Strategies to deal with avian flu: Will Canada start vaccinating poultry?

Canadian experts are discussing whether the country should begin vaccinating poultry as a way to prevent highly pathogenic avian influenza from spreading and potentially infecting humans, attendees at the Canadian Immunization Conference heard. More than 30 countries have used a vaccine to combat spread of avian influenza, explained Alyson Kelvin, virologist and vaccinologist at the vaccine and infectious disease organization at the University of Saskatchewan in Saskatoon, Saskatchewan. France vaccinated ducks against the H5N1 clade 2.3.4.4b last year, which reduced outbreaks by 95%, according to a study available in pre-print. Vaccine use in poultry is on track for approval in the European Union, Brazil and the U.K.Vaccinating poultry could impact human health. In a review of control strategies for H5 and H7 avian influenza viruses, the authors note that in 2016 there were 766 human cases of avian H7N9 influenza virus infections in China. After China introduced a strategy that included vaccinating poultry against H7N9, there were only four human cases in subsequent waves and there have been no human cases since 2019.Read: What to tell colleagues and patients about avian influenza (‘bird flu’)While vaccinating animals could decrease transmission and environmental contamination, there are challenges, Kelvin noted. Vaccinating large numbers of poultry is logistically difficult and could increase the risk of the virus mutating. A test differentiating infected from vaccinated animals (known as a DIVA test) would be needed before vaccinated poultry can be transported off the farm. Canadian experts also have to decide what vaccination strategy to adopt—outbreak response or ongoing maintenance—and when to start. Controlling the spreadCases of avian influenza have been detected in North America sporadically, but in 2020 a new clade of highly pathogenic avian influenza was identified in China. This H5N1 clade 2.3.4.4b was then found in North American in the winter of 2021-2022. It infected cattle in the U.S., and in birds in Canada and the U.S.. A May 2024 paper in Journal of Virology notes it was found in wild birds in New York city. There have been a few cases in humans, including one in British Columbia. Read: From transmission to symptoms, what to know about avian flu after B.C. caseThe main concern is the avian flu in livestock, said Kelvin. “This is an amplification zone.”Before 2022, the idea of vaccinating poultry wasn’t on the table, said Dr. Cathy Furness, deputy chief veterinary officer of the Canadian Food Inspection Agency (CFIA). Now, CFIA has a task force to see if that strategy might work in Canada, but “we still do not have any decisions in place about using vaccines,” Furness said. Canada is now in “wave six” of the H5N1 outbreak, Furness said. As of December 3, there were 479 infected premises with cases of avian influenza. “This, for CFIA, is unprecedented because of the scope,” Furness said.Canada will need to embrace a number of strategies to reduce the number of outbreaks. “Vaccination alone will not prevent this,” she said.One of the most important defence mechanisms to protect Canadian livestock from high pathogenic avian influenza is biosecurity, Dr. Furness said. This translates into farming practices that keep wild birds and mammals away from livestock, such as managing litter on the farm and not leaving extra feed outside. Read: Build vaccine stockpile, use wastewater testing for H5N1 bird flu, experts urgeBeing alert and prepared for more cases in humansDr. Deena Hinshaw, a clinical professor in the division of preventative medicine at the University of Alberta in Edmonton, said that healthcare professionals “need to remind ourselves that we have very effective tools” and are well positioned in technical skills to deal with any avian influenza outbreaks.There are human vaccines for H5N1, although none are available for the public. Health Canada has recently approved and purchased some of the vaccines.“The good news is we also have antivirals as another tool,” said Dr. Kanta Subbarao, professor in the department of microbiology and immunology at Laval University in Québec.Surprisingly, birth year will affect how much avian flu will impact a person because of immune imprinting, Dr. Subbarao said. Whatever wild influenza virus a person has been exposed to in the past will provide some immunity if they encounter similar viruses, including avian influenza viruses. Influenza is caused by a wide range of viruses, and the only way to identify the strain is through a lab test, Dr. Subbarao said. Physicians should maintain a high degree of suspicion of possible avian influenza if they see a cluster of cases where or when they wouldn’t expect to see one, or if it’s connected to exposure to animals.Check for conjunctivitis, Dr. Subbarao added. It was a symptom seen in U.S. human cases not usually seen in seasonal flu. This may have been because the human cases were in dairy cattle workers, who might have accidentally rubbed their eyes after touching milking equipment or may have been exposed to aerosols related to the procedure, said Dr. Matthew Miller, director of the Michael G. DeGroote Institute for Infectious Disease Research at McMaster University in Hamilton, Ont. Dr. Miller was interviewed by Canadian Press. Human and avian influenza viruses differ in the types of receptors with which they most commonly bind. Unlike human influenza virus receptors, avian influenza virus receptors are present in the lower respiratory tract such as the trachea and bronchi, Dr. Subbarao explained This means infections could lead to more severe outcomes. More information for healthcare professionals about Avian influenza is available from Health Canada.The Canadian Immunization Conference was held in Ottawa in late November. Read: What do you do when a goose dies in your backyard, amid concerns about avian flu?

Strategies to deal with avian flu: Will Canada start vaccinating poultry?

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