The Pig's Pandemic
In the U.S., many outside the agricultural world have never heard of African Swine Fever. However, this deadly-to-pigs infection offers an example of how devastating—and hard to fight—viral diseases can be.
Unfortunately, COVID-19 isn’t the only pandemic on the
planet these days.
In recent years, another viral disease known as African
Swine Fever has spread swiftly throughout much of the
world, and especially across China, where it has killed 50 percent
of the country’s pigs. The disease—which only affects pigs—is not
dangerous to humans, but it provides an illustration of how difficult
treating and mitigating viral pathogens can be.
The ASF virus—which is not related to COVID-19—is, however, also
highly contagious. It can wipe out entire herds of hogs in a matter of
days with up to a 100 percent mortality rate.
As its name implies, ASF first appeared in Africa in 2007, where
it’s thought to have originated in wild hogs. From there, ASF spread
into parts of Europe, South America, and the Caribbean. Since its
appearance, it has been reported in multiple countries across Africa,
Asia, and Europe in both domestic and wild pigs. To date, it has not
appeared in the U.S., although many fear it may do so one day. If it
does, it would be devastating to pork producers across the country,
which is why researchers have been studying it intently for years.
In August 2018, one of scientists’ worst fears became a reality:
ASF developed a strong foothold in China, the world’s largest consumer and producer of pork. Despite efforts to contain and control
the outbreak by culling entire herds and disposing of affected pigs,
ASF still swept across the country. It resulted in the devastating loss
of an estimated 50 percent of China’s pigs, and consequently 25
percent of the world’s supply of pork.
Gordon Spronk (D.V.M. ’81), president and CEO of Pipestone, an agribusiness specializing in animal health and operations for farmers, has made more than 300 trips to China to observe ASF firsthand. He doesn’t mince words. “ASF is a different virus than any of us—veterinarians or producers—has ever dealt with in North America,” Spronk says. “It’s the worst virus that pigs can be infected with in the world. If you get the deadliest strain, up to 100 percent of the pigs die. We can’t say that with any other virus. This is the worst animal welfare situation you’ll probably ever see.”
Not only does ASF lead to the worst-case
animal welfare scenario, it also has serious
implications for the economy. Pork accounts
for more than one-third of meat produced
worldwide and is an important component
of global food security, agricultural
economies, and trade. (The recent closure
of hog-processing plants in the U.S. because
of COVID-19 infections among workers has
also demonstrated this fragility within the
The struggle that China is going through
to fight the spread of ASF is also a reminder
of how hard it is to stop a deadly disease
from reaching wildfire proportions. And
while vaccines are being developed, no
definitive one is on the market yet.
John Deen, D.V.M., a Distinguished Global
Professor in the Department of Veterinary
Population Medicine, specializes in the
epidemiology of swine diseases and swine
health. He points out that outbreaks grow as
a result of human behavior. “When you try to
control an outbreak, you have to recognize
that you’re fighting against nature,” Deen
says. “We have to ask ourselves how we
must change our behavior so that we’re not
inadvertently supporting the epidemic.”
Transportation of pigs across long
distances is a prime example of human
behavior that spreads ASF. Because this
virus transmits through live pigs and pork
products (even frozen pork) and can remain
infectious over long periods of time, the
need to halt transportation to contain an
outbreak is paramount. In March, the USDA
announced that if any cases of ASF are
found in the U.S., all shipment of pigs will be
fully stopped for at least three days.
For Deen and other researchers at the
College of Veterinary Medicine, biosecurity
is a big focus. They’re looking closely at how to keep viruses and harmful bacteria out of
pig populations and recommend that farmers install air filtration systems in barns. This
and careful sanitation and clean equipment
are good disease-prevention methods.
Deen also researches how viruses like ASF
get transmitted from one pig to another
and across herds, and he develops models
to understand webs of interconnectivity
that spread disease across populations.
Preparedness in the event of an outbreak
still keeps him up at night.
“Pig farmers in North America are reliant
on exports to maintain a viable enterprise,
and we’re selling in excess of 25 percent
of pork outside the U.S. If an agent such
as ASF is recognized in pigs in the U.S., it
would shut down a lot of those markets
and collapse the price for pork products,”
Deen says. “We have to ask ourselves, can it
happen? Have we identified all the potential
points of entry? Frankly, we haven’t, but
what can we do?”
Deen still offers reassurance, suggesting
that compared to China, the U.S. would
be better able to quickly respond should
ASF ever be detected here. The U.S. also
has a stronger diagnostic capability for the
disease, he says, and is already carefully
monitoring for its presence. Further, authorities have already put a plan in place to shut
down all movement if ASF appears.
“We have to have a vision that we can keep ASF out of the U.S.,” Spronk says. “We have to be intentional about how we behave and make decisions. Set it in your mind: We are going to keep ASF out of our national herd.”