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Avian Influenza: Past, Present, and Future
In 1996, an H5 avian influenza was identified in geese in Guangdong, China. Almost 20 years later, a variation of that virus wiped out 48 million birds in the U.S.
How did the virus get from China to the U.S.? Why did it take 20 years? And how did it spread so rapidly? Those are questions that Travis Schaal, internal technical services manager at Hy-Line International, is trying to answer to ensure that the devastation caused by the virus from 2014 to 2015 isn’t repeated again. This effort is particularly important because the bird flu was detected in an Indiana flock earlier this month, prompting the extermination of 400,000 turkeys and egg-laying hens.
Who is Hy-Line International?
Founded in 1936, Hy-Line was one of the first modern layer genetics companies to incorporate hybridization and hybrid vigor into its breeding program on a commercial scale. These methods were used with genetic selection and scientific statistical analysis to develop and improve one of the world’s most extensive gene pools.
Today, Hy-Line provides the primary breeding stock for nearly half of the world’s commercial egg-laying industry. This stock is housed in Iowa, where there were 77 cases of avian influenza last year. For this reason, Schaal, one of six veterinarians on staff at Hy-Line, was determined to understand how avian influenza was spreading and, more importantly, how to keep Hy-Line’s flocks healthy.
The spread of avian influenza worldwide
After the first detection of H5 in China, the virus almost disappeared until 2004. When it returned, it did so with a vengeance, sweeping across Asia in 2004, Eastern Europe in 2005, and then moving across the Middle East and the rest of Europe in 2006.
Avian influenza is spread through the feces and nasal discharges of wild waterfowl. For the most part, wild birds don’t show clinical signs of infection. These seemingly healthy birds continue following their respective flyways.
There are roughly nine different flyway patterns and, besides the North American flyways, most of these overlap in the North Pole. This is probably where wild birds from Asia, with this lineage of the virus, spread the virus to other wild birds who carried it to their home countries.
This led to a multitude of avian influenza outbreaks in Europe, Asia, the Middle East, and parts of Africa from 2005 to 2013. North and South America, however, remained mostly unscathed. That all changed in December of 2014.
The spread of avian influenza within the U.S.
The North Pole isn’t the only place where flyways overlap. The waterfowl flyways from eastern Asia and North and South America also converge in Alaska. This is the most likely source of cross-contamination between Eurasian and North American waterfowl populations, according to Schaal.
Another alternative is that Asian birds with the virus got lost during migration and ended up in North America. “Birds don’t know how to read maps. They don’t have a GPS in their head, so they mess up flyway patterns all the time,” explains Schaal.
Regardless of how it ended up in North America, once the virus was here, it spread rapidly. From December of 2014 through June of 2015, avian influenza was detected 223 times. The majority of the cases were in Minnesota and Iowa.
In Minnesota, avian influenza was detected on 104 premises – 99 of which were for turkeys and five were laying hens. Almost 9 million birds were killed. At final tally, Iowa lost 31.7 million birds from 77 different sites, split almost evenly between turkey and laying hen premises. The surprising difference between these two states is how the virus spread.
“In 40 of the Minnesota cases, the virus came directly from an infected wild bird to the commercial flock. We can tell this by examining the genome of the virus,” says Schaal. “However, in Iowa this only happened twice. The virus was being spread between farms – not by wild birds.”
Semi trucks driving from infected sites to healthy barns or contract workers who work at multiple poultry facilities may have spread the virus across Iowa. The long life of the virus in cool, wet conditions made it difficult to determine what the cause was on most farms.
"So the virus could be on a farm for 21 days before chickens started dying."
“The virus wasn’t well adapted to chickens,” says Schaal. “So the virus could be on a farm for 21 days before chickens started dying. A producer might think a mistake was made a few days ago when a truck wasn’t washed before coming onto a property, but in reality it could have been an incident three weeks ago that caused the infection.”
Would Iowa producers have lost as many birds if more strict biosecurity procedures had been in place? Most likely not, which is why it’s critical for producers to focus on biosecurity moving forward.
How poultry producers can protect their flocks
Producers should start by implementing a biosecurity plan, which might include hiring a biosecurity officer. The plan should include ways to protect the flocks, including reducing the amount of shared equipment and employees as well as educating employees about how the virus spreads. It should also include a way to depopulate the entire farm within 24 hours of the virus being detected. This proved especially challenging during the 2015 outbreaks, which also contributed to the spread of the disease.
Other factors were found to decrease the likelihood of avian influenza, including having a true wash station for trucks on site, being more than 100 miles from the egg processing site used, and being more than 100 meters from a public road.
Even something as simple as having cement or gravel around buildings instead of grass can help. “This is what we do at the Hy-Line barns. It allows exposure to sunshine and helps disinfect the site,” explains Schaal.
H5N2, the specific avian influenza that hit the states, isn’t going to disappear. “Young waterfowl will carry the virus for another season,” says Schaal. “It could continue to affect the globe for the next three to five years. It’s also likely that new viruses will emerge.”
In anticipation of further cases, the USDA and industry experts have explored different ways to stop avian influenza. Vaccines and resistant birds are two possible options that have been discussed in addition to biosecurity. Schaal is hesitant about both.
Using vaccinations could prevent the U.S. from exporting poultry products to other countries. It would also be difficult to match the vaccine exactly with the specific strain of the virus, and the virus could mutate in vaccinated birds, explains Schaal.
Birds that are resistant to avian influenza may operate similarly to today’s wild ducks and geese. They would appear healthy but could still possibly spread the disease to other birds. This would also allow for comingling of the viruses. For these reasons, Schaal feels that biosecurity is the best option moving forward.
The recent H7N8 high and low pathogenic avian influenza in Indiana highlight the dynamic influenza situation. The H7 virus is a North American lineage that likely started as low pathogenic and became high path, as opposed to the Asian lineage H5 that entered the U.S. as a high path virus.