statens serum institut outbreak of shigellosis in denmark associated with imported baby corn –...

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

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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

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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

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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

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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

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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