Lyme disease surveillance in Michigan

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Lyme disease surveillance in Michigan
Pamela Roy Michigan Department of Community
Health April 4, 2008
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Lyme in MI - Background

• The first official reported human case in 1985 in
  Menominee County
• Surveillance for blacklegged ticks (Ixodes
  scapularis) began in the 1980s
• LD became reportable in 1989 by emergency rule

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20 years later

• Menominee County, southwest and lakeshore
• I. scapularis populations
• LD cases that meet the national case definition
  for surveillance
• Ongoing active and passive surveillance by
  academic institutions and state agencies

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Lyme disease surveillance

• Cases of disease in humans
• Ecological components
• Ixodes scapularis
• Questing
• On wildlife hosts
• Borrelia burgdorferi

Photo Graham Hickling
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Endemicity, Exposure, Established

• Endemicity is defined as 2 or more
  culture-confirmed cases per year in a county
• Exposure is defined as having been in wooded or
  brushy areas where LD is endemic within 30 days
  prior to onset
• Established a county where 6 or more
  blacklegged ticks or 2 or more life stages have
  been found in one year

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Methods

• Cases of Lyme disease were reported by local
  health departments using the Michigan Disease
  Surveillance System (MDSS)
• Blacklegged ticks were collected by
• dragging
• surveying hunter-harvested deer
• trapping small mammals and birds
• submissions from local health departments,
  physicians and veterinarians

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How widespread is LD in MI?

• Limited distribution, only a few areas of risk
• Menominee only endemic county
• Perhaps this definition needs to be expanded?

No additional culture-confirmed cases outside of
Menominee County
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Because LD is rare in MI

• Physicians INAPPROPRIATELY test for LD
• False positive IgM WBs are common, MUST be
  preceded by an EIA antibody screening test
• An appropriate test depends on season, travel
  history, symptoms and exposure

• Inappropriate winter testing without history
  of tick exposure

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Early vs. late disease
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Criteria for diagnosing a case

• CONFIRMED
• Case of EM with a known exposure to Lyme
• Case of EM with laboratory evidence of Lyme
• Case with late manifestation and lab evidence
• Laboratory evidence 2-step testing
• EIA antibody screening of serum
• Positive and equivocal tests ( 0.80) followed by
  appropriate WB

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Data used to compile tick distribution map

• MSU student research
• Dragging
• Hunter-harvested deer surveys
• Small mammal and bird trapping
• Submissions to MDA
• CDC National Tick Survey
• MDCH LHD surveillance

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Conclusions

• Need to consider all available ecological and
  epidemiological data together in order to get a
  complete picture of Lyme disease risk in
  Michigan.
• Most counties with established
  I. scapularis populations are along the shore of
  Lake Michigan.

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Collecting tick data
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Tick submission procedure

• For physicians, veterinarians and citizens
• www.michigan. gov/lymedisease

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Take home message

• Case reporting
• Onset date
• Tick exposure, include travel
• 2-step testing
• Tick submission
• Not just cases, ecology too
• Presence of vector
• Presence of pathogen

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Quiz

• 70 yo female, c/o arthritic pains in January
• Dr. orders a test for IgM WB
• WB positive!
• No onset date, no travel history
• Does this case meet our surveillance criteria?

NO!
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Thanks to

• Sarah Hamer
• Melvin Poplar
• Mary Grace Stobierski
• Ned Walker
• Jean Tsao
• Kim Signs
• Erik Foster
• Graham Hickling