As the H5N1 avian influenza virus spreads among poultry and cattle in the US and infects a dairy worker in Texas, public health and infectious diseases experts in Canada eagerly await surveillance updates to better understand North American risks.
On May 3, Canadian health and food agencies announced increased livestock and milk testing and surveillance. The Canadian Food Inspection Agency reported that pasteurized milk, properly cooked chicken, and eggs are safe against the highly pathogenic avian influenza.
Our time is undetermined. We must be concerned that H5N1 was likely in US cattle for a few months before it was recognized and before cow movement controls were put in place “Scott Weese, DVM, professor of pathobiology at the Ontario Veterinary College and director of the University of Guelph’s Centre for Public Health and Zoonoses, Guelph, Ontario, Canada, told Medscape Medical News.
He replied, “We have no proof of it, but we need to study and take more time to determine if it’s made it here.
As of May 14, the CDC had found H5N1 in 46 dairy herds in nine states, including new cases in Colorado, Idaho, and Michigan on May 7 and 8. Iowa State University, Ames, Iowa, researchers reported that numerous household cats died in March after consuming raw milk from sick cows on a north Texas dairy farm. In a preprint report, California and Georgia researchers found viral growth at 59 wastewater treatment plants nationwide.
H5N1 transmission
On May 8, the CDC said current flu surveillance systems can detect H5N1 transmission and early alterations, adding that the “current risk to the general public remains low.” Close or long exposure to diseased birds or livestock increases the risk of respiratory infection, the government stated.
“We only have incomplete US data. Weese said the US Department of Agriculture is communicating more but has big testing gaps. “Farms’ unwillingness to let workers test limits on-farm surveillance. Confirmation of surveillance in Canada was welcome.”
The CFIA, Health Canada, and PHA launched a program to monitor retail milk samples. Per Medscape Medical News, CFIA laboratories will use polymerase chain reaction to evaluate milk samples, with the first findings expected by mid-May. The CFIA website will post the results.
“There is currently no evidence that food, including milk and meat, can transmit avian influenza to humans,” the CFIA media team reported. “Canada has strong food safety regulations in place to protect the Canadian food supply.”
Canadian agencies now require negative test results for US-imported lactating dairy cattle and volunteer testing of cows without clinical indications of the virus.
Transparency and data sharing
The CFIA is also broadening its advice for private vets collecting and submitting cow samples for voluntary testing. Updates will be “available in coming days,” the FDA informed Medscape Medical News.
“I hope we’re taking a proactive approach — if we wait and see, we’ll always be left behind,” Isaac Bogoch, MD, University of Toronto associate professor of medicine and University Health Network infectious diseases expert, said.
“With any outbreak response, transparency and data sharing are important, as well as working with any groups that are impacted, such as building trust with the farming community,” stated.
“What are the motivations for screening cattle, and what may be the economic impact of a positive test? We must consider agricultural screening incentives and remuneration.”
Bogoch said public health professionals are concerned about the increased burden of H5N1 infection in mammals, especially since infectious diseases specialists have tracked it for years since it was found in geese in China in 1996 and infected 18 people in Hong Kong in 1997.
“H5N1 has been known to be an infection of pandemic potential for over 25 years,” stated. “This is the prototype virus that people who work in emerging and reemerging infectious diseases have been looking at for decades, and when you see more of the virus around and it’s doing things it wasn’t doing before, it raises a red flag to say we should get on this.”
Novel flu strains
Due to its unsuitability for people, Weese said most infectious disease and animal health experts aren’t worried about this flu strain spreading from person to person. Instead, they’re worried about more flu viruses.
“The more circulation and the more species that are involved, the greater the chance for more adaptation and recombination with other flu viruses,” stated. “Whether it’s cattle, cats, or other species, we don’t want novel flu strains in circulation, especially in domestic animals that we have contact with.”
Infected Texas dairy worker contracted a slightly different flu strain than in US cattle outbreaks, raising questions about virus mutation, mammal-to-mammal spread, and mammal-to-human adaptation, said Allison McGeer, MD, University of Toronto professor of laboratory medicine and pathobiology and Sinai Health System infectious diseases specialist.
“We’ll see in the next couple of weeks what the surveillance shows here,” said. “It’s a good thing for those of us in Canada that the US has identified this and is moving on it as quickly as possible, and we’ll keep our fingers and toes crossed that it hasn’t crossed the border.”
In the interim, experts advised considering human trials. McGeer highlighted that combined viral testing kits in Canada may detect COVID-19, flu strains, and respiratory syncytial virus, but H5N1 proteins require further testing. In addition, sick patients may not request testing or contact a doctor.
“The human surveillance aspect is OK but not brilliant, and that’s what everybody in every jurisdiction seems to be feeling,” said. “We’re watching, and adding to the current efforts takes time, energy, and resources, so it’s hard to judge right now what to do and how quickly and how far to move.”
She noted that monitoring effluent samples and asymptomatic cattle while waiting for Canadian preliminary results is crucial.
“Then we need to brace ourselves and think about the next steps, depending on what we find,” he said. “Outbreak control measures can be expensive and difficult, so we need to think about how to support the dairy industry and make sure they’re getting through this as safely and effectively as possible.”
Source: Medscape
