Bird flu’s recent jump from poultry to cows is not reason enough for “all out panic”, though it is a “small step along that line”, warns the Jameel Institute at Imperial College London’s Dr Thom Rawson.
Such a step was taken when H5N1 was found in US cows last year, adds Dr Rawson, whose focus area is tracking the pathogen, specifically within commercial poultry flocks.
“If you’d asked me a year-and-a-half ago about H5N1 crossing over into cattle, I would have said absolutely not possible. Cows don’t get this influenza,” he says.
Though the reason Dr Rawson believes farming, food and the world have taken a step closer to higher panic levels is because “any time a pathogen leaps to another reservoir,” it creates a potential new issue.
“It’s also humbling that there are these surprises blindsiding us,” he says.
Peak bird flu season, however, is over and the world is in the latter parts of the pathogen’s infection cycle. Although cases are going up even now, with farms in Scotland reporting infections, it wasn’t as bad this year as previous ones.
How many cows infected with bird flu?
So why are H5N1-infected cows in the States of concern to Dr Rawson and his colleagues?
“Cattle is more hands on than poultry,” he explains. “There’s more automation in poultry, but dairy farmers tend to be more involved with the livestock.”
This heightens the risk of workers contracting bird flu, with bird-to-human cases remaining low due to farmers' ability to limit contact.
It is unknown how bird flu jumped to cows. Though it has been discovered cows’ udders or mammary tissues are similar to chickens' gut tissue and human lung tissue.
Experts do believe it could be possible a cow came into contact with infected bird faeces by lying in it. Infection would have been caused on contact with the cow’s udder. Equipment in milking parlours would have then been contaminated and it would have passed from cow to cow that way.
The US’s farm animal tracking systems, specifically for cattle, aren’t as stringent as Europe’s and the UK’s, which are especially strict following the devastating BSE outbreak in the 1990s.
In response to H5N1 detected in cows – cases of which stood at 917 dairy herd infections last week – the USDA launched a voluntary monitoring and tracking program.
However, of the 36,000 US herds just 75 have signed up to the system.
A fund of nearly $2bn to combat and stop the spread in animals was also announced by the Biden administration, with $1.5m going to the USDA.
Will EU cows become HN51 infected?
“It’s very unlikely it will make its way over from the US to the EU,” says Dr Rawson of the variant found in cows.
Preventing a cross from birds into cows in Europe would also, on paper, be easy to control and a case of correctly sanitising milking equipment.
“Now we know cow udders have these receptors, it’s plausible we could have a one-in-a-million kind of event elsewhere. It’s something you have to think could happen,” explains Dr Rawson, who says Europe could have similar cases of bird-to-cow infections.
Dairy contaminated with H5N1 can be cleansed by pasteurisation. US health authorities are currently testing non-pasteurised cheeses and products.
The most effective way of controlling bird flu infection and spread, however, is communication, Dr Rawson believes.
Cases of H5N1 in cows in the US “shows the real need for keeping a good relationship between farms, government and industry”, he says.
“A relationship that doesn’t seem – or the communications – as effective in the US as it is in the EU."