Ixodes scapularis & Lyme disease spread in Canada: Climate change & migratory birds

1. Ixodes scapularis & Lyme disease spread in Canada: Climate change & migratory birds Nick Ogden

2. What is Lyme disease? • A disease caused by a spirochaete bacterium Borrelia burgdorferi • It is a multisystem disease in humans (and animals) • It is non-fatal but chronic and debilitating if not treated early • Difficult to diagnose by doctors (clinical presentation and serology) • ~ 20 000 cases a year in USA despite high level of awareness by the public & medical practitioners • It is an infection of wildlife (rodents, birds, mustelids NOT deer) that is transmitted from one animal to another by ticks • Ticks are not very choosy about who they bite and bite people by accident • The geographic range of Lyme disease is tied to that of its tick vectors

3. Adult ticks feed on deer in spring and autumn Infected larvae moult into infected nymphs next spring Infected nymphs infect rodents or birds Larvae feed on rodents and birds in late summer Nymphs feed on rodents and birds in spring Infected rodents or birds infect larvae Borrelia burgdorferi transmission cycle Adult E Adult POP Tick development and activity depend on temperature Eggs Nymph E Nymph Larva E Larva PEP

4. Temperatures are expected to rise dramatically this century: global warming

5. What’s in store for Canada? Temperature rise: • One of the most seriously affected places on earth • Mean annual surface temperature rises of ca 4ºC in southern Ontario/Quebec, up to 10ºC in Nunavut Change in rainfall: • Slight increase in rain in the east? Reduced rain in the prairies and the west • Change in pattern: heavy rainfall events accompanied by flooding interspersed by droughts The greater the mitigation, the less severe the effects, hence Kyoto • General expectation that the geographic range of arthropods (such as ticks) will expand north with global warming

6. Where are the ticks now:In the USA! Ixodes pacificus Ixodes scapularis

7. In Canada we have only a few reproducing (and self-sustaining) I. scapularis populations For Lyme to more seriously affect Canada the range of I. scapularis would have to expand

8. AdultI. scapularisticks are already submitted to Health Canada by the public from a very wide geographic range: How come?

9. Northern-migrating ground-feeding birds stop-over in tick-infested habitat We hypothesize that migratory ground-feeding birds are bringing I. scapularis into, and through, Canada Spring migration coincides with spring activity period of Ixodes scapularis nymphs Nymphs feed continuously on birds for 5 days, then drop off into the habitat

10. Why study ticks on migratory birds? • Many nymphal ticks carried by migratory birds survive and molt into adult ticks, which can bite people and infect them with Lyme disease. • Understanding the distribution of these ticks will help alert health workers and the public as to where the risks are from these ticks • Reproducing (established) tick populations carry much risk more because: • The ticks are more numerous • Nymphal ticks are present, which are highly infected, difficult to see and more likely to infect people than adult ticks • With global warming we expect that the range of reproducing populations of ticks to expand • Where ticks are being dropped in the greatest numbers by the birds now is where populations are likely to establish

11. Now: And forecast for e.g. 2020 1739-2145 1102-1738 695-1101 1102-1738 1739-2145 160-266 267-433 434-694 160-266 267-433 695-1101 434-694 47-90 91-159 91-159 1-46 1-46 47-90 0 0 Index of tick abundance at model equilibrium Index of tick abundance at model equilibrium We have developed a simulation model of I. scapularis populations to identify where temperature conditions are OK for I. scapularis

12. The range of I. scapularis may continue toexpand through this century 2050s Now 2080s 2020s

13. Our research conclusions so far are: • A northward expansion of the range of Ixodes scapularis, associated with climate change, is likely because: • Tick survival increases dramatically • Ticks are being carried into Canada each year on migratory birds • The habitat in many areas is suitable for tick survival • Chaotic weather (heavy rainfall and droughts) may inhibit spread • Spread into central Provinces may be limited by low rainfall • Diagnostic expertise by clinicians and laboratories will be crucial in detecting and monitoring the increased risk of Lyme disease • We can help by identifying where ticks are landing now, and thus where tick populations may set up in the future

14. The role of migratory birds: what we need to know • What bird species are responsible for carrying ticks into Canada: • What species carry ticks (finding ticks on birds) • How many ticks are carried, on average, by each individual bird (counting and collecting ticks) • How abundant the birds are (banding records) • Where these birds are going: • From analysis of isotopes in retrices • Banding recoveries • Ecological niche modeling • Where the ticks are going: • Using the above data in simulation models (‘network analysis’: equivalent to methods used by airlines to estimate where passengers get on and off planes) • Existing maps of I. scapularis distribution in the USA (CDC) • Range of 5 days flying time for Nymph, 3 days for a Larva

15. Depends on phenology of tick which depends on climate A basic model of tick dispersion by migratory birds Number of ticks Questing in USA woodland in spring Number of ticks dropping on location X in Canada 5 days flight time

16. Numbers of ticks carried per bird Species: timing of migration Species: behaviour contacting ticks Species: migration route Species: speed of migration Number of ticks Questing in USA woodland in spring Number of ticks dropping on location X in Canada 5 days flight time

17. Bird behaviour and contact with Ixodes scapularis: A meta-analysis of previous studies • Data from 15 studies on I. scapularis infestations of birds (migrating and resident) in the USA and Canada • Negative binomial regressions with outcome = number of birds infested and number examined as an offset • Explanatory variables: foraging behaviour, nesting site, habitat and ‘taxonomic groupings’. Study ID was a random effect • Significant factors +ve association with parasitism: ground feeding behaviour, ground nesting, woodland/ecotone habitat and some family groupings

18. Species selected by meta-analysis • Corvids: Blue Jay • Sparrows: Eastern Towhee, Chipping Sparrow, Song Sparrow, Swamp Sparrow • Icterids: Brown-headed Cowbird, Common Grackle • Mimids: Brown Thrasher, Grey Catbird • Tanagers: Northern Cardinal • Thrushes: American Robin, Veery, Grey-cheeked, Hermit, Swainson’s & Wood Thrushes • Warblers: Worm-eating, Hooded & Canada Warblers, Ovenbird, Northern Waterthrush, Common Yellowthroat • Wrens: House Wren

19. Common Yellowthroat American robin Coincidence of migration with tick questing 42.5o 40o 35o

20. Data from the field: Spring migration 2005 in Canada • Corvids: Blue Jay 4 • Sparrows: Eastern Towhee 2, Chipping Sparrow 2, Song Sparrow 13, Swamp Sparrow 7 (WT WC ST Fox GH Lincoln 43) • Icterids: Brown-headed Cowbird 1, Common Grackle 2 • Mimids: Brown Thrasher 14, Grey Catbird 4 • Tanagers: Northern Cardinal 1 • Thrushes: American Robin 2, Veery 2, Grey-cheeked 2, Hermit 21, Swainson’s 3 & Wood Thrushes • Warblers: Worm-eating, Hooded & Canada Warblers, Ovenbird 3, Northern Waterthrush, Common Yellowthroat 3 • Wrens: House Wren 9 + BC chickadee 1, Black & white warbler 1, Black-throated blue warbler 1, Magnolia warbler 1, Nashville warbler 1, Yellow warbler 1, RC Kinglet 2, Starling 2, RW Blackbird 9

21. Acknowledgements The team: • Bird Studies Canada: • Audrey Heagy • Canadian Wildlife Service • Charles Francis • Saint-Hyacinthe, QC: • Alex Thompson (Université de Montréal) • Michel Bigras-Poulin (Université de Montréal) • Kingston, ON: • Chris O’Callaghan (Queens University) • Toronto, ON: • Abdel Maarouf (Environment Canada, York University) • Guelph, ON: • Dominique Charron (Public Health Agency of Canada) • Ian Barker (University of Guelph) • Winnipeg, MB: • Robbin Lindsay (Public Health Agency of Canada) Funding by NRC Climate Change Impacts & Adaptations Programme