The rise in cases of avian flu on farms in the United States, the contamination of herds of cows and cases recently transmitted to humans worry Canadian authorities who say they are monitoring the situation very closely.
Avian influenza, more precisely avian influenza subtypes H5 and H7, is a disease subject to mandatory reporting in Quebec since it is a zoonosis, that is to say it can be transmitted between animals and humans.
Human cases of bird flu are very rare, but last spring, three human cases associated with infected dairy farms were reported in the United States. Two infected people had eye symptoms and the third person had a respiratory infection.
Globally, 15 human cases of a specific H5N1 clade have been reported since the clade emerged in 2022: two cases in China, two cases in Spain, five cases in the United Kingdom, four cases in the United States, one case in Ecuador and one case in Chile.
The majority of cases (11 out of 15) had a history of exposure to poultry, the Quebec Ministry of Health said. “Given the small number of human cases reported to date globally, the virus appears to have a limited capacity to infect humans,” wrote the Ministry of Health in an email sent to The Canadian Press.
“We know that several humans have shown clinical signs. (…) The good news is that it is not transmitted between humans. The day that happens is the day we will miss COVID,” commented Dr. Jean-Pierre Vaillancourt, full professor at the Faculty of Veterinary Medicine at the Université de Montréal.
“In Canada, we have had H5N1 for many years, but it is weakly pathogenic. What is generally increasing worldwide are highly pathogenic viruses. (…) To give a simple definition of highly pathogenic, it is that for four infected birds, at least three die,” summarized Mr. Vaillancourt.
According to him, it is unlikely that things will get complicated in humans, but the risk is not zero. “In general the risk is very minimal while here the risk is low to very low. But low to very low, being a politician or consultant to a politician, I would say: you had better not neglect this, especially in the post-COVID period,” he warns.
The specialist in the epidemiology of zoonoses explained that avian flu is a virus that replicates and sometimes its mutation allows it to become “a super virus”.
To date, no cases of transmission of the disease to humans have been observed in Quebec or Canada.
Strengthen protective measures
We have a pandemic in wild birds of a series of H5N1 variants that are highly pathogenic, said Dr. Vaillancourt.
“Currently, the series of H5N1 variants that concern us – we have them in Quebec and in Canada – we have identified them in at least 489 species of birds and in more than 200 species of mammals,” he said.
In the United States, the virus has been detected in wild birds in every state, in dairy cows in 12 states, and in more than 200 mammals from more than 20 species across the country.
No infected dairy cow farms have been detected in Quebec or Canada, nor in dairy products.
Following the detection of highly pathogenic avian influenza H5N1 in cattle and goats in the United States, the Public Health Agency of Canada (PHAC) conducted a risk assessment in April. It estimates that for the general Canadian population, the likelihood of human infection with H5N1 acquired from livestock over the next three months remains “very low.”
The situation remains worrying. The Ministry of Health has also mandated the National Institute of Public Health of Quebec (INSPQ) to develop recommendations for protection measures for workers in the sheep, beef and pork industries in the event of an outbreak.
“Indeed, it is a concern that it has entered the ruminant sector such as dairy cattle, kids and alpacas,” said Martin Pelletier, agronomist and coordinator of the Quebec Poultry Disease Control Team (EQCMA).
“This means that the virus is taking hold and this represents additional exposure for the poultry sector which is more affected by this disease than other types of animals.”
Dr. Vaillancourt shares his concern. “With cows, there are more and more mammals, more and more opportunities for the virus to replicate. On the front lines, it’s a concern for people in direct contact with these animals,” he explains.
The Quebec Ministry of Agriculture, Fisheries and Food (MAPAQ) and its industry partners have invited dairy cattle breeders to increase their vigilance and biosecurity measures.
The Canadian Food Inspection Agency (CFIA) has also enhanced its protection and surveillance measures, notably by requiring that lactating dairy cows imported from the United States into Canada obtain a negative test result for highly pathogenic avian influenza.
Worried producers
In 2022, 23 poultry production sites were affected by avian flu in Quebec and this rose to 28 last year. Since the start of the year, three poultry farms have declared the presence of H5N1, according to the Ministry of Health.
“The potential source of contamination is wild birds which are carriers, and they can spread it mainly through their droppings or secretions,” explains Mr. Pelletier. The crux of the matter is therefore to create a barrier between the exterior of the buildings and the interior.
Benoît Fontaine, general director of the Quebec Poultry Disease Control Team, is also worried about the situation in our southern neighbors.
According to him, producers are concerned and have made health improvements, for example destroying ponds that attract birds or having separate tractors for the fields, installed away from buildings.
He talks about improvements that go beyond the norm, like having a dividing bench at the entrance to the hen house or washing hands. “I believe that everyone has increased their biosecurity and that is perhaps one of the reasons why cases are down (this year),” said Mr. Fontaine.
The protocol for a site contaminated with avian flu requires that producers exterminate all their birds and disinfect the building.
If there were cases in cattle, the CFIA would not intervene as it does in the poultry sector, Pelletier said. There would be no depopulation of herds. “It doesn’t have the same impact. For cattle, it manifests itself through certain clinical signs, but there is no mortality,” he explained.
“This is why in Quebec, the MAPAQ, with the industry, is developing an action plan for a voluntary self-quarantine and control intervention to minimize the risks of spreading the disease,” continues Mr. Pelletier.
In addition to a self-quarantine period for the entry and exit of animals, milk from sick or positive animals would be discarded, MAPAQ said. As an additional precaution, milk from healthy animals in the herd will be sent to a plant that exclusively pasteurizes milk, which destroys the virus.
