Pa. ’s Egg Quality Programs
Go Nationwide
David J. Henzler, D.V.M.,
Marlin Henninger,~and
Phil Deßok, D.V.M.
Pa. Dept, of Ag
The Pennsylvania Egg Qual
ity Assurance Program
(PEQAP) is a voluntary industry
program intended to minimize
Salmonella enteritidis contami
nation of chicken eggs. Preven
tive measures include placement
of S. enteritidis clean chicks, in
tensive rodent control, cleaning
and disinfecting between flocks,
and comprehensive environ
mental monitoring of pullet and
layer houses with continuous
testing of eggs from any envi
ronmentally positive houses.
Positive eggs are diverted for
pasteurization or hard cooking.
The Pennsylvania Department
of Health provides technical
advice regarding public health
implications. The University of
Pennsylvania, New Bolton
Center, and Penn State Univer
sity assist in culturing of sam
ples and oversight.
Egg quality assurance pro
grams will likely soon be man
dated by FDA, USDA and other
government agencies as directed
by the Egg Safety Action Plan
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THE WORLD'S MOST TRUSTED NAME IN BELTS, HOSE AND HYDRAULICS
(December 1999) as part of the
President’s Food Safety Coun
cil. Indeed, this plan presently
calls for a 50 percent reduction
of human SE cases by 2005 from
eggs and related egg dishes. The
extended goal is to eliminate SE
illnesses associated with eggs by
2010. Quality assurance pro
grams implementing risk reduc
tion practices have achieved
success as measured by statistics
representing over 1100 commer
cial egg flocks in the Pennsylva
nia Egg Quality Assurance
Program (PEQAP) monitored
over a five year period (1994 to
1999). Furthermore well con
structed HACCP plans which
embrace significant findings as
sociated with the Pennsylvania
SE Pilot Project (1992 to 1994),
PEQAP, the New England Sal
monella enteritidis Control and
Reduction Program, the Califor
nia Egg Quality Assurance Pro
gram, the South Carolina Egg
Quality Assurance Plan, and
other research make good busi
ness sense and achieve measur
able public health milestones.
Important findings from the
Pennsylvania Salmonella enteri
tidis Pilot Project were that
older flocks were more likely to
have SE and that environment
tests don’t always identify SE
positive flocks. About 50 percent
of the flocks with SE positive en
vironments produced SE posi
tive eggs. In a limited study in
the immediate post molt period
(0-5 weeks after start of molt), a
significantly higher number of
SE positive eggs were laid than
background prevalence, e.g. 14.4
eggs/10,000 versus 2.75/10,000.
Further studies are needed on
field prevalence of SE contami
nated eggs from SE positive
flocks in the post mold period.
Other important research
from Maine (Henzler and Opitz,
1992) was that house mice (Mus
musculus), the common mouse
found in poultry houses, are
selectively sensitive to SE and
are more likely to have this
strain of Salmonella over other
strains which are more common
in poultry. Mice droppings can
contain over V* million SE bac
teria, and a mouse produces on
average 100 droppings a day. SE
is three times more likely to be
cultured from mice in a SE posi
tive-environment than environ
mental samples from the same
house. SE can remain in the
-pSiwli
1979
mice in houses after thorough
cleaning and disinfection, thus
serving to expose replacement
pullets to Salmonella enteritidis
if the producer doesn’t eliminate
mice from the previous flock.
Rats are similar. In other mouse
studies, researchers Fetter and
Henzler et. al., 1997, isolated
certain types of SE from mice
which were more likely to have
cell structures producing high
molecular weight lipopolysac
charides with enhanced ability
to contaminate eggs from hens.
A ten-fold greater risk of
flocks producing SE contami
nated eggs was noted in flocks
with high levels of SE isolated
from the manure as compared to
low numbers when compared
against 5 other potential risk
factors for hens producing con
taminated eggs (Henzler,
Kradel, and Sischo, 1998).
Hence, when 50 percent and
greater of the manure samples
taken from the hen house envi
ronment (pit) were positive for
S. enteritidis this was an indica
tor that the particular flock was
mo|;e likely to produce contami
nated eggs than flocks with less
than 50 percent of their manure
samples positive for SE.
In total, over 1100 commer
cial chicken flocks enrolled in
the Pennsylvania Egg Quality
Assurance Program (PEQAP)
over a five year period (1994-
1999) had an overall prevalence
(level of infection) of Salmonella
enteritidis of 13.9 percent. Over
85 percent of the Pennsylvania
layer industry are enrolled in
PEQAP representing 23,929,600
hens through April of 1999. A
subset of these flocks (houses)
present in 1992 in the SE Pilot
Project showed a 3.5 fold reduc
tion from 25.7 percent to 7.3 per
cent in the level of environ
mental contamination of SE.
Similarly, a 1.6 fold reduction in
the number of environmental
samples positive for SE resulted
from the intensive risk reduction
measures over the years.
The environments are
checked three times in the hen’s
life cycle at 30 and 45 weeks of
age and 5 to 7 weeks post molt.
Of these three environmental
tests, it is the 30-week test which
was most important in identify
ing a SE positive flock. This was
most apparent in complex
houses where 75.5 percent of
positive flocks were detected
with this 30-week test. In single
stand alone houses 40.9 per
cent of SE positive houses were
identified on this test. Over time,
it is clear that the HACCP risk
reduction practices were effec
tive in PEQAP. This is noted as
houses newly enrolled on the
project (having two or less flocks
in production through them)
had much higher incidence rates
of SE than established houses
(houses with three and greater
flocks in production through
them) across any of the three en
vironmental test periods. This
difference is likely due to the ef
fects of third party monitoring
(Pennsylvania Department of
Agriculture) and the producer’s
commitment to adhere to risk
reduction strategies. Flocks not
enrolled in an egg quality assur
ance program are less likely to
direct resources (labor and fi
nancial) for intensive rodent
control, thorough cleaning and
disinfection, sampling of the en
vironment (sometimes more
than a single time), and sam
pling of eggs for SE.
Similarly, the number of eggs
positive for SE have precipi
tously dropped from 1992 to
1998 in Pennsylvania flocks.
During the Pennsylvania SE
Pilot Project 647,000 were cul
tured from SE positive flocks
and an overall prevalence of S.
enteritidis egg contamination
Lancaster Farming, Saturday, July 8, 2000-A3l
was 0.0275 or 2.75 eggs/10,000
produced. In the five year
PEQAP monitoring from 1994
to 1999, a total of 933,900 eggs
were cultured from SE positive
flocks for a S. enteritidis con
tamination rate of 0.016 or 1.6
eggs/10,000 produced.
Another significant public
health statistic measure is the
reduction of human S. enteri
tidis isolation rates from the
four mid-Atlantic states in
which Pennsylvania is the chief
supplier of eggs (Pennsylvania,
Maryland, New York and New
Jersey). Between 43.5 percent
and 50.0 percent decrease in
these four states with a com
bined overall decrease in human
S. enteritidis isolation rate per
100.000 population of 49.4 per
cent was observed in the nine
year period 1989 to 1997 (CDC
based statistics). While the
PEQAP, alone, did not account
for this dramatic rate reduction
it was a likely contributor.
This is further measured by the
lower overall egg contamination
rate of 1.6 eggs versus 2.75 per
10.000 produced from SE envi
ronmental positive flocks and
the targeted diversion of any
identified flock producing SE
contaminated eggs to pasteu
rized or hard cooked eggs.
Flocks housed in single-stand
alone houses had 9.8 percent of
their environments contami
nated with S. enteritidis as com
pared, with 16.7 percent of flocks
housed in complexes. Hence,
complex-housed flocks were 1.7
times more frequently contami
nated than single houses. Diffi
culties associated with the
isolation of individual houses in
complexes likely contribute to
this higher contamination level.
Rodent control is not easy to
achieve on a prolonged basis
unless management closely
monitors the progress of baiting
programs and Rodent Indexing
(RI). It requires persistent and
continual weekly efforts to
maintain rodent control in com
mercial chicken houses with
both management and labor re
viewing records monthly house
by house to measure results.
Cleaning and disinfection of SE
environmental positive houses is
ongoing as new pullets are sub
sequently placed in the disin
fected house, and workers are
traveling amongst all flocks. The
risk this presents for transmis
sion of Salmonellae is not quan
tified or truly known.
Ventilation systems continue to
exhaust air containing feathers
and airborne bacteria, possibly
serving as a source of Salmonel
lae contamination of S. enteri
tidis clean hens or at least their
environments. Likely horizontal
transmission (bird to bird) of S.
enteritidis through airborne
methods has been demonstrated
in small-scale research facilities
(Cast, Mitchell, and Holt, 1998).
The ecology of the S. enteritidis
bacterium and its spread within
commercial flocks is not ade
quately studied. These factors
multiply the difficulty of actual
elimination of S. enteritidis es
pecially from multiple-house
complexes as these data suggest
from surveillance of 1,107 com
mercial chicken layer flocks
over greater than five years
(1994-1999).
This study was presented at:
2000 Southeastern Commercial
Egg Producers Forum, May 11-
12, 2000 Tybee Island, Georgia
and Pennsylvania Department
of Health Quarterly Epidemiol
ogy Meeting, Harrisburg, PA,
May 18,2000.
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