“Unlike affected poultry, I foresee there will be no need to depopulate dairy herds,” Texas Agriculture Commissioner Sid Miller said in a statement. “Cattle are expected to fully recover.”
Dairy cows in the US have caught bird flu (stock image) - Media
Credit: Jo-Anne McArthur / We Animals Media
Bird flu has been detected in dairy cows for the first time, the US
Department of Agriculture (USDA) has announced. A farm worker has
also become infected.
Milk samples from cows on farms in Texas and Kansas tested positive
for the H5N1 strain of the virus. The samples were collected for
testing after farmers reported that some cows had become ill. They
also reported that they had found dead wild birds on their
properties.
The H5N1 strain is deadly for birds, but none of the cows have died
so far. They are the latest in a number of mammal species to have
become infected as avian flu rages around the world.
How are cows affected
The USDA has said that the cows seem to have caught the virus from
wild birds, but it isn’t clear how transmission occurred.
Contamination of water or food on the farms by bird faeces or saliva
is one possibility. The USDA is conducting further tests.
The infected cows have displayed flu-like symptoms. These include
fever and thick and discolored milk, as well as a drop in how much
milk they could produce. Any contaminated milk will be destroyed,
while pasteurization would kill any virus that managed to enter the
food chain.
“Unlike affected poultry, I foresee there will be no need to
depopulate dairy herds,” Texas Agriculture Commissioner Sid Miller
said in a statement. “Cattle are expected to fully recover.”
The dairy worker who caught the virus has displayed mild symptoms,
mainly conjunctivitis. They are being treated with antiviral
medication, according to the Texas Department of State Health
Services (DSHS). They are only the second person in the US to ever
catch bird flu.
Transmission between species
Bird flu has affected millions of birds and jumped to 48 mammal
species. Infected mammals, which include sea lions, foxes, otters,
and bears, are most likely to have caught it from eating dead and
infected birds.
A man in a hazmat suit walking through a chicken farm. Adobe Stock
Millions of chickens have died as a result of bird flu.
The virus has reached even far flung locations. In late 2023,
penguins in the Antarctic tested positive for H5N1. Though they were
not showing symptoms and are still healthy, experts have warned they
could spread the disease to other species on the continent.
The risk of humans catching bird flu is low since there is no
evidence of human-to-human transmission. The main route for
infection being close contact with infected birds. Globally, several
people, including workers on chicken farms, have contracted various
strains of bird flu. Some have died as a result. Infectious diseases
experts warn that every transmission to mammals gives the virus a
chance to mutate into a strain that could more easily jump to
humans.
Wild birds not to blame
While wild birds have helped to transmit the virus around the globe
as they migrate vast distances, they are not to blame for its
lethalness.
The H5N1 strain is “highly pathogenic” – meaning, deadly – compared
to low pathogenic strains that naturally and mostly harmlessly
circulate in wild bird populations. H5N1 was first detected on a
goose farm in China in 1996 and reappeared on poultry farms in Hong
Kong in 1997. Experts believe that the growth of intensive poultry
farming have helped to H5N1 and other bird flu strains spillover to
wild birds.
Since bird flu began surging globally in 2021, hundreds of millions
of farmed birds have been culled in a bid to contain the virus. The
culling process itself can be extremely cruel; in the US, an
increasingly common method is ventilation shutdown. This suffocates
and essentially roasts the animals to death. Millions of wild birds
have died horrible deaths from the virus, which can cause
respiratory difficulties, diarrhea, and swelling in the head.