Australia is racing to contain the spread of highly pathogenic avian influenza (HPAI), which is now believed to have infected seven seabirds.
There are currently five confirmed or suspected cases of the H5N1 clade 2.3.4.4b strain in Western Australia, alongside one in South Australia and one in New South Wales.
HPAI is still not established in Australia, and currently poses little risk to human health. But the H5N1 strain has already devastated wildlife populations globally.
We’re yet to see how this deadly virus will affect our country’s wildlife. But an urgent concern is the potential for scavenger animals to spread H5N1 further by eating infected carcasses .
The role of scavengers
The term carcass, which refers to the body of a dead animal, may make you queasy. But carcasses are a natural and vital part of our ecosystems.
They provide food for scavengers, who in turn ensure our landscapes aren’t littered with dead animal material. Vultures are the most well-known example.
But Australia has no vultures. Instead, our “clean up crew” is made up of a hodgepodge list of native and invasive species including dingoes , Tasmanian devils , red foxes , feral pigs , quolls , raptors such as kites and sea eagles, and corvids such as crows and ravens.
We now know 48 species of Australian vertebrate animals will, in certain conditions, feed on carcasses. But scavenging isn’t limited to carnivores. In fact, research shows almost all animals will scavenge if needed, including herbivores such as brushtail possums.
Infected carcasses are a risk
H5N1 in Australia poses a risk to any species that scavenges, or even touches, an infected carcass.
Raptors, corvids and gulls commonly scavenge along shorelines and are most vulnerable to the virus. Mammals that forage along coastlines , such as red foxes, may also be more at risk.
The H5N1 strain can survive in infected carcasses for up to 30 days at 20°C, and 240 days at 4°C. This creates a wide window during which scavengers can be exposed to the virus.
A scavenger that eats a contaminated carcass may get sick. But they can also spread the virus by moving infected carcass material or infecting other animals through their bodily fluids. Scavengers may also die from the virus and contaminate any other scavengers that feed on their carcass .
It’s difficult to predict how H5N1 may spread through Australia’s scavenger species, because we don’t have any detailed research looking at which species actually eat dead birds.
However, international research shows mammals can be infected after consuming infected bird carcasses. Scientists have also observed high rates of H5N1 infection and death in vultures in Europe and the US .
Scavenging may be seasonal
Whether scavengers actually feed on carcasses often depends on the season . Research suggests birds and mammals scavenge more in winter compared to summer. That’s because there is typically less live prey available in the colder months.
This is concerning, given the H5N1 strain has arrived in the middle of the Australian winter. However, summer may slow the spread of the virus. One reason is scavenging insects such as flies, ants and beetles can consume carcasses extremely quickly, sometimes even faster than mammals and birds. In doing so, they may reduce how many infected carcasses scavengers are exposed to.
So, what can we do?
There are several ways we can curb the spread of H5N1 through our scavenger species.
One is to immediately remove any infected carcasses, particularly from high-value conservation areas. We should also limit activities likely to cause the build-up of carcasses, such as recreational duck or quail hunting.
Where we can’t get rid of carcasses, we must track scavenger activity. This is possible through carcass monitoring , which can help identify which species are actually eating dead birds and whether they are native or introduced. We want to protect our native scavengers, while limiting the harm introduced scavengers may do to our ecosystems.
We must also monitor the scavengers themselves. As with wild birds , this allows us to notice any virus-related health problems and measure overall infection rates.
Our bird flu response must prioritise the health and management of scavenger animals. Only then can we protect our animals, ecosystems and communities from a wider H5N1 outbreak.
