Do birds affect Lyme disease risk? Range expansion of the vector‐borne pathogen Borrelia burgdorferi

Abstract

Because of their capacity for long‐range movement, birds may play an important role in the spread and range expansion of zoonotic pathogens and their vectors. The black‐legged tick (Ixodes scapularis) is the principal vector for the Lyme disease bacterium Borrelia burgdorferi, and commonly parasitizes a wide variety of vertebrate hosts, including at least 71 species of North American birds. Although the role of birds in B burgdorferi transmission dynamics is often discounted, data compiled from published studies indicate that the majority (58.6%) of bird species that have been evaluated are capable of infecting larval I scapularis with B burgdorferi. We estimated – for two bird species – that the number of individual birds required to produce one infected I scapularis larva is as low as three, and we conclude that bird‐mediated tick movement is an important factor in the range expansion of both I scapularis and B burgdorferi.