Assessing the dispersal of viruses and parasites via migratory birds at the edges of North America

Wild birds may introduce viruses and parasites into naive host populations via migration. Therefore, sampling birds at the margins of North America, where the distribution of animals wintering in different regions overlap, may... [ view full abstract ]

Wild birds may introduce viruses and parasites into naive host populations via migration. Therefore, sampling birds at the margins of North America, where the distribution of animals wintering in different regions overlap, may be useful for detecting the dispersal of infectious agents and understanding the extent of viral and parasite exchange. Through the use of molecular methods and avian migration tracking, we assessed the evidence for viral and parasitic exchange at three edges of North America: the Arctic, Beringia, and the United States Gulf Coast. In the Arctic, we tested waterfowl for blood parasites and found evidence for locally-acquired Leucocytozoon infections, Haemoproteus parasites likely acquired at non-breeding areas, and an absence of Plasmodium. These results elucidate the contemporary range of avian malarial parasites relative to the Arctic and facilitate future assessments of parasite range shifts. In Beringia, we assessed viral and parasite exchange between East Asia and North America by migratory birds and found evidence for interhemispheric dispersal of influenza A viruses, avian paramyxovirus serotype 1, and two genera of blood parasites. Our results suggest that interhemispheric exchange of infectious agents by migratory birds may be extensive and that sampling in the Beringian region may facilitate early detection of introduction events. Through the sampling of blue-winged teal along the United States Gulf Coast, we found evidence for the exchange of influenza A viruses and blood parasites between North America and the Neotropics, including the acquisition of Plasmodium infections by teal at Neotropical wintering areas. These results highlight a southern pathway by which foreign-origin pathogens may be introduced by migratory birds into the United States. Collectively, this research demonstrates the active exchange of viruses and parasites at the margins of North America and identifies areas to consider for targeted surveillance for introductions and range expansions of non-endemic pathogens.