Parathion Poisoning in Sierra Leone

1. Parathion Poisoning in Sierra Leone

2. The Case • On 11 June 1986, a local health official in Kenya, Sierra Leone, telephoned public health authorities to request assistance in the investigation of a number of sudden illnesses and deaths in the Kenya district. It was learned that during May 1986, 80 people had sought care at local hospitals and clinics for unusual symptoms. The illness struck previously healthy people. It was characterized by excess tearing, excess salivation, muscle twitching, excess sweating and diarrhea. The most severely affected people experienced rapid onset of pulmonary edema, accompanied by convulsions and loss of consciousness. Those who did not die reportedly recovered completely within a day.

3. Can you determine if this is an epidemic? If not what additional information is needed? • No, not possible to determine if an epidemic exists, at this point. • Need information about admission and death rates before May 1986 in order to establish a pattern. See Chart of Table 1

4. Can you determine if this is an epidemic? If not what additional information is needed? • No, not possible to determine if an epidemic exists, at this point. • Need information about admission and death rates before May 1986 in order to establish a pattern. See Chart of Table 1

5. What does this bar chart suggest? • A sudden increase in hospital admissions in May, 1986 • Nearly five times higher than the average of the previous 11 months (80/16.8) • An increase in deaths in April and May of 1986 • Nearly four times higher than average of the previous 10 months (12/3.1) • Suggesting that something unusual had taken place

6. … an epidemic is suggested. What further information do you need? • What is the breakdown of hospital admissions during the month of May? • Who is affected? • What illnesses are involved? • What is the timeline for the illnesses (when did they occur)? • Where were the patients from? • Chart information provided by Table 2 of the Case Study

8. What does the bar chart suggest? • Surge of admissions during middle of the month • 6 to 13 fold increase on the 20th over background • 14 to 28 fold increase on the 21st over background • Appears the outbreak occurred on the 20th and 21st of May

9. How would one determine the Geographical extent of area affected? • Find out number of cases from specific locations around the area of Kenema, perhaps through a survey of referring “facilities” that would send patients to the Hospital • Doctors • Clinics • The possibility exists that not all patients were referred to the Hospital, suggesting that an awareness campaign might be needed

10. In this outbreak, cases were reported from two towns in eastern Sierra Leone • Kenema, 1st episode • population 39,000 • 27 ill (18 children and 9 adults) • 7 died (5 children and 2 adults) • Lalehun • population 2,000 • 13 ill (no breakdown) • 5 deaths (3 children and 2 adults) • Kenema, 2nd episode • 9 ill (no breakdown) • 2 deaths (2 children died

11. Goals of investigation given the symptoms • Presenting symptoms: • excess tearing, excess salivation, muscle twitching, excess sweating, diarrhea • progression to: • pulmonary edema, convulsions, loss of consciousness, and death • Need to know: • Etiologies of these symptoms • Cause of the symptoms (contaminant, etc.) • How exposure occurred

12. Preliminary Diagnostic Criteria – Box 1

13. Diagnostic Criteria based on Box 1 • Case definition: • Loss of consciousness and at least one symptom identified in Box 1 • Period of onset should include May 20 through May 31

14. How will you select a control group? • Need to be close in characteristics to the case group, such as • family members in same household • neighbors • Need to be healthy during time of outbreak of symptoms • Age requirements of over 6 months and in good health • Be available for interview

15. Cases and Controls from Table 3, using the case definition • Cases: ID#’s 2-9, 11-13, 25-26, 29, 32-34, 36, 38, 41 • Controls: ID#’s 1, 10, 14-22, 24, 27-28, 30-31, 35, 37, 39-40, 42-43

16. Questionnaire • What information do we need? • Age • Sex • Onset of illness (Date and Time) • Symptoms • Consumed food groups • other exposures?

17. Figure 1

18. Calculating Odds Ratios and Confidence Intervals: Odds Ratios: Odds Ratio=ad/bc Confidence Interval: OR1+(z/X2) Where X2 = [n(abs(ad-bc)-n(.5))2]/[(a+c)(b+d)(a+b)(c+d)]

19. Summary table of OR and CI

20. Interpretation of table • Bread • OR was significantly greater than other food items • OR was only food item that was greater than 1 • CI that did not include 1 • Cassava Leaves, Palm Oil • OR was less than 1 • Upper CI was above 1 • Strongly Suggests that Bread consumption was associated with the Illnesses • For children age 10 or below, OR = 13 (1.4 to 123.1)

21. Statistical association between bread and outbreak • Should investigation be closed? • No, true source or agent has not been determined. • Next step in investigation • Bread sources (bakeries and markets) • Determine ingredients and their sources • Samples taken at bakery • Bread samples • Analysis of the bread • How was bread transported • any changes during the month of May?

22. Precautions during specimen collection? • Do not want further contamination or cross-contamination • Establish sampling procedures • Clean gloves and containers for each sample • Package each sample in its own container • Establish a chain of custody • Every person involved in sample collection, handling, transport, and analysis • Learned that a Lalehun baker • Had a loaf of bread with Parathion levels of 410mg/kg • Also, baker discarded bread that had been eaten by ducks who died within minutes of ingestion

23. Bread is the vehicle & parathion is the agent! End investigation? • No, need to retrace steps to assure no other sources were present which caused symptoms. • Check general store flour storage • Outbreak took place in two locations • Contamination could be a common location • Check delivery trucks • Check flour suppliers

24. Flour contamination during transportation? • Check truck floor • Parathion was transported the same day as the flour. • Parathion was spilled in one section of the truck and was absorbed by the porous flour bags.

25. Toxic agent = parathion, Vehicle of transmission = bread • Cannot close investigation just yet • Check the bakery for parathion, since it was found on knives and boards • Must confirm that all bakeries have been tested and cleaned for parathion residue. • According to the properties of parathion, how long can it persist in the environment?

26. Properties of Parathion • Organophosphorous class, a Cholinesterase Inhibiter • Usually found as a pale yellow to dark brown liquid. • It is soluble in water and slowly decomposes in air. • It will attack some forms of plastics, rubber and coatings. • The EPA allows no more than 0.1 to 5.0 ppm of methyl parathion in food products. • NIOSH recommends an occupational exposure limit of 0.2 mg/m3 of methyl parathion for an 8-hour workday.

27. Exposure Mitigation • Have each bakery that could have been processed contaminated flour be thoroughly washed. (Workers should follow NIOSH guidelines for occupational exposure.) • Educate trucking company • Not to mix food and non-food grade materials. • Have all contaminated trucks cleaned • May be necessary between shipments of dissimilar materials

28. Risk Communication and Control Measures • Community Advisories should be distributed stating that bread bought from affected bakeries during specified time period should be discarded immediately. • Questions • Is a hazardous materials transport law already in place? • Is there a training program in place educate trucking companies about what makes a chemical hazardous? • Must the trucks carry placards when transporting materials? • The trucking company should be issued a significant penalty.