The Rural Voice, 1991-12, Page 16CATTLE
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12 THE RURAL VOICE
MYSTERY DISEASE - SOLVED AT LAST?
by DR. S.E. SANFORD
VETERINARY LABORATORY SERVICES
It has become customary for me to
give an annual update on the status of
SIRS (Swine Infertility Respiratory
Disease) or, as it is more popularly known,
Mystery Swine Disease (Rural Voice,
December 1989, page 18; December 1990,
page 12).
Over the past 12 months, several new
things have occurred that have led us to
believe that at long last we might have
found the cause of SIRS. Most of these
new occurrences have been in Europe,
especially Germany, Holland, and the
United Kingdom.
Blue Ear (Mystery) pig disease in
Europe
In November 1990, reports started
emerging of a devastating reproductive
and respiratory disease sweeping through
swine herds in Germany. By January
1991, similar reports came out of Holland,
and a few months later Belgium, and then
Spain. By spring, despite conscious
attempts to prevent its arrival in the UK,
herds were being quarantined in England
as outbreaks occurred there also.
These reports of sows going off feed,
sometimes with a fever, and then aborting
or delivering mummified, stillborn, or
weak pig'_ets were very familiar to us in
North America since they were virtually
identical to the outbreaks of SIRS that we
had been experiencing in our swine herds
in recent years.
One notable exception with the Euro-
pean disease has been the occurrence of a
blue discolouration, seen best in the ears,
of some (less than five per cent) of the
affected piglets, and occasionally the sows
... hence the popular name of Blue Ear
Pig Disease or Blue Abortion that emerged
in Europe. The disease has been officially
named Porcine Reproductive and Respira-
tory Syndrome (PRRS). At time of
writing, Germany had reported over 3,500
herds affected, Holland about 1,500,
Belgium about 50, Spain two, and the UK
had about 60 herds under quarantine.
Lelystad Virus Isolated
In July 1991, scientists at the Dutch
Central Veterinary Institute located at
Lelystad, the Netherlands, reported the
isolation of a virus from field cases of
PRRS that reproduced all aspects of the
disease and met fully all scientific criteria
as the cause of the disease in Europe.
They have named it Lelystad Virus (LV)
after the location of the Institute. Almost
simultaneously, researchers in Germany
reported isolation of a similar (or identi-
cal) virus meeting all the same criteria.
Over the summer, viruses believed to
be the same or similar to the Lelystad virus
have now been isolated from at least five
different University and private research
centres in the U.S. Furthermore, blood
samples from affected U.S. swine herds
sent to the Lelystad centre have tested
positive for LV. Blood samples have also
been tested at Lelystad from herds from
four Canadian provinces that had reported
outbreaks that resembled SIRS and/or the
Quebec pneumonia syndrome (Rural
Voice, December 1990, page 12). Blood
samples from a few herds from Quebec
and Ontario have tested positive for LV.
More work still has to be done to clar-
ify that the LV, which has been convinc-
ingly shown to be the cause of the Euro-
pean PRRS, is also the cause of the North
American SIRS. Most workers on both
sides of the Atlantic seem to be convinced
of this, but 100 per cent clarification still
has to be done.
Conclusions
Although it might still be too early to
draw any firm conclusions from these
recent findings, there are a few pointers
that can be made.
• It does appear as if we might at last
have found the true agent (virus) that is the
cause of SIRS (Mystery Disease).
• If we have indeed found the true
causative virus, a vaccine or some more
direct cures/preventions can be expected
soon.
• If the initial results from the testing on
the Canadian herds hold up, we might still
be dealing with yet another virus (eg. the
Atypical Influenza virus already isolated in
Quebec) that is causing a separate disease
in Quebec, and to a lesser extent, in
Ontario, and perhaps other provinces.0
We have tried to keep our topics timely
and informative. However, we would
welcome any suggestions from readers
for future topics. We would also invite
interested persons to tour the facilities at
the Diagnostic Laboratory at Huron Park.
We would ask that you make prior
arrangements by phoning 228-6691, Ext.
276.