Correlates of blood parasitism in a threatened marshland passerine: infection by kinetoplastids of the genus Trypanosoma is related to landscape metrics of habitat edge

Abstract

In birds, vector-borne parasites invading the bloodstream are important agents of disease, affect fitness and shape population viability, thus being of conservation interest. Here, we molecularly identified protozoan blood parasites in two populations of the threatened Aquatic Warbler Acrocephalus paludicola, a migratory passerine nesting in open marsh. We explored whether prevalence and lineage diversity of the parasites vary by population and whether infection status is explained by landscape metrics of habitat edge and individual traits (body mass, fat score, wing length and sex). Aquatic Warblers were infected by genera Plasmodium, Leucocytozoon and Trypanosoma, with seven, one and four lineages, and 29.9, 0.7 and 12.5% prevalence, respectively. No Haemoproteus infections were detected. Prevalence did not vary between the populations, but lineage diversity was higher in Polesie than in Biebrza for all the lineages pooled and for Plasmodium. Infection by Trypanosoma decreased with patch core area and increased with density of habitat edge. Infection status was not predicted by the individual traits. Our study is the first to show an association between edge-related landscape features and blood parasitism in an open habitat bird. This finding will support informed conservation measures for avian species of the globally shrinking marshland and other treeless habitats.

Heterozygosity and fitness in a threatened songbird: blood parasite infection is explained by single-locus but not genome-wide effects

“…This globally threatened passerine, a habitat specialist breeding in isolated wetlands, underwent a steep decline in population size (Briedis and Keišs 2016;Flade et al 2018), which could have lowered its genetic diversity and increased inbreeding rates. The Aquatic Warbler is infected by blood parasites of the genera Leucocytozoon, Plasmodium, and Trypanosoma; in males, infection with trypanosomes negatively correlates with fitness-related traits (Dyrcz et al 2005;Neto et al 2015;Kubacka et al 2019). These findings, converged with the previous results on haemosporidian parasites in other passerines (Merino et al 2000;Marzal et al 2005;Knowles et al 2010;Martínez-de La Puente et al 2010), indicate that blood parasitism likely affects the fitness status of the Aquatic Warbler.…”

“…We constructed three sets of candidate models, with the infection status by blood parasites pooled (candidate set 1), Plasmodium (candidate set 2), and Trypanosoma (candidate set 3) as a binary response variable, respectively. Because infection by Leucocytozoon was detected only in one individual (Kubacka et al 2019), this genus was included in the pooled parasites models, but we did not run a separate analysis for it. In each of the candidate sets, the global (full) model included IR, as well as region (Biebrza or Polesie), sex (male or female) and all the two-way interactions.…”

“…In each of the candidate sets, the global (full) model included IR, as well as region (Biebrza or Polesie), sex (male or female) and all the two-way interactions. This allowed us to control for factors that affect infection rates and/or HFCs, such as population structure, sex, or habitat (Reid et al 2007;Brekke et al 2010;Szulkin et al 2010;Sehgal 2015;Arct et al 2017;Kubacka et al 2019). Each candidate set contained a null model, which assumed that infection probability was constant in all individuals.…”

“…The blood samples were molecularly screened for the presence of blood parasites in a different project (Kubacka et al 2019). In brief, the DNA samples extracted following the phenol-chloroform protocol were used to PCR-amplify a 478 bp fragment of the mitochondrial cyt b gene to detect Leucocytozoon, Haemoproteus, and Plasmodium (Hellgren et al 2004), and a 326 bp fragment of the small subunit ribosomal RNA (SSU rRNA) gene to identify Trypanosoma (Sehgal et al 2001).…”

“…PCR products of positive samples were purified and sequenced. The obtained sequences were aligned to sequences available in the MalAvi database (Bensch et al 2009) for Leucocytozoon, Haemoproteus, and Plasmodium, and in GenBank for Trypanosoma (BLASTN, best hit match) (Kubacka et al 2019).…”