Researchers taking an oropharyngeal swab of a chicken with suspected influenza.
Researchers taking an oropharyngeal swab of a chicken with suspected influenza. Photo courtesy Texas A&M AgriLife / Flickr

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By Rose Hoban

With memories of this past spring’s outbreak of highly pathogenic avian influenza in the Midwest, veterinarians met with public health officials in a two-day conference this week on preventing a mass outbreak of the flu.

Researchers taking an oropharyngeal swab of a chicken with suspected influenza. Photo courtesy Texas A&M AgriLife /Flickr

This year’s “One Medicine” symposium, held at the Sheraton Imperial near Research Triangle Park, featured presentations on farm biosecurity, lessons learned from the H1N1 flu pandemic of 2009-10, how an outbreak of highly pathogenic avian influenza (HPAI) could affect zoos and the environment and the state of vaccines.

“We are really entering what’s considered the peak opportunity for the introduction of [HAPI] virus into this country,” said state veterinarian Doug Meckes, referring to flu viruses potentially carried by migratory waterfowl.

Meckes’ idea of a nightmare is what happened in Minnesota, Kansas, Wisconsin and Iowa this past spring, when farmers had to destroy millions of chickens and turkeys after HPAI outbreaks occurred in those states.

Bird biologists believe migratory wildfowl inoculated farms in those states, infecting the domesticated birds, causing sickness that swept through poultry houses and killing chickens and turkeys. Those animals that didn’t die were destroyed and, for the most part, composted on-site, often with the help of emergency management response teams from North Carolina.

Now, after spending the summer in the far northern parts of North America, migratory wildfowl are poised to return south for the winter, and Meckes worries they’ll carry avian influenza with them.

Birds, pigs and people

In the past, pandemic flu viruses have been called avian or swine flus, sometimes Asian flu, and there’s a thread of truth in each of these names.

This picture provides a 3D graphic representation of a influenza virion’s ultrastructure. The virion is covered by different proteins that give each flu its characteristic “appearance” to the immune system. Illustration credit: Dan Higgins, CDC

Influenza viruses are variable, re-assorting their genetic structures frequently as they’re carried around in their hosts. Meckes explained that an influenza virus thrives where it can replicate without killing the animal harboring it.

Better yet if that animal moves around, allowing the virus to spread. That makes migratory waterfowl the perfect hosts.

“It might be a few days of illnes…. Who knows if the duck has an elevated temperature?” Meckes asked. “The virus just lives fat, dumb and happy in the birds.”

The birds defecate onto fields and into ponds and streams, spreading the virus around. Then the duck or goose takes flight, on to the next field or stream.

“It’s the perfect symbiotic relationship,” Meckes said.

Then there are the pigs.

“The pig has receptors for human viruses and avian influenza viruses, and it would seem to be an opportunity for these viruses to come together and re-sort and make changes,” Meckes said.

That happens frequently on farms around the world where pigs and poultry and people all live in close proximity. It happens in parts of North Carolina too, where poultry farms butt up against swine farms, all tended by people who sometimes move between those farms.

“I used to take my kids to the Durham Museum of Life and Science when they were little, and I always enjoyed the part of the petting zoo where they had the duck and the pig share the pen together and the kids could come up,” joked Zack Moore, an epidemiologist from the Department of Health and Human Services. “And I thought, ‘This is it right here; this is North Carolina in a nutshell.’”

Image courtesy USDA

 

Anatomy of an outbreak

About this time last year, cases of HPAI started to be detected in wildfowl along the US-Canada border. U.S. Department of Agriculture scientists began testing wildfowl after outbreaks of HPAI in British Columbia, followed by other outbreaks along the Pacific Flyway in Oregon and California.

North American flyway map. In summer months, birds from each region of the continental U.S. mix in far northern Canada, swapping viruses before returning to their wintering grounds farther south. Map courtesy U.S. Fish and Wildlife Service

Then the disease appeared in the Midwest, along the flyways that span the middle of the country, ostensibly carried by those migratory waterfowl.

Emergency responders from North Carolina traveled there to help “depopulate” some the world’s largest poultry houses.

“There were 2.54 miles of turkey houses, and they depopulated it in four days with 100 percent mortality,” Meckes said.

North Carolina agriculture emergency workers have been training for years for just this kind of contingency; they use firefighting foam to suffocate the birds in the houses within minutes. Either way, infected farms will lose tens or hundreds of thousands of birds, because once the highly pathogenic virus is inside, most of the birds will die of respiratory disease.

Once summer came, the migratory waterfowl flew north, where they mingled with other birds from Asia and North America and sometimes Europe. Now that the weather is starting to cool, they’re headed south again.

“We’ve had an unusually warm fall, so some of the migratory birds haven’t even begun to make their way south,” Meckes said.

But one hard freeze in Canada and the Northeast, and birds will point south and take wing.

Humans not at risk

Julie Cassani, DHHS’ director of public health preparedness, quipped that medical scientists will always hedge their bets and say there’s “a possibility” of human infection from a bird flu. But she admitted that the possibility with this HPAI is very low.

“We’ve had no human illnesses from this flu, and there’s been lots of opportunity for that. So it looks good that we will not have any human cases,” she said. “During the HPAI in Minnesota, there was a fairly large outbreak of influenza B among the incident command staff. If there was opportunity for those flu viruses to do their thing, they could have potentially done something.”

“Humans are not good mixing pods for flu.”

Even though humans are not at risk, the poultry and swine industries – in particular, in the eastern part of the state – are.

Tires, undercarriage and the roll-off container are disinfected and washed as a biosecurity precaution before and after entering poultry farm property. Photo credit: Mike Milleson, USDA APHIS via flickr

That’s gotten Meckes thinking hard about biosecurity and questioning some of the ways things have been done here.

“Conceptually, is it in everyone’s best interest to put six million genetically identical birds in the same place?” Meckes asked. “Is it conceptually the best to put a laying house with three million birds immediately adjacent to an area that’s flooded every fall for duck hunters? Those are situations that actually exist.”

“So we really are going to begin to rethink conceptual biosecurity,” he said.

In the meantime, there’s lots of planning for biosecurity in the form of how to disinfect vehicles and equipment and people that move from farm to farm.

Mike Sprayberry, head of the state Division of Emergency Management, described extensive planning, tabletop exercises and preparations in place to respond once that first chicken starts to cough.

“We’re going to make sure that the people who are out there in the field … are logistically supported,” Sprayberry said. “We’re going to get a state of emergency, and that state of emergency could be just for one county. It might also be for all 100 counties.”

Meckes said he’s been concentrating most of his efforts over the past year on preventing HPAI from infecting poultry farms in North Carolina. But if those prevention efforts fail, he said he believes his people are ready, with equipment in place and teams ready to deploy in hours.

“We have trained for years for this eventuality,” he said.

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