Haemoproteus erythrogravidus n. sp. (Haemosporida, Haemoproteidae): Description and molecular characterization of a widespread blood parasite of birds in South America

Insights into the Biology of Leucocytozoon Species (Haemosporida, Leucocytozoidae): Why Is There Slow Research Progress on Agents of Leucocytozoonosis?

Blood parasites of the genus Leucocytozoon (Leucocytozoidae) only inhabit birds and represent a readily distinct evolutionary branch of the haemosporidians (Haemosporida, Apicomplexa). Some species cause pathology and even severe leucocytozoonosis in avian hosts, including poultry. The diversity of Leucocytozoon pathogens is remarkable, with over 1400 genetic lineages detected, most of which, however, have not been identified to the species level. At most, approximately 45 morphologically distinct species of Leucocytozoon have been described, but only a few have associated molecular data. This is unfortunate because basic information about named and morphologically recognized Leucocytozoon species is essential for a better understanding of phylogenetically closely related leucocytozoids that are known only by DNA sequence. Despite much research on haemosporidian parasites during the past 30 years, there has not been much progress in taxonomy, vectors, patterns of transmission, pathogenicity, and other aspects of the biology of these cosmopolitan bird pathogens. This study reviewed the available basic information on avian Leucocytozoon species, with particular attention to some obstacles that prevent progress to better understanding the biology of leucocytozoids. Major gaps in current Leucocytozoon species research are discussed, and possible approaches are suggested to resolve some issues that have limited practical parasitological studies of these pathogens.

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.

Prevalence of co-infection and genetic diversity of avian haemosporidian parasites in two rehabilitation facilities in Iran: implications for the conservation of captive raptors

Background

Various haemosporidian parasites infect raptors, especially captive hosts who may be more exposed. Diagnosis of threatening factors such as infectious diseases indirectly has a significant role in protecting endangered or threatened species that may boost the mortality or extinction resulting from declined reproduction. Few investigations have been performed in captive hosts to detect the prevalence of haemosporidian parasites and define genetic diversity in west Asia. For the first time, the current study was designed to determine the prevalence and genetic diversity of haemosporidian parasites in captive raptors by molecular methods in two rehabilitation facilities in North and North-east Iran and to define phylogenetic relationships of detected lineages circulating in raptors.

Results

Molecular characterization of the haemosporidian parasite was accomplished by PCR-based method and DNA sequencing in 62 captive raptors. The overall prevalence was ~ 36% with higher infection of Haemoproteus spp. than Leucocytozoon spp. Plasmodium infection was not detected in any host. Results showed that 22 individuals (of 10 species) were infected with unique lineages. Genus Haemoproteus was detected in 26.66% of examined individuals (of eight species) and Leucocytozoon was found in 10% of individuals (of four species). The molecular analysis could detect ten lineages (nine Haemoproteus spp. and one Leucocytozoon spp.) which were categorizes as new and six lineages which have been previously detected in the other investigations.

Conclusions

The Bayesian phylogenetic analysis derived from obtained data in the present study and published lineages in previous investigations indicated the probable host specificity of Haemoproteus and Leucocytozoon parasites in several sub-clades at hosts’ order and genus level. As monitoring the parasite loads of captive birds when admitted reduce the risk of infecting hosts in captivity at those locations, we designed this study to determine infection prevalence and genetic diversity of blood parasites in raptors examined in Iran. These results allow mapping of haemosporidian distribution and shed light on the depth of their diversity in Iran to protect species by identification of risk in rehabilitation facilities.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12862-022-02068-9.

Keys to the avian Haemoproteus parasites (Haemosporida, Haemoproteidae)

Background

Haemoproteus is a sister genus to malaria parasites (Plasmodium), which both belong to the order Haemosporida (Apicomplexa). Parasites of both genera are flourishing in birds, however, Haemoproteus species are noticeably less investigated. This is unfortunate because knowledge about close relatives of malaria pathogens is important for better understanding the evolutionary origin and basic biological features of the entire group of haemosporidian infections. Moreover, recent findings show that Haemoproteus species can cause severe damage of various bird organs due to megalomeronts and other exo-erythrocytic stages. These haemosporidians are remarkably diverse, but remain neglected partly due to difficulties in species identification. Hundreds of Haemoproteus genetic lineages have been reported in birds, and numerous new lineages are found each year, but most remain unidentified to the species level. Numerous new Haemoproteus pathogens were described during the past 20 years. However, keys for their identification are absent. Identification of Haemoproteus species remains a difficult task and is an obstacle for better understanding of the distribution and epidemiology of these parasites. This study aimed to develop comprehensive keys for the identification of described avian Haemoproteus species using morphological features of their blood stages (gametocytes).

Methods

Type and voucher preparations of avian Haemoproteus species were accessed in museums in Europe, Australia and the USA. Gametocytes of most described species were examined, and these data formed a background for this study. The data also were considered from published articles containing parasite species descriptions. The method of dichotomous keys was applied. The most difficult steps in the keys were accompanied with references to the corresponding parasite pictures.

Results

In all, 201 published articles were included in this review. Morphological diagnostic features of gametocytes of all described Haemoproteus species were analysed and compared. Illustrated keys for identification of these parasite species were developed. Available information about the molecular characterization of Haemoproteus parasites was provided.

Conclusion

This review shows that 177 described species of avian Haemoproteus can be distinguished and identified in blood films using morphological characters of their gametocytes and host cells. These species were incorporated in the keys. Information about possible morphologically cryptic parasites was provided. Molecular markers are available for only 42% of the described Haemoproteus parasites, calling for researchers to fill this gap.

Blood parasites of passerines in the Brazilian Pampas and their implications for a potential population supplementation program for the endangered Yellow Cardinal (Gubernatrix cristata)

Espinilho savanna ("seasonal steppe savanna") is a unique vegetation formation of the Pampas biome that is found near the tri-border of Brazil, Uruguay, and Argentina. The Yellow Cardinal (Gubernatrix cristata) is a flagship species of this ecosystem, but it is classified as "critically endangered" in Brazil due to habitat loss and poaching for the illegal trade. Population supplementation through the release of individuals that were captive-bred or apprehended by authorities from the illegal trade has been considered as a conservation strategy for this species; however, the risk of pathogen introduction is a critical concern. We used microscopy and molecular methods to investigate the occurrence of blood parasites in wild passerines (n = 64, including three Yellow Cardinals) at Espinilho State Park, Rio Grande do Sul, Brazil, and in captive Yellow Cardinals (n = 30) at three facilities in Brazil. Haemosporidian parasites were detected in the blood smears of 10.9% of the wild passerines, comprising the morphospecies Haemoproteus erythrogravidus in Rufous-collared Sparrow (Zonotrichia capensis), H. quiscalus in Grayish Baywing (Agelaioides badius), and H. tyranni in Great Kiskadee (Pitangus sulphuratus); these are the southernmost records for these morphospecies and their first record for the Pampas biome. No haemosporidian parasites were detected in the blood smears of the Yellow Cardinals, wild or captive. Microfilariae were detected in the blood smears of 14.1% of the wild passerines, including all wild Yellow Cardinals, and in 43.3% of captive Yellow Cardinals. Trypanosoma sp. was detected in the blood smear of one captive Yellow Cardinal. Nested PCR and gene sequencing of the cyt-b gene of Haemoproteus/Plasmodium was used to test a subset of wild passerines and captive Yellow Cardinals, allowing for the molecular barcoding of H. quiscalus lineage AGEBAD04 and H. tyranni lineage PITSUL01; additionally, DNA identical to that of lineage PITSUL01 was detected in the blood of one captive Yellow Cardinal. This study provides valuable data to support the conservation management of the Yellow Cardinal and other threatened passerines from the Pampas and highlights the need for further studies on the epidemiology and pathology of filarioid worms and trypanosomes in passerines from this biome.

Is Haemoproteus gabaldoni a valid species? An approach from morphology and molecular tools applied to parasites of Anseriformes

Currently, there are three recognized species of haemoproteids infecting Anseriformes: Haemoproteus nettionis, H. macrovacuolatus, and H. greineri. Unfortunately, genetic information associated with a morphotype is available only for H. macrovacuolatus. We recently found a parasite morphologically compatible with Haemoproteus gabaldoni, a species Bennet (1993) described in a Cairina moschata (Muscovy duck) from Venezuela. This species was synonymized to H. nettionis by Valkiūnas (2005), arguing not enough morphological differentiation between them; it was said that H. greineri could be as well a synonym of H. nettionis. In this study, we aimed to provide evidence to determine if Haemoproteus gabaldoni is a different species of H. nettionis and help to clarify other species status. We first performed morphological and morphometrical analyses and compared this information against the parahapantotypes of H. greineri, H. gabaldoni and material diagnosed as H. nettionis provided by the International Reference center for Avian Haematozoa (IRCAH), and H. macrovacuolatus from the Host-Parasite Relationship Study Group (GERPH, in Spanish Grupo de Estudio Relación Parásito Hospedero) biological collection. We used Principal Component Analysis (PCA) of dimensionless standard morphometrical variables from gametocytes. Furthermore, we amplified a small fragment of cytochrome b (cyt b) to compare the sequence with information in GenBank and Malavi through phylogenetic analyses and haplotype networks. PCA analyses revealed the presence of three distinct groups in the samples studied, supported in the morphological traits of each parasite species analyzed; phylogenetic analyses grouped parasite lineages separately according to the host and continent of provenance. Such results indicate that, H. gabaldoni, is a different species from H. nettionis. One more time, it is demonstrated the importance of linking barcode surveys to morphological studies. Finally, it is highlighted the importance of biological collections as repositories of worldwide biodiversity.

Avian Malaria and Related Parasites from Resident and Migratory Birds in the Brazilian Atlantic Forest, with Description of a New Haemoproteus Species

Determining the prevalence and local transmission dynamics of parasitic organisms are necessary to understand the ability of parasites to persist in host populations and disperse across regions, yet local transmission dynamics, diversity, and distribution of haemosporidian parasites remain poorly understood. We studied the prevalence, diversity, and distributions of avian haemosporidian parasites of the genera Plasmodium, Haemoproteus, and Leucocytozoon among resident and migratory birds in Serra do Mar, Brazil. Using 399 blood samples from 66 Atlantic Forest bird species, we determined the prevalence and molecular diversity of these pathogens across avian host species and described a new species of Haemoproteus. Our molecular and morphological study also revealed that migratory species were infected more than residents. However, vector infective stages (gametocytes) of Leucocytozoon spp., the most prevalent parasites found in the most abundant migrating host species in Serra do Mar (Elaenia albiceps), were not seen in blood films of local birds suggesting that this long-distance Austral migrant can disperse Leucocytozoon parasite lineages from Patagonia to the Atlantic Forest, but lineage sharing among resident species and local transmission cannot occur in this part of Brazil. Our study demonstrates that migratory species may harbor a higher diversity and prevalence of parasites than resident species, but transportation of some parasites by migratory hosts may not always affect local transmission.

Morphological and molecular characterization of Haemoproteus coatneyi and Haemoproteus erythrogravidus (Haemosporida: Haemoproteidae) in Passeriformes in Brazil's Atlantic Forest

Haemoproteus spp. are protozoan parasites found in birds around the world. These parasites are identified through the morphology of gametocytes, phylogenetic analysis based on the mitochondrial cytb gene, and the parasite's geographic distribution. The absence of erythrocytic merogony, high intraspecific genetic variation and low parasitemia in wild birds makes it essential to use integrative approaches that assist in the identification of these parasites. Thus, microscopic and molecular analyses, combined with spatial distribution, were carried out to verify the presence of Haemoproteus spp. in wild birds in Brazil. Light microscopy revealed one Tangara sayaca bird was parasitized by Haemoproteus coatneyi and, two specimens of Zonotrichia capensis presented Haemoproteus erythrogravidus. The morphology of the gametocytes of these two parasitic species showed high similarity. The molecular analysis revealed the presence of one lineage of H. coatneyi and two lineages of H. erythrogravidus, one of which is considered a new lineage. These lineages were grouped phylogenetically in separate clades, with low genetic divergence, and the H. erythrogravidus lineage emerged as an internal group of the lineages of H. coatneyi. The geographic distribution demonstrated that the two species occur in the American continent. This is the first report of H. erythrogravidus in Brazil.

Mosquito identification and haemosporidian parasites detection in the enclosure of the African penguins (Spheniscus demersus) at the SANBI zoological garden

The National Zoological Gardens (NZG) is a facility of the South African National Biodiversity Institute (SANBI) and the largest zoo in southern Africa. Among the 9000 captive animals kept by the NZG, is the endangered African penguin (Spheniscus demersus). There have been several post-mortem reports on deaths of penguins in the NZG due to haemosporidian infections, however, the haemosporidian lineages involved and possible insect vector are unknown. Haemosporidians are apicomplexan parasites that infect vertebrates through blood-sucking dipteran insects. Therefore, the current study aimed to identify mosquitoes that are potential vectors found within the African penguin enclosure as well as to detect the haemosporidian parasites from these insects using nested-PCR and real-time PCR (qPCR) analyses. Mosquito samples were collected using an overnight UV-light trap setup for 3 months. From the 65 pooled samples representing 325 mosquitoes, morphological and molecular analysis showed that Culex pipiens (52.31%) was the dominant species followed by Cx. t heileri (30.77%) and Cx. quinquefasciatus (16.92%). Nested-PCR detected parasite DNA of Leucocytozoon sp. and Plasmodium sp. The Cx. pipiens had the highest minimum infection rate (MIR) of 5.88% by nested-PCR and 9.41% by qPCR whilst Cx. quinquefasciatus had MIR of 3.64% in both assays and no haemosporidian parasites were detected from Cx. t heileri. One Cx. pipiens sample had a co-infection of both Plasmodium sp. and Leucocytozoon sp. detected by nested-PCR. These findings suggest that effective control measures for blood-sucking dipteran insects is required at the NZG and more studies should be conducted to determine the actual prevalence of these haemosporidian parasites among other bird species within NZG.

Evolutionary ecology, taxonomy, and systematics of avian malaria and related parasites

Haemosporidian parasites of the genera Plasmodium, Leucocytozoon, and Haemoproteus are one of the most prevalent and widely studied groups of parasites infecting birds. Plasmodium is the most well-known haemosporidian as the avian parasite Plasmodium relictum was the original transmission model for human malaria and was also responsible for catastrophic effects on native avifauna when introduced to Hawaii. The past two decades have seen a dramatic increase in research on avian haemosporidian parasites as a model system to understand evolutionary and ecological parasite-host relationships. Despite haemosporidians being one the best studied groups of avian parasites their specialization among avian hosts and variation in prevalence amongst regions and host taxa are not fully understood. In this review we focus on describing the current phylogenetic and morphological diversity of haemosporidian parasites, their specificity among avian and vector hosts, and identifying the determinants of haemosporidian prevalence among avian species. We also discuss how these parasites might spread across regions due to global climate change and the importance of avian migratory behavior in parasite dispersion and subsequent diversification.

The buffy coat method: a tool for detection of blood parasites without staining procedures

BACKGROUND

Blood parasites belonging to the Apicomplexa, Trypanosomatidae and Filarioidea are widespread in birds and have been studied extensively. Microscopical examination (ME) of stained blood films remains the gold standard method for the detection of these infections in birds, particularly because co-infections predominate in wildlife. None of the available molecular tools can detect all co-infections at the same time, but ME provides opportunities for this to be achieved. However, fixation, drying and staining of blood films as well as their ME are relatively time-consuming. This limits the detection of infected hosts during fieldwork when captured animals should be released soon after sampling. It is an obstacle for quick selection of donor hosts for parasite experimental, histological and other investigations in the field. This study modified, tested and described the buffy coat method (BCM) for quick diagnostics (~ 20 min/sample) of avian blood parasites.

METHODS

Blood of 345 birds belonging to 42 species was collected, and each sample was examined using ME of stained blood films and the buffy coat, which was examined after centrifugation in capillary tubes and after being transferred to objective glass slides. Parasite detection using these methods was compared using sensitivity, specificity, positive and negative predictive values and Cohen's kappa index.

RESULTS

Haemoproteus, Leucocytozoon, Plasmodium, microfilariae, Trypanosoma and Lankesterella parasites were detected. BCM had a high sensitivity (> 90%) and specificity (> 90%) for detection of Haemoproteus and microfilariae infections. It was of moderate sensitivity (57%) and high specificity (> 90%) for Lankesterella infections, but of low sensitivity (20%) and high specificity (> 90%) for Leucocytozoon infections. Trypanosoma and Plasmodium parasites were detected only by BCM and ME, respectively. According to Cohen's kappa index, the agreement between two diagnostic tools was substantial for Haemoproteus (0.80), moderate for Lankesterella (0.46) and fair for microfilariae and Leucocytozoon (0.28) infections.

CONCLUSIONS

BCM is sensitive and recommended as a quick and reliable tool to detect Haemoproteus, Trypanosoma and microfilariae parasites during fieldwork. However, it is not suitable for detection of species of Leucocytozoon and Plasmodium. BCM is a useful tool for diagnostics of blood parasite co-infections. Its application might be extended to studies of blood parasites in other vertebrates during field studies.

Molecular identification of Haemosporidia in avian endemics of Gorgona Island within a context for the eastern tropical Pacific region

Island bird populations and their obligate blood parasites are of interest for understanding the accumulation of biodiversity and the evolutionary relationship with their mainland congeners. We examined avian Haemosporidia cytochrome b gene among terrestrial birds on Gorgona Island National Park, Colombia. Three Haemoproteus haplotype groups found on Gorgona Island have a higher genetic similarity to Haemoproteus found in the eastern tropical Pacific than those documented in Africa, Asia, Europe and Oceania. Two of the haplotype groups on the island are generalists in terms of infecting multiple hosts and their wide geographical distribution within the eastern tropical Pacific region, a third Haemoproteus haplogroup appears endemic to Gorgona Island. The overall prevalence of haemosporidian parasites is 57,9% for birds on Gorgona island, which is higher than local reports of prevalence documented in other archipelagos or the mainland. The island population of Cyanerpes cyaneus gigas seems to be the most susceptible to Haemoproteus infection when compared to Thamnophilus atrinucha gorgonae and Coereba flaveola gorgonae. Our findings support an ubiquitous pattern of endemism among organisms including avian haemosporidian parasites on Gorgona Island and also highlight the potential exposure of island bird populations to avian malaria.

Molecular characterization of six widespread avian haemoproteids, with description of three new Haemoproteus species

Species of Haemoproteus (Haemosporida, Haemoproteidae) are widespread and often prevalent blood parasites of birds all over the word. They are particularly diverse in tropical countries. Due to limited knowledge of life cycles, these pathogens usually have been considered relatively benign and were neglected in veterinary medicine and bird management. However, recent molecular studies provided evidence that Haemoproteus parasites might cause severe diseases if they infect non-adapted (wrong) avian hosts due to marked damage of organs by exo-erythrocytic stages (megalomeronts). Additionally, high Haemoproteus infections are lethal to blood-sucking insects. Molecular markers are essential for reliable detection and species identification both at tissue stages in vertebrates and sporogonic stages in arthropods however, remain insufficiently developed for wildlife haemosporidian parasites. This study combined PCR-based and microscopic approaches and reported cytochrome b gene (cytb) and apicoplast gene (clpc) markers for characterization of six widespread species of haemoproteids parasitizing common birds wintering in tropics and subtropics of the Old World. Three new Haemoproteus species were described using morphological and molecular markers. Molecular characterization of haemoproteids parasitizing falcons was developed. Morphological and phylogenetic characterization of Haemoproteus tinnunculi (cytb lineage hFALSUB01), H. brachiatus (hLK03), H. parabelopolskyi (hSYAT1), H. homogeneae n. sp. (hSYAT16), H. homopicae n. sp. (hGAGLA07) and H. homominutus n. sp. (hCUKI1) was performed and provides clues for infections diagnostics. This study adds three species to the group of morphologically readily distinct Haemoproteus parasites, which differ in few base pairs (< 1%) in their partial cytb sequences, indicating that low genetic difference in such sequences often show between-species divergence and should be carefully applied in taxonomic biodiversity studies of haemosporidian parasites. Bayesian phylogenetic analysis identified the position of detected lineages in regard of other Haemoproteus species, suggesting that all reported parasites belong to subgenus Parahaemoproteus and likely are transmitted by Culicoides biting midges. Importance of clpc gene sequences was specified in haemosporidian parasite taxonomy on species levels.

Disentangling Leucocytozoon parasite diversity in the neotropics: Descriptions of two new species and shortcomings of molecular diagnostics for leucocytozoids

Avian communities from South America harbor an extraordinary diversity of Leucocytozoon species (Haemosporida, Leucocytozoidae). Here, of 890 birds sampled, 10 (1.2%) were infected with Leucocytozoon parasites. Among them, two new species were discovered and described. Leucocytozoon grallariae sp. nov. and Leucocytozoon neotropicalis sp. nov. were found in non-migratory highland passeriforms belonging to the Grallaridae and Cotingidae, respectively. They both possess gametocytes in fusiform host cells. However, due to combining microscopic examination and molecular detection, it was revealed that these parasites were present in co-infections with other Leucocytozoon species, which gametocytes develop in roundish host cells, therefore exhibiting two highly distant parasite lineages isolated from the same samples. Remarkably, the lineages obtained by cloning the mtDNA genomes were not captured by the classic nested PCR, which amplifies a short fragment of cytochrome b gene. Phylogenetic analyses revealed that the lineages obtained by the classic nested PCR clustered with parasites possessing gametocytes in roundish host cells, while the lineages obtained by the mtDNA genome PCR protocol were closely related to Leucocytozoon parasites possessing gametocytes in fusiform host cells. These findings suggest problems with the sensitivity of the molecular protocols commonly used to detect Leucocytozoon species. A detailed analysis of the primers used in the classic nested PCR revealed a match with DNA sequences from those parasites that possess gametocytes in roundish host cells (i.e., Leucocytozoon fringillinarum), while they differ with the orthologous regions in the mtDNA genomes isolated from the samples containing the two new species. Since these are mixed infections, none of the lineages detected in this study can be assigned accurately to the new Leucocytozoon morphospecies that develops in fusiform host cells. However, phylogenetic analyses allowed us to hypothesize their most probable associations. This study highlights the need for developing detection methods to assess the diversity of Leucocytozoon parasites accurately.

Genetic variation of avian malaria in the tropical Andes: a relationship with the spatial distribution of hosts

BACKGROUND

Avian haemosporidia are obligate blood parasites with an ample range of hosts worldwide. To understand how host communities may influence the diversity of parasites of the neotropics, the spatial genetic variation of avian Plasmodium, Haemoproteus, and Leucocytozoon was examined between areas of host endemism and along the elevational gradient in the tropical Andes.

METHODS

A total of 1686 accessions of the cytochrome b gene of avian haemosporidia were selected from 43 publications, that further provides additional information on 14.2% of bird species in the Neotropics. Haplotype groups were identified using a similarity-based clustering of sequences using a cut-off level ≥ 99.3% of sequence identity. Phylogenetic-based analyses were implemented to examine the spatial genetic structure of avian haemosporidia among areas of host endemism and the elevation gradient in the tropical Andes.

RESULTS

The areas of avian endemism, including the tropical Andes, can explain the differential distribution of the haemosporidia cytochrome b gene variation. In the tropical Andes region, the total number of avian haemosporidia haplotypes follows a unimodal pattern that peaks at mid-elevation between 2000 and 2500 m above sea level. Furthermore, the haplotype assemblages of obligate blood parasites tend to overlap towards mid-elevation, where avian host diversity tends to be maximized.

CONCLUSIONS

Spatial analyses revealed that richness and turnover in haemosporidia suggest an association with montane host diversity, according to elevation in the tropical Andes. In addition, the spatial distribution of haemosporidia diversity is closely associated with patterns of host assemblages over large geographical scale in the tropical Andes and areas of avian endemism nearby.

Genomic Advances in Avian Malaria Research

Haemosporidian parasites causing malaria-like diseases in birds are globally distributed and have been associated with reduced host fitness and mortality in susceptible bird species. This group of parasites has not only enabled a greater understanding of host specificity, virulence, and parasite dispersal, but has also been crucial in restructuring the evolutionary history of apicomplexans. Despite their importance, genomic resources of avian haemosporidians have proved difficult to obtain, and they have, as a result, been lagging behind the congeneric Plasmodium species infecting mammals. In this review, I discuss recent genomic advances in the field of avian malaria research, and outline outstanding questions that will become possible to investigate with the continued successful efforts to generate avian haemosporidian genomic data.

Spatial distribution, prevalence and diversity of haemosporidians in the rufous-collared sparrow, Zonotrichia capensis

BACKGROUND

Parasite prevalence and diversity are determined by the distribution of hosts and vectors and by the interplay among a suite of environmental factors. Distributions of parasite lineages vary based on host susceptibility and geographical barriers. Hemoparasites of the genera Haemoproteus and Plasmodium have wide distributions, and high prevalence and genetic diversity within perching birds (Order Passeriformes). The rufous-collared sparrow (Zonotrichia capensis) is widely distributed in Central and South America across an immense diversity of environments from sea level to more than 4000 meters above sea level. It therefore provides an excellent model to investigate whether altitudinal and latitudinal gradients influence the distribution, prevalence and diversity of haemosporidian parasites, their population structure and the biogeographical boundaries of distinct parasite lineages.

RESULTS

We assembled samples from 1317 rufous-collared sparrows spanning 75 locales from across Central and South America (between 9.5°N and 54°S; 10-4655 meters above sea level). We used DNA sequence data from a fragment of the mitochondrial cytochrome b gene (cytb) of Haemoproteus and Plasmodium from 325 positive samples and found prevalences of 22 and 3%, respectively. Haemoproteus exhibited a higher prevalence than Plasmodium but with comparatively lower genetic diversity. We detected a relationship of Plasmodium and Haemoproteus prevalence with altitude and latitude; however, altitude and latitude did not influence parasite diversity.

CONCLUSIONS

Parasite lineages showed a phylogeographical boundary coincident with the Andes Mountains, although we also observed a north-south disjunction in Peru for Haemoproteus. Haemosporidian distribution was not homogeneous but differed based on latitude and altitude. This is most probably due to environmental factors that have influenced both vector distribution and abundance, as well as parasite development. Our study provides key insights on the distribution of haemoparasite lineages and parasite dynamics within hosts.

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.

A new blood parasite of leaf warblers: molecular characterization, phylogenetic relationships, description and identification of vectors

BACKGROUND

Blood parasites of the genus Haemoproteus Kruse, 1890 are cosmopolitan, might be responsible for mortality in non-adapted birds, and often kill blood-sucking insects. However, this group remains insufficiently investigated in the wild. This is particularly true for the parasites of leaf warblers of the Phylloscopidae Alström, Ericson, Olsson & Sundberg the common small Old World passerine birds whose haemoproteid parasite diversity and vectors remain poorly studied. This study reports a new species of Haemoproteus parasitizing leaf warblers, its susceptible vector and peculiar phylogenetic relationships with other haemoproteids.

METHODS

Wood warblers (Phylloscopus sibilatrix Bechstein) were caught in Lithuania during spring migration, and blood films were examined microscopically. Laboratory reared Culicoides nubeculosus Meigen were exposed experimentally by allowing them to take blood meals on one individual harbouring mature gametocytes of the new Haemoproteus species (lineage hPHSIB2). To follow sporogonic development, the engorged insects were dissected at intervals. The parasite lineage was distinguished using sequence data, and morphological analysis of blood and sporogonic stages was carried out. Bayesian phylogeny was constructed in order to determine the phylogenetic relationships of the new parasite with other haemoproteids.

RESULTS

Haemoproteus (Parahaemoproteus) homopalloris n. sp. was common in wood warblers sampled after arrival to Europe from their wintering grounds in Africa. The new parasite belongs to a group of avian haemoproteid species with macrogametocytes possessing pale staining cytoplasm. All species of this group clustered together in the phylogenetic analysis, indicating that intensity of the cytoplasm staining is a valuable phylogenetic character. Laboratory-reared biting midges C. nubeculosus readily supported sporogony of new infections. Phylogenetic analysis corroborated vector experiments, placing the new parasite in the clade of Haemoproteus (Parahaemoproteus) parasites transmitted by biting midges.

CONCLUSIONS

Haemoproteus homopalloris n. sp. is the third haemoproteid, which is described from and is prevalent in wood warblers. Phylogenetic analysis identified a clade containing seven haemoproteids, which are characterised by pale staining of the macrogametocyte cytoplasm and with ookinetes maturing exceptionally rapidly (between 1 to 1.5 h after exposure to air). Both these features may represent valuable phylogenetic characters. Studies targeting mechanisms of sporogonic development of haemoproteids remain uncommon and should be encouraged. Culicoides nubeculosus is an excellent experimental vector of the new parasite species.

Primers targeting mitochondrial genes of avian haemosporidians: PCR detection and differential DNA amplification of parasites belonging to different genera

Haemosporida is a diverse group of vector-borne parasitic protozoa, ubiquitous in terrestrial vertebrates worldwide. The renewed interest in their diversity has been driven by the extensive use of molecular methods targeting mitochondrial genes. Unfortunately, most studies target a 478 bp fragment of the cytochrome b (cytb) gene, which often cannot be used to separate lineages from different genera found in mixed infections that are common in wildlife. In this investigation, an alignment constructed with 114 mitochondrial genome sequences belonging to four genera (Leucocytozoon, Haemoproteus, Plasmodium and Hepatocystis) was used to design two different sets of primers targeting the cytb gene as well as the other two mitochondrial DNA genes: cytochrome c oxidase subunit 1 and cytochrome c oxidase subunit 3. The design of each pair of primers required consideration of different criteria, including a set for detection and another for differential amplification of DNA from parasites belonging to different avian haemosporidians. All pairs of primers were tested in three laboratories to assess their sensitivity and specificity under diverse practices and across isolates from different genera including single and natural mixed infections as well as experimental mixed infections. Overall, these primers exhibited high sensitivity regardless of the differences in laboratory practices, parasite species, and parasitemias. Furthermore, those primers designed to separate parasite genera showed high specificity, as confirmed by sequencing. In the case of cytb, a nested multiplex (single tube PCR) test was designed and successfully tested to differentially detect lineages of Plasmodium and Haemoproteus parasites by yielding amplicons with different sizes detectable in a standard agarose gel. To our knowledge, the designed assay is the first test for detection and differentiation of species belonging to these two genera in a single PCR. The experiments across laboratories provided recommendations that can be of use to those researchers seeking to standardise these or other primers to the specific needs of their field investigations.

Molecular characterization and distribution of Plasmodium matutinum, a common avian malaria parasite

Species of Plasmodium (Plasmodiidae, Haemosporida) are widespread and cause malaria, which can be severe in avian hosts. Molecular markers are essential to detect and identify parasites, but still absent for many avian malaria and related haemosporidian species. Here, we provide first molecular characterization of Plasmodium matutinum, a common agent of avian malaria. This parasite was isolated from a naturally infected thrush nightingale Luscinia luscinia (Muscicapidae). Fragments of mitochondrial, apicoplast and nuclear genomes were obtained. Domestic canaries Serinus canaria were susceptible after inoculation of infected blood, and the long-lasting light parasitemia developed in two exposed birds. Clinical signs of illness were not reported. Illustrations of blood stages of P. matutinum (pLINN1) are given, and phylogenetic analysis identified the closely related avian Plasmodium species. The phylogeny based on partial cytochrome b (cyt b) sequences suggests that this parasite is most closely related to Plasmodium tejerai (cyt b lineage pSPMAG01), a common malaria parasite of American birds. Both these parasites belong to subgenus Haemamoeba, and their blood stages are similar morphologically, particularly due to marked vacuolization of the cytoplasm in growing erythrocytic meronts. Molecular data show that transmission of P. matutinum (pLINN1) occurs broadly in the Holarctic, and the parasite likely is of cosmopolitan distribution. Passeriform birds and Culex mosquitoes are common hosts. This study provides first molecular markers for detection of P. matutinum.