Foodborne botulism from home-canned bamboo shoots

Thailand, 1998

• Wongwatcharapaiboon P • Sriprasert P • Leksririvili S

• Thaikruea L• Nanthavas S • Thanawong A

Thai FETP

Acknowledgements• Nan Provincial Health Office and Hospital

• National Institute of Health

• Armed Force Research Institute of Medical

Science

• US Army Medical Research Institute for

infectious Disease

Thai FETP

Objective• Confirm and describe the outbreak

• Verify diagnosis

• Identify the source

• Develop control and prevention strategies

Thai FETP

To

Methodology• Reviewed medical records

• Interviewed patients in the hospital

• Performed

– Active case finding

– Case-control study

– Laboratory investigation

– Environmental survey

Thai FETP

Case definition• Resident of village A or B

• At least 3 symptoms between April 8 -17, 1998– Ptosis - Dysphagia

– Dysarthria - Dysphonia

– Dry mouth - Sore throat

– Diarrhea - Vomiting

– Symmetrical flaccid paralysisThai FETP

Descriptive results

• 13 cases with 2 deaths (CFR 15%)

– 12 (92%) lived in village A

– 9 (69%) were hospitalized

– 9 (69%) were female

– Median age 44 years (range: 38-68)

Thai FETP

Clinical manifestations (N=13)

23%

31%

31%

38%

54%

54%

62%

85%

0% 20% 40% 60% 80% 100%

Ptosis

Paralysis

Dysarthria

Diarrhea

Dysphonia

Vomiting

Dry mouth

Dysphagia

Thai FETP

Epidemic curve Villages A and B, April, 8-17, 1998 (n= 12)

01234567

8 9 10 11 12 13 14 15 16 17

No.cases

April 1998

Date of onsetThai FETP

01234567

8 9 10 11 12 13 14 15 16 17

Epidemic curve Villages A and B, April, 8-17, 1998 (n= 12)

No.cases Ate

breakfast together, April 10

April 1998

Date of onset

Thai FETP

Family XFamily Y

Food history of cases (N=13)

Food Number ofcases

Attack rate%

Home-cannedbamboo shoot

13 100

Distilled alcoholicbeverage

6 46

Undistilled alcoholicbeverage

8 62

Mushroom 3 23

Thai FETP

Case-control study

• Control definition

– Person who participated in cremation

of 2 dead cases

Thai FETP

Case-control study

• 66 controls,

• All were female

• 28 lived in village A

Thai FETP

Case-control study

Home-cannedbamboo shoots

case control

ate 13 4

not ate 0 62

OR = undetermined

Thai FETP

Case control study Suspected Foods OR 95% CI

Home-cannedbamboo shoots

undetermined

-

Distilled alcoholicbeverage

8.57 2.2 - 33.9

Undistilled alcoholicbeverage

2.62 0.8 - 8.9

Mushroom 0.94 0.2 - 3.8

Thai FETP

Case-control study

HeatedHome-cannedbamboo shoots

case control

ate 1 3

not ate 12 1

OR = 0.03 (95 % CI = 0.00 -0.95)

Thai FETP

Laboratory result

• EMG of 2 cases - consistent with botulism

• Stool culture -negative C. botulinum

• Home-canned bamboo shoots

– negative culture

– positive botulinum toxin type A by ELISA and

mouse antitoxin bioassay

Thai FETP

Laboratory result

• Soil samples from houses

surrounding that of the home- canned

bamboo shoots manufacturer

– negative for C. botulinum

Thai FETP

Botulism• Caused by toxin of anaerobic bacteria

• Outbreak usually due to home- canned

low acid foods ( pH < 4.5)

• Toxin is heat labile (100 oC, 10 min)

• Spores are destroyed in 120 oC, 30 min

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Interventions

• Prohibited sale of remaining 650 cans

• Extended loans

• Educated people to heat bamboo shoots

• Enforced high temperature processing

• Strengthened surveillance

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Discussion• Confirmed botulism outbreak

• Common source –Home-canned bamboo shoots

• Improper process– Low acid

– 100 oC

• Aware of other home-canned foodsThai FETP

Limitation

• Selection of controls

– only women

• Sample not collected under strictly

anaerobic condition

Thai FETP

Recommendation

• Quality control of home-canned food

• Clinical and laboratory surveillance

– Case and Toxin detection

• Antitoxin should be available

Thai FETP

Thank youfor your kind

attention

Thai FETP

Why did it not occur in the past?

• Culture of Thai people ate fresh foods

• Home canning was promoted in only past 2 years

• Screening abnormal can– Air detection by percussion– Abnormal smell or taste

• Depend on chance – To find spores in soils– To wash bamboo shoots incompletely

Result of EMG• Normal nerve conduction velocities

• Low amplitude response to single stimulus

• Decremental trend in amplitude to repetitive

low-frequency stimulation (2-5 Hz)

• Incremental (facilitation) trend to rapid

repetitive stimulation (20-50 Hz)Thai FETP