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Climate Change and the Potential Range Expansion of the Lyme Disease Vector Ixodes scapularis in Canada

Climate Change and the Potential Range Expansion of the Lyme Disease Vector Ixodes scapularis in Canada Journal Club of Veterinary Medicine April 2007 Ogden NH, Maarouf A, Barker IK, Bigras-Poulin M, Lindsay LR, Morshed MG, O’Callaghan CJ, Ramay F, Waltner-Toews D, Charron DF

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Climate Change and the Potential Range Expansion of the Lyme Disease Vector Ixodes scapularis in Canada

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  1. Climate Change and the Potential Range Expansion of the Lyme Disease Vector Ixodes scapularis in Canada Journal Club of Veterinary Medicine April 2007 Ogden NH, Maarouf A, Barker IK, Bigras-Poulin M, Lindsay LR, Morshed MG, O’Callaghan CJ, Ramay F, Waltner-Toews D, Charron DF Presented by Brian Lassen Ph.d student Estonian University of Life Sciences International Journal of Parasitology, 36 (2006) 63-70

  2. Why? Mean annual temperature Mean air temp. Tartu 1866-2000

  3. Table. Reported cases or estimated cases and incidence by European country, source Eurosurveillance Editorial Advisors and others.large variation in methods used to acquire data in different European countries Why? Is Lyme disease a growing problem? Smith R,Takkin J, Lyme borreliosis: Europe-wide coordinated surveillance and action needed?, Eurosurveillance (2006) vol 11 (6)

  4. Latitude orientaiton

  5. World Climate

  6. World average rainfall

  7. Forrest

  8. Life Cycle of Ixodes scapularis

  9. Model design (Ogden et al. 2005) Eggs μeDaily, per-capita mortality rate of eggs (0.002) ELAt−y Number of egg-laying adult females at time t−y (initial value 0) Et−q Number of eggs at time t−q (initial value 0) q Time delay for the pre-eclosion period of eggs (34,234×[Temperature−2.27]) Mean annual degree days >00C (DD >00C)

  10. Project Objectives • Gegeographical range increasements? • Reduction in threshold of immigrating ticks? • Seasonal timing = endimic cycles of tick pathogens

  11. Methods Objective: Geographical distribution of ticks Tool: Maps on Ogdens model (2005) for DD >00C 2020 2050 2080

  12. Methods Objectives: Northern limits of tick survial Northern edge seasonal tick activity period Tool: Population model Ogdens (2005) Location: four sites in Ontario Canada

  13. Methods DD >00C map CGCM2 HadCM3 + atmosphere-ocean interaction Daily min/max/mean Mean annual DD >00C

  14. Methods DD >00C under climate change scenarios Scenarios CGCM2 A2 (pesimistic/realistic) HadCM3 B2 (optimistic) Plotting of map lines: With and without temperature adjustments for great water bodies

  15. Methods Theoretical limit for I. scapularis establishment Annual maximum number of adult ticks at model equilibrium y Tick die out Tested on historical data from 12 meterological stations for calibration x DD >00C from Canadian meterological stations

  16. Results Simulated maximum increase of annual adult ticks with DD>00C increase Fig.2 Objective 2 Ontario Wiarton ▲ Timmins ■ Picton ○ Chatham 2875 DD>00C Less water surface cooling inlands Northern locations less likely to be affected by water surface cooling

  17. Results Theoretical limits for I. scapularis establishment at climate change scenarios Fig.1 Objective 1 Non-cooled Cooled B2 lower

  18. Results Seasonal tick survival under climate change scenarios Fig.3 Objective 3 Larvae Nymphal Adult Cantham, Ontario Established tick population CGCM2 model A2 emission Timmins, Ontario No current tick population

  19. Results Seasonal tick survival under climate change scenarios Fig.3 Objective 3 Lower annual mortality Faster development Larvae Nymphal Adult More ticks over time Earlier activity period Longer activity period CGCM2 model A2 emission

  20. Discussion Model limitations Depends on host finding success DD>00C is limited as projection: Mean DD>00C flawed for local seasonal variations on survival Insensitve to arid habitats (prairies) limiting spread Insensitive to local rainfall variations and humidity Stochastic extinsions of ticks Conflict with Brownstein et al. 2005 (lower border projections) Correlation with USA data on borders to Canada

  21. Discussion Thoughts Disease mostly southern problem (population density) Migrating birds may spread ticks (range extention) Changes leads to deer incresement in rodent areas (reservoirs) Forests will also expand with climate change (habitats)

  22. Discussion Conclusions Historical correlation (good model) Realistic that I. scapularis populations will establish northwards Double by 2020 With temperature increase larvae are active and feed earlier Transmission and rain models needed

  23. NEXT JOURNAL CLUB IS THE 17th MAY 2007 PRESENTERS NEEDED!

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