Clipping Bird Flu’s Wings with Biosecurity in Zoos
When you think of avian influenza, you probably think of birds. But earlier this year, the U.S. state of Texas confirmed that dairy cattle had contracted the virus and spread it to a human—the first time a transmission of this type has occurred.
Authorities detected the highly pathogenic avian influenza (HPAI) virus after an individual who’d worked directly with dairy cattle experienced eye inflammation and was tested for flu. The positive H5NI virus strain result was then confirmed in a second round of testing by the U.S. Centers for Disease Control and Prevention (CDC).
“Avian influenza A (H5N1) is a type of flu virus that usually infects wild birds and can spread to domestic birds and other animals,” according to the Texas Department of State Health Services (DSHS). “It occasionally infects people, though it is extremely rare for it to be transmitted from one person to another. Initial testing shows the virus has not changed in a way to make it more likely to spread among humans.”
DSHS also emphasized that while the dairy cows were infected with H5N1, there was no risk to the commercial milk supply because requirements are in place mandating that dairies destroy or divert milk from sick cows. The pasteurization process, required in the United States, also kills avian flu viruses.
HPAI Origins
The March transmission of H5N1 to a human marks just the second time the virus has passed from an animal to a human in the United States. It also highlights how important disease monitoring and response plans are to limit exposure and contain the spread.
H5N1 is an HPAI virus that is hosted by wild aquatic birds and waterfowl, such as ducks, geese, and swans. Flocks of infected birds can spread the virus to other birds—like chickens and turkeys—and cause severe disease with high mortality rates, often within 48 hours, according to the CDC.
HPAI became endemic in Asia in the 1990s before spreading to other parts of the globe via birds’ migration patterns. The last outbreak appeared in North America in Canada before moving down the West Coast into the United States in 2014, says Dr. Julie Barnes, vice president of animal care and health at the Santa Barbara Zoo in Santa Barbara, California.
Barnes started working at the zoo in 2011 and says when the North American HPAI outbreak occurred in 2014, her team was worried about the risk to birds in their collection. The Zoo and Aquarium All Hazards Partnership (ZAHP) collaborated with the U.S. Department of Agriculture (USDA) to set up a Concept of Operations (CONOPs) exercise with several zoos within the United States, including the Santa Barbara Zoo.
“We effectively went through this tabletop exercise with the USDA, because it regulates the poultry industry and they would have regulation over what happened to our birds in our zoos at that point in time,” Barnes explains.
The exercise explored the scenarios of an HPAI outbreak occurring within 100 miles of a zoo and a positive case on zoo property. These scenarios then helped the Santa Barbara Zoo strengthen its biosecurity plan by including steps to reach out to local public health officials to coordinate response to diseases that are zoonotic (spread between people and animals).
In the United States, public health officers often have police powers that allow them to enforce inspections, isolation, and quarantines of people to prevent the spread of disease.
“The local health officer is essentially the chief security officer for the county for anything biological,” says Charity Dean, CEO and founder of PHC Global, and public health officer for Santa Barbara County from 2011 to 2019.
After the CONOPs exercise, Barnes contacted Dean, and they went through a tabletop exercise together for responding to HPAI and other potential zoonotic diseases at the Santa Barbara Zoo. Dean calls that connection a “light-bulb moment” about the potential risk of zoonotic disease.
“The whole world understands now from COVID that these viruses mutate,” Dean says. “These viruses mutate to select more fit versions of themselves. What we’re always worried about is not just a highly pathogenic avian influenza that sweeps through the birds and kills a lot of birds, but we’re always worried about the jump to humans and then the sustained human-to-human spread.”
Dean and Barnes then talked through a playbook on the steps they would take to collect scattered data points—such as a person has a symptom that aligns with HPAI and several animals have died recently—and understand they had a spillover event that needed to be responded to quickly.
“I would use my police powers as the local health officer,” Dean says. “She would deal with the animal side, and together, we would have a shot at containing this thing in one geographic location of the zoo and surrounding area, versus having it spread, and spread, and spread.”
This would be done by identifying when the initial event happened and who the first case was (known as patient zero). They would then conduct contact tracing to determine what other animals and people were potentially exposed to the virus and try to limit any further exposure through quarantine and isolation measures.
“If you can pull the trigger on the playbook for rapid containment and isolation, when the humans are only incubating the virus, you’ve won,” Dean adds. “If it’s two weeks later, and that thing has an incubation period of 10 days and you’re at day 14, you’ve already lost because that means the virus is out in the wild infecting more people.”
Going through this process was not a unique experience for the Santa Barbara Zoo—other zoos took similar steps. But it did help further create a culture of creating response plans for a range of incidents and updating them as circumstances changed.
“The frequency that we’re developing these plans seems to be increasing,” Barnes says. “We have a basic biosecurity plan, and then we also create a more detailed plan depending on what the specific infectious disease concern or threat is and what types of species it’s going to affect, whether it’s zoonotic, and so on.”
Mitigation Measures
Fortunately, the HPAI response plans have never been fully put into action because the zoo has yet to have a positive HPAI case on its grounds and California has yet to have a human test positive with HPAI.
But the zoo’s mitigation measures have played a role in deterring cases, including testing sick or dead wild birds found on zoo grounds as well as birds prior to integrating them into the zoo’s collection. After passing that initial round of tests, all birds are examined annually through either a visual examination or a hands-on examination.
“In terms of catching more immediate things, our keepers see these animals every day,” Barnes says. “They know their animals really well. They know when something is not right with an animal, so we can respond very quickly. We have veterinarians on site and available every day over 24 hours.”
If a bird were exhibiting unusual behavior, which could include symptoms consistent with HPAI, it would be isolated immediately, staff would don personal protective equipment (PPE), test the bird, send the test to a lab for analysis, and provide supportive care to the bird.
“If it were positive, it would remain in isolation and we would provide treatment and wait to see if the bird survived,” Barnes says. “If it’s not positive, then we would make the decision whether the bird can go back out to its original home enclosure or whether we need to keep it isolated just for treatment.”
The zoo also takes steps to limit its animal collections’ exposure to wild birds that might be carrying HPAI.
“We’ve drained pools to discourage wild ducks and other waterfowl from landing in pools,” Barnes says. “We have set up deterrents to make it harder for them to land in spaces. Sometimes we move birds into protected spaces when there is an imminent threat so they’re not going to have contact with wild birds, particularly any species that are highly susceptible.”
There are also mitigation measures to prevent zoo staffers from inadvertently bringing HPAI to work with them. This includes wearing uniforms while at work and requirements for changing shoes at the zoo to avoid tracking contaminated material into animal enclosures, as well as training on transmission risks if staffers have contact with birds outside of the workplace.
The 2014 CONOPs exercise illuminated a hole in the zoo’s biosecurity plan—that it lacked a respiratory protection program. The zoo had disposable masks available for staff to use, but HPAI is spread by respiratory droplets, so Barnes says the zoo decided to invest in a PPE upgrade.
“People were fitted with half-face respirators with cartridges, and we’ve continued to maintain that respiratory protection program,” she explains. “It has come in handy for HPAI that’s now circulating, and for COVID, and could be used in many situations where there’s a concern for aerosol transmission or toxic aerosol exposure.”
Remaining Current
The 2014 HPAI outbreak was successfully stamped out, but a current outbreak of HPAI in the United States is likely to become endemic and pose an ever-present risk, Barnes adds. And while HPAI is something veterinarians, farmers, and members of the poultry industry have paid attention to for over a decade, COVID-19 and Monkeypox were eye-openers for other people about the risk of transmission of a virus from an animal to a human.
“As veterinarians, we’re very used to dealing with zoonotic diseases,” Barnes says. “Whether you’re in private practice and worrying about the pet owner who might contract something from their animal, to in zoos where we’re worried about any potential zoonotic disease risk to our staff or to any of our guests. I think veterinarians have been ahead of the game in terms of being concerned about spillover and zoonotic disease concerns for a very, very long time.”
This means that maintaining strong relationships between zoo staff and local public health officials is important, Dean says.
“The local health officer—and in some cases it’s the state health officer—carries police powers and that is really useful for a zoo to know because they may need to do a rapid evacuation of the zoo, redirect traffic, or a rapid quarantine of exposed humans,” she explains. “Their local health officer can be the key to unlock a lot of that, if they have those relationships set up ahead of time.”
So, too, is regularly reviewing incident response plans to evolve them to new and emerging risks, whether it is HPAI, COVID, or a new virus, Barnes adds.
Every situation calls for “constantly adapting your plans, depending on what the disease is, which species are at risk, and the zoonotic potential,” she says. “You’re always reflecting on those plans to really deal with whatever the imminent risk is.”
Megan Gates is senior editor of Security Management. Connect with her at [email protected] or on LinkedIn. Follow her on X or Threads: @mgngates.
