The Avian Influenza, otherwise known as the Bird Flu, has been infecting dairy cattle in the U.S., causing batches of milk to be discarded.
This highly pathogenic avian influenza, otherwise known as H5N1 or the bird flu, has been infecting wild birds and domestic poultry for decades, and recently it has been found to be infecting dairy cows South of the border.
According to Professor of Global Health and Infectious Diseases at the University of Calgary, Frank van der Meer, avian influenza is so pathogenic in birds that if a flock of poultry catches the H5N1 virus, it has a very high mortality.
"That has been circulating in birds from the early '90s, this particular strain," explains van der Meer. "And has slowly made it all the way up to North America. And what we now see is that this particular bird strain has made its way, one way or another, into the dairy industry."
According to the General Manager of Services and Research in the Animal Agriculture Business Unit at Telus Agriculture and Consumer Goods, Calvin Booker, when domesticated poultry becomes infected, the birds need to be quarantined and the birds are killed to help prevent the avian flu from spreading.
"For the most part, those viruses stay confined to poultry operations and to the wild bird populations," Booker explains. "And as you can imagine, as wild birds migrate from North to South in the fall and then return and migrate back North again when we get to the Spring, that creates the opportunity for them to interact with our domestic poultry and livestock operations."
While that hasn't caused too many cases of the bird flu affecting non-poultry animals, back in the first quarter of 2024, some cattle in the Texas panhandle and western Kansas areas were found to be infected with the H5N1 virus.
But, they didn't know they were infected with the H5N1 virus when the cattle first began to show symptoms.
"Dairy cows became sick with a syndrome that didn't really fit any of the normal dairy cow diseases. And as the veterinarians and pathologists and others that did the disease investigations worked through things, they were able to identify that it was, in fact, a version of this H5N1, highly pathogenic, avian influenza virus that had spilled over into the cow population," Booker says.
This was causing large numbers of cows to get sick in a herd, but there were low mortality levels.
In fact, according to van der Meer, roughly 40 per cent of the infected cattle become quite sick.
"It would, sort of, go through like the flu does in the human population, where some people don't get sick, lots of people do get sick. Very few people, generally speaking, have serious adverse events. And then over a course of a couple weeks it runs its course, and the animals recover," said Booker
Booker adds that after the virus was examined, they found that the exact same virus fingerprint was found in other dairy farms as well, meaning the virus was being spread from cow to cow.
"Probably, both, from movement of cattle between herds. Shared equipment, shared personnel that worked on more than one farm. Lots of different things that happened, but it started to spread very quickly and spread to adjacent states."
Many cattle, according to Booker, were being moved to other states before people fully understood how the virus spread amongst cows.
Booker believes there are over 900 dairy herds across the States that have been identified to be carrying this virus.
"One of the things that's a really unique characteristic is that the mammary gland of dairy cattle, of cows, but specifically of dairy cattle, has one the same receptors that this H5N1 virus attaches to. And once it gets in the mammary gland, it produces large amounts of viral particles," Booker explains. "That's part of the reason milking dairy cows have been susceptible to the virus and why it spreads so much."
While the virus has been spreading through dairy cattle quite quickly, it has been determined that it offers very few public health risks, but those who work with the dairy cows are at a slight risk of catching the H5N1 virus.
When people have caught this strain of the virus, their primary symptoms include conjunctivitis, otherwise known as pink eye.
Due to how the virus is spreading in dairy cows, the United States Department of Agriculture has implemented a variety of movement restrictions and requirements with cattle, including mandatory bulk tank milk testing for the virus, even in herds that don't show evidence of the disease.
As part of the bulk milk testing, a farm in Nevada was tested for H5N1, and they found that their cattle were infected with a slightly different version of the virus than what was found on other farms.
According to Booker, a farm in Arizona was recently found to have the second version of the virus as well.
"Doesn't appear anything else has really changed for the virus. It's not particularly infectious to humans," Booker says.
While the virus isn't currently presenting too much of a risk to humans, there is always the concern the virus will mutate.
"When these viruses replicate in other species, there's always the risk that there are some adaptations or mutations that allow the virus to actually colonize humans at a much different rate. And then that's what creates the risk to the human population," Booker explains
The reason why the virus can spread from dairy cows to humans is because the human eye, not only shares some of the same receptors as birds, it has the same receptors that are found in the mammary glands of cattle.
Because the receptor isn't widely spread out in the body, the virus will primarily affect human eyes, such as causing conjunctivitis, but doesn't pose a significant risk to humans.
That is unless the virus mutates.
As van der Meer says, because humans are more closely related to mammal animals than birds, as more cattle get the bird flu, there is an increased chance the virus will adapt.
"Let's say you get an H5N1 plus an H1N1 or an H3N2, so the bird flu with the seasonal flu combined, there's a good chance that there will be a recombination. Viruses are able to swap out pieces of the genome of the RNA."
By doing that, the virus that results from that new combination is more adapted to humans and can be very pathogenic.
Other animals, such as cats, skunks, and rodents, have all been found to be susceptible to the virus, and cats are likely to pass away when infected with the virus.
While most cases have been mild, there was a report of a youth in British Columbia who was infected, which caused some respiratory issues, and a person in Louisiana actually passed away from the bird flu.
The person who passed away, though, had other secondary medical conditions that could have caused the bird flu to be worsened.
When cattle are infected with the avian flu, at first it appears as though the cattle are producing less milk, eating less, and there will be a few sick cows in the herd.
"That's what you saw if you were a stock attendant or a dairy worker or a veterinarian on those operations. What we know now is that by the time we see those signs, that's probably two or three weeks into when the first animal in the herd became positive. And it is wildly spread amongst every pen and every animal by the time you see those symptoms at that level happening."
By that time, trying to quarantine the sick animals from other cattle on the farm won't help much, because it has already spread to the other animals on the farm.
Because of that, when the cattle get infected by the virus, the animals receive supportive care instead, and it's important to make sure they are drinking enough water.
If a dairy cow gets infected with the H5N1 virus, will the virus be in the milk as well?
As part of normal dairy practices and normal production practices on a dairy farm, when a cow goes to get milked, the milk gets assessed to make sure it looks normal.
If the milk doesn't look or appear normal, it doesn't enter the bulk milk tank.
But, if the milk does look normal, it goes into the bulk tank that contains the milk from all the cows on the farm.
"Going back to the 1800s, fortunately, Louis Pasteur realized that, at the time I'm pretty sure it was tuberculosis, he realized if milk was contaminated with bacterial pathogens, that posed a risk to people that drank it," Booker explains. "And so, he developed the process of pasteurization, which is where we bring the milk up to a certain temperature for a certain defined period of time, and it actually inactivates any bacterial viruses and other things that are in the milk."
In Canada, Federal law states that all milk must be pasteurized prior to it being sold, to help keep Canadians from catching these bacterial viruses.
"The milk is safe when you're buying pasteurized milk. The risk is for those that potentially decide to consume raw milk. Which is unpasteurized milk. That's not commonly sold commercially in grocery stores, because we learned, like, 150 years ago that that was a risk factor for disease," says Booker.
But, in the States, not everywhere requires milk to be pasteurized before it is sold.
Bookers adds that there are people who believe drinking raw milk is more beneficial than pasteurized milk, but the risks outweigh any benefits.
Currently, there have been no reports of cattle in Canada being infected with the H5N1 virus, and Booker says that's because very few dairy cows come up to Canada from the United States, which has helped to prevent the spread.
But van der Meer says that if a farmer suspects their cattle is infected with the bird flu, it should be reported to the Canadian Food Inspection Agency.
As the bird flu epidemic progressed in the States, very strict protocols and procedures were put in place for cattle coming into the country.
Not only that, but because the bird flu was infecting cattle in the States prior to it coming to Canada, Canadian dairy farmers were able to put testing procedures in place quickly.
Booker adds that with the amount of bird flu that is currently in the States, there is the concern that when the birds migrate back north in the spring, they may bring the H5N1 virus with them.