Infection Prevalence of Borrelia burgdorferi in Ticks Collected from Songbirds in Far-Western Canada

Worldwide, wild birds play a vital role in the dispersal of ticks that harbour tick-borne pathogens, including Borrelia burgdorferi, the Lyme disease bacterium. Passerine birds (order: Passeriformes), commonly called songbirds, are hosts for certain hard-bodied ticks (Ixodida: Ixodidae) that carry pathogenic microorganisms.

In this paper, the authors aimed to determine: 1) the infection prevalence of B. burgdorferi in bird-feeding ticks and 2) pinpoint passerine species that are most heavily involved in tick infestations and enzootic maintenance of Lyme disease spirochetes. Ticks were collected from wild-caught songbirds at various times.

Using PCR testing, we found 124 (31%) of 405 ticks (4 species) to be infected with B. burgdorferi. Transstadial transmission of B. burgdorferi occurred from larva to nymph, plus nymph to adult, in the avian coastal tick, Ixodes auritulus, collected from songbirds in British Columbia (B.C). Collectively, all 3 motile life stages (larva, nymph, adult) of this tick had an infection prevalence of 31% for B. burgdorferi, which suggests vector competency. A Pacific Wren was highly infested with I. auritulus immatures, and 20 (44%) of 45 ticks (2 nymphs, 43 larvae) were infected with B. burgdorferi. This heavy infestation shows the high potential to initiate a new population of ticks and to disseminate Lyme spirochetes. Epidemiologically, B. burgdorferi-infected I. auritulus larvae collected from the Spotted Towhee, Swainson’s Thrush, Pacific Wren, and Fox Sparrow suggested that these avian hosts act as reservoirs for B. burgdorferi.

In conclusion, resident and migratory songbirds are disseminators of borreliae. The present study provides additional evidence to show that all 3 motile stages of I. auritulus play a vital role in maintaining B. burgdorferi in the environment along the Pacific Coast. Besides, because songbirds widely disperse Lyme disease vector ticks, primary health providers and the general public must be vigilant that outdoors people may be bitten by B. burgdorferi-infected ticks throughout far-western Canada.

Article by John D. Scott, et al, from Canada and USA.

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