A farm worker became the first reported human case of bird flu in Ohio. They join dozens who have become ill with the virus in the U.S. and one person in Louisiana who died.
Millions of chickens have been euthanized on poultry farms, and dairy cows have become infected with highly pathogenic H5N1 avian influenza. Wild birds are also dying. The death of 200 snow geese in the Allentown area has been attributed to the disease. Even wild mammals like foxes and sea lions are susceptible. Dr. Justin Brown, DVM, PhD, is a Penn State professor and veterinarian who specializes in wildlife.
“The virus that we’re dealing with now emerged in China in the late 90s,” Brown said.
The most recent strain causes severe illness and death in chickens and other poultry and has become well-established within wild bird populations. It’s distinct from a low pathogenic variety that has long circulated among wild birds. Brown said it is unlike anything he’s seen in 25 years of practice.
The Allegheny Front’s Kara Holsopple talked with Brown about the risks.
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Kara Holsopple: How is avian flu spread among wild bird populations?
Justin Brown: It’s typically done through a fecal-oral route. The most common species we think of infected with flu viruses, in general, would be our waterfowl species: ducks, geese, and swans, and then gulls and shorebirds. Often the environment is highly involved. They may be on a shared piece of water, and one duck excretes their feces into the environment, and then the other ducks or geese are swimming around and become infected that way.
When we think about highly pathogenic influenza viruses, ducks, in general, have been the species that are most likely to be infected without clinical signs. We do tend to see more respiratory shedding of those highly pathogenic viruses, but it’s going to be excreted both respiratory and in the feces and then spread between birds that way.
“Other species are more likely to exhibit signs of disease and mortality…like snow geese, raptors, vultures, and some of our other avian scavengers.”
Kara Holsopple: Are there wild bird species that are susceptible to infection and then also becoming ill and dying?
Justin Brown: We see a lot of variation in the birds that are infected, and then we see a lot of variation in the outcome of infection. Certain species like ducks, they’re the most likely to be infected and not show outward signs of disease. It allows them to be what we might call an asymptomatic reservoir.
And then other species, if they’re exposed, are more likely to exhibit signs of disease and mortality. Some of those species might be things like snow geese, raptors, vultures, and some of our other avian scavengers, and in other waterbird species, we’ve seen really high mortality.
Kara Holsopple: And how is bird flu impacting other wildlife populations, including mammals?
Justin Brown: With this strain of highly pathogenic avian influenza that’s been circulating since the late 90s, we have seen sporadic mortality in some of our mammalian scavengers. There have been reports from Asia and Europe of individual animal mortality, particularly in things like red foxes.
Kara Holsopple: Is that because they feed on infected birds?
Justin Brown: It’s a combination of them feeding on the birds and then the individual species susceptibility. Some carnivores or scavengers are going to be highly susceptible, and if they scavenge or become infected and die, then others will scavenge, and likely, we just don’t even know that they’re infected because they’re not susceptible to disease.
We’ve really seen a change and an increase in our mammalian scavengers since its introduction into North America in around 20 2122. Since that time, we’ve seen a variety of species that are scavengers or carnivores that have been susceptible and died from highly pathogenic avian influenza.
We’ve seen quite a bit of mortality in red foxes, a lot of our wild felids. It’s so like mountain lions, bobcats, a lot of our mustelids, things like skunks, raccoons. And then we’ve seen fairly high mortality in some parts of North and South America in our marine mammal species.
Kara Holsopple: I wanted to ask you about marine animals. Are they infected through bird droppings?
Justin Brown: We don’t really know. At this point, we think that it is a spillover from wild birds to marine mammals, but we don’t really at this point know the mechanism, whether it might be a scavenging or droppings on the beach.
Kara Holsopple: Why does avian flu seem to be so pervasive now? Is there something different about it? Has it changed?
Justin Brown: One of the things about flu that’s a constant is that it’s always going to change. It mutates. It’s an RNA virus that is more prone to mutations. So it’s always mutating, which generally leads to more relatively small changes in the virus.
And then because the virus genome or genetic material has no individual segments, it allows the virus to be what we call reabsorbed. So if two influenza viruses infect the same host, they can mix and match those genetic segments and create a completely new hybrid virus.
Flu viruses can and always will continue to change. And so, certainly, the strain we’re dealing with now is unique, both genetically and biologically. One of the other things that makes this strain a lot different than, say, 2014-15, is it appears to have a much higher involvement of wild birds. We’re seeing it’s been much longer duration and it’s much more widespread.
Kara Holsopple: We’ve all seen news articles about infected poultry flocks that have to be euthanized. What can be done in the wild to prevent bird flu?
Justin Brown: Certainly, it’s a lot more challenging and we’re much more limited on what we can do. This is unique in many ways because we often will think of flu as wildlife as a source, and then it spills over and causes disease in domestic animals, be that a domestic cat, a cow, or a chicken.
“We’re not just managing wildlife to prevent spillover to domestic animals, but in some cases, we might be managing wildlife…for their own benefit.”
One of the really unique things with this virus that we haven’t dealt in the wildlife sector with as much, is this one actually has potential for population-level impacts. So we’re not just managing wildlife to prevent spillover to domestic animals, but in some cases, we might be managing wildlife because of the wildlife itself for their own benefit — certain species like California condors, which are susceptible and endangered, and there have been some concerns…of our raptor species like eagles.
Some of the things that have been considered are vaccination. I know that’s happening in some countries and with some species. That is quite a novel approach, something we haven’t done historically with the flu virus. Other things may just be carcass pickup to limit the extent of the outbreak when it is occurring in a population with things like vultures and species like that.
Kara Holsopple: We know that poultry farm workers and other agricultural workers are most at risk for being infected by the virus. How could people contract avian influenza directly from wildlife?
Justin Brown: There is always going to be a risk. And so these are the kinds of conversations we have: how do we reach out to people that are in those high-risk categories to make sure that they are making any effort they can to sort of reduce that risk as much as possible?
People like hunters, particularly waterfowl hunters, are going to be harvesting their animals, they’re going to be processing them, eating them. Those are all have a certain level of risk with them. So consider things like PPE, proper processing and cooking of products that you may have from harvested animals.
Now that it’s moving into more what we may consider companion animals, and particularly with cats being the most susceptible, I think it’s really important that pet owners realize the risks and where the virus is.
So if there is an active outbreak in your state or in your area, be aware of the risks, particularly if your cat has access to outdoors or things like feeding them raw food diets that may be potentially contaminated with the virus. Those are all things to consider as pet owners.
I think one of the best things they can do is be aware of the animal showing clinical signs, and if you do see anything that’s of concern, bring it to you or your veterinarian and express those concerns. I think it’s also important that vets now consider this on their rule-out lists of things that may make a cat sick. We have a whole bunch of diseases that can make a cat have respiratory signs or show neurologic disease. And historically, flu has not been on that list.
Dr. Justin Brown is a wildlife veterinarian and an assistant teaching professor of veterinary and biomedical sciences at Penn State. He says one thing you can do to stay informed about bird flu outbreaks is to check with the PA Game Commission.
