Avian haemosporidians in haematophagous insects in the Czech Republic

Avian haemosporidian parasites from wild-caught mosquitoes with new evidence on vectors of Plasmodium matutinum

Avian haemosporidian parasites are spread worldwide and pose a threat to their hosts occasionally. A complete life cycle of these parasites requires two hosts: vertebrate and invertebrate (a blood-sucking insect that acts as a vector). In this study, we tested wild-caught mosquitoes for haemosporidian infections. Mosquitoes were collected (2021-2023) in several localities in Lithuania using a sweeping net and a CDC trap baited with CO2, morphologically identified, and preparations of salivary glands were prepared (from females collected in 2022-2023). 2093 DNA samples from either individual after dissection (1675) or pools (418 pools/1145 individuals) of female mosquito's abdomens were screened using PCR for the detection of haemosporidian parasite DNA. Salivary gland preparations were analyzed microscopically from each PCR-positive mosquito caught in 2022 and 2023. The average prevalence of haemosporidian parasites for all analyzed samples was 2.0 % and varied between 0.6 % (2021) and 3.5 % (2022). DNA of Plasmodium ashfordi (cytochrome b genetic lineage pGRW02), P. circumflexum (pTURDUS1), P. homonucleophilum (pSW2), P. matutinum (pLINN1), P. vaughani (pSYAT05), Haemoproteus brachiatus (hLK03), H. majoris (hWW2), and H. minutus (hTUPHI01) were detected in mosquitoes. Coquilletidia richiardii (3.5 %) and Culex pipiens (2.9 %) were mosquito species with the highest prevalence of haemosporidian parasite DNA detected. Mixed infections were detected in 16 mosquitoes. In one of the samples, sporozoites of P. matutinum (pLINN1) were found in the salivary gland preparation of Culex pipiens, confirming this mosquito species as a competent vector of Plasmodium matutinum and adding it to the list of the natural vectors of this avian parasite.

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.

Phylogeographic Patterns of Haemoproteid Assemblages of Selected Avian Hosts: Ecological and Evolutionary Implications

Background: While the dynamics of disease emergence is driven by host–parasite interactions, the structure and dynamics of these interactions are still poorly understood. Here we study the phylogenetic and morphological clustering of haemosporidian parasite lineages in a local avian host community. Subsequently, we examine geographical patterns of parasite assemblages in selected avian hosts breeding in Europe. Methods: We conduct phylogenetic and haplotype network analyses of Haemoproteus (Parahaemoproteus) lineages based on a short and an extended cytochrome b barcode region. Ordination analyses are used to examine changes in parasite assemblages with respect to climate type and geography. Results: We reveal relatively low phylogenetic clustering of haemoproteid lineages in a local avian host community and identify a potentially new Haemoproteus morphospecies. Further, we find that climate is effectively capturing geographical changes in parasite assemblages in selected widespread avian hosts. Moreover, parasite assemblages are found to vary distinctly across the host’s breeding range, even within a single avian host. Conclusions: This study suggests that a few keystone hosts can be important for the local phylogenetic and morphological clustering of haemoproteid parasites. Host spatio-temporal dynamics, both for partially and long-distance migratory birds, appear to explain geographical variation in haemoproteid parasite assemblages. This study also gives support to the idea that climate variation in terms of rainfall seasonality can be linked to the propensity for host switching in haemosporidians.

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.

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.

Atypical behavior of a black fly species connects cavity-nesting birds with generalist blood parasites in an arid area of Spain

BACKGROUND

The feeding behavior of bloodsucking insects determines the transmission, distribution, host spectrum and evolution of blood parasites in the wild. Conventional wisdom suggests that some vector groups (e.g. black flies, family Simuliidae) are consistently exophagous daytime biters. We aimed to understand more about the exceptions to this pattern by combining targeted trapping and molecular identification of parasites in vectors.

METHODS

In this study, we collected black flies in nest boxes used by European rollers Coracias garrulus in southeastern Spain. We molecularly analyzed 434 individual insects, identifying the black fly species caught in the nest boxes, their potential vertebrate blood meals, and the haemosporidian parasite lineages that they carried.

RESULTS

Only one black fly species, Simulium rubzovianum, appeared to enter the nest boxes of rollers. Among the trapped specimens, 15% contained vertebrate DNA, which always belonged to rollers, even though only half of those specimens were visibly engorged. Furthermore, 15% of all black flies contained Leucocytozoon lineages, indicating previous feeding on avian hosts but probably not on infected adult rollers. The known vertebrate hosts of the recorded Leucocytozoon lineages suggested that large and/or abundant birds are their hosts. Particularly represented were cavity-nesting species breeding in the vicinity, such as pigeons, corvids and owls. Open-nesting species such as thrushes and birds of prey were also represented.

CONCLUSIONS

Our data strongly suggest that S. rubzovianum bites uninfected roller nestlings and infected individuals of other species, potentially incubating adults, inside nest boxes and natural cavities. This simuliid does not appear to have a strong preference for specific host clades. Contrary to the general pattern for the group, and possibly enhanced by the harsh environmental conditions in the study area, this black fly appeared to intensively use and may even have a preference for confined spaces such as cavities for feeding and resting. Preferences of vectors for atypical microhabitat niches where hosts are less mobile may enable social and within-family transmission and parasite speciation in the long term. At the same time, a lack of host preference in concentrated multispecies communities can lead to host switches. Both processes may be underappreciated driving forces in the evolution of avian blood parasites.

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.

Blood parasites in vectors reveal a united blackfly community in the upper canopy

Background

The behaviour of blood-sucking arthropods is a crucial determinant of blood protozoan distribution and hence of host-parasite coevolution, but it is very challenging to study in the wild. The molecular identification of parasite lineages in vectors can be a useful key to understand the behaviour and transmission patterns realised by these vectors.

Methods

In this study, we collected blackflies around nests of three raptor species in the upper forest canopy in central Europe and examined the presence of vertebrate DNA and haemosporidian parasites in them. We molecularly analysed 156 blackfly individuals, their vertebrate blood meals, and the haemosporidian parasite lineages they carried.

Results

We identified nine species of Simulium blackflies, largely belonging to the subgenera Nevermannia and Eusimulium. Only 1% of the collected specimens was visibly engorged, and only 4% contained remains of host DNA. However, in 29% of the blackflies Leucocytozoon lineages were identified, which is evidence of a previous blood meal on an avian host. Based on the known vertebrate hosts of the recorded Leucocytozoon lineages, we can infer that large and/or abundant birds, such as thrushes, crows, pigeons, birds of prey, owls and tits are the main targets of ornithophilic blackflies in the canopy. Blackfly species contained similar proportions of host group-specific parasite lineages and thus do not appear to be associated with particular host groups.

Conclusions

The Leucocytozoon clade infecting thrushes, crows, and pigeons present in most represented blackfly species suggests a lack of association between hosts and blackflies, which can increase the probability of host switches of blood parasites. However, the composition of the simuliid species differed between nests of common buzzards, goshawks and red kites. This segregation can be explained by coinciding habitat preferences between host and vector, and may lead to the fast speciation of Leucocytozoon parasites. Thus, subtle ecological preferences and lack of host preference of vectors in the canopy may enable both parasite diversification and host switches, and enforce a habitat-dependent evolution of avian malaria parasites and related haemosporidia.

Morphological and molecular characterization of Plasmodium cathemerium (lineage PADOM02) from the sparrow Passer domesticus with complete sporogony in Culex pipiens complex

Avian malaria is a mosquito-borne disease caused by Plasmodium spp. protozoa. Although these parasites have been extensively studied in North America and Eurasia, knowledge on the diversity of Plasmodium, its vectors and avian hosts in Africa is scarce. In this study, we report on natural malarial infections in free-ranging sparrows (Passer domesticus) sampled at Giza Governorate, Egypt. Parasites were morphologically characterized as Plasmodium cathemerium based on the examination of thin blood smears from the avian host. Sequencing a fragment of the mitochondrial cytochrome b gene showed that the parasite corresponded to lineage PADOM02. Phylogenetic analysis showed that this parasite is closely related to the lineages SERAU01 and PADOM09, both of which are attributed to P. cathemerium. Experimental infection of Culex pipiens complex was successful, with ookinetes first detected at 1-day post infection (dpi), oocysts at 4 dpi and sporozoites at 6 dpi. The massive infection of the salivary glands by sporozoites corroborates that Cx. pipiens complex is a competent vector of PADOM02. Our findings confirm that Plasmodium lineage PADOM02 infects sparrows in urban areas along the Nile River, Egypt, and corroborate that Cx. pipiens complex is a highly competent vector for these parasites. Furthermore, our results demonstrate that this lineage corresponds to the morphospecies P. cathemerium and not P. relictum as previously believed.

Identification of a new vector species of avian haemoproteids, with a description of methodology for the determination of natural vectors of haemosporidian parasites

BACKGROUND

Haemosporidian parasites are transmitted by dipteran blood-sucking insects but certain vectors remain unidentified for the great majority of described species. Sensitive PCR-based methods are often used for the detection of haemosporidian infection in wild-caught insects. However, this approach alone cannot distinguish between different sporogonic stages and thus is insufficient to demonstrate that the parasites produce the infective stage (sporozoite), which is essential for transmission. To prove that PCR-positive insects could act as vectors, the record of sporozoites is needed. We developed a methodology for the determination of natural vectors of avian Haemoproteus species and other haemosporidians. The essence of this approach is to apply PCR-based and microscopic diagnostic tools in parallel for sporozoite detection in insects.

METHODS

Culicoides biting midges transmit avian Haemoproteus parasites, but certain insect species, which are involved in transmission, remain insufficiently investigated. Biting midges were collected in the wild and identified; parous females were dissected and preparations of thorax content containing salivary glands were prepared. Remnants of the dissected midges were screened using PCR-based methods. Only thorax preparations of PCR-positive biting midges were examined microscopically.

RESULTS

In total, 460 parous females belonging to 15 species were collected and dissected. DNA of haemosporidians was detected in 32 (7%) of dissected insects belonging to 7 species. Of the thorax samples PCR-positive for Haemoproteus parasites, two preparations were microscopically positive for sporozoites. Both biting midges were Culicoides kibunensis. Haemoproteus pallidus (hPFC1) was identified, indicating that transmission of this infection occurs at the study site. It was proved that seven species of biting midges take bird blood meals naturally in the wild.

CONCLUSIONS

Culicoides kibunensis is a new vector species of avian haemoproteids and is a natural vector of H. pallidus. Numerous studies have identified vectors of Haemoproteus parasites experimentally; however, this is the first direct identification of a natural vector of Haemoproteus infection in the Old World. We suggest using the described methodology for vector research of Haemoproteus and other haemosporidians in the wild.

Louse flies of Eleonora's falcons that also feed on their prey are evolutionary dead-end hosts for blood parasites

Host shifts are widespread among avian haemosporidians, although the success of transmission depends upon parasite‐host and parasite‐vector compatibility. Insular avifaunas are typically characterized by a low prevalence and diversity of haemosporidians, although the underlying ecological and evolutionary processes remain unclear. We investigated the parasite transmission network in an insular system formed by Eleonora's falcons (the avian host), louse flies that parasitize the falcons (the potential vector), and haemosporidians (the parasites). We found a great diversity of parasites in louse flies (16 Haemoproteus and 6 Plasmodium lineages) that did not match with lineages previously found infecting adult falcons (only one shared lineage). Because Eleonora's falcon feeds on migratory passerines hunted over the ocean, we sampled falcon kills in search of the origin of parasites found in louse flies. Surprisingly, louse flies shared 10 of the 18 different parasite lineages infecting falcon kills. Phylogenetic analyses revealed that all lineages found in louse flies (including five new lineages) corresponded to Haemoproteus and Plasmodium parasites infecting Passeriformes. We found molecular evidence of louse flies feeding on passerines hunted by falcons. The lack of infection in nestlings and the mismatch between the lineages isolated in adult falcons and louse flies suggest that despite louse flies’ contact with a diverse array of parasites, no successful transmission to Eleonora's falcon occurs. This could be due to the falcons’ resistance to infection, the inability of parasites to develop in these phylogenetically distant species, or the inability of haemosporidian lineages to complete their development in louse flies.

Host use patterns of Culicoides spp. biting midges at a big game preserve in Florida, U.S.A., and implications for the transmission of orbiviruses

Culicoides spp. biting midges (Diptera: Ceratopogonidae) are vectors of pathogens that have a significant economic impact on the livestock industry. White-tailed deer (Odocoileus virginianus), a farmed species in the U.S.A., are susceptible to two Culicoides spp. borne orbiviruses: bluetongue virus and epizootic haemorrhagic disease virus. Elucidating host-vector interactions is an integral step in studying disease transmission. This study investigated the host range of Culicoides spp. present on a big game preserve in Florida on which a variety of Cervidae and Bovidae freely roam. Culicoides were captured with Centers for Disease Control and Prevention (CDC) miniature light traps run twice weekly on the preserve for 18 consecutive months (July 2015-December 2016). Host preference was quantified through forage ratios, based upon PCR-based bloodmeal analysis of Culicoides spp. and overall animal relative abundance on the preserve. Culicoides stellifer preferentially fed on Cervus spp. and fallow deer (Dama dama) and displayed a relative avoidance of Bovidae and white-tailed deer. Culicoides debilipalpis preferred white-tailed deer and avoided all Bovidae. Culicoides pallidicornis and Culicoides biguttatus showed preferences for white-tailed deer and Père David's deer (Elaphurus davidianus), respectively. These results add to current knowledge of preferred hosts of Florida Culicoides spp. and have implications for the spread of orbiviruses. Copyright © 2018 John Wiley & Sons, Ltd.

Blood parasite infections in a wild population of ravens (Corvus corax) in Bulgaria

BACKGROUND

Blood parasites have been studied intensely in many families of avian hosts, but corvids, a particularly cosmopolitan family, remain underexplored. Haemosporidian parasites of the common raven (Corvus corax) have not been studied, although it is the largest, most adaptable, and widespread corvid. Genetic sequence data from parasites of ravens can enhance the understanding of speciation patterns and specificity of haemosporidian parasites in corvids, and shed light how these hosts cope with parasite pressure.

METHODS

A baited cage trap was used to catch 86 ravens and a nested PCR protocol was used to amplify a 479 bp fragment of the haemosporidian cytochrome b gene from the samples. The obtained sequences were compared with the MalAvi database of all published haemosporidian lineages and a phylogenetic tree including all detected raven parasites was constructed. An examination of blood smears was performed for assessment of infection intensity.

RESULTS

Twenty blood parasite lineages were recovered from ravens caught in a wild population in Bulgaria. The prevalence of generalist Plasmodium lineages was 49%, and the prevalence of Leucocytozoon lineages was 31%. Out of 13 detected Leucocytozoon lineages six were known from different corvids, while seven others seem to be specific to ravens. A phylogenetic reconstruction suggests that Leucocytozoon lineages of ravens and other corvids are not monophyletic, with some groups appearing closely related to parasites of other host families.

CONCLUSIONS

Several different, morphologically cryptic groups of Leucocytozoon parasites appear to infect corvids. Ravens harbour both generalist corvid Leucocytozoon as well as apparently species-specific lineages. The extraordinary breeding ecology and scavenging lifestyle possibly allow ravens to evade vectors and have relatively low blood parasite prevalence compared to other corvids.

Avian Plasmodium in Eastern Austrian mosquitoes

Background

Insect vectors, namely mosquitoes (Diptera: Culicidae), are compulsory for malaria parasites (Plasmodium spp.) to complete their life cycle. Despite this, little is known about vector competence of different mosquito species for the transmission of avian malaria parasites.

Methods

In this study, nested PCR was used to determine Plasmodium spp. occurrence in pools of whole individuals, as well as the diversity of mitochondrial cytochrome b gene sequences in wild-caught mosquitoes sampled across Eastern Austria in 2013–2015.

Results

A total of 45,749 mosquitoes in 2628 pools were collected, of which 169 pools (6.43%) comprising 9 mosquito species were positive for avian Plasmodium, with the majority of positives in mosquitoes of Culex pipiens s.l./Culex torrentium. Six different avian Plasmodium lineages were found, the most common were Plasmodium vaughani SYAT05, Plasmodium sp. Linn1 and Plasmodium relictum SGS1. In 2014, mosquitoes of the Culex pipiens complex were genetically identified and Culex pipiens f. pipiens presented with the highest number of avian Plasmodium positives (n = 37; 16.74%). Despite this, the minimum infection rate (MIR) was highest in Culex torrentium (5.36%) and Culex pipiens f. pipiens/f. molestus hybrids (5.26%). During 2014 and 2015, seasonal and annual changes in Plasmodium lineage distribution were also observed. In both years P. vaughani SYAT05 dominated at the beginning of the sampling period to be replaced later in the year by P. relictum SGS1 (2014) and Plasmodium sp. Linn1 (2015).

Conclusions

This is the first large-scale study of avian Plasmodium parasites in Austrian mosquitoes. These results are of special interest, because molecular identification of the taxa of the Cx. pipiens complex and Cx. torrentium enabled the determination of Plasmodium prevalence in the different mosquito taxa and hybrids of this complex. Since pools of whole insects were used, it is not possible to assert any vector competence in any of the examined mosquitoes, but the results are nonetheless valuable in providing an overview of avian Plasmodium species and lineages present in Austria.

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.

Do mosquitoes transmit the avian malaria-like parasite Haemoproteus? An experimental test of vector competence using mosquito saliva

Background

The life-cycle of many vector-borne pathogens includes an asexual replication phase in the vertebrate host and sexual reproduction in the insect vector. However, as only a small array of parasites can successfully develop infective phases inside an insect, few insect species are competent vectors for these pathogens. Molecular approaches have identified the potential insect vectors of blood parasites under natural conditions. However, the effectiveness of this methodology for verifying mosquito competence in the transmission of avian malaria parasites and related haemosporidians is still under debate. This is mainly because positive amplifications of parasite DNA in mosquitoes can be obtained not only from sporozoites, the infective phase of the malaria parasites that migrate to salivary glands, but also from different non-infective parasite forms in the body of the vector. Here, we assessed the vectorial capacity of the common mosquito Culex pipiens in the transmission of two parasite genera.

Methods

A total of 1,560 mosquitoes were allowed to feed on five house sparrows Passer domesticus naturally infected by Haemoproteus or co-infected by Haemoproteus/Plasmodium. A saliva sample of the mosquitoes that survived after 13 days post-exposure was taken to determine the presence of parasite DNA by PCR.

Results

Overall, 31.2% mosquito’s head-thorax and 5.8% saliva samples analysed showed positive amplifications for avian malaria parasites. In contrast to Haemoproteus DNA, which was not found in either the body parts or the saliva, Plasmodium DNA was detected in both the head-thorax and the saliva of mosquitoes. Parasites isolated from mosquitoes feeding on the same bird corresponded to the same Plasmodium lineage.

Conclusions

Our experiment provides good evidence for the competence of Cx. pipiens in the transmission of Plasmodium but not of Haemoproteus. Molecular analyses of saliva are an effective method for testing the vector competence of mosquitoes and other insects in the transmission of vector-borne pathogens.

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

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

Haemosporidian infections in the Tengmalm's Owl (Aegolius funereus) and potential insect vectors of their transmission

Sedentary bird species are suitable model hosts for identifying potential vectors of avian blood parasites. We studied haemosporidian infections in the Tengmalm's Owl (Aegolius funereus) in the Ore Mountains of the Czech Republic using molecular detection methods. Sex of owl nestlings was scored using molecular sexing based on fragment analysis of PCR-amplified CHD1 introns. Observed infection prevalences in nestlings and adult owls were 51 and 86 %, respectively. Five parasite lineages were detected. Most of the infections comprised the Leucocytozoon AEFUN02 and STOCC06 lineages that probably refer to distinct Leucocytozoon species. Other lineages were detected only sporadically. Mixed infections were found in 49 % of samples. The main factor affecting the probability of infection was host age. No effect of individual sex on infection probability was evidenced. The youngest infected nestling was 12 days old. High parasite prevalence in the Tengmalm's Owl nestlings suggests that insect vectors must enter nest boxes to transmit parasites before fledging. Hence, we placed sticky insect traps into modified nest boxes, collected potential insect vectors, and examined them for the presence of haemosporidian parasites using molecular detection. We trapped 201 insects which were determined as biting midges from the Culicoides genus and two black fly species, Simulium (Nevermannia) vernum and Simulium (Eusimulium) angustipes. Six haemosporidian lineages were detected in the potential insect vectors, among which the Leucocytozoon lineage BT2 was common to the Tengmalm's Owl and the trapped insects. However, we have not detected the most frequently encountered Tengmalm's Owl Leucocytozoon lineages AEFUN02 and STOCC06 in insects.

Blood parasites in northern goshawk (Accipiter gentilis) with an emphasis to Leucocytozoon toddi

Haemosporidians and trypanosomes of the northern goshawk (Accipiter gentilis) population in the Czech Republic were studied by morphological and molecular methods. Despite the wide distribution of these medium-large birds of prey, virtually nothing is known about their blood parasites. During a 5-year period, altogether 88 nestlings and 15 adults were screened for haemosporidians and trypanosomes by microscopic examination of blood smears and by nested PCR. Both methods revealed consistently higher prevalence of blood protists in adults, Leucocytozoon (80.0 % in adults vs. 13.6 % in nestlings), Haemoproteus (60.0 vs. 2.3 %), Plasmodium (6.7 vs. 0 %), and Trypanosoma (60.0 vs. 2.3 %). Altogether, five haemosporidian lineages were detected by cytochrome b sequencing. Two broadly distributed and host nonspecific lineages, Plasmodium (TURDUS1) and Leucocytozoon (BT2), were detected only sporadically, while three newly described northern goshawk host-specific Leucocytozoon lineages (ACGE01-03) represent the absolute majority of the haemosporidians identified by molecular methods. Our findings support evidences that in falconiform birds the Leucocytozoon toddi group is formed by several host-specific clusters, with Leucocytozoon buteonis in buzzards and Leucocytozoon mathisi in hawks. Between-year comparisons revealed that the infection status of adults remained predominantly unchanged and individuals stayed uninfected or possessed the same parasite lineages; however, two gains and one loss of blood parasite taxa were also recorded.

Host preferences of ornithophilic biting midges of the genus Culicoides in the Eastern Balkans

Many biting midges of the genus Culicoides Latreille, 1809 (Diptera: Ceratopogonidae) are competent vectors of a diverse number of pathogens. The identification of their feeding behaviour and of vector-host associations is essential for understanding their transmission capacity. By applying two different nested polymerase chain reaction (PCR) assays, of which one targeted the avian cyt b gene and the other targeted the COI gene of a wide range of vertebrates, we identified the blood hosts of six biting midge species including Culicoides circumscriptus, Culicoides festivipennis, Culicoides punctatus, Culicoides pictipennis, Culicoides alazanicus and Culicoides cf. griseidorsum, the latter two of which are reported in Bulgaria for the first time. Bird DNA was found in 50.6% of 95 investigated bloodmeals, whereas mammalian DNA was identified in 13.7%. Two Culicoides species were found to feed on both birds and mammals. There was remarkable diversity in the range of avian hosts: 23 species from four orders were identified in the abdomens of four Culicoides species. The most common bird species identified was the magpie, Pica pica (n = 7), which was registered in all four ornithophilic biting midge species. Six bloodmeals from the great tit, Parus major, were recorded only in C. alazanicus. None of the studied species of Culicoides appeared to be restricted to a single avian host.

Avian malaria parasites in the last supper: identifying encounters between parasites and the invasive Asian mosquito tiger and native mosquito species in Italy

BACKGROUND

The invasive Asian tiger mosquito Aedes albopictus has dramatically expanded its distribution range, being catalogued as one of the world's 100 worst invasive alien species. As vectors of pathogens, Ae. albopictus may create novel epidemiological scenarios in the invaded areas.

METHODS

Here, the frequency of encounters of Ae. albopictus with the avian malaria parasite Plasmodium and the related Haemoproteus was studied in an area with established populations in northeastern Italy and compared with those from four native mosquito species, Anopheles maculipennis s.l., Culex hortensis, Culex pipiens, and Ochlerotatus caspius. The abdomens of mosquitoes with a recent blood meal were used to identify both the blood meal source and the parasites harboured.

RESULTS

Aedes albopictus had a clear antropophilic behaviour while An. maculipennis and Oc. caspius fed mainly on non-human mammals. Birds were the most common hosts of Cx. pipiens and reptiles of Cx. hortensis. Parasites were isolated from three mosquito species, with Cx. pipiens (30%) showing the highest parasite prevalence followed by Cx. hortensis (9%) and Ae. albopictus (5%).

CONCLUSIONS

These results are the first identifying the avian malaria parasites harboured by mosquitoes in Italy and represent the first evidence supporting that, although Ae. albopictus could be involved in the transmission of avian malaria parasites, the risk of avian malaria parasite spread by this invasive mosquito in Europe would be minimal.

Trypanosomes and haemosporidia in the buzzard (Buteo buteo) and sparrowhawk (Accipiter nisus): factors affecting the prevalence of parasites

The prevalences of heteroxenous parasites are influenced by the interplay of three main actors: hosts, vectors, and the parasites themselves. We studied blood protists in the nesting populations of raptors in two different areas of the Czech Republic. Altogether, 788 nestlings and 258 adult Eurasian sparrowhawks (Accipiter nisus) and 321 nestlings and 86 adult common buzzards (Buteo buteo) were screened for parasites by the microscopic examination of blood smears and by cultivation. We examined the role of shared vectors and parasite phylogenetic relationships on the occurrence of parasites. In different years and hosts, trypanosome prevalence ranged between 1.9 and 87.2 %, that of Leucocytozoon between 1.9 and 100 %, and Haemoproteus between 0 and 72.7 %. Coinfections with Leucocytozoon and Trypanosoma, phylogenetically distant parasites but both transmitted by blackflies (Simuliidae), were more frequent than coinfections with Leucocytozoon and Haemoproteus, phylogenetically closely related parasites transmitted by different vectors (blackflies and biting midges (Ceratopogonidae), respectively). For example, 16.6 % buzzard nestlings were coinfected with Trypanosoma and Leucocytozoon, while only 4.8 % with Leucocytozoon and Haemoproteus and 0.3 % with Trypanosoma and Haemoproteus. Nestlings in the same nest tended to have the same infection status. Furthermore, prevalence increased with the age of nestlings and with Julian date, while brood size had only a weak negative/positive effect on prevalence at the individual/brood level. Prevalences in a particular avian host species also varied between study sites and years. All these factors should thus be considered while comparing prevalences from different studies, the impact of vectors being the most important. We conclude that phylogenetically unrelated parasites that share the same vectors tend to have similar distributions within the host populations of two different raptor species.

Degree of associations among vectors of the genus Culicoides (Diptera: Ceratopogonidae) and host bird species with respect to haemosporidian parasites in NE Bulgaria

The occurrence of haemosporidians in biting midges of the genus Culicoides is examined in North-East Bulgaria in order to reveal their potential role for parasite transmission. A PCR-based technique amplifying part of the mitochondrial cytochrome b gene of the parasite is applied on naturally infected biting midges. Totally, 640 parous individuals of four species and 95 blood-fed individuals of six species of Culicoides are examined for the presence of DNA of haemosporidians. Haemosporidian genetic lineages are identified in individuals of three insect species: Culicoides alazanicus (12 lineages, nine lineages of Haemoproteus and three lineages of Plasmodium), Culicoides festivipennis and Culicoides circumscriptus (with two and one lineages of Haemoproteus, respectively). Two genetic lineages of Haemoproteus are recorded in more than one vector species. These results demonstrate variations in the specificity of Haemoproteus genetic lineages to their potential vectors, since some lineages are recorded in a single vector species and others occur in two or more vector species.

Haemoproteus infections (Haemosporida, Haemoproteidae) kill bird-biting mosquitoes

Haemoproteus parasites (Haemosporida, Haemoproteidae) are widespread; some species cause severe diseases in avian hosts. Heavy Haemoproteus infections are often lethal for biting midges (Ceratopogonidae), which transmit avian haemoproteids, but there is no information regarding detrimental effect on other blood-sucking insects. We examined effects of Haemoproteus tartakovskyi (lineage hSISKIN1), Haemoproteus lanii (lineages hRB1and hRBS2) and Haemoproteus balmorali (lineage hCOLL3) on the survival of Ochlerotatus cantans, a widespread Eurasian mosquito. Wild-caught females were infected by allowing them to feed on naturally infected birds with light (0.01%) and high (3.0-9.6%) parasitaemia. Mosquitoes fed on uninfected birds were used as controls. Both experimental and control groups were maintained under the same laboratory conditions until 20 days post-exposure (dpe). Dead insects were counted daily and used for parasitological examination and PCR-based testing. No difference was discernible in the survival rate of control mosquitoes and those fed on meal with light parasitaemia. There was a highly significant difference in the survival rate between the control group and all groups fed on meals with high parasitaemia, with the greatest mortality reported 1-3 dpe. For 4 dpe, the percentage of survived control mosquitoes (88%) was 2.2-, 3.6- and 4-fold greater than that of groups fed on meals with high parasitaemia of H. balmorali, H. tartakovskyi and H. lanii, respectively. Numerous ookinetes were observed in the gut area and adjacent tissues located in the head, thorax and abdomen of infected insects 0.5-1 dpe. The migrating parasites damage organs throughout the entire body of mosquitoes; that is the main reason of mortality. To the end of this study, 46% of mosquitoes survived in control group, but the survival rates of experimental mosquitoes fed on meals with high parasitaemia were between 2.6- and 5.8-fold lower. This study indicates that widespread Haemoproteus infections are markedly virulent for bird-biting mosquitoes, which rapidly die after feeding on heavily infected blood meals.

Seasonal pattern of avian Plasmodium-infected mosquitoes and implications for parasite transmission in central Panama

Aedeomyia squamipennis and Culex (Melanoconion) ocossa, two ubiquitous Neotropical mosquito species, are likely involved in the transmission of several bird pathogens in Gamboa, central Panama. However, knowledge on their eco-epidemiological profiles is still incomplete. Our goal in this study was to investigate temporal trends of vector density and their relationship with avian plasmodia prevalence. This information is central to identifying the risk posed by each vector species to the avian community locally. We found that A. squamipennis maintains stable population size across climatic seasons and thus maybe a more efficient vector of avian malaria than C. ocossa. In contrast, C. ocossa, which undergoes considerable population expansion in the rainy season and contraction in the dry season, is likely only an important avian malaria vector during part of the year. This is consistent with the larger number of parasite isolations and Plasmodium cyt b lineages recovered from A. squamipennis than from C. ocossa and might be explained by marked differences in their seasonality and host-feeding preferences. More Plasmodium PCR testing in mosquito communities from other areas of Panama might reveal additional vectors of avian plasmodia.

On the study of the transmission networks of blood parasites from SW Spain: diversity of avian haemosporidians in the biting midge Culicoides circumscriptus and wild birds

Background

Blood-sucking flying insects play a key role in the transmission of pathogens of vector-borne diseases. However, at least for the case of avian malaria parasites, the vast majority of studies focus on the interaction between parasites and vertebrate hosts, but there is a lack of information regarding the interaction between the parasites and the insect vectors. Here, we identified the presence of malaria and malaria-like parasite lineages harbored by the potential vector Culicoides circumscriptus (Kieffer). Also, we identified some nodes of the transmission network connecting parasite lineages, potential insect vectors and avian hosts by comparing Haemoproteus and Plasmodium lineages isolated from insects with those infecting wild birds in this and previous studies.

Methods

Using a molecular approach, we analysed the presence of blood parasites in a total of 97 biting midges trapped in the Doñana National Park (SW Spain) and surrounding areas. Also, 123 blood samples from 11 bird species were analyzed for the presence of blood parasite infections. Blood parasites Haemoproteus and Plasmodium were identified by amplification of a 478 bp fragment of the mitochondrial cytochrome b gen.

Results

Thirteen biting midges harboured blood parasites including six Haemoproteus and two Plasmodium lineages, supporting the potential role of these insects on parasite transmission. Moreover, ten (8.1%) birds carried blood parasites. Seven Plasmodium and one Haemoproteus lineages were isolated from birds. Overall, six new Haemoproteus lineages were described in this study. Also, we identified the transmission networks of some blood parasites. Two Haemoproteus lineages, hCIRCUM03 and GAGLA03, were identical to those isolated from Corvus monedula in southern Spain and Garrulus glandarius in Bulgaria, respectively. Furthermore, the new Haemoproteus lineage hCIRCUM05 showed a 99% similarity with a lineage found infecting captive penguins in Japan.

Conclusions

The comparison of the parasite lineages isolated in this study with those previously found infecting birds allowed us to identify some potential nodes in the transmission network of avian blood parasite lineages. These results highlight the complexity of the transmission networks of blood parasites in the wild that may involve a high diversity of susceptible birds and insect vectors.

Haemosporidian parasites of a European passerine wintering in South Asia: diversity, mixed infections and effect on host condition

We studied haemosporidian parasites in the scarlet rosefinch Carpodacus erythrinus in a small isolated semicolony during an eight-year period using molecular methods of parasite detection. The scarlet rosefinch is an interesting model of parasite host species. It winters in South Asia which represents a rare exception among European passerines. Males express yellow to red carotenoid-based plumage ornament which is a good predictor of male reproductive success. In 240 blood samples originating from 199 adult individuals, the total parasite prevalence reached 60%. Prevalence varied among years from 36 to 81% in Haemoproteus, 8 to 22% in Plasmodium, and 0 to 14% in Leucocytozoon. Twenty parasite lineages were detected (Haemoproteus: 5 lineages, Plasmodium: 10 lineages, and Leucocytozoon: 5 lineages). Among them, the Haemoproteus ROFI2 lineage, which is a host-specific parasite lineage of the scarlet rosefinch, was the most frequently found. Parasite lineages showed varying degree of lineage specificity. While Haemoproteus lineages detected in the scarlet rosefinch have relatively narrow host breadth restricted mainly to Fringillidae family, Leucocytozoon and Plasmodium lineages generally showed wider host range. The presence of some parasite lineages hitherto detected in sedentary European passerines (SISKIN1, CCF3, BT2) or in Culicoides biting midges at the same locality (ROFI1) suggest local transmission. On the contrary, lineages LK05 and FANTAIL1 that were previously reported exclusively from Asian hosts imply parasite transmission at the scarlet rosefinch wintering sites in South Asia. Mixed infections were found in 17% of infected samples and comprised mainly the most frequent lineages. The pattern of concomitant infections seemed to be rather random and matched expected levels based on lineage frequencies. Between-year comparisons revealed that in a majority of the repeatedly captured individual hosts the infection status remained unchanged (individuals stayed uninfected or possessed the same parasite lineages). However, 16 gains and 8 losses of lineages were also reported. We have not found any effect of haemosporidians on male carotenoid ornament expression or host body mass.