The deadly rabies virus was once common across Europe. A bite from an infected dog, wolf or fox could be fatal.
Authors
- Andrew S. Flies
Senior Research Fellow in Immunology, University of Tasmania
- Prithul Chaturvedi
Doctoral Student in Medical Engineering, University of Tasmania
But then came a breakthrough: an edible vaccine. Since 1978, a billion baits containing the vaccine have been distributed by 30 European nations. Many European nations are now considered rabies-free.
Our research team has been developing edible bait vaccines for Tasmanian devils to protect them from devil facial tumour disease. This approach could be adapted to protect devils and other scavenging mammals from bird flu.
What's missing is the right vaccine. Bird flu vaccines for mammals are still largely experimental. Getting a new vaccine tested and approved in time to be useful during this outbreak of bird flu would be very challenging - but not impossible.
The good news is that vaccine development took a huge leap forward during the COVID pandemic. Vaccines were being tested in humans about two months after genomic sequencing of the novel coronavirus.
Investing in new bird flu vaccines for wildlife will be useful to help prepare for future outbreaks.
How to dispense a vaccine
Tassie devils suffer from one of the world's few known contagious cancers. When devils tussle and bite, they spread the tumour . Mortality rates are high.
In 2019, we began work on an oral bait vaccine to help prevent transmission of the disease. In fieldwork, we have tested use of a bait dispenser and several types of baits to increase how many are eaten by wild devils. Possums, quolls, pademelons and rats also eat these baits.
We recently developed a motion-activated smart bait dispenser able to recognise devils in milliseconds and deliver bait.
Our dispenser includes a microchip scanner so we know which animal likely took the bait and their current body temperature. Data is transmitted in real time. We don't know if devil facial tumour disease or influenza would give devils a fever, but this system will help us find out.
In the lab, we developed a vaccine which stays stable in baits and can infect the cells of devil facial tumours . We hope to start small-scale trials in devils in the near future.
Which species could this help?
We can't vaccinate all Australian wildlife - and we don't have the data to predict which Australian species will be most vulnerable to bird flu - or to future diseases.
Given this, it makes sense to try different vaccination methods and focus on threatened species. Official estimates suggest up to 10% of Australian mammal species are at high to extreme risk from bird flu.
We believe our approach could quickly be used for devils and scavenging mammal species if a new bird flu vaccine was developed. It could potentially work for colonies of birds which scavenge on land such as brown skuas - the first species found to have bird flu in Australia.
It's important to protect scavengers, as these animals can get a massive dose of bird flu after eating from a carcass . This gives the virus more opportunities to mutate and adapt to their new hosts.
But our approach won't work for seals, sea lions and other pinnipeds, as they do not eat while on land. Vaccines could instead be administered with dart guns. This is how bison and elephants can be vaccinated.
But our approach won't work for seals, sea lions and other pinnipeds, because of where and how they eat. It would also be challenging to use the dart guns used for animals such as bison and elephants. Hand injections or the use of needles on a pole could be an alternative.
We will need to find a solution. More than 13,000 southern elephant seal pups died after the H5N1 strain of bird flu arrived on Australia's Heard Island last year . Testing confirmed the virus was present in carcasses.
But not all species are affected equally - infections were detected in six other bird and mammal species on Heard Island, but mass die-offs were seen only in elephant seals. An Australia fur seal has now died after infection.
Better vaccines urgently needed
To date, Australia has a single bird flu vaccine approved for emergency use in little penguins and captive birds .
This vaccine uses dead flu viruses that are designed to be injected. Unfortunately, this type of vaccine doesn't work well for baits. We need to use weakened or modified live viruses, as they can more readily enter host cells to create an immune response.
In the United States, researchers have trialled a new vaccine which inserts a bird flu target into a weakened human virus. The vaccine protected mice from bird flu and induced a similar immune response in cattle. This approach is similar to both our Tassie devil tumour vaccine and a highly successful US rabies bait vaccine . This vaccine is generally distributed by aircraft with no follow up booster drops.
Oral rabies vaccines have been hugely successful despite the fact we don't know how many baits each wild animal eats. Some may eat several and others none. To make sure this approach is safe, Canadian scientists tested much stronger doses on key species and found no ill effects. In the US, an exhaustive review found the approach was safe and effective.
Approving new vaccines for animals often takes years. Authorities often include strict dosing requirements. Both of these may have to change if we are to tackle bird flu in time.
The success of edible rabies vaccines suggests it's worth making dose schedules more flexible. Vaccine development, too, could be sped up.
If we want better options to tackle bird flu and future wildlife diseases, we need to start now.
Andrew S. Flies has received funding from the Tasmanian Department of Natural Resources and the Environment, Wildcare Tasmania, Animal Control Technologies Australia, the Australian Research Council, Save the Tasmanian Devil Appeal, Wedgetail Foundation and UTAS Holdings.
Prithul Chaturvedi has received funding from the Menzies Institute for Medical Research (PhD Top-up Scholarship) and Save the Tasmanian Devil Appeal.
