. Mistakes can be deadly.

Dancing with elephants

The keepers lead the first pair of elephants — mother Mali and calf Roi-Yim — from their sleeping area to metal enclosures in the barn.

They're kept separate but within view of each other to keep them calm.

One keeper has treats and a whistle to reinforce positive behaviour as Roi-Yim leans his 1 tonne frame against the enclosure.

The elephants are trained similar to the way a dog might be trained at home.

"It's all on their terms," Ms Truelson explains.

"You'll see that they are so enthusiastic, these calves. They want to learn, they're curious."

Roi-Yim seems content to get treats in exchange for keeping his back leg available to another keeper, who works with Dr Rourke to prep his skin for the jab.

After his thigh is washed and scrubbed, and everything is ready, Dr Rourke takes a syringe and plunges it through the calf's hide.

It seems like he's barely noticed, happily using his trunk to grab more snacks from the keepers.

"He's not moved a muscle from that position," Ms Truelson says.

"He's just concentrating on the yummy food that he's getting to eat."

Then, as quickly as it began, Roi-Yim and his mum are out onto the savanna for the day, and the team is onto the next mother-and-calf pair.

Seeing the next generation of elephants have a shot at safety from EEHV three years after the death of Man Jai is a special moment for Ms Truelson.

"What Man Jai did for us is really solidify our commitment to fighting this disease … this vaccine trial is one of those ways [we can do that]," she says.

"It's his legacy."