By the time the last bat was gently moved into its temporary new home, the Durrell team had been working non-stop for 12 hours.
It had been a long, tense day – not only because relocating 80 rare bats is logistically challenging, but because those same bats were in the middle of fighting a silent killer: a bacterial infection that had already claimed 10 lives.
Earlier this year, an outbreak of pasteurella, which can cause serious disease in a range of animals, swept through Durrell’s Livingstone’s fruit bat colony, the largest of its kind in Europe.
The outbreak forced the zoo’s popular bat tunnel to close, and triggered an extraordinary response from Durrell’s keepers and veterinary team.
But, as curator-turned-interim zoological director Matt Goetz told Megan Davies, the crisis has since opened the door to something remarkable…
“We identified an infection in our around 80-strong bat colony, and that caused disease, and we obviously had to immediately tackle that situation,” Mr Goetz explained.
“We identified a bacterium called Pasteurella that causes the disease. We confirmed that in-house and with external laboratories.”
A deadly diagnosis
The bacteria doesn’t just affect bats – it can also infect cats, dogs, livestock, birds, and other mammals. For this rare fruit bat species, it posed a particularly grave threat.
First was the emergency response. The entire colony had to be moved out of the 800-square-metre bat tunnel, which is home to three-quarters of the world’s captive population of Livingstone’s fruit bats, and into four separate enclosures under strict quarantine.
“We had to move 80 bats within one day. This was an extremely taxing thing,” Mr Goetz recalled.
Drawing on expertise across departments, the team created an hour-by-hour plan. The bats had to be safely caught, checked, treated, and relocated. A process that might sound like a conservationist’s version of military logistics.
“There are welfare considerations, welfare assessments to be taken first, risk assessments.
“We had a very detailed plan written out: who is doing what, when, how, which bats go where, when, in what fashion.”
The operation lasted from early morning into the evening, and went without a hitch.
“They are doing well and are recovering. I couldn’t be more happy with the situation and how it eventually turned out, or any more proud of the team who pulled that together.”
Tragedy and recovery
Not every bat made it, however.
“We had, sadly, some deaths in the early stages, because obviously the treatment is not immediately effective after the first dose,” Mr Goetz said.
“It needs to take its course of effect, and then you have individual immune responses in the bats.
“Some are weaker, some are stronger, and in the initial stages, until the effect of the treatment was [spread] throughout the remaining animals and in the offshore areas, we lost ten bats to the disease.”
This had been “extremely tough on the keepers”, Mr Goetz added, and the blow is even harder when animals die of disease.
“The strength we take is that the actions we took were the right ones, even though it was very difficult.”
While the bats are in their four quarantine homes, they require medication and attention. Staff wear PPE – overalls with face masks, gloves and shoes – and use foot baths. On days when they work with bats, they aren’t allowed to work with any other species to avoid the bacteria spreading.
Mr Goetz praised the staff, who didn’t just pull a 12-hour shift to move the bats to their temporary homes, but also give medication to 80 bats every day.
“Try this with 80 kids – that’s already difficult enough!”
“They know every bat individually. So seeing them not being well is incredibly difficult for everybody.”
It is impossible to tell how many bats were affected by the disease. Some might have bacteria in their blood but responded to the treatment before getting sicker.
Another factor is that animals often hide their symptoms.
“If you don’t, every single day, test every single animal, then often you wouldn’t know what’s going on. And there’s also a limit of tests they can do because the tests need to exist. They need to have been developed in the first place.”
Tests and vaccines are more likely to have been developed for species that have an obvious economic value – something Mr Goetz is “very aware of” as a reptile curator.
“In mammals, for example, you have much more incentive for laboratories to develop tests for certain diseases because it’s very closely related to humans. But in reptiles, we have a lot of parasites, we have a lot of potential disease agents, but the research is not necessarily there because the incentive is not there.”
In comparison, livestock – where there is an economic incentive to develop tests – already have vaccinations against the same bacterium that is now hitting the bats.
The potential silver lining – despite the losses – is that samples of the strain that hit Durrell’s bat colony have been sent to a UK company who are developing a vaccine.
Ridgeway Biologicals, based in Berkshire, create vaccines for animals ranging from livestock to fish and zoo animals, based off of samples sent in by veterinary teams.
With a 14-week timeline, Durrell expect the vaccine to be ready at the end of July. The development will have cost Durrell around £2,000-£2,500.
“Having had that outbreak, that was the first time this bacterium caused any problems in our bats. Having seen that happen, we decided that we can prevent this from happening ever again.”
The samples have been sent to the lab and a vaccine is on the way.
Once it is ready, it will be administered by injection.
Veterinary vaccines like this have to be tailored to the specific species and the specific strain of bacterium, but they will later be able to share the vaccine with other colonies in the UK and Europe.
Durrell’s colony is the largest colony of Livingstone’s fruit bats in Europe, but they have sent bats to other institutions – including zoos in Zurich and Bristol. These will also be able to use the vaccine, Mr Goetz said.
“For us as a conservation organisation and working together with other zoos… it is obvious that we not just share animals and knowledge of husbandry and breeding, but also any tools that make that easier or more effective and better for the bats. That is what’s behind everything.
“So if the vaccine is available and works for us, then of course we will let everybody else know and then they can also apply it.”
The vaccine should also cover similar strains of the bacteria and even if a new strain comes along in a decade, it would be “very unusual indeed” for it to have evolved to override the vaccine, Mr Goetz said.
The future
In an anniversary year that is also on course to be marked by celebrations for what would have been Gerald Durrell’s 100th birthday, it’s important for the Zoo to bring back one of its star attractions as soon as it can.
With no fixed timeline as of yet for the repairs, Mr Goetz said, the Trust was behind the decisions made.
“We sat together many times, going through all the options, the risk assessments, welfare assessments, we planned, what can be done?
“The bats – keeping them safe and treating them effectively was the absolute priority for us.”
And when the tunnel does reopen, it’ll be a moment of hope and celebration, as much for the staff and bats, as for the species’ long-term future.
