Transport of ticks infected with Ehrlichia chaffeensis in USA by migratory song-birds

Ticks are an ideal example of efficient ecto-parasites that are able to steal blood, a rich source of nutrients, from their vertebrate hosts for prolonged periods of time. Migrating birds are known to play a role as long distance vectors for many microbial pathogens. Ticks transmit a number of disease causing agents including Ehrlichia chaffeensis. This is the etiological agent of human monocytic ehrlichiosis, an emerging and life-threatening tick-borne human zoonosis. In spring 2010, we captured migrating song-birds and collected 109 attached ticks and 300 bird-blood samples for pathogen detection. The DNA was extracted from the blood samples and ticks. The presence of E. chaffeensis was tested using a nested PCR. We obtained 300 blood samples from the birds, along with 109 ticks removed from the birds. Out of the 300 blood samples, 26 blood samples showed amplification of VLPT gene product. Thirty ticks also showed amplification of a VLPT gene product. Furthermore, all amplified gene products were sequenced to confirm the presence of E. chaffeensis. In conclusion, migrating birds host epidemiologically important vector ticks and Ehrlichia species and contribute to the geographic distribution of ticks and Ehrlichial agents and their diseases.