Great-tailed Grackles (Quiscalus mexicanus) as a tolerant host of avian malaria parasites

Abstract

Great-tailed Grackles (Quiscalus mexicanus) are a social, polygamous bird species whose populations have rapidly expanded their geographic range across North America over the past century. Before 1865, Great-tailed Grackles were only documented in Central America, Mexico, and southern Texas in the USA. Given the rapid northern expansion of this species, it is relevant to study its role in the dynamics of avian blood parasites. Here, 87 Great-tailed grackles in Arizona (a population in the new center of the range) were screened for haemosporidian parasites using microscopy and PCR targeting the parasite mitochondrial cytochrome b gene. Individuals were caught in the wild from January 2018 until February 2020. Haemosporidian parasite prevalence was 62.1% (54/87). A high Plasmodium prevalence was found (60.9%, 53/87), and one grackle was infected with Haemoproteus (Parahaemoproteus) sp. (lineage SIAMEX01). Twenty-one grackles were infected with P. cathemerium, sixteen with P. homopolare, four with P. relictum (strain GRW04), and eleven with three different genetic lineages of Plasmodium spp. that have not been characterized to species level (MOLATE01, PHPAT01, and ZEMAC01). Gametocytes were observed in birds infected with three different Plasmodium lineages, revealing that grackles are competent hosts for some parasite species. This study also suggests that grackles are highly susceptible and develop chronic infections consistent with parasite tolerance, making them competent to transmit some generalist haemosporidian lineages. It can be hypothesized that, as the Great-tailed Grackle expands its geographic range, it may affect local bird communities by increasing the transmission of local parasites but not introducing new species into the parasite species pool.

Leucocytozoon cariamae n. sp. and Haemoproteus pulcher coinfection in Cariama cristata (Aves: Cariamiformes): first mitochondrial genome analysis and morphological description of a leucocytozoid in Brazil

“…on the slides we analysed (1 parasite detected during the examination of 200 microscopic fields at 1000× magnification) agrees with the general low parasitaemia observed in natural Leucocytozoon infections (Chagas et al ., 2023; Valkiūnas and Iezhova, 2023). Indeed, microscopy alone underestimates the prevalence of haemosporidian parasites (Pacheco et al ., 2022). However, this technique informs about host competence via visualization of gametocytes in blood smears (Valkiūnas and Iezhova, 2023), making it an important tool in avian Haemosporida research.…”

“…gametocyte among high numbers of H. pulcher gametocytes, we recommend that future studies targeting Leucocytozoon in Neotropical areas conduct thorough blood smear analyses to avoid missing infections with such low parasitaemia. This has been reported in other haemosporidian parasites (Pacheco et al ., 2022). This will also avoid underestimating possible coinfections, a common feature in Leucocytozoon infections (Chagas et al ., 2023).…”

“…However, the recent identification of diverse Leucocytozoon genetic lineages in blood samples from non-migratory birds across most Brazilian biomes (Fecchio et al, 2018(Fecchio et al, , 2019Carvalho et al, 2022) provides evidence of broader geographical and environmental scale transmission in the Neotropics. Such findings suggest that microscopy alone may have lower sensitivity to detect infections with low parasitaemia, called submicroscopic infections (Pacheco et al, 2022). Leucocytozoon sporozoites injected from the vector can remain viable for up to 11 days in the host (Khan et al, 1969) and may be amplified by polymerase chain reactions (PCRs) (Valkiūnas et al, 2009).…”

Haemosporidians in Non-Passerine Birds of Colombia: An Overview of the Last 20 Years of Research

“…Although the association of parasite lineages with a morphological parasite species was the main aim of this investigation, particularly for this study, such values were underestimated since the molecular determination was made only on samples whose smear was positive. As PCR methods are more sensitive than microscopy [25,84], they can detect infections that are non-patent and might be part of the transmission cycles [25]. This is common in other vertebrates, such as humans, where asymptomatic patients with submicroscopic infections can infect malaria vectors [85].…”

“…The first record of a PCR-based diagnosis of haemosporidian parasites in neotropical non-passerine birds was done by Durrant et al [24] in 2006 (Figure 1). Given the higher detection rate of molecular methods over microscopy (e.g., [25]), the number of explored avian orders has increased (Figure 1). The first Leucocytozoon species reported in Apodiformes (Hummingbirds) came from Colombia, and was published in 2014 [20].…”