statens serum institut outbreak of shigellosis in denmark associated with imported baby corn –...
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STATENS SERUM INSTITUT
Outbreak of shigellosis in Denmark associated with
imported baby corn
– August 2007
Hannah Lewis
EPIET Fellow, Statens Serum Institut, Copenhagen, Denmark
Presented at EpiTrain V, October 26 2007
STATENS SERUM INSTITUT
Background - Shigella spp.
Faecal-oral routeLow infective dose Incubation period: 1 - 3 days Illness: 4 - 7 days
– Diarrhoea, often bloody (dysentery)– Fever and nausea
Sh. sonnei cases in Denmark– Usually travel-related
STATENS SERUM INSTITUT
Lab Notifications Sh. sonnei January 2000 – September 2007
Episodes by Month
0
50
100
150
200
250
2000
Year
No. cases
2000 2001 2002 2003 2004 2005 2006 2007
STATENS SERUM INSTITUT
Thursday 16 Aug - Detection
Call from Medical Officer of Health/Regional Food Authority East– 2 cases Shigella sonnei infection
– Ate from salad bar in workplace
– Both eaten raw “exotic veg”
– 2 different companies
“Cateringgruppen” supplied canteens– 206 companies, 4700 employees
– Had received complaints
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Thursday 16 August
Case Finding– 35 employees with GI symptoms
– 5 culture confirmed
– Baby corn & sugar snaps
Possibly not restricted to ´Cateringgruppen’
Large and widespread outbreak?
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Friday 17 Aug - Control Measures
Product recall - precautionary principle– Baby corn and sugar snaps – One wholesaler, Thailand– Distributed at beginning of August
Press Release - Cook baby corn and sugar snaps
Medical Officers of Health and clinical microbiologists informed
Early Warning Response System alert
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Descriptive Epidemiology - Demography
218 confirmed cases (1/08 – 30/09)– Excluded: 12 travel, 3 secondary, 2 alternative exposures
201 domestic primary cases
Country-wide
75% female
Median age 38 years (IQR:18, range: 2-92 years,)
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Descriptive Epidemiology - Clinical
Of 52 cases interviewed:
45% dysentery
13% hospitalised
No deaths
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Cases of Sh. sonnei infection in Denmark by day of onset, August 2007 (n=94)
Recall of products
Outbreak identified
Last onset
EWRS
Cohort & micro results RASSF
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Retrospective Cohort study
Large company, 20+ symptomatic cases Electronic web-based questionnaire
–Demographics & symptoms–Ate in canteen on 6-10 August? –Foods eaten on 6th & 7th August?
Case definition: – Employee – Diarrhoea plus nausea or stomach cramps– Ate in the company canteen 6 - 10 August– Excluded travel-related cases
STATENS SERUM INSTITUT
Wednesday 22 Aug - Cohort Results
103 questionnaires (response rate 61%) 23 cases Significant association between baby corn and
illness
Multi-variable analysis - no other products
Food Date Cases/Total Attack Rate Relative Risk
95% CI
Baby corn 6 Aug 13/18 72 % 4.6 2.0 - 10.9 Baby corn 7 Aug 13/20 65 % 4.0 1.7 - 9.6 Sugar snaps 7 Aug 12/26 46 % 2.1 0.9 - 5.1
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Wed 22 August - Microbiology Results
Baby corn analysis– High levels E. coli (>2000 cfu/g)– Serotypes of Salmonella enterica– No Shigella spp.
New press release & RASFF- Product details
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Molecular Microbiology 11 isolates same antibiotic resistance pattern
– Resistant: tetracycline, ampicillin, sulfonamides, cephalothin, and streptomycin
– Susceptible: nalidixic acid, ciprofloxacin, chloramphenicol, mecillinam and gentamicin
Indistinguishable PFGE profile Sh. sonnei PFGE profiles
– PulseNet US DB: 20,000 entries
– Profile - 23 times Pulsenet US, Europe & Asia
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Friday 31 August – Visit from Thai Trading Company & Authorities
Packing house A
Packing house B
Trader X
(Exporter)
Wholesaler Y
(Importer)
Denmark
Complicated production chainGood records
Farms 100+
Farms 100+
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Friday 31 Aug: Connection Down-Under
Danish Outbreak - Eurosurveillance– Same Antibiotic resistance pattern
12 cases, onset 9 - 27 August– Concurrent to Danish OB
Acquired infection in Queensland
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September: Link between outbreaksPFGE profile shared
– PFGE profile indistinguishable
Trace-back – Common Thai packing house– 3 further countries
WHO INFOSAN Alert
– No associated cases
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Source of Outbreak?
Thai Authorities conducting investigation Environment and food handlers swabbed Probably post-harvest
– Washing?
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Conclusion
Cohort study, food trace-back and microbiology = strong evidence for baby corn from Thailand
Prevented additional cases of illness – Baby corn – long shelf-life (3 weeks)
Previous large Sh. sonnei outbreak in Denmark– 1998– Raw baby corn imported from Thailand
STATENS SERUM INSTITUT
Recommendations
Cooking or blanching exotic vegetables Improved quality standards for imported fresh produce Sharing information internationally
– At early stage
– Using all available communication channels (International Health Regulations)
Eurosurveillance
EWRS RASFF
Enternet Pulsenet
WHO Infosan
STATENS SERUM INSTITUT
Acknowledgments: Outbreak Team
Department of Epidemiology, Statens Serum Institut, Denmark – S. Ethelberg, C. Kjelsø, L. Vestergaard, K. Qureshi, M. Howitz,
K. Mølbak
Department of Bacteriology, Mycology and Parasitology, Statens Serum Institut, Denmark – K.E.P Olsen, E.M Nielsen
Regional Veterinary and Food Control Authority East, Denmark – M. Lisby, S.B. Madsen, P. Rasmussen
OzFoodNet, Australia– M. Kirk, R. Stafford