First microscopic, pathological, epidemiological, and molecular investigation of Leucocytozoon (Apicomplexa: Haemosporida) parasites in Egyptian pigeons

Introduction

Leucocytozoon is an intracellular blood parasite that affects various bird species globally and is transmitted by blackfly vectors. This parasite is responsible for leucocytozoonosis, a disease that results in significant economic losses due to reduced meat and egg production. There is limited knowledge about the epidemiological pattern of leucocytozoonosis and its causative species in Egypt, particularly in pigeons.

Methods

The current study involved the collection of 203 blood samples from domestic pigeons from various household breeders and local markets across Qena Province, Upper Egypt. Samples were initially examined for potential Leucocytozoon infection using blood smears, followed by an evaluation of associated risk factors. Molecular identification of the parasite in selected samples (n = 11), which had initially tested positive via blood smears, was further refined through nested PCR and sequence analysis of the mitochondrial cytochrome b gene to ascertain the Leucocytozoon species present. Additionally, histopathological examination of the liver, spleen, and pancreas was conducted on animals that tested positive by blood smears.

Results

Interestingly, 26 out of 203 samples (12.08%) had confirmed Leucocytozoon infections based on microscopic analysis. Additionally, all 11 samples that initially tested positive via blood smears were confirmed positive through nested PCR analysis, and their sequencing revealed the presence of Leucocytozoon sabrazesi, marking the first report of this parasite in Egypt. The study into potential risk factors unveiled the prevalence of Leucocytozoon spp. seems host gender-dependent, with males exhibiting a significantly higher infection rate (33.33%). Additionally, adult birds demonstrated a significantly higher infection prevalence than squabs, suggesting an age-dependent trend in prevalence. Seasonality played a significant role, with the highest occurrence observed during summer (37.25%). Histopathological examination revealed the presence of numerous megaloschizonts accompanied by lymphocytic infiltration and multiple focal areas of ischemic necrosis.

Conclusion

To our knowledge, this is the first study to shed light on the epidemiological characteristics and molecular characterization of leucocytozoonosis in pigeons in Egypt. Further research endeavors are warranted to curb the resurgence of Leucocytozoon parasites in other avian species across Egypt, thereby refining the epidemiological understanding of the disease for more effective control and prevention measures.

Herpesvirus and Subsequent Usutu Virus Infection in a Great Grey Owl (Strix nebulosa) at the Ljubljana Zoo, Slovenia

Herpesvirus (HV) has been known to cause disease in owls, with various clinical signs and outcomes for the last several decades. The HV DNA polymerase gene was detected in oropharyngeal and cloacal swabs of a male great grey owl (Strix nebulosa) in a zoological collection in Ljubljana, Slovenia. In the following 4 months, despite continuous HV detection in swabs, no clinical signs with a clear link to HV disease were observed. Hepatoprotective and immunostimulant therapies applied during this period did not prevent HV shedding. Therefore, peroral antiviral therapy with acyclovir (150 mg/kg q24 h for seven days) was performed, and the owl tested negative at the next sampling and remained negative for the next 8 months. After that, the owl again tested positive for HV presence, and the same protocol with antiviral therapy was performed. After 3 weeks with a negative test for HV presence, without any clinical signs of illness, the owl suddenly died because of Usutu virus (USUV) infection. Among all the owls at the zoo, interestingly, only the HV-positive great grey owl died because of USUV infection. The USUV sequence detected and obtained in this study clusters together with other Europe 2 sequences detected in neighboring countries. Our study shows the potential of acyclovir therapy in the prevention of herpesvirus shedding and, moreover, lowering the possibility for spreading HV to other owls and birds. To the best of our knowledge, this is the first report of HV presence and USUV infection in a great grey owl in Slovenia.

Molecular survey and genetic diversity of Plasmodium sp. infesting domestic poultry in northeastern Thailand

Introduction

Haemosporidian parasites are prevalent worldwide and can cause economic losses in poultry production. These parasites are arousing interest in Thailand and are found in many avian species. There is insufficient information on the genetic diversity of these alveolates from the largest families - Plasmodidae, Haemoprotidae and Leucocytozoidae - specifically parasitising ducks, turkeys, and geese.

Material and Methods

Blood samples from 116 backyard poultry (60 ducks, 36 turkeys and 20 geese) in northeastern Thailand were investigated for Plasmodium spp., Haemoproteus spp. and Leucocytozoon spp. infections using microscopic examination and molecular approaches.

Results

A total of 37/116 birds (31.9%) had confirmed Plasmodium infections. The prevalence was 69.4% (25/36) in turkeys, 18.3% (11/60) in ducks, and 5.0% (1/20) in geese. Of these 37 positives, 86.5% were Plasmodium sp., 10.8% were P. gallinaceum and 2.7% were P. juxtanucleare. Sequence analysis based on the cytochrome b gene identified seven lineages, of which two were new lineages in backyard poultry.

Conclusion

This is the first report on the prevalence of haemosporidian parasites in backyard poultry in northeastern Thailand. The results provide important data for better understanding the molecular epidemiology of haemosporidian parasites infection in poultry in this region, which will be helpful in controlling these blood parasites.

Differences in haemosporidian parasite prevalence and diversity in migratory and resident birds of prey species revealed by a non-invasive sampling method

Avian haemosporidian parasites are widespread globally and infect numerous wild bird species. However, they have primarily been studied in passerine birds. Accordingly, the prevalence and diversity of these parasites in birds of prey remain understudied. This lack of research is primarily due to the international protection status of many of these species, their sparse distribution across ecosystems and difficulty to capture in the wild. The aim of this study was to examine the prevalence and diversity of haemosporidian parasites in two species of birds of prey, namely white-tailed eagle and lesser spotted eagle. To achieve this, a non-invasive approach was employed, involving the extraction of DNA from blood spots present in moulted feathers. Freshly moulted feathers were collected from the ground under nests or within the nests of these birds during the breeding season. A visible blood spot located at the junction of the calamus and rachis was removed and fixed in SET buffer for molecular analysis. The identification of haemosporidian parasites (Plasmodium, Haemoproteus and Leucocytozoon) was conducted using PCR-based methods. Overall, parasite DNA was successfully detected in shed feathers that were kept in their original form at least decade prior to analysis. Among the studied individuals, resident white-tailed eagles showed significantly lower infection rates of haemosporidian parasites compared to migratory lesser spotted eagles. A total of nine genetic lineages of haemosporidian parasites were detected, with seven of them being new to science based on partial sequences of the cytb gene. Additionally, the phylogenetic relationships among these new lineages and previously described ones were established. These findings highlight the suitability of non-invasive sampling for investigating the prevalence and diversity of haemosporidian parasites in wild birds of prey populations. Moreover, this approach holds promise for studying other challenging-to-reach and protected bird species. According to our research, there is a greater chance of finding haemosporidian parasites in freshly gathered feathers.

Co-infecting Haemoproteus species (Haemosporida, Apicomplexa) show different host tissue tropism during exo-erythrocytic development in Fringilla coelebs (Fringillidae)

Avian haemosporidians of the genera Plasmodium, Haemoproteus, and Leucocytozoon are common blood parasites in wild birds all over the world. Despite their importance as pathogens potentially compromising host fitness and health, little is known about the exo-erythrocytic development of these parasites, particularly during co-infections which predominate in wildlife. This study aimed to address this issue using Haemoproteus parasites of Fringilla coelebs, a common bird species of the Western Palearctic and host to a variety of haemosporidian parasite lineages. Blood and tissue samples of 20 F. coelebs, positive for haemosporidians by blood film microscopy, were analysed by PCR and sequencing to determine cytochrome b lineages of the parasites. Tissue sections were examined for exo-erythrocytic stages by histology and in situ hybridization applying genus-, species-, and lineage-specific probes which target the 18S rRNA of the parasites. In addition, laser microdissection of tissue stages was performed to identify parasite lineages. Combined molecular results of PCR, laser microdissection, and in situ hybridization showed a high rate of co-infections, with Haemoproteus lineages dominating. Exo-erythrocytic meronts of five Haemoproteus spp. were described for the first known time, including Haemoproteus magnus hCCF6, Haemoproteus fringillae hCCF3, Haemoproteus majoris hCCF5, Haemoproteus sp. hROFI1, and Haemoproteus sp. hCCF2. Merogonic stages were observed in the vascular system, presenting a formerly unknown mode of exo-erythrocytic development in Haemoproteus parasites. Meronts and megalomeronts of these species were distinct regarding their morphology and organ distribution, indicating species-specific patterns of merogony and different host tissue tropism. New pathological aspects of haemoproteosis were reported. Furthermore, phylogenetic analysis of Haemoproteus spp. with regard to their exo-erythrocytic stages points towards separation of non-megalomeront-forming species from megalomeront-forming species, calling for further studies on exo-erythrocytic development of haemosporidian parasites to explore the phylogenetic character of this trait.

Contribution to ecological environmental factors and the occurrence of haemosporidians in birds in Zhongar Alatau National Park, Kazakhstan

In addition to the presence of a suitable host and vector, the prevalence of haemosporidians is influenced by several important factors, including the environmental conditions of the habitat, which depend on broader geographic characteristics. The aim of this study is to perform a preliminarily assessment of the distribution of blood parasites in birds from the mountainous area of Zhongar Alatau NP and to find potential new sites for research on their ecology in Kazakhstan. The results of this research constitute the first report on the occurrence of blood parasites from this area. A total of 58 birds, from the order Passeriformes and one individual from the order Caprimulgiformes, were examined during the study. The overall prevalence of infections caused by haemosporidian parasites (Haemoproteus, Leucocytozoon) was 18.6%. Neither the genus Plasmodium nor the presence of trypanosomes and microfilariae was detected in the birds examined. Three birds (5.1% prevalence) were infected with parasites of the genus Haemoproteus, in all eleven positive birds the analyses showed the presence of parasites of the genus Leucocytozoon (18.6% prevalence). The presence of parasites genus Haemoproteus was detected only in birds that were also infected with Leucocytozoon parasites. More infections with parasites of the genus Leucocytozoon are predicted due to the higher altitude and ecological factors at the capture sites, which are more favourable for the development of vectors of this genus. The species Haemoproteus majoris was detected in the host Emberiza cioides and species Haemoproteus minutus in host Turdus merula. Other species of this genus in the hosts Cyanistes cyanus and Turdus atrogularis were not determined. The species Leucocytozoon fringilinarum was detected in the hosts Cyanistes cyanus and Parus major, Leucocytozoon dubreuili was detected in Turdus atrogularis and Turdus merula. In the other host species Aegithalos caudatus, Emberiza cioides and Periparus aterus, it was not possible to dermine the species of the genus Leucocytozoon.

Hemoparasite occurrence and hematological/serum chemistry variations in Podocnemis vogli turtles: A comparative analysis between wild-residing infected specimens and captive non-infected counterparts

Reptiles show a high occurrence of hemoparasites in the wild; however, little is known about the impact of such infections on their hosts' physiology and health status. Podocnemis vogli is an ancient turtle distributed in South America, frequently infected by blood parasites. Specifically, we analyzed the hematological and serum chemistry parameters of 78 wild turtles. We compared these values with those obtained from non-infected turtles of the same species in ex-situ conditions, considering factors such as sex and coinfections. Two orders of hemoparasites were detected under microscopic analyses: Adelorina, represented by Haemogregarina sp. (98.72 ± 0.28%), and Haemosporida, represented by Haemocystidium sp. (30.77 ± 1.16%), the latter genus being always in coinfection with Haemogregarina. Significant differences were observed in 20 parameters between infected (free living) and uninfected (living in captivity) turtles. The ALP, PCV, Hb, and MCV were significantly different by sex; albumin, cholesterol, creatinine, percentage of heterophils, lymphocytes, and basophils differed in coinfection. This is the first report of reference intervals of P. vogli in the wild and the first study comparing hematological and blood biochemistry values between hemoparasite-infected and uninfected P. vogli turtles. However, the limited knowledge of these parameters in wild reptiles and the wide range of interval values makes it difficult to determine any significant impact on turtle health. Nevertheless, this study highlights the need for more in-depth research to explore the potential effects of blood parasite infections on turtles, including immune response and coevolution studies.

The first detection of avian haemosporidia from Culicoides biting midges in Japan, with notes on potential vector species and the transmission cycle

BACKGROUND

Biting midges (Ceratopogonidae) are capable of transmitting a variety of pathogens including viruses, trypanosomes and haemosporidia. The majority of Haemoproteus parasites are transmitted by biting midges predominantly of the genus Culicoides and are known to cause significant physical and reproductive impacts on both wild and domestic birds. In Japan, Haemoproteus had been detected from various avian hosts, but not from arthropod vectors. In this study, we investigated the prevalence of avian haemosporidia at an educational forest in central Japan in attempt to reveal possible vector species of Haemoproteus, which would help to better understand the transmission cycle of Haemoproteus within Japan and to develop preventative measures for captive and domestic birds.

METHODS

Biting midges were caught using UV light traps from 2016 to 2018. The collected samples were morphologically identified, and haemosporidian parasites were detected using PCR-based methods. The detected lineages were phylogenetically analyzed and compared with lineages previously detected from birds. Bloodmeal analyses were also carried out for part of the blood-fed individuals.

RESULTS

Six Haemoproteus lineages were detected from 17 of 1042 female Culicoides (1.63%), including three species (C. sigaensis, C. arakawae, and C. pictimargo) in which Haemoproteus was detected for the first time. All detected lineages were placed in the subgenus Parahaemoproteus clade and were previously detected from crows of central Japan, strongly suggesting that parasites of these genetic lineages are transmitted between Culicoides and crows. Two Plasmodium lineages were also detected but are thought to be transmitted between Culex mosquitoes and birds of the educational forest based on previous detections. No amplifications were seen in bloodmeal analysis, possibly due to insufficient amount of blood, denaturation via digestion, or insufficient detectability of the used protocol.

CONCLUSION

Haemoproteus DNA was detected from Culicoides for the first time in Japan, suggesting that transmission is possible within the country. These findings highlight the necessity to investigate Culicoides populations and Haemoproteus infections dynamics in Japan. However, vector competence could not be confirmed in this study and further studies are anticipated.

Exo-Erythrocytic Development of Avian Haemosporidian Parasites in European Owls

Simple Summary

Avian haemosporidians of the genera Plasmodium, Haemoproteus, and Leucocytozoon are vector-borne blood parasites, which commonly infect birds all over the world, except for Antarctica. Although called blood parasites, these pathogens develop not only in the blood cells of vertebrate hosts, but also in the tissues of various organs. While the blood stages have been studied quite intensively, the tissue stages, patterns of their development, and their effect on the vertebrate host are not well understood, especially in wild, non-passerine birds. The present study aimed at gaining new knowledge about avian haemosporidian parasites naturally infecting owls in Austria and Lithuania. Organ samples of 121 owls were investigated for blood parasites using molecular and histological methods. Over 70% of the owls were infected, revealing seven new genetic variants (lineages) of avian haemosporidian parasites. Tissue stages of Leucocytozoon spp. and Haemoproteus syrnii, a common parasite in owls, were discovered, providing new insights into the parasites’ tissue development. This study contributes new knowledge to a better understanding of the biodiversity and life cycles of avian haemosporidian parasites. These data are crucial for avian medicine and bird protection and indicate directions for further research on the tissue development of haemosporidian infections.

Abstract

Avian haemosporidian parasites (Haemosporida, Apicomplexa) are globally distributed and infect birds of many orders. These pathogens have been much investigated in domestic and wild passeriform birds, in which they are relatively easy to access. In birds belonging to other orders, including owls (order Strigiformes), these parasites have been studied fragmentarily. Particularly little is known about the exo-erythrocytic development of avian haemosporidians. The goal of this study was to gain new knowledge about the parasites infecting owls in Europe and investigate their exo-erythrocytic stages. Tissue samples of 121 deceased owls were collected in Austria and Lithuania, and examined using polymerase chain reactions (PCR), histology, and chromogenic in situ hybridization (CISH). PCR-based diagnostics showed a total prevalence of 73.6%, revealing two previously unreported Haemoproteus and five novel Leucocytozoon lineages. By CISH and histology, meronts of several Leucocytozoon lineages (lASOT06, lSTAL5, lSTAL7) were discovered in the brains, heart muscles, and kidneys of infected birds. Further, megalomeronts of Haemoproteus syrnii (lineage hSTAL2) were discovered. This study contributes new knowledge to a better understanding of the biodiversity of avian haemosporidian parasites infecting owls in Europe, provides information on tissue stages of the parasites, and calls for further research of these under-investigated pathogens relevant to bird health.

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.

Parasite-associated mortality in birds: the roles of specialist parasites and host evolutionary distance

The factors that influence whether a parasite is likely to cause death in a given host species are not well known. Generalist parasites with high local abundances, broad distributions and the ability to infect a wide phylogenetic diversity of hosts are often considered especially dangerous for host populations, though comparatively little research has been done on the potential for specialist parasites to cause host mortality. Here, using a novel database of avian mortality records, we tested whether phylogenetic host specialist or host generalist haemosporidian blood parasites were associated with avian host deaths based on infection records from over 81 000 examined hosts. In support of the hypothesis that host specialist parasites can be highly virulent in novel hosts, we found that the parasites that were associated with avian host mortality predominantly infected more closely related host species than expected under a null model. Hosts that died tended to be distantly related to the host species that a parasite lineage typically infects, illustrating that specialist parasites can cause death outside of their limited host range. Overall, this study highlights the overlooked potential for host specialist parasites to cause host mortality despite their constrained ecological niches.

Fatal toxoplasmosis in Little Penguins (Eudyptula minor) from Penguin Island, Western Australia

Routine post mortems of deceased penguins from Penguin Island, Western Australia, found that a temporal cluster of cases presented with characteristic gross and microscopic changes, namely birds in good body condition with hepatomegaly and splenomegaly, multifocal hepatic and splenic necrosis and numerous, 1–2 μm diameter protozoan parasites within the necrotic foci.

Electron microscopy identified the protozoa as belonging to the phylum Apicomplexa. Molecular investigations by PCR gave inconsistent results. PCR performed by an external laboratory identified a novel Haemoproteus spp. organism in samples from 4 of 10 cases from this group, while PCR at Murdoch University identified Toxoplasma gondii in 12 of 13 cases (including 9 of the 10 assayed at the external laboratory). Immunohistochemistry of formalin fixed tissues also identified Toxoplasma in the hepatic and splenic lesions.

The distinctive mortalities which were observed in this group of penguins are attributed to a fulminant toxoplasmosis, with a concurrent Haemoproteus infection in some cases. Though the clinical signs of infection are unknown, the gross and microscopic appearance at post mortem is sufficiently characteristic to allow a diagnosis to be made on these features. Definitive confirmation of Toxoplasma infection can be made by immunohistochemistry or PCR.

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Deaths in Little Penguins were associated with necrosis in the liver and spleen.

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The necrotic lesions contained protozoa, free and in cysts.

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The protozoa were identified as Toxoplasma by PCR and immunohistochemistry.

Massive Infection of Lungs with Exo-Erythrocytic Meronts in European Robin Erithacus rubecula during Natural Haemoproteus attenuatus Haemoproteosis

Simple Summary

Haemoproteus parasites are cosmopolitan bird pathogens belonging to the order Haemosporida (Apicomplexa). A majority of the described species are transmitted by Culicoides biting midges, which inject infective stages (sporozoites) in birds during blood meals. The sporozoites initiate tissue merogony, resulting in numerous merozoites, part of which penetrate red blood cells and produce blood stages (gametocytes), which are infective for vectors. The blood stages of Haemoproteus parasites have been relatively well-investigated, although tissue stages and patterns of their development remain unidentified in the majority of Haemoproteus species. Nevertheless, they often damage various organs which makes them important for bird health. This study contributes new knowledge about tissue merogony of Haemoproteus attenuatus, which parasitize birds of the Muscicapidae. Naturally infected European robins Erithacus rubecula were caught in Lithuania during autumnal migration. Parasites were identified using morphological features of gametocytes and DNA sequence analysis. Organs of infected birds were examined using histological methods. Tissue stages (meronts) were present only in the lungs, where they were numerous and markedly varied in shape, size and maturation stage. Description of meronts was provided and molecular phylogenetic analysis identified closely related lineages that could present similar exo-erythrocytic development in lungs. Lung damage caused by meronts of H. attenuatus and closely related lineages is worth attention due to their possible implications on a bird’s health.

Abstract

Haemoproteus species are widespread avian blood parasites belonging to Haemoproteidae (Haemosporida). Blood stages of these pathogens have been relatively well-investigated, though exo-erythrocytic (tissue) stages remain unidentified for the majority of species. However, recent histopathological studies show that haemoproteins markedly affect bird organs during tissue merogony. This study investigated the exo-erythrocytic development of Haemoproteus (Parahaemoproteus) attenuatus (lineage hROBIN1), the common parasite of flycatchers (Muscicapidae). Naturally infected European robins Erithacus rubecula were examined. Parasite species and lineage were identified using microscopic examination of blood stages and DNA sequence analysis. Parasitaemia intensity varied between 0.8 and 26.5% in seven host individuals. Organs of infected birds were collected and processed for histological examination. Tissues stages (meronts) were seen in six birds and were present only in the lungs. The parasites were usually located in groups and were at different stages of maturation, indicating asynchronous exo-erythrocytic development. In most parasitized individuals, 100 meronts were observed in 1 cm² section of lungs. The largest meronts reached 108 µm in length. Mature meronts contained numerous roundish merozoites of approximately 0.8 µm in diameter. Megalomeronts were not observed. Massive merogony and resulting damage of lungs is a characteristic feature during H. attenuatus infections and might occur in related parasite lineages, causing haemoproteosis.

The prevalence of Leucocytozoon spp. in nestlings of three wild raptor species including implications on haematological and blood chemistry values

Leucocytozoonosis is a vector-borne infection of birds, caused by members of the haemosporidian genus Leucocytozoon. The clinical presentation may range from asymptomatic to severe disease. Consequences of Leucocytozoon infection on blood profiles remain to be described, especially for different host species in the wild. In the current study, the prevalence of Leucocytozoon infection was determined in wild nestlings of three European raptor species, the common buzzard (Buteo buteo, n = 464), red kite (Milvus milvus, n = 46) and northern goshawk (Accipiter gentilis, n = 18). Among 528 nestlings, 51.9% (n = 274) were infected with Leucocytozoon spp., whereby the highest prevalence was found in common buzzards (54.9%), followed by red kites (32.6%) and northern goshawks (22.2%). For a subset of 87 individuals (50 common buzzards, 29 red kites, 8 northern goshawks), a detailed analysis of differential leukocyte counts and several blood chemistry parameters in response to infection was conducted: AP (alkaline phosphatase), AST (aspartate aminotransferase), GLDH (glutamate dehydrogenase), LDH (lactate dehydrogenase), GGT (gamma glutamyl transferase), CK (creatine kinase), BuChE (butyrylcholinesterase), BA (bile acids), ALB (albumin) and TP (total protein). Even though in the physiological range, infected nestlings displayed significantly increased levels of heterophils, aspartate aminotransferase, lactate dehydrogenase, bile acids and butyrylcholinesterase, but decreased lymphocyte and monocyte values compared to uninfected ones. Furthermore, significant species differences with regard to blood parameters, but no sex differences were found. Overall, obtained results show a high prevalence, but a low pathogenicity of Leucocytozoon spp. in wild raptor chicks, presumably resulting from coevolutionary adaptation, but show signatures of infection in the haematological and blood chemistry profiles.

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Leucocytozoon prevalence in nestlings of three wild raptor species was 52%.

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Common buzzards (Buteo buteo) showed the highest prevalence (55%).

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Examined blood parameter values varied with species, age and infection status.

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Leucocytozoon infections were associated with increased AST and BuChE.

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Leucocytozoon infections in Accipitridae nestlings seem to be of minor pathogenicity.

A citizen science-based survey of avian mortality focusing on haemosporidian infections in wild passerine birds

Background

Haemosporidioses are common in birds and their manifestations range from subclinical infections to severe disease, depending on the involved parasite and bird species. Clinical haemosporidioses are often observed in non-adapted zoo or aviary birds, whereas in wild birds, particularly passerines, haemosporidian infections frequently seem to be asymptomatic. However, a recent study from Austria showed pathogenic haemosporidian infections in common blackbirds due to high parasite burdens of Plasmodium matutinum LINN1, a common parasite in this bird species, suggesting that virulent infections also occur in natural hosts. Based on these findings, the present study aimed to explore whether and to what extent other native bird species are possibly affected by pathogenic haemosporidian lineages, contributing to avian morbidity.

Methods

Carcasses of passerine birds and woodpeckers were collected during a citizen science-based survey for avian mortality in Austria, from June to October 2020. Tissue samples were taken and examined for haemosporidian parasites of the genera Plasmodium, Haemoproteus and Leucocytozoon by nested PCR and sequencing the mitochondrial cytb barcode region, histology, and chromogenic in situ hybridization applying genus-specific probes.

Results

From over 160 dead bird reportings, 83 carcasses of 25 avian species were submitted for investigation. Overall haemosporidian infection rate was 31%, with finches and tits prevailing species counts and infections. Sequence analyses revealed 17 different haplotypes (4 Plasmodium, 4 Haemoproteus, 9 Leucocytozoon), including 4 novel Leucocytozoon lineages. Most infected birds presented low parasite burdens in the peripheral blood and tissues, ruling out a significant contribution of haemosporidian infections to morbidity or death of the examined birds. However, two great tits showed signs of avian malaria, suggesting pathogenic effects of the detected species Plasmodium relictum SGS1 and Plasmodium elongatum GRW06. Further, exo-erythrocytic tissue stages of several haemosporidian lineages are reported.

Conclusions

While suggesting generally little contribution of haemosporidian infections to mortality of the investigated bird species, the findings indicate a possible role of certain haemosporidian lineages in overall clinical manifestation, either as main causes or as concurrent disease agents. Further, the study presents new data on exo-erythrocytic stages of previously reported lineages and shows how citizen science can be used in the field of haemosporidian research.

Graphic abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-03949-y.

First Report of Haemoproteus (Haemosporida, Haemoproteidae) Megalomeronts in the Brain of an Avian Host, with Description of Megalomerogony of Haemoproteus Pastoris, the Blood Parasite of the Common Starling

Simple Summary

Birds are hosts to diverse blood parasites belonging to many taxonomic groups. Among them, numerous haemosporidian parasites of the genus Haemoproteus are transmitted globally. These pathogens develop in the blood and internal organs of birds. The blood stages (gametocytes) are known for about 150 described species, but the tissues stages or exo-erythrocytic stages (meronts and megalomeronts) are known only fragmentarily for about 10% of the described species. Knowledge on merogony is important in avian medicine for better understanding of pathologies during haemoproteosis. This study reported and characterized the megalomeronts of Haemoproteus pastoris, a parasite of the widespread Common starling (Sturnus vulgaris). Parasites were identified using molecular and microscopy examination tools. Five individual naturally infected birds were sampled, and their organs were examined histologically. Megalomeronts were found in eight different organs. The parasites were described and illustrated. The largest megalomeront, of all observed forms and shapes, reached 800 μm in length. Importantly, Haemoproteus megalomeronts were reported in the brain of avian hosts for the first time, indicating non-described pathology during avian haemoproteosis. This study contributes to a better understanding of the life cycle of avian haemoproteids and opens new perspectives in pathology research during avian haemoproteosis, which is important for birds’ health.

Abstract

Species of Haemoproteus (Haemoproteidae, Haemosporida) are common bird pathogens. Recent molecular studies combined with histopathology research have reported development of megalomeronts of these parasites in various organs, sometimes resulting in the death of the avian host. Five Common starlings (Sturnus vulgaris) were found naturally infected with Haemoproteus pastoris lineage hLAMPUR01. The parasite was identified using microscopic examination of blood films and DNA sequences. Infected bird organs were investigated histologically for (i) the presence of exo-erythrocytic stages and (ii) the patterns of development (morphology and localization) in different host individuals. For the first time, megalomeronts of Haemoproteus parasites were seen developing in the brain, while numerous others at different stages of maturation were found in the intestine, pancreas, kidneys, lungs, esophagus, spleen, gizzard, and trachea. Megalomeronts were predominantly roundish or oval, up to 800 μm, they were surrounded by a capsular-like wall and developed asynchronously in the same bird individual. After megalomeront maturation and rupture, a massive infiltration of blood cells occurred, indicating the hemorrhagic processes. Review of available data showed that different Haemoproteus species produce markedly different megalomeronts, morphology of which can probably be predicted using phylogenetic analysis based on partial sequences of cytochrome b gene.

Exo-erythrocytic stages of Haemoproteus sp. in common buzzard (Buteo buteo): A histopathological and molecular study

Haemosporidian parasites are responsible for anemia, acute tissue degeneration, and depopulation in wild birds. This study aimed to investigate the prevalence of haemosporidians and also morphologic and molecular evaluation of tissue stages of Haemoproteus sp. in common buzzards (Buteo buteo). Eleven free-living common buzzards were referred to the Avian Clinic of Veterinary School of Lorestan University with lethargy, weight loss, and ataxia. Gametocytes of Leucocytozoon buteonis were found in blood smears of six (54.5 %) birds, while one had simultaneous infection with blood stages of Haemoproteus and Leucocytozoon. During histopathological examinations, exo-erythrocytic stages of the genus Haemoproteus were seen in the lung and kidney of a dead bird. This study is the first report of exo-erythrocytic infection of Haemoproteus in common buzzards. Molecular assays confirmed the infection of Haemoproteus sp. (lineage BUTBUT15) in tissue samples. Phylogenetic analysis using cytochrome b gene suggested that BUTBUT15 was more closely related to the lineages isolated from the family Falconidae in contrast to the Accipitridae.

Impact of Subclinical Haemoproteus columbae Infection on Farmed Domestic Pigeons from Central Java (Yogyakarta), Indonesia, with Special Reference to Changes in the Hemogram

Pigeon haemoproteosis caused by Haemoproteus columbae (Apicomplexa: Haemosporida: Haemoproteidae) is globally prevalent in rock doves (Columba livia), although little is known regarding this disease in pigeons and doves in Indonesia. Blood samples of 35 farmed domestic pigeons (C. livia f. domestica) from four localities in Yogyakarta Special Region, Central Java, Indonesia, were collected from March to June, 2016, subjected to a hemogram, and analyzed for the presence of hemoprotozoan infections. Microscopic examination of blood smears revealed a prevalence of 62.5–100% of H. columbae at the four localities (n = 8–10 for each locality), and geometric means of 3.0–5.6% of erythrocytes were parasitized by young and mature gametocytes, suggesting that all infected pigeons were in the chronic phase of infection with repeated recurrences and/or reinfections. Nucleotide sequencing of mitochondrial cytochrome b gene (cytb) for haemosporidian species demonstrated the distribution of four major cytb lineages of H. columbae (mainly HAECOL1, accompanied by COLIV03, COQUI05, and CXNEA02 according to the MalAvi database). Hemogram analysis, involving the estimation of packed cell volume, erythrocyte counts, mean corpuscular volume, mean corpuscular hemoglobin concentration, and plasma protein and fibrinogen levels of 20 parasitized pigeons and five non-infected pigeons demonstrated significant macrocytic hypochromic anemia with hypoproteinemia and hyperfibrinogenemia in the infected pigeons. This study shows the profound impact of long-lasting subclinical pigeon haemoproteosis caused by H. columbae on the health of farmed domestic pigeons.

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.

A fatal case of a captive snowy owl (Bubo scandiacus) with Haemoproteus infection in Japan

Parasites of the genus Haemoproteus are vector-borne avian haemosporidia commonly found in bird species of the world. Haemoproteus infections are typically considered relatively benign in birds. However, some Haemoproteus species cause severe disease and mortality, especially for captive birds removed from their original habitat. In September 2018, a captive 15-year-old snowy owl (Bubo scandiacus), kept in a zoological garden of Japan, died subacutely after presenting leg dysfunction. This case showed significantly low PCV and elevated AST, ALT, CK, and LDH values. Many megalomeronts with prominent morphological characteristics of Haemoproteus were observed in the left leg muscles. Those megalomeronts exhibited multilocular structures and were internally filled with merozoites. A new lineage of Haemoproteus was detected by subsequent PCR for the cytochrome b (cytb) gene of avian haemosporidia from DNA extracted from several organ tissues. The detected lineage was classified in the subgenus Parahaemoproteus and was similar to those from the wild birds inhabiting the region including the study area, suggesting that this snowy owl likely acquired its infection from wild birds. This is the first report of a fatal case of a captive bird with a locally transmitted Haemoproteus infection in Japan. We considered the pathogenicity of this infection in conjunction with the clinical course and hematology results. We surmise that snowy owls may be particularly susceptible to infection with Haemoproteus parasites, and warming northern temperatures may exacerbate the overall health of these and other high latitude birds. Further research into the prevalence of Haemoproteus in wild birds near zoological gardens and potential biting midge vectors is necessary for the ex situ conservation of introduced birds.

Haemoproteus syrnii (Haemosporida: Haemoproteidae) in owls from Brazil: morphological and molecular characterization, potential cryptic species, and exo-erythrocytic stages

Haemoproteus syrnii is a haemosporidian parasite found in owls. Although morphological and molecular data on the species is available, its exo-erythrocytic development was never researched. In this study, we provide the morphological, morphometric, and molecular characterization of H. syrnii populations found in owl species from Minas Gerais, southeast Brazil. We also characterized the coalescent species delimitation based on the molecular and histopathology data. Samples from 54 owls from six different species were analyzed, generating 11 sequences of the cyt b gene, from which six were new sequences. The overall prevalence of infection was high (72.22%). The H. syrnii sequences were grouped into two well-supported independent clades, which included other Haemoproteus (Parahaemoproteus) species. This was supported by both the coalescent species delimitation analysis and by the genetic divergence between lineages of these distinct clades. There were small morphological and morphometric differences within the population presented in this study. However, when compared with other studies, the molecular analysis demonstrated considerable intraspecific variation and suggests potential cryptic species. The histopathological analysis revealed, for the first time, that lungs and skeletal muscle are exo-erythrocytic stage location of H. syrnii, and that the parasite is linked to the histopathological changes found in owls. This study brings new data from Haemoproteus species biology and host infection, and improves host-parasite relationship understanding under an owl conservation perspective.

Penguins are competent hosts of Haemoproteus parasites: the first detection of gametocytes, with molecular characterization of Haemoproteus larae

Background

The majority of penguins (Sphenisciformes) have evolved in areas with weak or absent transmission of haemosporidian parasites and are usually naïve to avian haemosporidian infections. Plasmodium parasites are transmitted by mosquitoes, and lethal avian malaria has been often reported in captive penguins in many countries. The related haemosporidian parasites belonging to Haemoproteus and Leucocytozoon have also been detected in penguins but less often than Plasmodium infections. The majority of Haemoproteus infection reports in penguins are based solely on PCR-based diagnostics. It remains unclear if haemoproteids can complete their life-cycle and produce infective stages (gametocytes) in penguins or whether these infections are abortive in penguins, and thus dead ends for transmission. In other words, it remains unknown if penguins are competent hosts for Haemoproteus parasites, which cause disease in non-adapted birds.

Methods

Two captive African penguins (Spheniscus demersus) and two Magellanic penguins (S. magellanicus) were found to be positive for Haemoproteus infection in two open-air aquariums in Japan, and the parasites were investigated using both PCR-based testing and microscopical examination of blood films. Samples from a black-tailed gull (Larus crassirostris) and previously tested gulls were used for comparison.

Results

The lineage hSPMAG12 was detected, and gametocytes of Haemoproteus sp. were seen in the examined penguins and gull. Observed gametocytes were indistinguishable from those of Haemoproteus larae, which naturally parasitize birds of the genus Larus (Laridae). The detected sequence information and Bayesian phylogenetic analysis supported this conclusion. Additionally, morphologically similar gametocytes and closely related DNA sequences were also found in other gull species in Japan. Phylogenetic analysis based on partial cytb sequences placed the lineage hSPMAG12 of H. larae within the clade of avian haemoproteids which belong to the subgenus Parahaemoproteus, indicating that Culicoides biting midges likely transmit the parasites between penguins and gulls.

Conclusions

This study shows that some species of Haemoproteus parasites complete their development and produce gametocytes in penguins, which may be source of infection for biting midges transmitting haemoproteosis. To prevent haemosporidiosis in zoos, we call for control not only of mosquitoes, but also biting midges.

Haemoproteus spp. and Leucocytozoon californicus Coinfection in a Merlin (Falco colombarius)

The Leucocytozoon genus comprises numerous widely distributed parasites which have been less investigated than other avian hemoprotozoa. Their occurrence is common, with very variable prevalence values and pathogenicity degrees. Leucocytozoon species are characterized by a great taxonomic diversity, and infections are usually restricted to birds of the same family. In the present paper, a mixed hemosporidia infection by Leucocytozoon californicus and Haemoproteus sp. in an adult male merlin (Falco columbarius) which died during hospitalisation is reported, indicating, for the first time, a newly described avian host species. A molecular investigation was carried out through cytochrome b gene analysis, revealing a 100% match with L. californicus and Haemoproteus spp. A blood smear examination allowed us to detect Leucocytozoon fusiform mature gametocytes and different degrees of maturity of Haemoproteus gametocytes. Histopathology revealed foci of necrosis, hemorrhagic areas and extramedullary hematopoiesis in the liver, the presence of microthrombi in the heart and lung and scattered hemorrhages in the lung.

Haemoparasites in red-legged partridge (Alectoris rufa): first record of Haemoproteus sp. in Italy?

During a health survey in the Province of Alessandria (NW Italy) 267 free ranging red-legged partridge (Alectoris rufa; 137 males and 130 females) were captured in 2009 (n = 101), 2010 (n = 130) and 2011 (n = 36). After biometric data and blood samples collection, animals were released on site. Blood samples were used for the preparation of blood smears. A total of 1.5% of smears presented parasites with a light blue finely granular cytoplasm in red blood cells. The parasites were identified, on the basis of their morphology (no molecular identification was possible), as being Haemoproteus sp. juvenile forms. The infestation prevalence was 0.8% in 2010 and 8.3% in 2011. No parasite was observed in 2009. The size of the infested erythrocytes was not altered (P > 0.05) and the nuclear displacement ratio was 0.8 ± 0.2. All the birds were apparently in good health status. To our knowledge this is the first description of Haemoproteus sp. in red-legged partridge, and more in general in birds belonging to Galliformes Order in Italy.

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.

Haemosporidioses in wild Eurasian blackbirds (Turdus merula) and song thrushes (T. philomelos): an in situ hybridization study with emphasis on exo-erythrocytic parasite burden

Background

Passerine birds are frequently infected with diverse haemosporidian parasites. While infections are traditionally considered benign in wild birds, recent studies demonstrated mortalities of passerine species due to exo-erythrocytic development of the parasites, which can damage organs in affected hosts. However, exo-erythrocytic development remains insufficiently investigated for most haemosporidian species and thus little is known about the virulence of tissue stages in wild passerine birds. The aim of the present study was to investigate natural haemosporidian infections in deceased Eurasian blackbirds (Turdus merula) and song thrushes (Turdus philomelos) and to determine parasite burden and associated histological effects.

Methods

For molecular analysis, blood and tissue samples from 306 thrushes were screened for Plasmodium, Haemoproteus and Leucocytozoon parasites by nested PCR. For the detection of parasite stages in organ samples, tissue sections were subjected to chromogenic in situ hybridization (CISH) using genus- and species-specific probes targeting the rRNAs of parasites. Exo-erythrocytic parasite burden was semi-quantitatively assessed and histological lesions were evaluated in haematoxylin–eosin-stained sections.

Results

By PCR, 179 of 277 Eurasian blackbirds and 15 of 29 song thrushes were positive for haemosporidians. Parasites of all three genera were detected, with Plasmodium matutinum LINN1 and Plasmodium vaughani SYAT05 showing the highest prevalence. CISH revealed significant differences in exo-erythrocytic parasite burden between lineages in Eurasian blackbirds, with P. matutinum LINN1 frequently causing high exo-erythrocytic parasite burdens in various organs that were associated with histological alterations. Song thrushes infected with P. matutinum LINN1 and birds infected with other haemosporidian lineages showed mostly low exo-erythrocytic parasite burdens. Two Eurasian blackbirds infected with Leucocytozoon sp. TUMER01 showed megalomeronts in various organs that were associated with inflammatory reactions and necroses.

Conclusion

This study suggests that P. matutinum LINN1, a common lineage among native thrushes, regularly causes high exo-erythrocytic parasite burdens in Eurasian blackbirds, which may result in disease and mortalities, indicating its high pathogenic potential. The findings further illustrate that the same parasite lineage may show different levels of virulence in related bird species which should be considered when assessing the pathogenicity of haemosporidian parasite species. Finally, the study provides evidence of virulent Leucocytozoon sp. TUMER01 infections in two Eurasian blackbirds caused by megalomeront formation.

Haemoproteosis lethality in a woodpecker, with molecular and morphological characterization of Haemoproteus velans (Haemosporida, Haemoproteidae)

A juvenile White-headed woodpecker (Dryobates albolarvatus) fitted with a radio tag was located dead at approximately 22-days post-fledging in Yakima county in central Washington in July 2015. Postmortem examination revealed an enlarged liver and spleen plus evidence of iron sequestration. Microscopic examination observed young gametocytes within the cytoplasm of erythrocytes, and exo-erythrocytic meronts within the cytoplasm of capillary endothelial cells, hepatocytes, and myocytes, and free in the tissues. These attributes implicated a haemosporidian infection that likely resulted in mortality. Subsequent sampling results of local woodpecker species in the same area during the breeding season in June-July 2016 and May-July 2017 showed other individuals infected with Haemoproteus parasites. Nested Polymerase Chain Reaction (PCR), sequencing, and microscopic analyses for avian haemosporidians revealed infections with Haemoproteus velans (Haemosporida, Haemoproteidae). This parasite was characterized molecularly and morphologically. This is the first report of a haemosporidian infection in a White-headed woodpecker anywhere in its range, and the first reported suspected mortality from haemoproteosis for a woodpecker (Piciformes, Picidae). The use of radio-tagged birds is an asset in wildlife haemosporidian studies because the effect of the pathogen can be monitored in real time. Additionally, this methodology provides opportunities to collect fresh material for microscopic and histological examination from wild birds that have died from natural causes.

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.

Experimental characterization of the complete life cycle of Haemoproteus columbae, with a description of a natural host-parasite system used to study this infection

Characterization of complete life cycles of haemoparasites requires the maintenance of suitable susceptible vertebrate hosts and vectors for long periods in captivity, in order to follow the complete parasitic cycle in definitive and intermediate hosts. Currently, there are few host-parasite models established in avian haemosporidian research, and those have been developed mainly for species of Passeriformes and their parasites. This study aimed to develop an experimental methodology to access the complete life cycle of Haemoproteus columbae (cytb lineage HAECOL1), which parasitizes the Rock Pigeon (Columba livia) and louse fly (Pseudolynchia canariensis). A colony of louse flies, which are the natural vectors of this parasite, was established. Thirty newly emerged insects were exposed to H. columbae infection and used to infect naïve Rock Pigeons. The peak of parasitaemia (acute stage) was seen between 27 and 32 days p.i. when up to 70.8% of red blood cells were infected. The crisis occurred approximately 1 week after the peak, and the long-lasting chronic parasitaemia stage followed. Exo-erythrocytic meronts were seen mainly in the lungs where extensive tissue damage was reported, but also in the kidneys and spleen. In the vector, the sporogonic cycle of H. columbae was completed between 13 and 16 days p.i., at an average temperature ranging between 12 and 15 °C. This host-parasite model is tractable for maintenance in captivity. It is recommended for use in studies aiming for detailed characterization of host-parasite relationships in areas such as physiology, pathology, immunobiology, genetics, as well as for evaluative treatments and to follow the infection in any stage of parasite development both in the vertebrate or invertebrate host.

Molecular probes for the identification of avian Haemoproteus and Leucocytozoon parasites in tissue sections by chromogenic in situ hybridization

Background

Avian haemosporidian parasites can cause severe disease in their hosts due to excessive exo-erythrocytic merogony and anaemia caused by blood stages. Notably, the development of megalomeronts by species of Haemoproteus and Leucocytozoon has been associated with mortalities in birds. Diagnosis of lethal infections is currently accomplished by the detection of parasites’ tissue stages in histological sections combined with PCR and sequencing. However, sequences frequently are not reliably obtained and the generic discrimination of exo-erythrocytic tissue stages based on morphological characters is challenging. Therefore, the present study aimed at developing specific molecular probes for the identification of Haemoproteus spp. and Leucocytozoon spp. in histological sections using chromogenic in situ hybridization.

Methods

Parasite subgenus-specific oligonucleotide probes were designed to target the 18S ribosomal RNA of Haemoproteus species (subgenus Parahaemoproteus) and Leucocytozoon spp. (subgenus Leucocytozoon) and were in situ hybridized to sections from formalin-fixed, paraffin-embedded tissue samples determined positive for these parasites by PCR and histopathology. To confirm the presence of parasites at sites of probe hybridization, consecutive sections were stained with haematoxylin–eosin and examined.

Results

Parahaemoproteus- and Leucocytozoon-specific probes labelled erythrocytic and exo-erythrocytic stages of Haemoproteus spp. and Leucocytozoon spp., respectively. Binding of probes to parasites was consistent with detection of the same exo-erythrocytic meronts in consecutive haematoxylin–eosin-stained sections. Cross-reactivity of the probes was ruled out by negative chromogenic in situ hybridization when applied to samples positive for a parasite of a genus different from the probes’ target.

Conclusions

Chromogenic in situ hybridization using 18S ribosomal RNA-specific oligonucleotide probes reliably identifies and discriminates Haemoproteus and Leucocytozoon parasites in tissue sections and enables unequivocal diagnosis of haemosporidioses.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3536-2) contains supplementary material, which is available to authorized users.

Blood parasites in Passeriformes in central Germany: prevalence and lineage diversity of Haemosporida (Haemoproteus, Plasmodium and Leucocytozoon) in six common songbirds

Background

Avian Haemosporida are vector-borne parasites that commonly infect Passeriformes. Molecular analyses revealed a high number of different lineages and lineage specific traits like prevalence and host-specificity, but knowledge of parasite prevalence and lineage diversity in wild birds in Central Germany is still lacking.

Results

Blood samples from a total of 238 adult and 122 nestling songbirds belonging to six species were investigated for infections with avian haemosporidian genera and lineages (Haemoproteus spp., Plasmodium spp., Leucocytozoon spp.) and Trypanosoma avium using PCR, targeting the parasite mitochondrial cytochrome b gene and 18S ribosomal RNA. In total, the prevalence in adult birds was 31.3% infected with Haemoproteus, 12.5% with Plasmodium and 71.0% with Leucocytozoon (nestlings excluded). None of the tested birds was infected with Trypanosoma avium. Only in two nestling birds, aged 12–17 days, a Leucocytozoon spp. infection was proven. Among 225 successfully sequenced samples, we found four Haemoproteus, three Plasmodium and 19 Leucocytozoon lineages, including two new Leucocytozoon lineages. Furthermore, we report two new host-lineage associations.

Conclusions

As first study investigating avian haemosporidian parasites in Central Germany, we provide new information on genetic diversity of Haemosporida infecting Passeriformes. We show that even with a small sample size new lineages as well as previously unknown linkages between certain lineages and host species can be detected. This may help to elucidate the diversity of lineages as well as lineage-host-connections of avian Haemosporida.

Haemoproteus minutus is highly virulent for Australasian and South American parrots

Background

Haemoproteus and Plasmodium species are widespread avian blood parasites. Several Plasmodium species are known for their high virulence and have caused significant declines in naïve bird populations. The impact of closely related Haemoproteus parasites is largely unknown. Recently we reported a lethal disease in two parrot aviaries caused by Haemoproteus parasites.

Results

Here we show that the causative pathogen Haemoproteus minutus is responsible for further 17 lethal outbreaks in parrot aviaries in Denmark, Germany and Great Britain. All affected parrots are endemic to Australasia and South America. We sequenced the cytochrome b gene from megalomeront-infected muscle tissue of 21 parrots and identified the two lineages TUPHI01 and TURDUS2 as causative agents, commonly naturally infecting the common blackbird (Turdus merula) and the song thrush (Turdus philomelos), respectively, in the Palaearctic. No intraerythrocytic parasite stages were found in any of the parrots. We failed to detect H. minutus in invasive Indian ring-necked parakeets (Psittacula krameri) in Germany. Together this suggests that abortive infections with two virulent lineages of H. minutus are lethal for naïve parrot species from Australasia and South America. We asked whether we could detect H. minutus in New Zealand, where its Turdus hosts were introduced in the 1800s. We therefore tested invasive blackbirds and song thrushes, and the co-existing endemic red-fronted parakeet (Cyanoramphus novaezelandiae) population on three New Zealand islands. No Haemoproteus spp. DNA was detected in all blood samples, indicating absence of transmission.

Conclusions

The results of this study show that captive parrots in Europe are threatened by two lineages of an otherwise benign parasite of Turdus spp. Aviary collections of parrots should be protected from Culicoides spp. vectors in Europe. Animal trade and climate changes extending the current vector and parasite distribution have to be considered as potential risk factors for the introduction of the disease in naïve parrot populations.

Haemoproteus paraortalidum n. sp. in captive Black-fronted Piping-guans Aburria jacutinga (Galliformes, Cracidae): High prevalence in a population reintroduced into the wild

Haemosporidian parasites of the genus Haemoproteus are widespread and can cause disease and even mortality in birds under natural and captive conditions. The Black-fronted Piping-guan (Aburria jacutinga) is an endangered Neotropical bird of the Cracidae (Galliformes) going through a reintroduction program to avoid extinction. We used microscopic examination and partial cytochrome b DNA sequencing to describe a new Haemoproteus species infecting Black-fronted Piping-guans bred and raised in captivity that were reintroduced into the Atlantic rainforest. Haemoproteus (Parahaemoproteus) paraortalidum n. sp. was detected in the blood of 19 out of 29 examined birds. The new species is distinguished from other haemoproteids due to the shape of gametocytes, which have pointed ends in young stages, and due to the presence of vacuole-like unstained spaces in macrogametocytes and numerous volutin granules both in macro- and microgametocytes. Illustrations of the new species are provided. Phylogenetic inference positioned this parasite in the Parahaemoproteus subgenus clade together with the other two Haemoproteus genetic lineages detected in cracids up to date. We discuss possible implications of the reintroduction of birds infected with haemosporidian parasites into the wild. Treatment of Haemoproteus infections remains insufficiently studied, but should be considered for infected birds before reintroduction to improve host reproductive and survival rates after release.

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.

PREVALENCE AND PHYLOGENETIC ANALYSIS OF AVIAN HAEMOSPORIDIA IN WILD BIRDS IN THE REPUBLIC OF KOREA

Avian blood parasites, including Plasmodium spp. and Haemoproteus spp., are found worldwide but only limited information of their occurrence is available in the Republic of Korea (ROK). We determined the prevalence of Plasmodium and Haemoproteus and their phylogenetic characteristics in wild birds in ROK. Blood samples were collected from 118 wild birds of 27 species in the Chonbuk Province, ROK. While 43 (36%) were positive for avian haemosporidia on microscopic examination of blood smears, 53 (45%) were positive by PCR targeting the cytochrome b gene. By direct sequencing of PCR amplicons, 47 (89%) were identified as Haemoproteus spp. and 6 (11%) as Plasmodium spp. Phylogenetic analysis using the cytochrome b gene revealed that resident and migrant birds have very similar genetic lineages of both parasites in ROK, suggesting the possibility that migrant birds may act as a mediator for the parasite among Asian countries.

HAEMOPROTEUS ( PARAHAEMOPROTEUS) SPP. IN CAPTIVE-BRED BOBWHITE QUAIL ( COLINUS VIRGINIANUS) IN SOUTHERN UTAH, USA

A captive-bred Bobwhite Quail ( Colinus virginianus) ranch in southern Utah, US experienced high mortality rates in the late summer and fall of 2012. Nine juvenile birds were necropsied at the Utah Veterinary Diagnostic Laboratory. Gross lesions included pale skeletal muscle with multifocal hemorrhages and petechiae in the air sacs and serosal surfaces of most organs. Histologically there was moderate to severe, multifocal, degenerative myositis with intramyofiber schizonts and minimal lymphoplasmacytic infiltrates in the proventriculus, ventriculus, heart, and skeletal muscle. There was also moderate fibrinoid to heterophilic vasculitis in multiple organs with vascular intraendothelial or intravascular merozoites and scattered thrombosis. In the liver and spleen there were multiple degenerative schizonts that had ruptured. Blood smears from three of the birds were stained with Wright-Giemsa stain and examined at a referral laboratory. Although the blood cells were deteriorated (postmortem artifact), life stages (exact stages not specified) consistent with Haemoproteus spp. were identified in erythrocytes. Polymerase chain reaction done on pooled tissues from two birds produced an amplicon in both pooled samples, and direct sequencing confirmed the presence of 533 base pairs of a Haemoproteus sp. in the subgenus Parahaemoproteus. The identification of Parahaemoproteus spp. in quail in southern Utah implies that appropriate Culicoides spp. vectors are present in the state and that there is potential risk to other birds such as zoo and aviary populations, wild turkeys, and other game birds.

Case Series: Virulent hemosporidiosis infections in juvenile great horned owls (Bubo virginianus) from Louisiana and California, USA

A total of eight juvenile great horned owls (Bubo virginianus) were found lethargic and on the ground in spring 2015, 2016, and 2017, including one fledgling from Louisiana, USA and seven nestlings from California, USA. One bird survived to release after rehabilitation; seven birds died or were euthanized due to poor prognosis and were necropsied. Necropsy findings were similar and included general pallor of all tissues, particularly the subcutis and lungs, and enlarged liver and spleen. Histopathology revealed multi-organ necrosis, abundant meronts containing merozoites, and intracytoplasmic pigmented haemosporidian parasites in blood cells in one bird. Leucocytozoon lineages lSTOCC16 and BUVIR06 were identified by polymerase chain reaction and genetic sequencing. The systemic Leucocytozoon infections were likely associated with morbidity and mortality in these owls. A second parasite, Haemoproteus lineage hSTVAR01, was also identified in an owl from Louisiana. This is the first identification of Leucocytozoon lineages that have been associated with mortality in young great horned owls.

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.

From Galapagos doves to passerines: Spillover of Haemoproteus multipigmentatus

Haemoproteus (Haemoproteus) multipigmentatus, a haemosporidian parasite thought to be specific to columbiform birds, was detected in passeriform birds on Santiago Island in the Galapagos archipelago. We surveyed birds along an altitudinal gradient on the islands of Santa Cruz, Isabela and Santiago between June 2013 and July 2015. Molecular screening of 2254 individuals from 25 species of endemic and introduced birds revealed clusters of passerine birds positive for H. multipigmentatus on Santiago Island that coincide with captures of Galapagos doves at sampled sites. Of 507 individuals from 10 species of endemic passerines sampled on Santiago, 58 individuals from 6 species were found positive (11% prevalence). However, no gametocytes were found in the blood smears of positive passerines, suggesting that these species are not competent hosts for the parasite. All 31 doves captured were positive and gametocytes were found upon microscopic examination of all thin blood smears (averaging 357 gametocytes per 10,000 erythrocytes). These findings indicate parasite spillover from doves to passerines, but that passerines are possibly not competent hosts for further parasite transmission. The endemic Galapagos dove acts as a reservoir host for the introduced H. multipigmentatus, however the effect of this parasite on passerines has not been studied. We report on these findings because parasites can have large effects on individual host populations and on the ecology of a community, but may go undetected.

Avian haemosporidian detection across source materials: prevalence and genetic diversity

Avian haemosporidians make up one of the most widely distributed and diverse vector borne parasite systems, found nearly worldwide in tropical and temperate areas. Despite the clear relationship between avian host fitness measures and infection, few studies have addressed the importance of source material selection when assessing these relationships. We show that source material, here blood and pectoral muscle, do not yield equivalent results when assessing prevalence and genetic diversity of haemosporidian genera. We find higher prevalence and genetic diversity are recovered from blood versus pectoral muscle for Haemoproteus. Contrastingly, we find that a higher prevalence of Plasmodium is detected from pectoral muscle, while higher genetic diversity is recovered from blood. Our results indicate that source material may bias parasite detection and be an important factor in study design, which is not only related to parasite infection, but by extension to the ecology and fitness of avian hosts.

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.

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.

Blood parasites of penguins: a critical review

Blood parasites are considered some of the most significant pathogens for the conservation of penguins, due to the considerable morbidity and mortality they have been shown to produce in captive and wild populations of these birds. Parasites known to occur in the blood of penguins include haemosporidian protozoans (Plasmodium, Leucocytozoon, Haemoproteus), piroplamid protozoans (Babesia), kinetoplastid protozoans (Trypanosoma), spirochete bacteria (Borrelia) and nematode microfilariae. This review provides a critical and comprehensive assessment of the current knowledge on these parasites, providing an overview of their biology, host and geographic distribution, epidemiology, pathology and implications for public health and conservation.

Exo-erythrocytic development of avian malaria and related haemosporidian parasites

BACKGROUND

Avian malaria parasites (Plasmodium spp.) and related haemosporidians (Haemosporida) are responsible for diseases which can be severe and even lethal in avian hosts. These parasites cause not only blood pathology, but also damage various organs due to extensive exo-erythrocytic development all over the body, which is not the case during Plasmodium infections in mammals. However, exo-erythrocytic development (tissue merogony or schizogony) remains the most poorly investigated part of life cycle in all groups of wildlife haemosporidian parasites. In spite of remarkable progress in studies of genetic diversity, ecology and evolutionary biology of avian haemosporidians during the past 20 years, there is not much progress in understanding patterns of exo-erythrocytic development in these parasites. The purpose of this review is to overview the main information on exo-erythrocytic development of avian Plasmodium species and related haemosporidian parasites as a baseline for assisting academic and veterinary medicine researchers in morphological identification of these parasites using tissue stages, and to define future research priorities in this field of avian malariology.

METHODS

The data were considered from peer-reviewed articles and histological material that was accessed in zoological collections in museums of Australia, Europe and the USA. Articles describing tissue stages of avian haemosporidians were included from 1908 to the present. Histological preparations of various organs infected with the exo-erythrocytic stages of different haemosporidian parasites were examined.

RESULTS

In all, 229 published articles were included in this review. Exo-erythrocytic stages of avian Plasmodium, Fallisia, Haemoproteus, Leucocytozoon, and Akiba species were analysed, compared and illustrated. Morphological characters of tissue stages that can be used for diagnostic purposes were specified.

CONCLUSION

Recent molecular studies combined with histological research show that avian haemosporidians are more virulent than formerly believed. The exo-erythrocytic stages can cause severe disease, especially in non-adapted avian hosts, suggesting the existence of a group of underestimated malignant infections. The development of a given haemosporidian strain can be markedly different in different avian hosts, resulting in significantly different virulence. A methodology combining the traditional histology techniques with molecular diagnostic tools is essential to speed research in this field of avian malariology.

Multiyear Survey of Coccidia, Cryptosporidia, Microsporidia, Histomona, and Hematozoa in Wild Quail in the Rolling Plains Ecoregion of Texas and Oklahoma, USA

We developed nested PCR protocols and performed a multiyear survey on the prevalence of several protozoan parasites in wild northern bobwhite (Colinus virginianus) and scaled quail (Callipepla squamata) in the Rolling Plains ecoregion of Texas and Oklahoma (i.e. fecal pellets, bird intestines and blood smears collected between 2010 and 2013). Coccidia, cryptosporidia, and microsporidia were detected in 46.2%, 11.7%, and 44.0% of the samples (n = 687), whereas histomona and hematozoa were undetected. Coccidia consisted of one major and two minor Eimeria species. Cryptosporidia were represented by a major unknown Cryptosporidium species and Cryptosporidium baileyi. Detected microsporidia species were highly diverse, in which only 11% were native avian parasites including Encephalitozoon hellem and Encephalitozoon cuniculi, whereas 33% were closely related to species from insects (e.g. Antonospora, Liebermannia, and Sporanauta). This survey suggests that coccidia infections are a significant risk factor in the health of wild quail while cryptosporidia and microsporidia may be much less significant than coccidiosis. In addition, the presence of E. hellem and E. cuniculi (known to cause opportunistic infections in humans) suggests that wild quail could serve as a reservoir for human microsporidian pathogens, and individuals with compromised or weakened immunity should probably take precautions while directly handling wild quail.

Local parasite lineage sharing in temperate grassland birds provides clues about potential origins of Galapagos avian Plasmodium

Oceanic archipelagos are vulnerable to natural introduction of parasites via migratory birds. Our aim was to characterize the geographic origins of two Plasmodium parasite lineages detected in the Galapagos Islands and in North American breeding bobolinks (Dolichonyx oryzivorus) that regularly stop in Galapagos during migration to their South American overwintering sites. We used samples from a grassland breeding bird assemblage in Nebraska, United States, and parasite DNA sequences from the Galapagos Islands, Ecuador, to compare to global data in a DNA sequence registry. Homologous DNA sequences from parasites detected in bobolinks and more sedentary birds (e.g., brown‐headed cowbirds Molothrus ater, and other co‐occurring bird species resident on the North American breeding grounds) were compared to those recovered in previous studies from global sites. One parasite lineage that matched between Galapagos birds and the migratory bobolink, Plasmodium lineage B, was the most common lineage detected in the global MalAvi database, matching 49 sequences from unique host/site combinations, 41 of which were of South American origin. We did not detect lineage B in brown‐headed cowbirds. The other Galapagos‐bobolink match, Plasmodium lineage C, was identical to two other sequences from birds sampled in California. We detected a close variant of lineage C in brown‐headed cowbirds. Taken together, this pattern suggests that bobolinks became infected with lineage B on the South American end of their migratory range, and with lineage C on the North American breeding grounds. Overall, we detected more parasite lineages in bobolinks than in cowbirds. Galapagos Plasmodium had similar host breadth compared to the non‐Galapagos haemosporidian lineages detected in bobolinks, brown‐headed cowbirds, and other grassland species. This study highlights the utility of global haemosporidian data in the context of migratory bird–parasite connectivity. It is possible that migratory bobolinks bring parasites to the Galapagos and that these parasites originate from different biogeographic regions representing both their breeding and overwintering sites.

Hemosporidian parasites of free-living birds in the São Paulo Zoo, Brazil

Numerous studies addressed the diversity of bird Plasmodium and Haemoproteus parasites. However, a few have been carried out in continental avian hotspot regions such as Brazil, a country with markedly different biomes, including Amazon, Brazilian Savanna, Atlantic Forest, Caatinga, Pantanal, and Pampas. We present the first study on hemosporidian (Haemosporida) parasites in free-living birds from an Atlantic Forest fragment where more than 80 avian species have been reported. Within this area, the São Paulo Zoo locates, and it is the fourth largest zoo in the world and the largest in Latin America. A total of 133 free-living bird samples representing 12 species were collected in the zoo, with the overall hemosporidian prevalence of 18 % by PCR-based diagnostics. Twenty-four positive PCR signals were reported from four different bird species, including migratory ones. Columba livia, an urban species, considered nowadays a pest in big cities, showed 100 % prevalence of Haemoproteus spp., mainly Haemoproteus columbae. We discuss the epidemiological importance of new parasites introduced by migratory birds in the São Paulo Zoo area and the risk it poses to the captive species, which are natives or exotics. We also warn about the influence these parasites can have on the biodiversity and the structure of host populations by altering the competitive interaction between the free-living and the captive birds.