The Past, Present and Future of Salmonella Control in Poultry:

1
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

2
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

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The genus Salmonella (Lignieres, 1900)

• 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

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Classification of Salmonellainto subgenera/
species

• Kauffmann 1964 LeMinor 1970
• Subgenus I species enterica
• Subgenus II species salamae
• Subgenus IIIa species arizonae
• Subgenus IIIb species diarizonae
• Subgenus IV species houtenae
• Subgenus VI species indica

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Salmonella species

• Three species
• S. cholerae-suis, S. typhosa, S. kauffmanni
• S. cholerae-suis, S. typhi, S. enteritidis
• One species
• S. enteritidis
• Two species
• S. enterica , S. bongori

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Terminology of Salmonella

• the complete nomenclature
• S. enterica, subsp. enterica serovar
  Enteritidis
• or Salmonella enterica ser. Enteritidis
• Salmonella ser. Enteritidis
• Salmonella Enteritidis

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Antigenic formulae of some serovars of
Salmonella enterica

• Group A 1,2,12a1,5 ser. Paratyphi-A
• Group B 1,4,5,12b1,2 ser. Paratyphi-B
• 1,4,5,12i1,2 ser. Typhimurium
• Group C 6,7c1,5 ser. Choleraesuis
• Group D 1,9,12--
  ser. Pullorum
• 1,9,12--
  ser. Gallinarum
• 1,9,12g,m1,7
  ser. Enteritidis
• 1,9,12g,p-
  ser. Dublin

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SalmonellaEpidemiological Classification

• Group 1. Anthropophilic serovars
• Salmonella Typhi
• Group 2. Zoophilic serovars
• Salmonella Gallinarum poultry
• Salmonella Choleraesuis swine
• Group 3. Serovars with no particular host
• All other serovars, including SE

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Incidence of Salmonella Enteritidis infections in
laying flocks

• Environmental samples from 7.1 of commercial
  laying houses in the USA were positive for
  Salmonella Enteritidis
• USDA, 2000

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Salmonella Enteritidis infection in manin 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

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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

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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

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Control of External Contaminationof eggs

• Measures
• Stringent regulation for shell eggs inspection
• Pasteurization of liquid egg products
• Results
• Eggs were nearly eliminated as significant
  source of human disease

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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

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Epidemiology of Salmonella Enteritidis in poultry

• Colonization of intestinal tract
• Shedding in feces
• Horizontal transmission
• Invasion and dissemination
• Deposition inside eggs
• Vertical transmission

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Internal contamination of eggs

• Principally before oviposition
• Fecal contamination and penetration of the shell
• Contamination during breaking

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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 lt10
  Humphrey, UK
• 78 of contaminated eggs in experimental
  infection contain lt50 Gast, USA

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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

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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

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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

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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

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Detection of Salmonella Enteritidisin eggs is
difficult

• Low incidence of contamination
• needs large number of eggs
• to be examined, 10-30 eggs
• Low level of bacterial cells
• needs long incubation
• for one or more days

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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

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Problems of Salmonella control in poultry

• 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

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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

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Reducing egg contamination

• Prevention of infection
• Elimination of sources and reservoirs of SE in
  poultry flocks and facilities
• Control of transmission of SE within and between
  flocks

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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

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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

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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

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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

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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)

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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

• 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

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Controversial susceptibility issue

• Forced molting of laying hens
• by feed deprivation can increase frequency,
  transmission and severity of SE infection
• (Holt, 1993,1995)

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Back to the title of the lecture

• The Past, Present and Future
• of Salmonella Control in Poultry

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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

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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

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Trace-back Testing Program

• Evaluation 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

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Trace-back Testing Program

• Evaluation 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

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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

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Control of Salmonella Enteritidis in the USA
Present efforts

• Risk Reduction Program
• Microbiological Quality Assurance
• Implemented by federal, state and poultry
  industry

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Risk Reduction Program

• Use certified SE-free chicks
• Control pests, especially rodents
• Thorough cleaning disinfection
• Heightened biosecurity
• Washing refrigeration of eggs

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Risk Reduction Program

• Intensive testing approach
• qualifying serological tests
• series of environmental tests
• Certification of negative flocks
• Diversion of eggs from flocks to pasteurization

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Pennsylvania Egg Quality Assurance Program

• 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

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National Poultry Improvement Plan, monitoring
breeding flocks

• 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

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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

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Risk Reduction Program

• Alternative program
• Single environmental test
• Positive result requires
• extra cleaning and disinfection
• overall review of control program
  implementation

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United Egg Producers5-Star Quality Assurance
Program

• 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

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Control of Salmonella Enteritidis in the USA
The future

• The most effective and sustainable approaches to
  control foodborne disease involve risk reduction
  practices that address a broad spectrum of
  current and prospective pathogens

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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

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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

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Thank you for your attention

• Prof. Dr. Mohamed Refai
• Department of Microbiology
• Faculty of Veterinary Medicine
• Cairo University
• Mohrefai_at_yahoo.com