Haemoproteus minutus and Haemoproteus belopolskyi (Haemoproteidae): Complete sporogony in the biting midge Culicoides impunctatus (Ceratopogonidae), with implications on epidemiology of haemoproteosis

Natural Vector of Avian Haemoproteus asymmetricus Parasite and Factors Altering the Spread of Infection

Avian haemosporidians (Apicomplexa, Haemosporida) are widespread blood protists, often causing severe haemosporidiosis, pathology, or even mortality in their hosts. Migrant birds regularly bring various haemosporidian parasites from wintering grounds to European breeding areas. Some haemosporidian parasites are prevalent in breeding sites and complete their life cycles in temperate climate zones and can be transmitted, but others do not. The factors altering the spread of these haemosporidians are not fully understood. Culicoides biting midges (Diptera: Ceratopogonidae) play an important role in the transmission of worldwide distributed avian haemosporidian parasites belonging to the genus Haemoproteus, but this information is particularly scarce and insufficient. The key factors limiting the spread of these pathogens in temperate climate zones, which we suspect and aim to study, are the absence of susceptible vectors and the ecological isolation of birds from vectors during the breeding period when transmission occurs. The primary objective of this study was to evaluate how the habitats of biting midges and bird breeding sites influence parasite transmission while also seeking to expand our understanding of the natural vectors for these parasites. Biting midges were collected using UV traps on the Curonian Spit, Lithuania, in different habitats, such as woodland and reeds, from May to September. Parous Culicoides females were identified, dissected, and investigated for the presence of Haemoproteus parasites using both microscopy and PCR-based tools. Among the dissected 1135 parous Culicoides females, the sporozoites of Haemoproteus asymmetricus (genetic lineage hTUPHI01) have been detected for the first time in the salivary glands of Culicoides festivipennis. The sporozoites of four Haemoproteus lineages were detected in Culicoides segnis, C. festivipennis, and Culicoides kibunensis biting midges. PCR-based screening showed that the females of seven Culicoides species were naturally infected with Haemoproteus parasites. The DNA of the parasite of owls, Haemoproteus syrnii (hSTAL2), was detected for the first time in Culicoides punctatus. The highest abundance of collected Culicoides females was in June, but the highest prevalence of Haemoproteus parasites in biting midges was in July. The abundance of Culicoides was higher in the woodland compared with reeds during the season. The acquired findings indicate the varied abundance and diversity of biting midges throughout the season and across distinct habitats. This variability could potentially impact the transmission of Haemoproteus parasites among birds with diverse breeding site ecologies. These outcomes hold the potential to enhance our understanding of the epizootiology of Haemoproteus infections within temperate climatic zones.

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.

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.

Exploring the thermal limits of malaria transmission in the western Himalaya

Environmental temperature is a key driver of malaria transmission dynamics. Using detailed temperature records from four sites: low elevation (1800), mid elevation (2200 m), and high elevation (2600-3200 m) in the western Himalaya, we model how temperature regulates parasite development rate (the inverse of the extrinsic incubation period, EIP) in the wild. Using a Briére parametrization of the EIP, combined with Bayesian parameter inference, we study the thermal limits of transmission for avian (Plasmodium relictum) and human Plasmodium parasites (P. vivax and P. falciparum) as well as for two malaria-like avian parasites, Haemoproteus and Leucocytozoon. We demonstrate that temperature conditions can substantially alter the incubation period of parasites at high elevation sites (2600-3200 m) leading to restricted parasite development or long transmission windows. The thermal limits (optimal temperature) for Plasmodium parasites were 15.62-34.92°C (30.04°C) for P. falciparum, 13.51-34.08°C (29.02°C) for P. vivax, 12.56-34.46°C (29.16°C) for P. relictum and for two malaria-like parasites, 12.01-29.48°C (25.16°C) for Haemoproteus spp. and 11.92-29.95°C (25.51°C) for Leucocytozoon spp. We then compare estimates of EIP based on measures of mean temperature versus hourly temperatures to show that EIP days vary in cold versus warm environments. We found that human Plasmodium parasites experience a limited transmission window at 2600 m. In contrast, for avian Plasmodium transmission was not possible between September and March at 2600 m. In addition, temperature conditions suitable for both Haemoproteus and Leucocytozoon transmission were obtained from June to August and in April, at 2600 m. Finally, we use temperature projections from a suite of climate models to predict that by 2040, high elevation sites (~2600 m) will have a temperature range conducive for malaria transmission, albeit with a limited transmission window. Our study highlights the importance of accounting for fine-scale thermal effects in the expansion of the range of the malaria parasite with global climate change.

Culicoides segnis and Culicoides pictipennis Biting Midges (Diptera, Ceratopogonidae), New Reported Vectors of Haemoproteus Parasites

As bloodsuckers of birds, Culicoides biting midges (Diptera, Ceratopogonidae) play an important role in the transmission of avian haemosporidian (Haemoproteus) parasites, which are prevalent in many bird populations and cause disease, pathology, or even mortality in their hosts. Information about the role of the various Culicoides species in the transmission of Haemoproteus parasites remains insufficient. This presents an obstacle for the better understanding of the epizootiology of haemoproteosis. The aim of this study was to determine new Culicoides species involved in the transmission of Haemoproteus parasites in the wild. Biting midges were collected using UV traps on the Curonian Spit, Lithuania. Only parous Culicoides females were investigated: they were identified and were diagnosed for the presence of Haemoproteus parasites using both microscopy and PCR-based methods. We collected and dissected 420 parous Culicoides females. PCR-based screening showed that 28 parous Culicoides biting midges were infected with avian Haemoproteus parasites. Haemoproteid DNA was detected in Culicoides kibunensis, Culicoides pictipennis, Culicoides festivipennis, Culicoides segnis, Culicoides pallidicornis, and Culicoides obsoletus biting midges. The DNA of Haemoproteus palloris, genetic lineage hWW1, was found for the first time in C. pallidicornis. Haemoproteus sporozoites were detected in the salivary glands of two Culicoides segnis biting midges. According to the PCR results, one female contained Haemoproteus tartakovskyi (genetic lineage hHAWF1) DNA and another Haemoproteus majoris (genetic lineage hCCF5) DNA. The sporozoites of Haemoproteus parasites were also detected in the salivary glands of four C. pictipennis biting midges using microscopy, and this finding was confirmed by PCR as Haemoproteus parabelopolskyi DNA (genetic lineage hSYAT02) was detected in three out of the four biting midges. The obtained results supplement existing information about Culicoides biting midges as natural vectors of Haemoproteus spp. and add two new Culicoides species to the vector list, showing the low specificity of these parasites for the invertebrate hosts.

Description of Haemoproteus asymmetricus n. sp. (Haemoproteidae), with remarks on predictability of the DNA haplotype networks in haemosporidian parasite taxonomy research

Haemoproteus species (Haemosporida, Haemoproteidae) are cosmopolitan blood parasites, which have been neglected for over 100-years, but attracted attention recently due to reports of severe and even lethal haemoproteosis in birds and vectors. Approximately 150 species of avian Haemoproteus have been described and named, but molecular data suggest that hundreds of independently evolving molecular lineages might occur, indicating the existence of a remarkable undescribed species diversity. It is timely to develop a methodology, which allow the application of available genetic data in taxonomy of haemosporidians on species levels. This study aimed to test a hypothesis suggesting that DNA haplotype networks might aid in targeting genetically distinct, but still undescribed parasites, and might be used to direct taxonomic studies on haemosporidian species levels. Mainly, we tested a prediction that the lineage hTUPHI01, a common Haemoproteus parasite of Turdus philomelos, might be a new species, which is morphologically similar and genetically closely related to the parasites of Haemoproteus minutus group. Blood samples of T. philomelos naturally infected with this parasite lineage were collected and studied using microscopic examination of blood films and PCR-based methods. Haemoproteus asymmetricus n. sp. was found in this bird, described and characterised molecularly using partial cytochrome b (cytb) sequences. The new species shared some features with parasites of the H. minutus group, as was predicted by the DNA haplotype network. Due to the visualisation of closely related lineages as well as the evaluation of their host and geographic distributions, DNA haplotype networks can be recommended as the helpful methodology, able to direct and speed practical work on parasite species taxonomy and pathogen biodiversity. The combined molecular phylogenetic and morphological approaches showed that the well-supported clades in Bayesian phylogenetic trees based on the partial cytb gene sequences contain morphologically remarkably different Haemoproteus parasite species, which however, share some basic biological features. Phylogenetic analysis can be used for prediction of these basic features in still undescribed parasites. This study calls for further fusion of advanced molecular and microscopy approaches for better understanding haemosporidian parasite biology.

Culicoides biting midges involved in transmission of haemoproteids

BACKGROUND

Culicoides biting midges (Diptera, Ceratopogonidae) are known vectors of avian Haemoproteus parasites. These parasites cause diseases, pathology and even mortality in birds. The diversity of biting midges in Europe is great, but only four Culicoides species are known to be vectors of avian Haemoproteus parasites. In general, our knowledge about the role of the particular Culicoides species in the transmission of Haemoproteus parasites remains insufficient. Information gaps hinder a better understanding of parasite biology and the epizootiology of parasite-caused diseases. The aim of this study was to determine new Culicoides species involved in the transmission of Haemoproteus parasites.

METHODS

Biting midges were collected using a UV trap as well as sticky traps installed in bird nest boxes. Individual parous females were diagnosed for the presence of haemoproteids using both PCR-based and microscopic methods.

RESULTS

We collected and dissected 232 parous Culicoides females from 9 species using a UV trap and 293 females from 11 species from bird nest boxes. Culicoides obsoletus was the dominant species collected using a UV trap, and Culicoides kibunensis dominated among midges collected in nest boxes. PCR-based screening showed that 5.2% of parous biting midges collected using a UV trap and 4.4% of midges collected from nest boxes were infected with avian haemosporidian parasites. Haemoproteid DNA was detected in C. kibunensis, Culicoides pictipennis, Culicoides punctatus, Culicoides segnis and Culicoides impunctatus females. The sporozoites of Haemoproteus minutus (genetic lineages hTURDUS2 and hTUPHI01) were detected in the salivary glands of two C. kibunensis females using microscopy, and this finding was confirmed by PCR.

CONCLUSIONS

Culicoides kibunensis was detected as a new natural vector of Haemoproteus minutus (hTURDUS2 and hTUPHI01). Haemoproteid DNA was detected in females from five Culicoides species. This study contributes to the epizootiology of avian Haemoproteus infections by specifying Culicoides species as vectors and species that are likely to be responsible for the transmission of haemoproteids in Europe.

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.

Complete sporogony of the blood parasite Haemoproteus nucleocondensus in common biting midges: why is its transmission interrupted in Europe?

Haemoproteus species (Haemoproteidae) are widespread blood parasites and are transmitted by Culicoides biting midges and Hippoboscidae louse flies. Although these pathogens may cause morbidity or mortality, the vectors and patterns of transmission remain unknown for the great majority of avian haemoproteids. Haemoproteus nucleocondensus has been frequently reported in Europe in great reed warblers Acrocephalus arundinaceus after their arrival from African wintering grounds, but this infection has not been found in juveniles at the breeding sites. The factors that prevent its transmission remain unclear. This study was designed to test whether the sporogony of H. nucleocondensus (lineage hGRW8) can be completed in Culicoides impunctatus, one of the most abundant European biting midge species. Wild-caught females were infected with H. nucleocondensus from great reed warblers. Microscopic examination and PCR-based methods were used to detect sporogonic stages and to confirm species identity. This study showed that H. nucleocondensus completes sporogony in C. impunctatus, suggesting that there are no obstacles to its transmission from the point of view of vector availability and average temperature in Northern Europe. We discuss other ecological factors which should be considered to explain why the transmission of H. nucleocondensus and some other Southern origin haemosporidians are interrupted in North Europe.

The life-cycle of the avian haemosporidian parasite Haemoproteus majoris, with emphasis on the exoerythrocytic and sporogonic development

BACKGROUND

Haemoproteus parasites (Haemosporida, Haemoproteidae) are cosmopolitan in birds and recent molecular studies indicate enormous genetic diversity of these pathogens, which cause diseases in non-adapted avian hosts. However, life-cycles remain unknown for the majority of Haemoproteus species. Information on their exoerythrocytic development is particularly fragmental and controversial. This study aimed to gain new knowledge on life-cycle of the widespread blood parasite Haemoproteus majoris.

METHODS

Turdus pilaris and Parus major naturally infected with lineages hPHYBOR04 and hPARUS1 of H. majoris, respectively, were wild-caught and the parasites were identified using microscopic examination of gametocytes and PCR-based testing. Bayesian phylogeny was used to determine relationships between H. majoris lineages. Exoerythrocytic stages (megalomeronts) were reported using histological examination and laser microdissection was applied to isolate single megalomeronts for genetic analysis. Culicoides impunctatus biting midges were experimentally exposed in order to follow sporogonic development of the lineage hPHYBOR04.

RESULTS

Gametocytes of the lineage hPHYBOR04 are indistinguishable from those of the widespread lineage hPARUS1 of H. majoris, indicating that both of these lineages belong to the H. majoris group. Phylogenetic analysis supported this conclusion. Sporogony of the lineage hPHYBOR04 was completed in C. impunctatus biting midges. Morphologically similar megalomeronts were reported in internal organs of both avian hosts. These were big roundish bodies (up to 360 μm in diameter) surrounded by a thick capsule-like wall and containing irregularly shaped cytomeres, in which numerous merozoites developed. DNA sequences obtained from single isolated megalomeronts confirmed the identification of H. majoris.

CONCLUSIONS

Phylogenetic analysis identified a group of closely related H. majoris lineages, two of which are characterized not only by morphologically identical blood stages, but also complete sporogonic development in C. impunctatus and development of morphologically similar megalomeronts. It is probable that other lineages belonging to the same group would bear the same characters and phylogenies based on partial cytb gene could be used to predict life-cycle features in avian haemoproteids including vector identity and patterns of exoerythrocytic merogony. This study reports morphologically unique megalomeronts in naturally infected birds and calls for research on exoerythrocytic development of haemoproteids to better understand pathologies caused in avian hosts.

Sporogony of four Haemoproteus species (Haemosporida: Haemoproteidae), with report of in vitro ookinetes of Haemoproteus hirundinis: phylogenetic inference indicates patterns of haemosporidian parasite ookinete development

BACKGROUND

Haemoproteus (Parahaemoproteus) species (Haemoproteidae) are widespread blood parasites that can cause disease in birds, but information about their vector species, sporogonic development and transmission remain fragmentary. This study aimed to investigate the complete sporogonic development of four Haemoproteus species in Culicoides nubeculosus and to test if phylogenies based on the cytochrome b gene (cytb) reflect patterns of ookinete development in haemosporidian parasites. Additionally, one cytb lineage of Haemoproteus was identified to the species level and the in vitro gametogenesis and ookinete development of Haemoproteus hirundinis was characterised.

METHODS

Laboratory-reared C. nubeculosus were exposed by allowing them to take blood meals on naturally infected birds harbouring single infections of Haemoproteus belopolskyi (cytb lineage hHIICT1), Haemoproteus hirundinis (hDELURB2), Haemoproteus nucleocondensus (hGRW01) and Haemoproteus lanii (hRB1). Infected insects were dissected at intervals in order to detect sporogonic stages. In vitro exflagellation, gametogenesis and ookinete development of H. hirundinis were also investigated. Microscopic examination and PCR-based methods were used to confirm species identity. Bayesian phylogenetic inference was applied to study the relationships among Haemoproteus lineages.

RESULTS

All studied parasites completed sporogony in C. nubeculosus. Ookinetes and sporozoites were found and described. Development of H. hirundinis ookinetes was similar both in vivo and in vitro. Developing ookinetes of this parasite possess long outgrowths, which extend longitudinally and produce the apical end of the ookinetes. A large group of closely related Haemoproteus species with a similar mode of ookinete development was determined. Bayesian analysis indicates that this character has phylogenetic value. The species identity of cytb lineage hDELURB2 was determined: it belongs to H. hirundinis.

CONCLUSIONS

Culicoides nubeculosus is susceptible to and is a likely natural vector of numerous species of Haemoproteus parasites, thus worth attention in haemoproteosis epidemiology research. Data about in vitro development of haemoproteids provide valuable information about the rate of ookinete maturation and are recommended to use as helpful step during vector studies of haemosporidian parasites, particularly because they guide proper dissection interval of infected insects for ookinete detection during in vivo experiments. Additionally, in vitro studies readily identified patterns of morphological ookinete transformations, the characters of which are of phylogenetic value in haemosporidian parasites.

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.

High susceptibility of the laboratory-reared biting midges Culicoides nubeculosus to Haemoproteus infections, with review on Culicoides species that transmit avian haemoproteids

Haemosporidian parasites belonging to Haemoproteus cause avian diseases, however, vectors remain unidentified for the majority of described species. We used the laboratory-reared biting midges Culicoides nubeculosus to determine if the sporogonic development of three widespread Haemoproteus parasites completes in this insect. The midges were reared and fed on one common blackbird, white wagtail and thrush nightingale naturally infected with Haemoproteus minutus, Haemoproteus motacillae and Haemoproteus attenuatus, respectively. The engorged females were dissected in order to follow their sporogonic development. Microscopic examination was used to identify sporogonic stages. Bayesian phylogeny based on partial cytochrome b gene was constructed in order to determine phylogenetic relationships among Culicoides species-transmitted haemoproteids. All three parasites completed sporogony. Phylogenetic analysis placed Culicoides species transmitted haemoproteids in one well-supported clade, proving that such analysis readily indicates groups of dipteran insects transmitting avian haemoproteids. Available data show that 11 species of Culicoides have been proved to support complete sporogony of 18 species of avian haemoproteids. The majority of Culicoides species can act as vectors for many Haemoproteus parasites, indicating the low specificity of these parasites to biting midges, whose are globally distributed. This calls for control of haemoproteid infections during geographical translocation of infected birds.

New Haemoproteus parasite of parrots, with remarks on the virulence of haemoproteids in naive avian hosts

Haemoproteus infections can cause fatal disease in parrots (Psittaciformes), one of the most endangered groups of birds. The great diversity of parrots in tropical and subtropical ecosystems has been markedly understudied in terms of their parasite diversity. Only two psittacine Haemoproteus species have been described. Here we report a new Haemoproteus parasite, H. (Parahaemoproteus) homohandai n. sp. (lineage hARCHL01) found in erythrocytes of a Red-and-green macaw Ara chloropterus. We morphologically and genetically characterize the parasite based on a segment of the mitochondrial cytochrome b gene, which can be used for identification and diagnosis of infection. This is the first Haemoproteus species described from South American parrots and the first genetically characterized psittacine Haemoproteus sp. Haemoproteus homohandai n. sp. can be readily distinguished from other haemoproteids by its growing circumnuclear and close to circumnuclear macrogametocytes, which are strictly associated with erythrocyte nuclei, but do not touch the erythrocyte envelope along their entire margin and do not fill erythrocytes up to their poles. Illustrations of growing and mature gametocytes of the new species are given, and a phylogenetic analysis identifies the position of this parasite lineage in relation to other Haemoproteus parasites. Importantly, H. homohandai n. sp. and all other Haemoproteus lineages reported from parrots cluster with species of the subgenus Parahaemoproteus, indicating the transmission by Culicoides biting midges.

The widespread biting midge Culicoides impunctatus (Ceratopogonidae) is susceptible to infection with numerous Haemoproteus (Haemoproteidae) species

Background

Haemoproteus parasites are widespread, and some species cause disease in wild and domestic birds. However, the insect vectors remain unknown for the majority of species and genetic lineages of avian Haemoproteus. This information is crucial for better understanding the biology of haemoproteids, the epidemiology of haemoproteosis, and the development of morphological characters of sporogonic stages in wildlife haemosporidian parasites. It remains unclear whether the specificity of Haemoproteus parasites for vectors is broad or the transmission of a given parasite can be restricted to a single or few species of vectors. The aim of this study was to examine the sporogonic development of four species of common European avian haemoproteids in the common biting midge Culicoides impunctatus.

Methods

Wild-caught females of C. impunctatus were infected experimentally by allowing them to take blood meals on naturally infected Muscicapa striata, Cyanistes caeruleus, Ficedula hypoleuca and Motacilla flava harbouring mature gametocytes of Haemoproteus balmorali (genetic lineage hSFC9), H. majoris (hPARUS1), H. motacillae (hYWT1) and H. pallidus (hPFC1), respectively. Infected insects were collected, maintained under laboratory conditions and dissected daily in order to detect the development of ookinetes, oocysts and sporozoites. Microscopic examination and polymerase chain reaction based methods were used to detect the parasites. Bayesian analysis was applied to identify phylogenetic relationships among Haemoproteus lineages.

Results

All investigated parasites completed sporogony in C. impunctatus, indicating broad susceptibility of this biting midge for numerous Haemoproteus parasites. Ookinetes, oocysts and sporozoites were reported, described and compared morphologically. The investigated parasite species can be distinguished at the sporogony stage, particularly with regards to the morphology and rate of development of mature ookinetes. Analysis of data from the literature, and this study, shows that 12 genetically distantly related Haemoproteus parasites complete sporogony in C. impunctatus.

Conclusions

Susceptibility of C. impunctatus is broad for Haemoproteus parasites, indicating that this biting midge is an important natural vector of numerous species of avian haemoproteids in Europe. Some Haemoproteus species can be readily distinguished using morphological characters of ookinetes and sporozoites, as well as the rate of ookinete development. These characters can be used for the identification of Haemoproteus species during sporogony in vectors, and are worth more attention in these parasite taxonomy studies at the species levels.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-2317-z) contains supplementary material, which is available to authorized users.

Association between host species choice and morphological characters of main sensory structures of Culicoides in the Palaeartic region

Culicoides (Diptera: Ceratopogonidae) serve as vectors of several mammalian and avian diseases, including bluetongue, Schmallenberg, African horse sickness, avian malaria and Oropouche. Host preference investigations are necessary to assess the transmission routes of vector-borne diseases and to inform mitigation strategies. A recent study examining the main sensory structures (palps and antennae) of Culicoides species suggests that they be classified as ornithophilic or mammalophilic according to their feeding habits. We analyzed Culicoides host preferences according to the literature and carried out a multiple correspondence analysis linking these preferences with morphological data. Seven out of 12 variables were found to be reliable predictors of host preference in Culicoides species: Antenna Flagellomer-Sensilla Coeloconica-Number: (7-10) and (11-13); Antenna Flagellomer-Sensilla Coeloconica IV-X: presence; Palpus-size: wide and/or narrow opening and shallow pit; Palpus-Shape: strongly swollen; Antenna-Short sensilla trichodea-distal part segment IV to X-Number: 2 seta each. Our results demonstrate that the presence of sensilla coeloconica and the maxillary palpus can be used to separate ornithophilic and mammalophilic or ornithophilic/mammalophilic species.

Mechanisms of mortality in Culicoides biting midges due to Haemoproteus infection

We examined the effects of Haemoproteus infection on the survival and pathology caused in the biting midges. Forty-six females of Culicoides impunctatus were exposed experimentally by allowing them to feed on a naturally infected red-backed shrike infected with Haemoproteus lanii (lineage hRB1, gametocytaemia 5·2%). Seventeen females were fed on an uninfected bird (controls). Dead insects were collected, counted and used for dissection, histological examination and polymerase chain reaction-based testing. Parasites were present in all experimentally infected biting midges, but absent from control insects. Survivorship differed significantly between the control and infected groups. Twelve hours post-exposure (PE), 45 (98%) experimentally infected midges were dead, but all control midges remained alive, and many of them survived until 7 day PE. The migrating ookinetes of H. lanii overfilled midgut, markedly damaged the midgut wall, entered the haemocoel and overfilled the abdomen and thorax of exposed biting midges. Massive infection by migrating ookinetes led to damage of abdomen and thorax of biting midges. The parasites often present in large clumps in the haemocoel in abdomen and thorax, leading to the interruption of the haemolymph circulation. These are the main reasons for rapid death of biting midges after feeding on high-intensity infections of Haemoproteus parasites.

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

The great diversity of birds and ecosystems in the Andean mountains has been understudied in terms of their parasite species. We describe a new Haemoproteus parasite, H. (Parahaemoproteus) erythrogravidus infecting Zonotrichia capensis (Rufous-Collared Sparrow) in South America. The description of this blood parasite species is supported by morphological and molecular data based on a fragment of cytochrome b gene (cyt b) and complete mitochondrial genome sequences. The new species is closely related to H. (Parahaemoproteus) coatneyi, and it can be readily distinguished from the latter parasite due to morphology of its blood stages, particularly 1) the formation of a marked protrusion on envelope of infected erythrocytes by the majority of developing gametocytes, a feature which is unique for this Haemoproteus species and 2) the extremely attenuated width of the growing dumbbell-shaped macro- and microgametocytes. Additionally, Haemoproteus erythrogravidus is shown to be a monophyletic taxon that diverges from Haemoproteus coatneyi at the molecular level. We provide the complete mitochondrial DNA genome for both H. coatneyi and H. erythrogravidus. Molecular and morphological evidences indicate that H. erythrogravidus is present in Ecuador and Colombia, and genetic lineages with 100% of identity for the cyt b gene were reported in Chile, Perú, and Venezuela. Our study also indicates that H. erythrogravidus and H. coatneyi are sympatric sister taxa sharing Z. capensis as a host species across its distribution, which could be the result of sympatric speciation or complex biogeographic processes. Further studies on the distribution and evolutionary history of Z. capensis and its parasites H. erythrogravidus and H. coatneyi insight for our better understanding of the factors and dynamics driving parasite speciation.

Haemoproteus tartakovskyi (Haemoproteidae): Complete sporogony in Culicoides nubeculosus (Ceratopogonidae), with implications for avian haemoproteid experimental research

Numerous recent studies have addressed the molecular characterization, distribution and genetic diversity of Haemoproteus spp. (Haemoproteidae). Some species of these blood parasites cause severe disease in birds, and heavy infections are often lethal in biting midges (Ceratopogonidae) and other blood-sucking insects. However, information about the vectors of haemoproteids is scarce. This presents an obstacle for better understanding the mechanisms of host-parasite interactions and the epidemiology of haemoproteosis. Here we investigated the sporogonic development of Haemoproteus tartakovskyi, a widespread bird parasite, in experimentally infected biting midges, Culicoides nubeculosus. These biting midges are widespread in the Europe. The insects were cultivated under laboratory conditions. Unfed females were allowed to take blood meals on wild caught siskins Carduelis spinus naturally infected with H. tartakovskyi (lineage hSISKIN1). Engorged females were maintained at 22-23 °C, dissected at intervals, and examined for sporogonic stages. Mature ookinetes of H. tartakovskyi were seen in the midgut content between 6 and 48 h post infection, oocysts were observed in the midgut wall 3-4 days post infection (dpi). Sporozoites were first reported in the salivary gland preparations 7 dpi. In accordance with microscopy data, polymerase chain reaction amplification and sequencing confirmed presence of the corresponding parasite lineage in experimentally infected biting midges. This study indicates that C. nubeculosus willingly takes blood meals on birds and is a vector of H. tartakovskyi. These biting midges are readily amenable to cultivation under laboratory conditions. Culicoides nubeculosus transmits Haemoproteus parasites infecting parrots, owls and siskins, birds belonging to different families and orders. Thus, this vector provides a convenient model for experimental research with avian haemoproteids.

Biting midges (Culicoides, Diptera) transmit Haemoproteus parasites of owls: evidence from sporogony and molecular phylogeny

BACKGROUND

Haemoproteus parasites are widespread, and several species cause diseases both in birds and blood-sucking insects. These pathogens are transmitted by dipterans belonging to the Ceratopogonidae and Hippoboscidae, however certain vector species remain unknown for the majority of Haemoproteus spp. Owls are often infected by Haemoproteus parasites, but experimental studies on vectors of these infections are lacking. The aim of this study was to investigate sporogonic development of two widespread Haemoproteus parasites of owls, H. noctuae and H. syrnii in experimentally infected biting midges Culicoides impunctatus and Culicoides nubeculosus. We also followed in vitro sporogonic development of these infections and determined their phylogenetic relationships with Haemoproteus spp., for which vectors have been identified.

METHODS

Wild-caught C. impunctatus and laboratory reared C. nubeculosus were infected experimentally by allowing them to take blood meals on one individual long-eared owl (Asio otus) and one tawny owl (Strix aluco) harbouring mature gametocytes of H. noctuae (lineage hCIRCUM01) and H. syrnii (hCULCIB01), respectively. The engorged insects were maintained in the laboratory at 16-18 °C, and dissected at intervals in order to follow the development of ookinetes, oocysts and sporozoites. We also observed in vitro development of sexual stages of both parasites by exposure of infected blood to air. The parasite lineages were determined by polymerase chain reaction-based methods. Bayesian phylogeny was constructed in order to determine the relationships of owl parasites with other avian Haemoproteus spp., for which vectors have been identified.

RESULTS

Both H. noctuae and H. syrnii completed sporogony in C. nubeculosus, and H. noctuae completed sporogony in C. impunctatus. Ookinetes, oocysts and sporozoites of these parasites were reported and described. Gametes and ookinetes of both species readily developed in vitro. In accordance with sporogony data, the phylogenetic analysis placed both parasite lineages in a clade of Culicoides spp.-transmitted avian Haemoproteus (Parahaemoproteus) spp.

CONCLUSIONS

Culicoides nubeculosus and C. impunctatus are vectors of H. noctuae and H. syrnii. Phylogenies based on cytochrome b gene indicate parasite-vector relationships, and we recommend using them in predicting possible parasite-vector relationships and planning research on avian Haemoproteus spp. vectors in wildlife.