Transcript The Past, Present and Future of Salmonella control

The Past, Present and Future of
Salmonella Control in Poultry:
The Example of Salmonella enteritidis
Prepared by
Richard K. Gast
United States Department of Agriculture
Agricultural Research Service
Southeast Poultry Research Laboratory Athens,
Georgia
Modified and presented by
Prof. Dr. Mohamed Refai
Department of Microbiology
Faculty of Veterinary Medicine
Cairo University, Giza, Egypt
At the International Poultry Conference
in Cairo
The genus Salmonella
(Lignieres, 1900)
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Salmonella choleraesuis ( Salmon, 1885)
Salmonella typhi
(Schroeter, 1886)
Salmonella enteritidis (Gaertner, 1888)
Salmonella london, panama, cairo etc
Salmonella arizonae
(Kauffmann, 1964)
Salmonella bongori
(LeMinor, 1985)
Salmonella enterica
(LeMinor, 1987)
Now we have more than 2300 Salmonellae
Classification of Salmonella
into subgenera/ species
Kauffmann 1964
 Subgenus I
 Subgenus II
 Subgenus IIIa
 Subgenus IIIb
 Subgenus IV
 Subgenus VI
LeMinor 1970
= species enterica
= species salamae
= species arizonae
= species diarizonae
= species houtenae
= species indica
Salmonella species
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Three species
* S. cholerae-suis, S. typhosa, S. kauffmanni
* S. cholerae-suis, S. typhi, S. enteritidis
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One species
* S. enteritidis
Two species
* S. enterica , S. bongori
Terminology of Salmonella
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the complete nomenclature:
* S. enterica, subsp. enterica serovar
Enteritidis
* or Salmonella enterica ser. Enteritidis
Salmonella ser. Enteritidis
Salmonella Enteritidis
Antigenic formulae of some serovars
of Salmonella enterica
Group A
Group B
Group C
Group D
1,2,12:a:1,5
1,4,5,12:b:1,2
1,4,5,12:i:1,2
6,7:c:1,5
1,9,12:-:1,9,12:-:1,9,12:g,m:1,7
1,9,12:g,p:-
ser. Paratyphi-A
ser. Paratyphi-B
ser. Typhimurium
ser. Choleraesuis
ser. Pullorum
ser. Gallinarum
ser. Enteritidis
ser. Dublin
Salmonella
Epidemiological Classification
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Group 1. Anthropophilic serovars
 Salmonella
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Typhi
Group 2. Zoophilic serovars
 Salmonella
Gallinarum poultry
 Salmonella Choleraesuis swine
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Group 3. Serovars with no particular host
 All
other serovars, including SE
Incidence of Salmonella Enteritidis
infections in laying flocks
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Environmental samples from 7.1%
of commercial laying houses in the
USA were positive for Salmonella
Enteritidis
USDA, 2000
Salmonella Enteritidis infection in man
in the USA
Salmonella Enteritidis constitued
5% in 1976
25% in 1994
of human Salmonella reported to
CDC
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Sources of SE outbreaks in the
USA, 1995-1997
In 110 outbreaks reported by CDC
59% no confirmed vehicle
 34% contaminated shell eggs
 07% other than eggs
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Salmonella Enteritidis
contamination of shell eggs
The transmission of Salmonella
Enteritidis by eggs has
become a leading public health
issue in the USA
Sites of human SE outbreaks in
the USA, 1998-1999
Sites
Outbreaks
 Commercial food preparers
46
 Private homes
19
 Church/community events
10
 Colleges/schools/camps
7
 Nursing homes
5
 Prisons
2
The problem in the past
Before 1970
Cracked or dirty table eggs and
processed egg products were often
implicated in human salmonella
outbreaks
attention was directed to:
external contamination of eggs
Control of External Contamination
of eggs
Measures
*Stringent regulation for shell eggs
inspection
*Pasteurization of liquid egg
products
Results:
Eggs were nearly eliminated as
significant source of human disease
The new problem
A dramatic increase in incidence of
human Salmonella Enteritidis
infection is principally caused by
consumption of clean and intact
but internally contaminated table
eggs
Attention was directed to
Internal contamination of eggs
Epidemiology of Salmonella
Enteritidis in poultry
Colonization of intestinal tract
 Shedding in feces
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Horizontal transmission
Invasion and dissemination
 Deposition inside eggs
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Vertical transmission
Internal contamination of
eggs
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Principally before oviposition
Fecal contamination and penetration
of the shell
Contamination during breaking
Salmonella Enteritidis
egg contamination
Incidence is relatively low, 0.005% in USA
(USDA,2000)
Eggs contain small number of SE
• 95% of naturally contaminated eggs
contain <10
Humphrey, UK
• 78% of contaminated eggs in experimental
infection contain <50
Gast, USA
Salmonella Enteritidis infection in
chickens and egg contamination
Consequences
Dangerous increase of SE in
eggs not before the 3d week of
storage at ambient temperature
Humphrey & Whitehead,1993
Site of bacterial contamination
of eggs
* If it is within the nutrient-rich yolk
It would lead to rapid and explosive
multiplication
* If it is in the albumin
Multiplication would be restricted by
the several inhibitory factors
Site of bacterial contamination of
eggs in experimentally infected hens
(Gast and beard, 1990)
*SE was isolated from albumin or
entire yolk, including vitelline
membrane
*SE could not be isolated by
sampling only the interior contents of
yolk
Site of bacterial contamination
of eggs
Gast and Holt, 2000
• SE can penetrate through the yolk
membrane at warm temperature
• Instances were reported in which
yolk contamination occurred more
often than albumin contamination
Detection of Salmonella Enteritidis
in eggs is difficult
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Low incidence of contamination
needs large number of eggs
to be examined, 10-30 eggs
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Low level of bacterial cells
needs long incubation
for one or more days
Human Salmonella Enteritidis
outbreaks
Human infection requires:
* Ambient storage temperature that
allow multiplication of SE
* Cross-contamination of kitchen
surfaces and foods
* Improper food handling and
preparation practices
Problems of Salmonella control in
poultry
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Infections can be inapparent
Newly hatched poultry are highly susceptible to
Salmonella colonization
Salmonellae have a very wide host range
Salmonella can persist in the environment
Manure and dust are present in large quantities
in poultry houses
Salmonella Enteritidis Control
Strategies
Principal objectives
*To reduce incidence of infection in
egg-laying flocks
*To improve the microbial safety of
processing, storage and preparation
practices for egg and egg-containing
foods
Reducing egg contamination
Prevention of infection:
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Elimination of sources and
reservoirs of SE in poultry flocks
and facilities
Control of transmission of SE
within and between flocks
A. Elimination of sources and
reservoirs of Salmonella enteritidis
Sources of contamination
• Replacement chicks themselves
• Environment of the poultry house,
• Rodents, feeds, etc
 Measures
. Using uninfected chicks
• Hygiene (cleaning, disinfection, etc)
• Rodent control
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Cleaning and disinfection
Cleaning and disinfection
eliminated SE from about 50% of
environmentally positive houses
Henzler et al., 1998,
Schlosser et al.,1999
Rodent Control
Rodent control was the only practice
that correlated well with successful
control of SE in poultry houses
Henzler et al., 1998,
Schlosser et al.,1999
B. Control of Transmission within
and between flocks
Sources of contamination
• Direct contact between birds
• Carriage by vectors (biological or
physical)
• Contamination of materials and
surfaces within poultry houses
• Air movement of contaminated dust
B. Control of Transmission
within and between flocks
Measures
 Reducing the concentration of
the circulating particles by
negative ionization has reduced
experimental horizontal
transmission of SE in chicks
Gast et al., 1999
Control of Transmission within
and between flocks
2.Reducing the susceptibility of
chicks to SE infection by
vaccination of pullets or hens can
significantly reduce fecal
shedding, organ invasion and egg
contamination
(Gast et al., 1992, Zhang-Barber et al.,
1999)
Control of Transmission within
and between flocks
Vaccination does not create
impenetrable barrier against
infection
 Immunity is not solid and
protection is insignificant
Davison et al., 1999
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Control of Transmission within
and between flocks
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Prophylactic administration of
probiotic bacterial cultures for
competitive exclusion of pathogens
from the intestinal tract prevents
colonization
This approach is less useful in
protecting mature hens against
environmentally acquired SE
Controversial
susceptibility issue
Forced molting of laying hens
by feed deprivation can increase
frequency, transmission and
severity of SE infection
(Holt, 1993,1995)
Back to the title of the lecture
The Past, Present and Future
of Salmonella Control in
Poultry
Control of Salmonella Enteritidis in the
USA: Past efforts, 90-95
Trace-back Testing Program
When eggs are implicated as
source of human SE infection
*Laying flocks are identified
*Environmental samples,if + then
*Internal tissues are cultured
Trace-back Testing Program
In case of SE positive results:
• Selling shell eggs is restricted
• Producers have to choose between
*pasteurization of eggs or
*depopulating affected flocks
Trace-back Testing Program
Evaluation:
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During this program
304 SE outbreaks were reported
96 outbreaks were due to eggs
38 flocks were implicated
9 million layers were depopulated
I billion eggs were diverted for
pasteurization
Trace-back Testing Program
Evaluation:
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During this program
SE in cecal samples from hens at
slaughter increased from 27% in
1991 to 45% in 1995
SE in unpasteurized liquid eggs
increased from 13% to 19%
Trace-back Testing Program
Conclusion: Evident failure
due to :
* Eliminating a presumably small number
of infected flocks
*Potentially continuous reintroduction of
SE into flocks from diverse
environmental sources
Control of Salmonella Enteritidis
in the USA: Present efforts
Risk Reduction Program
Microbiological Quality Assurance
Implemented by federal, state and
poultry industry
Risk Reduction Program
* Use certified SE-free chicks
* Control pests, especially rodents
* Thorough cleaning & disinfection
* Heightened biosecurity
* Washing & refrigeration of eggs
Risk Reduction Program
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Intensive testing approach
* qualifying serological tests
* series of environmental tests
Certification of negative flocks
Diversion of eggs from + flocks to
pasteurization
Pennsylvania Egg Quality
Assurance Program
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Purchase chicks from uninfected breeder
flocks
Maintain rodent control and biosecurity
programs
Keep eggs under refrigeration
Culture environmental samples from chicks,
pullets and layers for SE
If +, culture eggs, if +, divert eggs, clean and
disinfect thoroughly between flocks
National Poultry Improvement
Plan, monitoring breeding flocks
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Chicks must originate from participating flocks
Feed must be free of SE
Hatching eggs must be promptly collected and
sanitized or fumigated
Blood samples from 300 birds are tested for
antibodies, if + culture for SE
Environmental samples are taken at 2-4 w and
every 30 days. If + do blood testing
Risk Reduction Program
Results
• 38% of 47 flocks + in 1992
• 12%
+ in 1995
**Egg diversion to pasteurization
without compensation renders it
unpopular by egg-producers
Risk Reduction Program
Alternative program
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Single environmental test
Positive result requires:
* extra cleaning and disinfection
* overall review of control
program implementation
United Egg Producers
5-Star Quality Assurance Program
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Cleaning & disinfecftion of poultry houses
Rodent and pest elimination
Proper egg washing
Biosecurity
Egg refrigeration from packing to delivery
Environmental testing
Positive results trigger extra cleaning and
disinfection plus review of program
implementation
Control of Salmonella Enteritidis
in the USA: The future
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The most effective and sustainable
approaches to control food–borne
disease involve risk reduction
practices that address a broad
spectrum of current and
prospective pathogens
Conclusions
The main aim of SE control is the consumer
protection which can be achieved by:
 Short-term measures
ensure that eggs are promptly refrigerated,
processed, stored, handled, prepared safely and
cooked adequately
 Long-term measures
patient and persistent participation in risk
reduction programs of verified efficacy
Final Concluion
Efforts to prevent or reduce
Salmonella Enteritidis infections
in poultry illustrate the evolution
of strategies for salmonella
control in general
which probably lead to control of
other food-borne diseases
Thank you for your attention
Prof. Dr. Mohamed Refai
Department of Microbiology
Faculty of Veterinary Medicine
Cairo University
[email protected]