Haemosporidian prevalence and parasitaemia in the Black-throated sparrow (Amphispiza bilineata) in central-Mexican dryland habitats

Avian haemosporidians of breeding birds in the Davis Mountains sky-islands of west Texas, USA

Avian haemosporidians are protozoan parasites transmitted by insect vectors that infect birds worldwide, negatively impacting avian fitness and survival. However, the majority of haemosporidian diversity remains undescribed. Quantifying this diversity is critical to determining parasite–host relationships and host-switching potentials of parasite lineages as climate change induces both host and vector range shifts. In this study, we conducted a community survey of avian haemosporidians found in breeding birds on the Davis Mountains sky islands in west Texas, USA. We determined parasite abundance and host associations and compared our results to data from nearby regions. A total of 265 birds were screened and infections were detected in 108 birds (40.8%). Most positive infections were identified as Haemoproteus (36.2%), followed by Plasmodium (6.8%) and Leucocytozoon (0.8%). A total of 71 haemosporidian lineages were detected of which 39 were previously undescribed. We found that regional similarity influenced shared lineages, as a higher number of lineages were shared with avian communities in the sky islands of New Mexico compared to south Texas, the Texas Gulf Coast and central Mexico. We found that migratory status of avian host did not influence parasite prevalence, but that host phylogeny is likely an important driver.

Survey of haemosporidian parasite infections in an endangered high alpine bird

The Brown-capped Rosy-Finch is an endangered high alpine specialist that breeds on cliffs in the Rocky Mountains of North America. We know little about the parasites that infect these birds but filling this knowledge gap is important for understanding their population decline. The aim of this study was to survey haemosporidian parasite infections in Brown-capped Rosy-Finches. We sampled 104 Brown-capped Rosy-Finches during their breeding season at six sampling sites spanning the Colorado Rocky Mountains where they are nearly endemic. We used nested PCR methods to screen birds for parasite infections, and Sanger sequencing data were used to identify parasite lineages. Four of the sampling sites had birds with infections. Females were more often infected than males (prevalence = 15.6% and 9.7%, respectively). We observed twice as many infected birds sampled in July compared to birds sampled in June (prevalence = 12.5% and 6.25%, respectively). The percent of infected birds by sampling site ranged from 0 to over 20%. In total we identified eight different genetic lineages of haemosporidian parasites infecting Brown-capped Rosy-Finches-seven were in the genus Leucocytozoon, and one was in the genus Haemoproteus. Network analysis clearly separates Haemoproteus from Leucocytozoon, with Leucocytozoon lineages comprising two major clusters. Based on reports made to the MalAvi database, all lineages in Cluster 1 have the same reported insect vector, Simulium silvestre. We report that Brown-capped Rosy-Finches experience infections with haemosporidian parasites and that the percentage of infected birds differed markedly between sampling sites. We hypothesize that vector ecology and associated variation in climate at sampling sites explain our observations.

Haemosporidian parasites in the ash-breasted Sierra finch (Geospizopsis plebejus): insights from an Andean dry forest population

Haemosporidian genera Plasmodium, Haemoproteus and Leucocytozoon, responsible for avian malarial infections, are highly diverse and have a wide range of health effects and predictors, depending on the host and its environmental context. Here, we present, for the first time, detailed information on the identity, prevalence and parasitaemia of haemosporidians and other haemoparasites that infect the ash-breasted Sierra finch, Geospizopsis plebejus, in an Andean dry forest. We study the consequences of infection in the host body and health conditions and explore the environmental and intrinsic factors that influence infection status and parasitaemia. We conducted diagnoses by cytochrome b (cytb) sequencing and morphological identification, and estimated the levels of parasitaemia based on microscopy. We identified 6 cytb lineages infecting G. plebejus. Two of them were new lineages: Haemoproteus sp. GEPLE01 and GEPLE02. We also detected Haemoproteus sp. ZOCAP08, Haemoproteus sp. AMAVIR01, Plasmodium homopolare BAEBIC02 and Plasmodium cathemerium ZONCAP15. By microscopy, we detected Haemoproteus coatneyi, Haemoproteus erythrogravidus, P. homopolare and other unidentified species of Haemoproteus, Plasmodium, Babesia sp. and 1 microfilaria. We found no evidence of Leucocytozoon. Additionally, we detected several coinfections by sequencing and microscopy. The prevalence of haemosporidian infections was high (87.7%), and the mean parasitaemia was 61.65 infected cells per 10 000 erythrocytes examined. Prevalence and parasitaemia were higher for Haemoproteus than for Plasmodium. Haemoproteus sp. AMAVIR01 showed the highest prevalence (43.1%) and mean parasitaemia (94.39/10 000 erythrocytes) and might be associated with H. coatneyi. Immature individuals showed a lower prevalence than adults, supporting previous findings.

Climate predictors and climate change projections for avian haemosporidian prevalence in Mexico

Long-term, inter-annual and seasonal variation in temperature and precipitation influence the distribution and prevalence of intraerythrocytic haemosporidian parasites. We characterized the climatic niche behind the prevalence of the three main haemosporidian genera (Haemoproteus, Plasmodium and Leucocytozoon) in central-eastern Mexico, to understand their main climate drivers. Then, we projected the influence of climate change over prevalence distribution in the region. Using the MaxEnt modelling algorithm, we assessed the relative contribution of bioclimatic predictor variables to identify those most influential to haemosporidian prevalence in different avian communities within the region. Two contrasting climate change scenarios for 2070 were used to create distribution models to explain spatial turnover in prevalence caused by climate change. We assigned our study sites into polygonal operational climatic units (OCUs) and used the general haemosporidian prevalence for each OCU to indirectly measure environmental suitability for these parasites. A high statistical association between global prevalence and the bioclimatic variables ‘mean diurnal temperature range’ and ‘annual temperature range’ was found. Climate change projections for 2070 showed a significant modification of the current distribution of suitable climate areas for haemosporidians in the study region.

Avian haemosporidian parasites of accipitriform raptors

Background

The order Accipitriformes comprises the largest group of birds of prey with 260 species in four families. So far, 21 haemosporidian parasite species have been described from or reported to occur in accipitriform birds. Only five of these parasite species have been characterized molecular genetically. The first part of this study involved molecular genetic screening of accipitriform raptors from Austria and Bosnia-Herzegovina and the first chromogenic in situ hybridization approach targeting parasites in this host group. The aim of the second part of this study was to summarize the CytB sequence data of haemosporidian parasites from accipitriform raptors and to visualize the geographic and host distribution of the lineages.

Methods

Blood and tissue samples of 183 accipitriform raptors from Austria and Bosnia-Herzegovina were screened for Plasmodium, Haemoproteus and Leucocytozoon parasites by nested PCR, and tissue samples of 23 PCR-positive birds were subjected to chromogenic in situ hybridization using genus-specific probes targeting the parasites’ 18S rRNAs. All published CytB sequence data from accipitriform raptors were analysed, phylogenetic trees were calculated, and DNA haplotype network analyses were performed with sequences from clades featuring multiple lineages detected in this host group.

Results

Of the 183 raptors from Austria and Bosnia-Herzegovina screened by PCR and sequencing, 80 individuals (44%) were infected with haemosporidian parasites. Among the 39 CytB lineages detected, 18 were found for the first time in the present study. The chromogenic in situ hybridization revealed exo-erythrocytic tissue stages of Leucocytozoon parasites belonging to the Leucocytozoon toddi species group in the kidneys of 14 infected birds. The total number of CytB lineages recorded in accipitriform birds worldwide was 57 for Leucocytozoon, 25 for Plasmodium, and 21 for Haemoproteus.

Conclusion

The analysis of the DNA haplotype networks allowed identifying numerous distinct groups of lineages, which have not yet been linked to morphospecies, and many of them likely belong to yet undescribed parasite species. Tissue stages of Leucocytozoon parasites developing in accipitriform raptors were discovered and described. The majority of Leucocytozoon and Haemoproteus lineages are specific to this host group, but most Plasmodium lineages were found in birds of other orders. This might indicate local transmission from birds kept at the same facilities (raptor rescue centres and zoos), likely resulting in abortive infections. To clarify the taxonomic and systematic problems, combined morphological and molecular genetic analyses on a wider range of accipitriform host species are needed.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-04019-z.

A Case Report of Avian Malaria (Plasmodium spp.) in Pen-Reared Pigeons (Columba livia)

One dead 6-wk-old male racing pigeon (Columba livia) was submitted for postmortem evaluation after presenting with weight loss, anorexia, dry shanks, dehydration, and lethargy. The bird belonged to a confined flock with 12 other pigeons raised by a hobbyist. Two pigeons in the flock reportedly had died with a history of similar clinical signs. On gross examination, the liver and the spleen were diffusely dark brown to black. Histopathology revealed moderate to large amounts of anisotropic, intracytoplasmic black pigment, compatible with hemozoin, in the spleen, liver, lung, and kidneys, with small amounts in the heart and meninges of the brain. Marked plasmacytic infiltrates were observed in liver, lungs, heart, and kidneys. Blood smears from a clinically affected concomitant pigeon from the flock revealed numerous light-blue, round to oval, intraerythrocytic trophozoites and meronts suggestive of Plasmodium spp. PCR and sequencing tests were performed from spleen and ceca with fragments of the 18S ribosomal RNA and the mitochondrial cytochrome b (cytB) genes. Sequencing results confirmed the presence of Plasmodium in the affected pigeon. Although an exact genetic match could not be determined, the most similar species to the isolate from this study are Plasmodium relictum, Plasmodium matutinum, Plasmodium lutzi, and Plasmodium homocircumflexum.

Avian haemosporidian infections in rufous-collared sparrows in an Andean dry forest: diversity and factors related to prevalence and parasitaemia

Despite intensive research during the last few decades, understanding of ecological and physiological factors related to haemosporidian infections in birds is still fragmentary. Since more model organisms are needed in order to understand these infections in the wild, we analysed avian haemosporidian infections in the rufous-collared sparrow (Zonotrichia capensis, Emberizidae) in a dry forest of the Ecuadorian Andes. Parasite diversity was screened using molecular and morphological approaches. By molecular diagnosis, we identified three linages that were phylogenetically placed in the context of molecular haemosporidian diversity and associated with a morphospecies. By microscopy, we identified five described morphospecies and one additional undescribed morphospecies. We found that avian haemosporidian prevalence on the study site was 76.3%. Additionally, we used a series of generalized linear models to explore the potential relationship of parasite prevalence and parasitaemia with a set of variables related to physiological and environmental conditions. Although our results revealed associations of haemosporidian infections with precipitation, age and sampling site, the models only explained a small fraction of the variation.

Low occurrence of hemosporidian parasites in the Neotropic cormorant (Phalacrocorax brasilianus) in Chile

Hemosporidian parasites rarely infect aquatic birds. Few studies have been conducted in South America identifying some lineages of the genera Plasmodium, Leucocytozoon, and Haemoproteus, but none has been done in the Neotropic cormorant (Phalacrocorax brasilianus). This species is widely distributed through the American continent, from Southern USA to Tierra del Fuego, using a wide range of aquatic habitats. We molecularly studied the occurrence and diversity of hemosporidian lineages infecting individuals of Neotropic cormorant across a broad latitudinal gradient in Chile (Arica to Tierra del Fuego). As expected, a very low occurrence of individuals infected by Plasmodium sp. (4/123, 3.3%) and Leucocytozoon sp. (2/123, 1.6%) was detected. We found no evidence of Haemoproteus sp. We identified one lineage of Plasmodium (ZEMAC01) and one new lineage of Leucocytozoon (PHABRA01) infecting cormorants. Individuals infected by Plasmodium sp. were birds from only one site (i.e., Chillán), whereas Leucocytozoon sp. was found in one bird from Valdivia and another one from Tierra del Fuego. Our results expand the known range of hemosporidian parasite lineages in aquatic birds providing an essential baseline data that contribute to a better understanding of the geographic range of hemosporidian parasites infecting Phalacrocoracidae in South America.