The Rural Voice, 1992-11, Page 16"Our experience
assures lower cost
water wells"
92 YEARS' EXPERIENCE
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Thames Bend offers
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available privately at all times and
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Richard Stein
R.R. 6, Woodstock, Ont.
519-655-2942
Warren Stein
R.R. 2, Tavistock, Ont.
519-462-2704
12 THE RURAL VOICE
Diagnostics
Swine dysentery control
by Dr. Gaylan Josephson
Veterinary Laboratory Services
Swine dysentery, also known as
"bloody scours" or "bloody
diarrhoea", has been identified as a
severe economic problem in the pork
industry for many years. The disease
is caused by a bacterium Serpulina
Hyodyseteriae (formerly Treponema
Hyodysenteriae), that affects the large
intestine only, causing a
bloody diarrhoea primarily
in pigs between 15 and 70
kg (35 - 150 lbs).
Symptoms can occasionally
occur in adult pigs and
even in nursing piglets,
particularly in previously
unexposed herds.
Under natural condi-
tions, 90 per cent of pigs in
a herd may be affected,
with a death rate of up to 30 per cent,
if left untreated. In many cases, dys-
entery outbreaks are cyclical, with
bouts of diarrhoea occurring every 17
to 21 days, even with treatment. Out-
breaks are often stress related, and
seen in conjunction with prolonged
spells of hot weather. In most cases,
chronic swine dysentery will eventu-
ally result in a diarrhoea problem that
is very difficult to treat. This is partly
due to the fact that the causative
organism, S. hyodysenteriae, can
readily dapt and develop resistance to
a specific drug. This in turn means
any drug has a relatively limited
useful life.
A producer with swine dysentery in
his herd now has three methods of
dealing with the problem.
Trying to live with the disease by
using long-term feed medication was
the only procedure available for many
years. However the disease is a costly
one to try to live with, with annual
costs of feed related antibiotics for
control purposes ranging from $80 to
over $100 per sow, and from $4 to
over $5 per pig produced. During an
actual outbreak, feed consumption is
markedly reduced, and mass medica-
tion must be given through the water.
On top of the obvious expense of
medication, it has been estimated that
average daily gain is negatively
affected by 10 to 20 per cent, and feed
conversion by 2.8 to 4.2 per cent, even
in the absence of signs of scouring.
Recent attempts at eradication of
the disease from farrowing -to -finish
operations have been based on a
depopulation -repopulation program.
This program has several serious
drawbacks as related to swine dysen-
tery eradication, including the diffi-
culty in accurately diagnosing the con-
dition in non -scouring pigs.
Clinical signs of scouring,
microscopic examination of
sections of large intestine
and culturing of the bacteria
(now routinely attempted at
the Guelph and Huron Park
laboratories) are the only
methods now available to
assist in making a diagno-
sis. Reliable blood tests are
not yet available. Similar-
ly, an effective vaccine has not yet
been developed.
On farms with two -site production
units and one of them being a grower -
finisher unit that is separate from the
farrowing -weaning operation, the
disease can be eliminated by depopu-
lating the finishing unit and medicat-
ing the nursery pigs and breeding
stock. Five major factors are essential
in such a program: (1) timing, (2)
rodent control, (3) sanitation, (4) drug
therapy, and (5) herd security.
Since the organism does not live
long in a hot, dry environment, the
program must be initiated in the sum-
mer. Rodents, particularly mice, act
as secondary hosts for the organisms,
therefore an extensive rodent control
program must be in place before an
eradication program begins.
Sanitation includes emptying the
barn of grower -feeder pigs, removal
of manure, high-pressure washing of
the premises, using disinfectants, and
leaving the building empty for some
time.
Drugs known to eliminate S. Hyo -
dysenteriae from the intestinal tract of
pigs should be used in the medication
program. All pigs on the premises
must be treated for a period ranging
from seven to 10 weeks (the specific
program used varies according to the
drug that is used). Medicated Early
Weaning and Pulse Medication are
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