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

Why? Mean air temp. Tartu Mean annual temperature

Why? 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 Smith R,Takkin J, Lyme borreliosis: Europe-wide coordinated surveillance and action needed?, Eurosurveillance (2006) vol 11 (6) Is Lyme disease a growing problem?

Latitude orientaiton

World Climate

World average rainfall

Forrest

Life Cycle of Ixodes scapularis

Model design (Ogden et al. 2005) Mean annual degree days >0 0 C (DD >0 0 C) Eggs μ e Daily, 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])

Project Objectives 1.Gegeographical range increasements? 2.Reduction in threshold of immigrating ticks? 3.Seasonal timing = endimic cycles of tick pathogens

Tool: Maps on Ogdens model (2005) for DD >0 0 C Objective: Geographical distribution of ticks Methods

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

DD >0 0 C map Daily min/max/mean Mean annual DD >0 0 C CGCM2 HadCM3 + atmosphere-ocean interaction Methods

DD >0 0 C under climate change scenarios CGCM2 HadCM3 Scenarios A2 (pesimistic/realistic) B2 (optimistic) Plotting of map lines: With and without temperature adjustments for great water bodies Methods

Theoretical limit for I. scapularis establishment Annual maximum number of adult ticks at model equilibrium DD >0 0 C from Canadian meterological stations Tick die out x y Tested on historical data from 12 meterological stations for calibration

Simulated maximum increase of annual adult ticks with DD>0 0 C increase Results Ontario Wiarton ▲ Timmins ■ Picton ○ Chatham 2875 DD>0 0 C Less water surface cooling inlands Northern locations less likely to be affected by water surface cooling Fig.2 Objective 2

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

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

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

Discussion Depends on host finding success Model limitations DD>0 0 C is limited as projection: Mean DD>0 0 C 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 (lower border projections) Correlation with USA data on borders to Canada

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

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

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