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Ticks Tick Borne Dis. 2015 Sep;6(6):715-20. doi: 10.1016/j.ttbdis.2015.06.004. Epub 2015 Jun 12.

How far north are migrant birds transporting the tick Ixodes scapularis in Canada? Insights from stable hydrogen isotope analyses of feathers.

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National Microbiology Laboratory, Public Health Agency of Canada, Saint Hyacinth, QC, Canada; Groupe de Recherche en Épidémiologie des Zoonoses et Santé Publique (GREZOSP), 3200 Sicotte, Saint-Hyacinthe, QC, Canada J2S 7C6. Electronic address:
Canadian Wildlife Health Cooperative, Department of Pathobiology, Ontario Veterinary College, University of Guelph, 50 Stone Road, Guelph, ON, Canada N1G 2W1. Electronic address:
Canadian Wildlife Service, Environment Canada, 1125 Colonel By, Ottawa, ON, Canada K1A 0H3. Electronic address:
Bird Studies Canada, 115 Front St., Port Rowan, ON, Canada N0E 1M0. Electronic address:
Zoonotic Diseases & Special Pathogens Division, Public Health Agency of Canada, National Microbiology Laboratory, 1015 Arlington Street, Winnipeg, MB, Canada R3E 3R2. Electronic address:
Environment Canada, 11 Innovation Blvd, Saskatoon, SK, Canada S7N 3H5. Electronic address:


Lyme disease is emerging in Canada because of northward range expansion of the tick vector Ixodes scapularis. It is hypothesised that I. scapularis feeding on passerine birds migrating north in spring are important in founding new I. scapularis populations leading to northward range expansion. However, there are no studies on how far north I. scapularis may be carried, only inferences from passive tick surveillance. We used stable hydrogen isotope (δ(2)H) analysis of rectrices collected from northward migrating, I. scapularis-carrying, passerine birds captured in Canada to estimate how far north I. scapularis may be carried. Rectrices are usually grown close to breeding sites and their δ(2)H values reflect those in the environment, which vary strongly with latitude in North America. Passerines usually return to their breeding or natal sites so δ(2)H values of rectrices of northward migrating birds can identify the likely latitudinal bands of their intended destinations. In 2006 we analysed δ(2)H from rectrices of 73 I. scapularis-carrying birds captured at five migration monitoring stations, mainly from southern Ontario. Values of δ(2)H ranged from -33 to -124‰, suggesting 19/71 (26.7%) birds were destined for latitude band B (the most southerly part of Ontario), 40/71 (56.3%) birds were destined for band C (which extends from southern Ontario, Quebec and the Maritimes to southern James Bay) and 12/71 (16.9%) birds were destined for bands D and E (which extend from northern Ontario and Quebec into the southern Canadian Arctic). This indicates that many I. scapularis-carrying migratory birds in spring have destinations far north in Canada, including some farther north than the current region of climatic suitability for I. scapularis. These findings support the hypothesis that I. scapularis may continue to be spread north by spring migrating passerines. Some thrush species may be particularly implicated in far northward dispersion of I. scapularis.


Ixodes scapularis; Lyme disease; Migratory birds; Range expansion

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