Rapidly Mutating Influenza
Viruses Threaten Family Pets
Just in case you weren't panicking enough over the swine flu,
it turns out that the virus that causes it, H1N1, can make dogs,
cats and ferrets sick, too.
H1N1 got its nickname, the swine flu, due to its origin in pigs,
but it's really a genetic mashup of human, swine and bird viruses.
Because it can cause serious illness and even death in susceptible
humans, particularly infants and pregnant women, veterinarians
greeted the recent news that it could affect family pets with
The first cases in pets were reported in ferrets, which are notoriously
prone to influenza viruses. But when the American Veterinary Medical
Association (AVMA) reported last month that a sick cat in Iowa
had the disease, epidemiologists and virologists took notice.
It was the first time a cat had become ill from an influenza virus.
Since then, two more sick cats, one of whom died, tested positive
for H1N1, and Chinese officials announced Saturday that they had
isolated the virus in two sick dogs.
Dr. Tony Johnson, a clinical assistant professor at the Purdue
University School of Veterinary Medicine, said that it doesn't
look like our pets are a risk to us.
In fact, we're a risk to them -- every cat that's been diagnosed
with H1N1 lived with a human who had a respiratory illness shortly
before the cat became sick.
"So far there is no evidence that this virus can be passed
from cats to humans," Johnson said. "Sometimes a virus
can make a host sick, but not reproduce and become infectious
in that host."
That appears to be the case with the H1N1-positive dogs in China
as well. The Chinese Ministry of Agriculture reported that the
virus found in the dogs, whose breeds and ages were not given,
was 99 percent identical to the human swine flu, suggesting that
they contracted it from people.
"Only when the virus mutates within dogs will it be a new
threat to humans," Feng Zijian of the Chinese Center for
Disease Control and Prevention told China Daily.
Johnson acknowledged that feline to human transmission of the
virus can't be ruled out, but he asked cat owners not to over-react.
"The humans who gave the virus to their cats recovered, and
so will most cats," he said. "Common sense and a cool
head are better than flipping out and putting your cat out with
There may be many more undiagnosed cases of H1N1 in pets, because
it's rarely tested for and has symptoms similar to other canine
and feline diseases, which are usually mild.
The AVMA describes those symptoms as "lethargy, loss of
appetite, fever, runny nose and/or eyes, sneezing, coughing or
changes in breathing (including difficulty breathing)." But
as with humans, some dogs and cats with respiratory infections
will go on to develop pneumonia, and some of them will die.
With doomsday scenarios about mutant pathogens making headlines
around the globe, a certain amount of over-reaction isn't a surprise.
It doesn't help that one of the viruses that can be transmitted
between humans and dogs and cats is a pretty terrifying one: rabies.
But rabies in domesticated animals is very rare in the United
States, and most pets are vaccinated against the disease.
A handful of other diseases and parasites can affect humans,
dogs and cats, like fleas, intestinal worms and skin diseases
But until five years ago, no influenza virus had ever been known
to cause illness in a dog or cat, which is somewhat surprising
given that influenza viruses typically originate in farm animals
and wildlife, and dogs and cats have always lived closely with
humans and their livestock.
The H1N1 outbreak isn't the first time an influenza virus has
adapted to be able to cause illness in a dog, however.
That occurred in 2004, when an equine influenza virus, H3N8,
was identified as the cause of a deadly outbreak of respiratory
disease in racing greyhounds in Florida.
Woody, a flat-coated retriever, is a healthy adult dog today,
but when he was just a puppy in Texas, he came down with what
his breeder thought was "kennel cough," the dog version
of a cold.
But what Woody had was something no one thought to look for,
a brand new virus that posed a serious risk to very young, very
old and immune-compromised dogs.
"He spent the next month at the vet school at Texas A&M,
fighting for his life," said his owner, Gina Spadafori, who
lives in Sacramento. "He survived, but he was weak and spent
many weeks recuperating after that."
The bug that almost killed Woody was a viral changeling dubbed
H3N8. Originally thought only to affect horses, it had adapted
itself to be able to cause disease in another species, the dog.
Once researchers started looking for H3N8, they found dogs carrying
the virus in 30 states (including California) and the District
of Columbia, a wide distribution suggesting it had been spreading
without detection for quite some time.
The virus, now dubbed "canine influenza virus" or CIV,
probably went undiscovered for so long because its symptoms in
most dogs mimic the usually-mild kennel cough, officially known
as "canine respiratory disease complex."
"Canine influenza virus is generally a mild disease, with
typical symptoms of cough, some lethargy, fever and perhaps nasal
discharge," said Dr. Melissa Kennedy, a clinical virologist
at the University of Tennessee Veterinary Teaching College and
an infectious disease and immunology consultant for the Veterinary
But for some dogs, like Woody, that risk is much greater. "As
with the human influenza, there is a risk for secondary bacterial
infections which can be serious," Kennedy said. "This
risk is highest among puppies and elderly dogs, where immunity
may not be as good as in healthy adult animals."
Researchers at Iowa State University estimate around 80 percent
of infected dogs become ill, and even the 20 percent who don't
can still infect other dogs. Around 10 percent of sick dogs develop
pneumonia, and somewhere between 1 and 5 percent die.
A full list of h1n1 vaccine ingredients, alerts and warnings.
Reference Sources: sfgate.com
December 2, 2009