The Rural Voice, 2005-03, Page 36':'. Resech
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diseases pigserseveral
and humans
share at Centralia
,Swine Research
Update.
Why not to kiss a pig
From concerns about pigs' potential role in a world-wide influenza pandemic
to Salmonella and Campylobacter, pigs and humans share many diseases
From the Walkerton E. coli
water contamination tragedy to
BSE to concerns of the spread
of bird flu to humans, the ability of
disease to migrate from animals to
humans has taken on new immediacy
in recent years.
Among several presentations
about diseases shared by pigs and
people at the 24th Annual Centralia
Swine Research Update at Kirkton,
January 26 was a worrisome report
by Dr. Don McDermid from Pfizer
Animal Health on the possibility pigs
could bridge the gap between bird
and humans in creating the next
influenza pandemic much-discussed
by public health officials around the
world.
While the avian influenza
outbreak in Southeast Asia made
worldwide headlines and killed at
least 32 people, in general humans
aren't readily susceptible to viruses
from birds. Even in the cases of
people in Asia infected, there doesn't
seem to be any human -to -human
transfer of this form of the flu.
The concern is that pigs are
susceptible to infections of human
influenza as well as avian influenza
viruses because the cells in the swine
32 THE RURAL VOICE
By Keith Roulston
respiratory tract express receptors for
both viruses.
"Pigs are believed to serve as the
'mixing vessels' in which avian and
human influenza viruses can
exchange genetic material,"
McDermid said. The fear is that a pig
already harbouring human influenza
may be infected with avian influenza
and the virus may evolve into one
that can be transmitted between
people. This new strain could then be
transferred back to people who could
spread it to other people.
While it seems the poor pig is
taking the brunt of speculation, there
is a precedent for the concern. In
1918-1919 soldiers returning from
the First World War brought with
them the Spanish flu which killed 40-
50 million people world wide, many
times the number of people killed in
the war itself. There's speculation
that influenza may have been the
result of birds infecting pigs which in
turn infected humans with a new
virus. Certainly it was noted in 1918,
that pigs were showing the same
symptoms as humans. Swine flu has
affected the U.S. swine population
ever since.
It wasn't until 1981, however, that
the first classic swine flu outbreak
was recorded in Ontario and since
then these have been periodic swine
flu outbreaks here, generally in fall
and winter.
Recently veterinarians have been
dealing with a new form of swine
influenza in Canadian herds. Pigs in
nurseries and grow -finish barns have
suffered chronic, low-grade
respiratory problems year-round, not
just in the winter months. "The
endemic form of SIV (swine
influenza virus) may be mild in
nature but the severity of the
respiratory disease can increase
dramatically in the presence of the
more common PRDC pathogens such
as Mycoplasma hyopneumoniae and
PRRS virus," McDermid said.
"The reasons why the clinical
presentation of SIV has changed
during the past few years are
unknown, but it's likely that larger
farms, pig flow and population
dynamics within barns have each
played a role," he said.
Not only is this new form of virus
economically important to farmers
but it may also be transmitted to
humans, McDermid said. It's likely
numerous people associated with