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Effect of carcass decontamination at pig slaughterhouses on the number of human
Salmonella cases in Denmark.
Søren Aabo
Section for Food HygieneDepartment of Microbiology and Risk Assessment
National Food InstituteThe Technical University of Denmark
Contributors:
Kristen BarfodTove Christensen Pia ChristiansenTina Bech HansenRikke KragHelle Mølgaard SommerMorten Mørkbak
Sanco workshop february 20092 DTU Food, Technical University of Denmark
Danish project:
“DECONT”: 2005- 2009
“Efficacy cost benefit and consumer perception of post harvest carcass decontamination of slaughter pigs”
• Data generation• Effect of steam, hot water and lactic acid
decontamination• Risk modelling • Cost effect modelling• Consumer perception• Willingness to pay
Sanco workshop february 20093 DTU Food, Technical University of Denmark
Background for focus on carcass decontamination of pork in Denmark:
E.C. regulation 853, article 3, 2004 opens up for physical decontamination in EU.
Political wish to approach the low Swedish Salmonella levels in pork.
Exhaustion of the current control programs.
Increased industrial interest for end-point decontamination. A simple (and relative cheap) way to improve food safety compared to herdintervention.
Experience with Hot Water Decontamination of 0,5-1 % of production.
Possible significant impact on food safety.
Could be outbreak protective.
No information on decontamination of pork available from other EU countries.
Sanco workshop february 20094 DTU Food, Technical University of Denmark
Concerns about decontamination
•Toxicity of compounds?
•May lead to poor slaughterhygiene?
•Discolouration of meat
•Excessive water consumption (Hot Water Decontamination).
•Consumer acceptance
•May not be installed in small slaughterhouses (Practical/economical reasons)
•Small slaughterhouses – significant suppliers of fresh meat in DK
•Unknown effect on human ilnesses
Sanco workshop february 20095 DTU Food, Technical University of Denmark
Development of the prevalence of Salmonella onswine carcasses 2001-2007Bacteriological fresh meat surveillance at slaughterhouses
Source: Danish Veteriunary and Foos AdministrationOpdateret 03-03-2008
0,00
0,50
1,00
1,50
2,00
Jan2001
Jul Jan2002
Jul Jan2003
Jul Jan2004
Jul Jan2005
Jul Jan2006
Jul Jan2007
Jul
Måned
% p
ositi
ve p
røve
r
% positive % positive, moving avg. for 12 month
Sanco workshop february 20096 DTU Food, Technical University of Denmark
Salmonella source attribution of 1775 registered human cases in Denmark in 2006
Ducks (0.2-1.3%)
Imported pork (0.7-2.6%)
Broilers (0.2-1.0%)
Table eggs (4.9-7.5%)
Imported chicken (7.4-11.0%)
Imported turkey (4.1-6.6%)
Imported ducks (0.3-1.2%)
Travel (mean: 25%)
Imported beef (0.7-2.1%)
Beef (0.8-2.0%)Pork(4.6-7.8%)
Outbreak, source unknown (5.9%)
Unknown (33.5-39.4)
Pork associated:107 (82-138).
Sanco workshop february 20097 DTU Food, Technical University of Denmark
Figure 1: CSLM of hair follicle with green fluorescent Yersinia enterocolitica moving into the cavity by capillary force. X10
Source: Rikke Krag, KU/ DTU
Decontamination methods investigated:
Steam ultra sound
Hot Water Treatment
Lactid acid
Bacteria hide themselves – a challenge to decontamination
Sanco workshop february 20098 DTU Food, Technical University of Denmark
Figure 2Pork skin inoculated with gfp-tagged Yersinia enterocolitica and decontaminated with Sono Steam for 2 sec. After decontamination few bacteria are identified and mainly in deeper tissue structures.
Gfp-tagged Yersiniaenterocolitica in hair follicles
Sanco workshop february 20099 DTU Food, Technical University of Denmark
Steam ultrasound - SonoSteam®
Sanco workshop february 200910 DTU Food, Technical University of Denmark
Effect of Sonosteam treatment on Salmonella Typhimurium seeded (10^7cfu/cm2) on skin and meat side of jaw samples
(n=6) ± SD
0,00
1,00
2,00
3,00
4,00
Treatment time (seconds)
log
(10)
redu
ctio
n
SkinMeat
Skin 0,57 2,05 2,33 3,21
Meat 0,44 1,23 1,52 2,03
0.5 1.0 1.5 2.0
Sanco workshop february 200911 DTU Food, Technical University of Denmark
Hot water Decontamination80˚C for 15 seconds
Almost all level III herds and all S. Typhimurium DT104 infected herds
Sanco workshop february 200912 DTU Food, Technical University of Denmark
Prevalence of Salmonella on carcasses after Hot Water Decontamination
Almost all carcasses from Salmonella level III herds and S. TyphimuriumDT104 herds are Hot Water Treated in Denmark = 0,5-1 % of production
Serological level Salmonella prevalence (%)
- HWT +HWT
I 1,76 0,04
II 3,84 0,31
III 5,07 0,11
n=30.000 n=9000
Reduction in prevalence : 40-50 fold
Sanco workshop february 200913 DTU Food, Technical University of Denmark
Risk model
Modelling carcass contamination before and after decontamination
Modelling no. salmonella bacteria per serving
Dose response modelling and adjusting to the Danish source attribution model
Sanco workshop february 200914 DTU Food, Technical University of Denmark
Amount of faeces on carcass
N= 1920
Risk modellingExposure model – salmonella on carcasses
+
Salmonella bacteria in faeces
N=1440
=
Distribution for Salm_carcass/G6
M ean = 36,16174
X <=23,45%
X <=53,4795%
0
0,01
0,02
0,03
0,04
0,05
0,06
0 40 80 120
Sanco workshop february 200915 DTU Food, Technical University of Denmark
Salmonella per serving
• Salmonella per carcass (75 kg)
• Salmonella per serving (200 g)
• Reduction factor for foodpreparation
• Salmonella per prepared serving
Sanco workshop february 200916 DTU Food, Technical University of Denmark
Beta-Poisson Dose-response
00,10,20,30,40,50,60,70,80,9
1
0 1 2 3 4 5 6 7 8 9 10log Dose
P_ill 2.5th 97.5th
Pinf = 1-(1+Dose/β)-α (α,β = 0.132, 51.5, FAO/WHO 2008)
Ducks (0.2-1.3%)
Imported pork (0.7-2.6%)
Broilers (0.2-1.0%)
Table eggs (4.9-7.5%)
Imported chicken (7.4-11.0%)
Imported turkey (4.1-6.6%)
Imported ducks (0.3-1.2%)
Travel (mean: 25%)
Imported beef (0.7-2.1%)
Beef (0.8-2.0%)Pork(4.6-7.8%)
Outbreak, source unknown (5.9%)
Unknown (33.5-39.4)
Sanco workshop february 200917 DTU Food, Technical University of Denmark
Predicting no. of cases from Relative Risk
Method Relative Risk No. of cases/year 2006
No decontamination 1 107
Hot water 80°C 5 secs 0.08 9
Hot water 80°C 15 secs 0.05 5
Hot water 80°C 15 secs 1% lactic acid
0.01 1
Hot water 55°C 2.5% lacticacid
0.12 13
Sanco workshop february 200918 DTU Food, Technical University of Denmark
Factors providing uncertaintyto the estimate
Transport Retail
Temperature abuse/growthDessication /reductionCross contaminationUnder cookingReady to eat sources
ConsumerTransport
Methodology and tissue associated effect of decontamination methods
Sanco workshop february 200919 DTU Food, Technical University of Denmark
Relative Risk for Human Salmonellosis
3,57
2,482,17
1,241,00
0,00
0,50
1,00
1,50
2,00
2,50
3,00
3,50
4,00
E B A D C
Abattoir
RR RR
Distribution for Salm_carcass/G6
M ean = 36,16174
X <=23,45%
X <=53,4795%
0
0,01
0,02
0,03
0,04
0,05
0,06
0 40 80 120
Sanco workshop february 200920 DTU Food, Technical University of Denmark
Perception of different risk reductions strategies
To solve the problem with pathogenic bacteria in meat it is OK to….
0
200400
600800
1.000
Freeze the meat
Treat with steam
Boil the meat in
water
Irrigate with hot water
Marinate meat with soy sauce
Irrigate the meat with chlorous comp...
Definitely234Not at all
Sanco workshop february 200921 DTU Food, Technical University of Denmark
ConclusionDecontamination methods available or under development
Potential significant impact on food safety, estimated to 10-100 fold decrease in human illness if all meat is treated.
Slaughter house hygiene have significant effect on human risk
Retail and consumer hygiene level influence the effect of carcass decontamination
Outbreak not included in model
Decontamination may be used for specific purposes (high risk carcasses, meat for fermented products)
Sanco workshop february 200922 DTU Food, Technical University of Denmark
Thank you for your attension
Sanco workshop february 200923 DTU Food, Technical University of Denmark
Table 2.Cost data for different decontamination technologies# Hot water
slaughtering Steam
ultrasound Lactic acid 2.5%
55 °C in 120 seconds
Carcass per year (1000) 740 740 740 Investment (1000 DKK#) 342 604 12 1000 € per year Capital cost 55 97 2 Energy and water cost 85 27 3 Labour cost 25 0 10 Other variable costs 25 27 5 Total cost 191 150 20 € per carcass Costs per carcass 0.26 0.20 0.03 # Danish Meat Institute (hot water), FORCE Technology (steam ultrasound), SFK Systems, (steam vacuum) and Spraying System (lactic acid spray)
Sanco workshop february 200924 DTU Food, Technical University of Denmark
0.0
20.0
40.0
60.0
80.0
100.0
120.0
88 89 90 91 92 93 94 95 96 97 98 99 00 01 02 03 04 05 06
Est
imat
ed n
umbe
r of h
uman
cas
es p
er 1
00,0
00
Broilers Pork Table eggsTotal cases
Source: D
anish Zoonoses Centre,
DTU
National Food Institute
Major foodborne human infections in Denmark 1988-2006
Sanco workshop february 200925 DTU Food, Technical University of Denmark
Prevalence of Salmonella positive carcassesfor herds in Level I, II, and III with and withoutHot water Dewcontamination (HWD)
Salmonella prevalence estimate (%)*
Level I Level II Level III
”Routine” slaughter, no HWD 1,76 3,84 5,07(Number of pools) (5130) (560) (6000**)
Sanitary slaughter with HWD 0,04 0,31 0,11(Number of pools) (919) (288) (621)*: adjusted for a sensitivity of 55% due to pooled sampling **: individual samples
Reduction in prevalence : 40-50 fold.
Sanco workshop february 200926 DTU Food, Technical University of Denmark
1,E+00
1,E+01
1,E+02
1,E+03
1,E+04
1,E+05
1,E+06
1,E+07
1,E+08
1,E+09
1,E+00 1,E+01 1,E+02 1,E+03 1,E+04 1,E+05 1,E+06
conc. E.coli in swabs (cfu/ml)
conc
. E.c
oli i
n Fa
eces
(cfu
/gr)
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
< 0.07 0.07-0.7 0.7-7.5 7.5-75 75-670 > 670
no. of Salmonella/gr faeces
prob
abili
ty
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
< 0.10 0.10-0.91 0.91-10.1 > 10.1
no. of Salmonella/ml from carcass swabs
prob
abili
ty
(Cswab , Cfaeces)
cfu/ml
cfu/cm2
cfu/carcass / cfu/gr faeces
Distribution of gram faeces
per carcass
Distribution of Salmonella
on carcassX
Salmonella
per gram faeces
=
Data to validate model output
a.)
b.)
c.)
Figure 1. Schematic representation of the simulation model. From a.) paired results of the concentration of E. coli in faeces and in carcass swab samples obtained from the same animal, the faecal contamination of the carcass is estimated (i.e cfu/ml in swab ⇒ cfu on 2800 cm2 swabbed surface ⇒ cfu on total carcass surface). Combining the estimate with b.) the probability distribution of the number of salmonellas per gram faeces from infected swine, results in an estimated number of salmonellas per carcass. The simulation results are validated through carcass measurements of Salmonella contamination described in c.) a probability distribution of the number of salmonellas per ml. from carcass swab samples.
Structure of model: Patogens on carcasses
Sanco workshop february 200927 DTU Food, Technical University of Denmark
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Slovenia
Sweden
Austria
Poland
Lithuania
Cyprus
Denmark
Latvia
Czech Republic
13 MS-group
The United Kingdom
France
Belgium
Ireland
Prevalence of Salmonella positive carcass swabs in selected EU countries
(EFSA Salmonella baseline in slaughter swine, carcass swabs, 2008)
13 MS group: 8.3% (95%CI: 6.3;11.0)
max: 20.0% (95%CI: 10.8;34.0)
Crude estimate of effect if all carcasses are treated:
0,1% 0,2% 0,4% 0,6% after Hot Water Treatment
5% 10% 15% 20% Before Hot Water Treatment
Sanco workshop february 200928 DTU Food, Technical University of Denmark
0 0.05 0.1 0.15 0.2 0.25 0.3 0.35 0.4
Slovenia
Sweden
Austria
Poland
Lithuania
Cyprus
Denmark
Latvia
Czech Republic
13 MS-group
The United Kingdom
France
Belgium
Ireland
Prevalence of Salmonella positive carcass swabs in selected EU countries
(EFSA Salmonella baseline in slaughter swine, carcass swabs, 2008)
13 MS group: 8.3% (95%CI: 6.3;11.0)
max: 20.0% (95%CI: 10.8;34.0)
Sanco workshop february 200929 DTU Food, Technical University of Denmark
Gfp-tagged Yersiniaenterocoliticaon the skin surface
Figure 1a,b and c.Pork skin inoculated with gfp-tagged Yersiniaenterocolitica and decontaminated with SonoSteam for 1 sec. After decontamination bacteria are located on skin surfaces and in deeper structures
Gfp-tagged Yersiniaenterocoliticain a hair follicle.