Low prevalence of haemosporidian parasites in shorebirds

Although shorebirds (Charadriiformes: suborders Scolopaci and Charadrii) face physiological stress during migration and experience a wide range of vector-suitable habitats across their distributions, haemosporidian parasites (order Haemosporida) have rarely been detected in these species worldwide. We ask whether shorebirds remain infection-free when wintering in areas where parasite transmission occurs among landbird species. Blood samples were collected at three locations in Argentina: Patagonia, with an avian assemblage dominated by shorebird species; Mar Chiquita Lagoon, a high-salinity water basin where shorebird and landbird species co-occur; and inland sites in Chaco and Cordoba provinces, where host assemblages included mostly landbird species. We screened 650 samples for the presence of haemosporidian infections and sequenced a part of the parasite mitochondrial cytochrome b gene to determine parasite lineages. Of 342 landbirds, 91 were infected with haemosporidian parasites, compared to only three of 318 shorebirds. Wintering location had no effect on the prevalence of haemosporidian parasites in shorebirds. Haemosporidian infections are rare in shorebirds even when these co-occur with landbird species in inland areas suitable for parasite transmission. The few infections detected in shorebirds might represent spillover infections from landbirds, as the parasite lineages were also found in common landbird species. We suggest that shorebirds are resistant to haemosporidian parasites, and either do not become infected or quickly clear occasional infections.