D2-L*nc«t«f Fanning. Saturday, Saptambar 9, 1995
PORCINE
REPRODUCTIVE AND
RESPIRATORY
SYNDROME (PRRS)
PRRS has been in the U.S. for
the past eight years. In that time, it
has not generated any sentimental
value.
Reproductive failures from
PRRS cost $lOO to $5lO per sow.
The respiratory problems asso
ciated with PRRS in the growing
pig reportedly cost an additional
$7.50 to $l5 per pig marketed,
although many would consider
these estimates too low.
The following article is based on
numerous published reports as
well as observations of several vet
erinarians Dr. Robert Graybill,
Dr. Jerome Harness, Dr. Larry
Hutchinson, and Dr. Timothy
Trayer.
Nature Of PRRS
The PRRS virus was identified
York Farm
Credit To
Issue
Patronage
Checks
YORK (York Co.)
Member-borrowers of
York Farm Credit will
receive paironage re
fund checks for 1994, it
was announced by Jay
V. Rush, president
The patronage refund
for borrowers of York
Farm Credit will total
more than $1.6 million.
Borrowers will receive,
on average, a rebate of
1.17 percent of the inter
est Farm Credit earned
on their loans in 1994.
Twenty-five percent or
$4OB thousand, of the
refund will be paid in
cash. The balance will
be placed in allocated
surplus m the names of
individual member-bor
rowers.
“York Farm Credit
had another successful
year in 1994, and we are
pleased to be able to
share our success with
our borrowers," said
Lester E. Marlin, chair-)
man of the York Farm
Credit Board and farmer
from Chambersburg.
“This is the fifth conse
cutive year we’ve paid a
patronage refund. Since'
1990, York Farm Credit
has returned a total of
51. 6 million to its mem
ber-borrowers through
patronage refunds and
surplus revolvements.”
in Lelystad, Netherlands in 1991,
some four years after the disease
was first characterized. A short
time later, it was also isolated in
the U.S. and Germany.
The virus affecting hogs in Eur
ope is essentially the same virus as
that found in this country. Howev
er, there are*ciifferent strains, and
based on recent studies at lowa
Slate University, there may be a
five-fold difference in virulence
among various strains.
What the disease looks like will
depend upon the disease organ
isms already present on the farm.
In the reproductive form, PRRS
results in 1-4 months of reproduc
tive failure. Sows often go off feed,
run a fever (104-106 degrees F),
and abort (usually late in pregnan
cy) or deliver pigs at 105 to 112
days.
Death rates in sows following
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infection can be high in some
herds, according to Dr. Harness.
The virus can cross the placenta
and infect fetuses, causing an
increase in stillboms and mummi
fied pigs. The mummies will be
delivered full size early in the
course of the disease, and become
smaller in the weeks to follow.
Once all breeding groups have far
rowed, reproductive performance
may improve, but it often doesn’t
because of virus recirculation.
In the respiratory form, thedust
and bacteria-eating macrophages
in the lung are destroyed. Because
of this, growing pigs often suffer
from other diseases.
The most common secondary
invaders include Pasteurella, Strep
suis, Haemophilus parasuis,
hemolytic E, coli, Mycoplasma,
Salmonella cholerasuis, Bordatel
la and Actinobacillus. This stage
of the disease often follows the
reproductive “storm,” but it can
also occur without reproductive
problems.
Newborn pigs infected with
PRRS are weak at birth, become
lethargic, take on a rough hair coat,
and may suffer from bacterial sep
ticemia and diaVthea. Mortality
and cull rates are high, especially
in farrow-to-finish enterprises.
Pigs in the finishing phase have
mild to moderate respiratory dis
ease, depending on the presence of
other respiratory problems.
Transmission
The PRRS virus is extremely
infectious. Jeff Zimmerman, a
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DVM researching PRRS at lowa
State University, suggests that the
dose level may approach one virus
particle.
Scientists are still uncertain how
the virus spreads from pig to pig or
farm to farm. Zimmerman reports
that fecal shedding is the main way
PRRS is spread. Reconsiders nose
to nose contact and aerosol trans
mission secondary (attempts to
make the virus spread just 20 feet
through the air have failed). How
ever, Dr. Robert Graybill, DVM
from Lancaster, Pa., believes the
aerosol route is a major factor.
A field study in Germany sug
gests that airborne transmission is
significant up to 1.24 miles. Clear
ly, the PRRS virus is persistent in
the upper respiratory tract, and at
least two studies have demon
strated difficulty in isolating virus
from manure.
The virus also can be shed in
semen for as long as 43 days after
infection. A study in Britain indi
cated PRRS was likely spread to
non-infected farms via purchased
semen. Researchers at South
Dakota State University have
shown that gilts can become
infected by artificial insemination
using unextended semen from
experimentally infected boars.
Studies at lowa State University
show that the PRRS virus may
affect fertility, and vaccinating
boars with the PRRS vaccine may
reduce virus shedding in the
semen.
Diagnosis
PRRS diagnostic workups
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should include symptoms in thi
pig, as well as characteristii
lesions in the tissue, virus isolatioi
from tissues or blood, and bloot
tests to detect the presence ol
antibodies.
At present, blood samples can
be submitted to any of Pennsylva
nia’s animal diagnostic labs (Penn
State, Summerdale, or University
of Pennsylvania) for the ELISA
test The state labs can also per
form virus isolation.
Control
The strategy for controlling
PRRS (stopping virus spread) is
simple in theory but difficult in
practice. Often populations of
negative animals exist beside
groups of positive animals. If a
negative animal picks up the virus,
the resulting infection leads to
heavy virus shedding and subse
quent infection of other “naive”
pigs. This phenomenon is espe
cially true in breeding herds that
receive replacement gilts every
month or so. As a result, the level
of immunity never stabilizes and
virus shedding persists.
The following cleanup steps are
those recommended by Dr. Scott
Dee, DVM from Morris, Minn.:
■ Step 1. Isolate and vaccinate
(under veterinary supervision)
incoming gilts. Gilts should be
vaccinated upon arrival and iso
lated off-site. After 30 days, vacci
nate again and isolate another 30
days. After this two-month period,
gilts can be moved to the breeding
herd.
(Turn to Page D 3)
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HONESUALE SPREADING
SERVICE INC.
SOS Cliff St.
Honesdale, PA 18431
(717) 253-2410
CHIDESTER FARMS
RD 2, Box 75
Kingsley, PA 18826
(717) 289-4260
MELVIN G. MILLER
RT 2, Spring Mills, PA 16875
(814) 422-8279 •
PIKEVILLE
EQUIPMENT INC.
RT 2, CHey, PA 19547
(215) 987-6277
BHM FARM EQUIP. INC.
RR 1, Annville, PA 17003
(717) 887-2211
SHOW EASE STALL CO.
573 Willow Rd
Lancaster. PA 17601
(717) 299-2536
DEERFIELD AG &
TURF CENTER, INC.
RD 2, Box 212
Watsontown, PA 17777
(717) 538-3557
HEFLIN SALES
& SERVICE
12312 Oak Hill Rd.
Woodsboro, MD 21798
(301) 898-3233
CHAMBERSBURG
FARM SERVICE
975 S. Mam St.
Chamborsburfl, PA 17201
(717) 264-3533
SOMERSET BARN EQ.
R.D #5
Somerset, PA 15501
(814) 445-5555
McMILLEN BROS.
RD 1 Box 134
Loysvllle, PA 17047
(717) 789-3961
HESS' EQUIPMENT
Sales & Service
RR 3, Mlfflinburg, PA 17844
(717) 966-2720
966-1908