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 International Journal of Parasitology, 36 (2006) 63-70(2006) 63-70

Ogden NH, Maarouf A, Barker IK, Bigras-Ogden NH, Maarouf A, Barker IK, Bigras-Poulin M, Lindsay LR, Morshed MG, Poulin M, Lindsay LR, Morshed MG, O’Callaghan CJ, Ramay F, Waltner-O’Callaghan CJ, Ramay F, Waltner-

Toews D, Charron DFToews D, Charron DF

Journal Club of Veterinary Medicine

April 2007

Why?

Mean air temp. Tartu 1866-2000

Mean annual temperature

Why?

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2001 2002 2003 2004 2005

Year

Cas

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yme

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Finland

Estonia

Latvia

Lithuania

Poland

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 >00C (DD >00C)

Eggsμe 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 >00C

2020 2050 2080

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 >00C map

Daily min/max/mean

Mean annual DD >00C

CGCM2

HadCM3

+ atmosphere-ocean interaction

Methods

DD >00C 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

MethodsTheoretical limit for I. scapularis establishment

Annual maximum number of adult ticks at model equilibrium

DD >00C 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>00C increaseResults

Ontario

Wiarton

▲ Timmins

■ Picton

○ Chatham

2875 DD>00C

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 scenariosResults

Non-cooledNon-cooledCooledCooled

B2 lower

Fig.1

Objective 1

Seasonal tick survival under climate change scenariosResultsFig.3

Objective 3

Larvae

Nymphal

AdultCantham, Ontario

Timmins, OntarioNo current tick population

Established tick population

CGCM2 model

A2 emission

Seasonal tick survival under climate change scenariosResultsFig.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>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

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!