Oral Presentation 64th International Conference of the Wildlife Disease Association 2015

Avian migrants facilitate invasions of Neotropical ticks and tick-borne pathogens into the United States (#11)

Emily Cohen 1 , Lisa Auckland 2 , Peter Marra 1 , Sarah Hamer 2
  1. Smithsonian Conservation Biology Institute, Washington, District of Columbia, United States
  2. Texas A&M University, College Station, Texas, United States

Migratory birds may play an under-recognized role in facilitating the invasion of ticks and tick-borne pathogens, leading to new human and animal health threats. Every spring, billions of birds migrate north across the Gulf of Mexico in route to breeding grounds across eastern North America. Because ticks typically stay attached to their hosts for up to a week, this annual migratory movement provides an opportunity for birds to transport ticks from South and Central America to the US. Furthermore, the stress of migration may be associated with increased circulation of pathogens within bird blood. Over two spring seasons (2013 and 2014), we captured birds on the Northern coast of the Gulf of Mexico in Texas, where high densities of migrants aggregate in the coastal marsh habitats.  In the field, we searched each bird and collected ticks, obtained a blood sample, and attached a leg band prior to release.  In the laboratory, we identified ticks to life stage and species using both morphologic and molecular features, and screened ticks and blood for infection with pathogens in the genera Rickettsia, Borrelia, and Ehrlichia using PCR and DNA sequencing. Based on examination of 3,844 birds of 85 species, we found 2.9% of birds of 36 species were infested by larval or nymphal ticks.  Migratory birds harbored eight different tick species, including seven in the genus Amblyomma and one in the genus Ixodes, only two of which are known to be established in the US. Among the human pathogens detected within ticks and birds included Borrelia miyamotoi (a relapsing fever group spirochete), Rickettsia parkeri (a spotted fever group Rickettsia) and at least three other Rickettsia species implicated in human disease in Central and South America.  Avian migrations may provide a mechanism for the geographic expansion of neotropical tick-borne disease risk.