Migratory birds as vehicles for parasite dispersal? Infection by avian haemosporidians over the year and throughout the range of a long‐distance migrant

Abstract

Aim The role of migratory birds in the spread of parasites is poorly known, in part because migratory strategies and behaviours potentially affecting transmission are not easy to study. We investigated the dynamics of infection by blood parasites through the annual cycle of a long‐distance Nearctic–Neotropical migratory songbird to examine the role of this species in dispersing parasites between continents. Location The Americas. Taxon Grey‐cheeked Thrush (Catharus minimus, Aves, Passeriformes, Turdidae), Birds. Methods We used molecular and microscopy screening of haemosporidian parasites (Plasmodium, Haemoproteus, and Leucocytozoon) to examine the prevalence, distribution, and diversity of lineages through the annual cycle (breeding, migration, and wintering) of the grey‐cheeked thrush in North and Central America, Santa Marta mountains, the Andes, and the Amazon. We aimed to identify transmission areas, to examine the degree of sharing of haemosporidian lineages with resident birds in various areas and to assess the potential role of immunologically naïve juvenile individuals in parasite transmission. Results Prevalence and lineage diversity of haemosporidians varied significantly over time, being higher during breeding and fall and spring migration, and declining during wintering. Grey‐cheeked thrush shared few parasite lineages with tropical resident birds and slightly more lineages with other migratory and resident boreal species. We detected gametocytes in blood during spring migration stopover, but these were of lineages not found in resident tropical birds, indicating relapses of parasites transmitted elsewhere. Transmission likely occurs mostly on the breeding grounds, where juveniles and adults carried lineages restricted to closely related species of thrushes and other species of boreal birds. Main conclusions Long‐distance migratory songbirds are likely not important dispersers of blood parasites because there are ecological and evolutionary barriers to the interchange of parasites across vastly separated areas. Further work with thorough spatial and temporal sampling across other species, and considering the role of vectors, is necessary to understand the ecological and evolutionary factors explaining the distribution of parasites over broad scales.

Neotropical migratory and resident birds occurring in sympatry during winter have distinct haemosporidian parasite assemblages

“…Nonetheless, the geographic and host distributions of OZ14, OZ45, MI05 and KZ01 suggest that despite host mobility between breeding and wintering regions, some lineages transmitted on North American breeding grounds have not established transmission cycles in the Caribbean. Based on descriptions of parasite assemblages in resident hosts in the Caribbean region (Fallon et al, ; Ricklefs et al, ; Soares et al, ), Ecuador (Moens & Pérez‐Tris, ; Svensson‐Coelho et al, ), Colombia (González, Lotta, García, Moncada, & Matta, ; Pulgarín‐R et al, ) and Brazil (Fecchio et al, ), resident birds of the Neotropics appear to be either incompetent or suboptimal hosts for lineages that commonly occur in North America.…”

“…Transmission peaks and relapse of infections tend to occur during the avian breeding season (Cornet, Nicot, Rivero, & Gandon, ; Hellgren et al, ; Pérez‐Rodríguez, Hera, Bensch, & Pérez‐Tris, ). Therefore, many individuals of migratory species are infected with haemosporidian parasites prior to travelling to wintering areas (Hellgren et al, ; Pulgarín‐R et al, ; Ricklefs et al, , ), yet the potential for parasite exchange between migratory and resident avian host assemblages on the wintering grounds is poorly understood.…”

“…Of 11 parasite lineages with assigned transmission areas, only two were transmitted on the wintering grounds, and only one was transmitted during both breeding and wintering phases of the annual cycle. The second study described circannual variation of haemosporidian infections in a sample of 541 grey‐cheeked thrushes ( Catharus minimus ), a Nearctic migratory species that breeds at high latitudes in North America and winters in the Amazon basin in South America (Pulgarín‐R et al, ). Parasite prevalence was lowest during winter (21%) and the highest during the breeding season (65%).…”

“…Therefore, many individuals of migratory species are infected with haemosporidian parasites prior to travelling to wintering areas (Hellgren et al, 2013;Pulgarín-R et al, 2019;Ricklefs et al, 2017Ricklefs et al, , 2005), yet the potential for parasite exchange between migratory and resident avian host assemblages on the wintering grounds is poorly understood.…”

“…The second study described circannual variation of haemosporidian infections in a sample of 541 grey-cheeked thrushes (Catharus minimus), a Nearctic migratory species that breeds at high latitudes in North America and winters in the Amazon basin in South America (Pulgarín-R et al, 2019). Parasite prevalence was lowest during winter (21%) and the highest during the breeding season (65%).…”