Spatial feeding preferences of ornithophilic mosquitoes, blackflies and biting midges

Blood parasites (Trypanosoma, Leucocytozoon, Haemoproteus) in the Eurasian sparrowhawk (Accipiter nisus): diversity, incidence and persistence of infection at the individual level

BACKGROUND

A high prevalence of parasites may result from life-long persistence of infection or from high reinfection rates. We have studied blood parasites in a breeding population of the accipitrid raptor, Eurasian sparrowhawk (Accipiter nisus), to determine parasite diversity and turnover.

METHODS

During this 7-year study, 210 adult Eurasian sparrowhawks breeding in the city of Prague were checked for parasites using several diagnostic methods.

RESULTS

In both female and male raptors, parasites of the genus Leucocytozoon were the most prevalent (92% and 85%, respectively) followed in decreasing order of prevalence by those of genus Trypanosoma (74% and 68%, respectively) and genus Haemoproteus (46% and 16%, respectively). The prevalence of all parasites increased with age in both sexes, with the females at each respective age having the higher prevalence. There was a positive association between Haemoproteus and Leucocytozoon infections. Persistence at the individual level was higher than incidence for Trypanosoma and Haemoproteus. In the case of Leucocytozoon and Trypanosoma, most individuals probably become infected in their first year of life or even before dispersal from the nest. The detected parasites belonged to Trypanosoma avium sensu stricto, Leucocytozoon sp. (haplotypes ACNI1 and ACNI3) and Leucocytozoon mathisi (haplotype ACNI4) and two new lineages of the Haemoproteus elani complex (ACCNIS6 and ACCNIS7). Detailed analysis of parasite lineages in individuals that were repeatedly sampled revealed lineage turnover that would otherwise remain hidden. Phylogenetic analysis revealed that the detected Haemoproteus belongs to a phylogenetically distant group whose taxonomic position requires further analysis.

CONCLUSIONS

All three genera of blood parasites persist in infected individuals, thus enabling sustainability of vector transmission cycles. Prevalence increases with age; however, there is a high turnover of Leucocytozoon lineages. No clear evidence of parasite-induced mortality was found, and most of the individuals were infected early in life, particularly in the case of Leucocytozoon.

Habitat-dependent Culicoides species composition and abundance in blue tit (Cyanistes caeruleus) nests

Wild birds are hosts of Culicoides from as early on as the nesting stage when constrained to their nests. However, the environmental factors which determine the abundance and composition of Culicoides species within each bird nest are still understudied. We sampled Culicoides from Eurasian blue tit (Cyanistes caeruleus) nests found in 2 types of forests located in southern Spain. Firstly, we monitored the abundance of Culicoides species in bird nests from a dry Pyrenean oak deciduous forest and a humid mixed forest comprising Pyrenean and Holm oaks throughout 2 consecutive years. During the 3rd year, we performed a cross-fostering experiment between synchronous nests to differentiate the role of rearing environment conditions from that of the genetically determined or maternally transmitted cues released by nestlings from each forest. We found 147 female Culicoides from 5 different species in the birds' nests. The abundance of Culicoides was higher in the dry forest than in the humid forest. Culicoides abundance, species richness and prevalence were greater when the nestlings were hatched later in the season. The same pattern was observed in the cross-fostering experiment, but we did not find evidence that nestling's features determined by the forest of origin had any effect on the Culicoides collected. These results support the notion that habitat type has a strong influence on the Culicoides affecting birds in their nests, while some life history traits of birds, such as the timing of reproduction, also influence Culicoides abundance and species composition.

Updated occurrence and bionomics of potential malaria vectors in Europe: a systematic review (2000-2021)

Despite the eradication of malaria across most European countries in the 1960s and 1970s, the anopheline vectors are still present. Most of the malaria cases that have been reported in Europe up to the present time have been infections acquired in endemic areas by travelers. However, the possibility of acquiring malaria by locally infected mosquitoes has been poorly investigated in Europe, despite autochthonous malaria cases having been occasionally reported in several European countries. Here we present an update on the occurrence of potential malaria vector species in Europe. Adopting a systematic review approach, we selected 288 papers published between 2000 and 2021 for inclusion in the review based on retrieval of accurate information on the following Anopheles species: An. atroparvus, An. hyrcanus sensu lato (s.l.), An. labranchiae, An. maculipennis sensu stricto (s.s.), An. messeae/daciae, An. sacharovi, An. superpictus and An. plumbeus. The distribution of these potential vector species across Europe is critically reviewed in relation to areas of major presence and principal bionomic features, including vector competence to Plasmodium. Additional information, such as geographical details, sampling approaches and species identification methods, are also reported. We compare the information on each species extracted from the most recent studies to comparable information reported from studies published in the early 2000s, with particular reference to the role of each species in malaria transmission before eradication. The picture that emerges from this review is that potential vector species are still widespread in Europe, with the largest diversity in the Mediterranean area, Italy in particular. Despite information on their vectorial capacity being fragmentary, the information retrieved suggests a re-definition of the relative importance of potential vector species, indicating An. hyrcanus s.l., An. labranchiae, An. plumbeus and An. sacharovi as potential vectors of higher importance, while An. messeae/daciae and An. maculipennis s.s. can be considered to be moderately important species. In contrast, An. atroparvus and An. superpictus should be considered as vectors of lower importance, particularly in relation to their low anthropophily. The presence of gaps in current knowledge of vectorial systems in Europe becomes evident in this review, not only in terms of vector competence but also in the definition of sampling approaches, highlighting the need for further research to adopt the appropriate surveillance system for each species.

The drivers of avian‐haemosporidian prevalence in tropical lowland forests of New Guinea in three dimensions

Haemosporidians are among the most common parasites of birds and often negatively impact host fitness. A multitude of biotic and abiotic factors influence these associations, but the magnitude of these factors can differ by spatial scales (i.e., local, regional and global). Consequently, to better understand global and regional drivers of avian‐haemosporidian associations, it is key to investigate these associations at smaller (local) spatial scales. Thus, here, we explore the effect of abiotic variables (e.g., temperature, forest structure, and anthropogenic disturbances) on haemosporidian prevalence and host–parasite networks on a horizontal spatial scale, comparing four fragmented forests and five localities within a continuous forest in Papua New Guinea. Additionally, we investigate if prevalence and host–parasite networks differ between the canopy and the understory (vertical stratification) in one forest patch. We found that the majority of Haemosporidian infections were caused by the genus Haemoproteus and that avian‐haemosporidian networks were more specialized in continuous forests. At the community level, only forest greenness was negatively associated with Haemoproteus infections, while the effects of abiotic variables on parasite prevalence differed between bird species. Haemoproteus prevalence levels were significantly higher in the canopy, and an opposite trend was observed for Plasmodium. This implies that birds experience distinct parasite pressures depending on the stratum they inhabit, likely driven by vector community differences. These three‐dimensional spatial analyses of avian‐haemosporidians at horizontal and vertical scales suggest that the effect of abiotic variables on haemosporidian infections are species specific, so that factors influencing community‐level infections are primarily driven by host community composition.

Effects on ectoparasites and nestling body condition of experimental modification of relative humidity in nest cavities of European rollers Coracias garrulus in an arid environment

Climate change effects on host–parasite interactions have been poorly studied in arid or semi-arid habitats. Here, we conducted an experiment aimed to increase the temperature inside European roller Coracias garrulus nest boxes located in a semi-arid habitat on different nest-site types to look for effects on different ectoparasite abundances and nestling growth. Average nest temperature was slightly higher in heated nests than in control nests, although differences were not statistically significant. However, relative humidity was significantly lower at night in heated nests as compared to control nests. The abundance of sand flies, mites and carnid flies was significantly higher in heated, less humid, nests while biting midge abundance was significantly lower in heated nests. Other ectoparasites were not significantly affected by treatment. Relative humidity was high even in heated nests, reaching more than 60%. Sand fly abundance was higher in nests located in sandstone walls, while mite abundance was higher in isolated farmhouses. In addition, sand fly prevalence was higher in nests located in isolated farmhouses and sandstone walls. Heat treatment, nest-site type or ectoparasite abundances did not affect the nestling body mass, wing length or their growth at different nestling ages.

A comparison of BG Sentinel and CDC trap attractants for mosquito surveillance in urban and suburban areas of Montgomery and Prince George's Counties, Maryland, U.S.A

Monitoring mosquito populations is crucial for vector-borne disease surveillance. Routine mosquito surveillance in many regions of the United States is performed either by vector abatement districts or public health departments. These surveillance programs often use multiple trap types and attractants to target key mosquito species, however setting different traps with varying attractants can be expensive and labor intensive. Because funding for mosquito control is highly variable throughout the U.S., some programs may be limited in their surveillance capabilities. To determine whether a single trap-attractant combination could provide specificity for key vector and nuisance species, as well as sensitivity for rare species, we compared the BG-Sentinel 2 and CDC miniature light traps paired with CO₂, UV-LED, BG Lure, BG Sweetscent, octenol, or chicken feathers. Trapping was conducted biweekly from June/July-October 2019 and 2020 in Montgomery and Prince George's County, MD. BG traps collected significantly more Aedes albopictus than CDC traps when paired with BG Lure, Sweetscent, or octenol. BG/CO₂ traps collected both the greatest number of total mosquitoes and Culex pipiens. BG/CO₂, CDC/CO₂, and CDC/UV traps provided the most diverse collections. Trapping with the CO₂-baited BG-Sentinel is recommended as an effective strategy for general mosquito surveillance when resources are limited.

Understanding Mosquito Surveillance Data for Analytic Efforts: A Case Study

Mosquito surveillance data can be used for predicting mosquito distribution and dynamics as they relate to human disease. Often these data are collected by independent agencies and aggregated to state and national level portals to characterize broad spatial and temporal dynamics. These larger repositories may also share the data for use in mosquito and/or disease prediction and forecasting models. Assumed, but not always confirmed, is consistency of data across agencies. Subtle differences in reporting may be important for development and the eventual interpretation of predictive models. Using mosquito vector surveillance data from Arizona as a case study, we found differences among agencies in how trapping practices were reported. Inconsistencies in reporting may interfere with quantitative comparisons if the user has only cursory familiarity with mosquito surveillance data. Some inconsistencies can be overcome if they are explicit in the metadata while others may yield biased estimates if they are not changed in how data are recorded. Sharing of metadata and collaboration between modelers and vector control agencies is necessary for improving the quality of the estimations. Efforts to improve sharing, displaying, and comparing vector data from multiple agencies are underway, but existing data must be used with caution.

Host migration and environmental temperature influence avian haemosporidians prevalence: a molecular survey in a Brazilian Atlantic rainforest

Avian haemosporidians are parasites with great capacity to spread to new environments and new hosts, being considered a good model to host-parasite interactions studies. Here, we examine avian haemosporidian parasites in a protected area covered by Restinga vegetation in northeastern Brazil, to test the hypothesis that haemosporidian prevalence is related to individual-level traits (age and breeding season), species-specific traits (diet, foraging strata, period of activity, species body weight, migratory status, and nest shape), and climate factors (temperature and rainfall). We screened DNA from 1,466 birds of 70 species captured monthly from April 2013 to March 2015. We detected an overall prevalence (Plasmodium/Haemoproteus infection) of 22% (44 host species) and parasite’s lineages were identified by mitochondrial cyt b gene. Our results showed that migration can be an important factor predicting the prevalence of Haemoproteus (Parahaemoproteus), but not Plasmodium, in hosts. Besides, the temperature, but not rainfall, seems to predict the prevalence of Plasmodium in this bird community. Neither individual-level traits analyzed nor the other species-specific traits tested were related to the probability of a bird becoming infected by haemosporidians. Our results point the importance of conducting local studies in particular environments to understand the degree of generality of factors impacting parasite prevalence in bird communities. Despite our attempts to find patterns of infection in this bird community, we should be aware that an avian haemosporidian community organization is highly complex and this complexity can be attributed to an intricate net of factors, some of which were not observed in this study and should be evaluated in future studies. We evidence the importance of looking to host-parasite relationships in a more close scale, to assure that some effects may not be obfuscated by differences in host life-history.

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.

Bird habitat preferences drive hemoparasite infection in the Neotropical region

The role that the environment plays in vector-borne parasite infection is one of the central factors for understanding disease dynamics. We assessed how Neotropical bird foraging strata and habitat preferences determine infection by parasites of the genera Haemoproteus, Plasmodium, Leucocytozoon, and Trypanosoma and filarioids, and tested for phylogenetic signal in these host-parasite associations. We performed extensive searches of the scientific literature and created a database of hemoparasite surveys. We collected data on host body mass, foraging strata, habitat preference, and migratory status, and tested if host ecological traits predict each hemoparasite occurrence and prevalence using a phylogenetic Bayesian framework. Species of Plasmodium tend to infect birds from tropical forests while birds from altitudinal environments are likely to be infected by species of Leucocytozoon. The probability of a bird being infected by filarioid or Trypanosoma is higher in lowland forests. Bird species that occur in anthropic environments and dry habitats of tropical latitudes are more susceptible to infection by species of Haemoproteus. Host foraging strata is also influential and bird species that forage in the mid-high and canopy strata are more prone to infection by species of Haemoproteus and filarioids. We also identified phylogenetic signal for host-parasite associations with the probability of infection of Neotropical birds by any hemoparasite being more similar among more closely related species. We provided a useful framework to identify environments that correlate with hemoparasite infection, which is also helpful for detecting areas with potential suitability for hemoparasite infection due to land conversion and climate change.

Haemosporidian prevalence, parasitaemia and aggregation in relation to avian assemblage life history traits at different elevations

The transmission of vector-borne protozoa such as parasites of the Order Haemosporida is dependent on both biotic and abiotic factors such as host life history traits and environmental conditions. This study aimed to identify the variables that determine haemosporidian prevalence, parasitaemia and aggregation within the context of elevation and avian life history traits in Central Veracruz, Mexico. We sampled 607 birds from 88 species; we used microscopy and the mtDNA cytochrome b gene to detect parasites. We found an overall prevalence of 32.3%. Haemosporidian prevalence was 21.6% in tropical sub-deciduous forest (at sea level), 38% in tropical deciduous forest (265 m above sea level (asl)), 19.4% in montane cloud forest (1630 m asl), and 51.7% in pine-oak forest (2790 m asl). The prevalence of each parasite genus was strongly influenced by elevation (a proxy of habitat type). Plasmodium showed the highest prevalence at low elevation. Haemoproteus increased in prevalence with elevation. Leucocytozoon displayed the highest prevalence at the highest elevation (pine-oak forest). Haemoproteus spp. and Leucocytozoon spp. prevalences were higher in open cup than in closed nests. Haemoproteus prevalence and haemosporidian parasitaemia were lower in solitary birds than birds with pairing and gregarious behavior. Haemosporidian aggregation decreased with elevation, yielding the significantly lowest values at the pine-oak forest. Elevation distribution patterns of prevalence for each genus were similar to those previously reported in other geographical areas (e.g., South America, Europe).

Biting Midges in Jamari National Forest, in the Brazilian Amazon, With 12 New Records of Culicoides Species (Diptera: Ceratopogonidae) for the State of Rondônia

Culicoides biting midges are small hematophagous flies, some species of which transmit pathogens to livestock and humans. In the Brazilian Amazon Basin, Culicoides diversity has remained largely unexamined. Jamari National Forest (JNF) is a conservation area in Rondônia State where research and environmental education are conducted in conjunction with the protection of natural resources, and the recovery of degraded areas. The present study augments our knowledge of Culicoides diversity in JNF. The survey collected 640 individuals from 41 species; 632 individuals were collected by HP light trap and 8 were collected by the BG Sentinel trap. Twelve species are first-time records for Rondônia: Culicoides acotylus Lutz, Culicoides albuquerquei Wirth & Blanton, Culicoides baniwa Felippe-Bauer, Culicoides bricenoi Ortiz, Culicoides brownei Spinelli, Culicoides carsiomelas Wirth & Blanton, Culicoides debilipalpis Lutz, Culicoides forattinii Ortiz, Culicoides ginesi Ortiz, Culicoides profundus Santarém, Felippe-Bauer & Trindade, Culicoides pseudoreticulatus Santarém, Felippe-Bauer & Castellón, and Culicoides spurius Santarém, Felippe-Bauer & Trindade. The most abundant species were Culicoides glabrior Macfie, Culicoides pseudodiabolicus Fox, Culicoides debilipalpis, Culicoides quasiparaensis Clastrier, and Culicoides brownei Spinelli. The present study updates the Culicoides species count in Rondônia to 55, and highlights the importance of JNF as a hotbed for biting midge diversity.

Host phylogeny matters: Examining sources of variation in infection risk by blood parasites across a tropical montane bird community in India

Background

Identifying patterns and drivers of infection risk among host communities is crucial to elucidate disease dynamics and predict infectious disease risk in wildlife populations. Blood parasites of the genera Plasmodium and Haemoproteus are a diverse group of vector-borne protozoan parasites that affect bird populations globally. Despite their widespread distribution and exceptional diversity, factors underlying haemosporidian infection risk in wild bird communities remain poorly understood. While some studies have examined variation in avian haemosporidian risk, researchers have primarily focused on host ecological traits without considering host phylogenetic relationships. In this study, we employ a phylogenetically informed approach to examine the association between host ecological traits and haemosporidian infection risk in endemic bird communities in the Western Ghats Sky Islands.

Methods

We used parasite sequence data based on partial mitochondrial cytochrome b gene, that was amplified from genomic DNA extracted from 1177 birds (28 species) across the Western Ghats to assess infection of birds with haemosporidian parasites. We employed a Bayesian phylogenetic mixed effect modelling approach to test whether haemosporidian infection risk was affected by seven species-specific and four individual-level ecological predictors. We also examined the effect of host phylogenetic relationships on the observed patterns of variation in haemosporidian infection risk by estimating phylogenetic signal.

Results

Our study shows that host ecological traits and host phylogeny differentially influence infection risk by Plasmodium (generalist parasite) and Haemoproteus (specialist parasite). For Plasmodium, we found that sociality, sexual dimorphism and foraging strata were important ecological predictors. For Haemoproteus, patterns of infection risk among host species were associated with sociality, species elevation and individual body condition. Interestingly, variance in infection risk explained by host phylogeny was higher for Haemoproteus parasites compared to Plasmodium.

Conclusions

Our study highlights that while host ecological traits promoting parasite exposure and host susceptibility are important determinants of infection risk, host phylogeny also contributes substantially to predicting patterns of haemosporidian infection risk in multi-host communities. Importantly, infection risk is driven by joint contributions of host ecology and host phylogeny and studying these effects together could increase our ability to better understand the drivers of infection risk and predict future disease threats.

Graphical abstract

Is it best on the nest? Effects of avian life-history on haemosporidian parasitism

Infectious diseases vary in prevalence and pathology among host species. Species may differ in prevalence of infection due to varying exposure and susceptibility to disease agents throughout their lifetime, which may be attributable to underlying differences in their phenology, physiology and behavior. A recently growing body of literature has focused on the utility of host life-history traits to provide mechanistic explanations for interspecific variation in host-parasite associations. In this study, we utilized diverse avian and haemosporidian assemblages in an African savanna to evaluate the link between haemosporidia prevalence (Plasmodium, Haemoproteus, Leucocytozoon) and avian life-history traits such as body size, mating system, nest care and nest structure. We found that variation of haemosporidia prevalence was consistent with life-history traits that pertain to the reproduction of avian host. Nest care was the single most important predictor of infection status. In birds with shared and female-only nest care, the expected rates of parasitism were between 8- and 12-fold higher than in avian brood parasites that provide no nest care. This finding supports the hypothesis that parental care is an evolutionarily costly life-history trait that increases species' risk of infection with vector-borne diseases. The influence of other host traits (nest structure, body size) was less consistent suggesting that differences in the vectors’ ecology and host-seeking behavior produce variable patterns of parasitism among haemosporidia genera. Nest structure influenced infection with Haemoproteus and Leucocytozoon only. Leucocytozoon infections were associated with ground-nesting birds, while Haemoproteus infections were associated with birds that build open nest structures. Body size was an important predictor of Leucocytozoon infections, particularly large-bodied birds like guineafowl and doves, which exhibited high prevalences.

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Variation in infection prevalence was consistent with reproductive traits in avian hosts.

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Avian species that invested less in nest care had lower infection rates than species with other nest care strategies.

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Leucocytozoon infections were high in ground-nesting birds; birds with open nests had higher Haemoproteus infections.

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Birds like guineafowl and doves with larger body size had more Leucocytozoon infections.

Blood-meal analysis of Culicoides (Diptera: Ceratopogonidae) reveals a broad host range and new species records for Romania

BACKGROUND

Culicoides biting midges are potential vectors of different pathogens. However, especially for eastern Europe, there is a lack of knowledge on the host-feeding patterns of this vector group. Therefore, this study aimed to identify Culicoides spp. and their vertebrate hosts collected in a wetland ecosystem.

METHODS

Culicoides spp. were collected weekly from May to August 2017, using Biogents traps with UV light at four sites in the Danube Delta Biosphere Reserve, Romania. Vectors and hosts were identified with a DNA barcoding approach. The mitochondrial cytochrome c oxidase subunit 1 was used to identify Culicoides spp., while vertebrate hosts were determined targeting cytochrome b or 16S rRNA gene fragments. A maximum likelihood phylogenetic tree was constructed to verify the biting midge identity against other conspecific Palaearctic Culicoides species. A set of unfed midges was used for morphological confirmation of species identification using slide-mounted wings.

RESULTS

Barcoding allowed the species identification and detection of corresponding hosts for 1040 (82.3%) of the 1264 analysed specimens. Eight Culicoides spp. were identified with Culicoides griseidorsum, Culicoides puncticollis and Culicoides submaritimus as new species records for Romania. For 39 specimens no similar sequences were found in GenBank. This group of unknown Culicoides showed a divergence of 15.6-16.3% from the closest identified species and clustered in a monophyletic clade, i.e. a novel species or a species without reference sequences in molecular libraries. For all Culicoides spp., nine mammalian and 24 avian species were detected as hosts. With the exception of C. riethi (n = 12), at least one avian host was detected for all Culicoides spp., but this host group only dominated for Culicoides kibunensis and the unknown Culicoides sp.. The most common host group were mammals (n = 993, 87.6% of all identified blood sources) dominated by cattle (n = 817, 70.6%).

CONCLUSIONS

Most Culicoides spp. showed a broad host-feeding pattern making them potential bridge vectors. At the same time, new records of biting midge species for Romania, as well as a potentially unknown Culicoides species, highlight the lack of knowledge regarding the biting midge species and their genetic diversity in eastern Europe.

Molecular detection of Trypanosoma (Kinetoplastida: Trypanosomatidae) in black flies (Diptera: Simuliidae) from Thailand

Trypanosomes are parasitic flagellate protozoans that are important disease causing agents in humans and animals including economically significant livestock. Many blood-sucking insects are known to be vectors of trypanosomes but there is no data for the haematophagous black fly species in Asia. In this study, a molecular approach based on the small subunit ribosomal RNA (SSU rRNA) gene was used to detect trypanosomes in black flies from Thailand. A total of 470 wild-caught adult black flies representing nine morphological species were examined. Ten (2%) specimens of two ornithophilic black fly species, Simulium asakoae complex (n = 4) and S. chumpornense (n = 6), were positive for trypanosomes. The SSU rRNA sequences revealed that all trypanosome DNA found in black flies from Thailand is closely related to Trypanosoma avium with >99% sequence similarity. This is also supported by a phylogenetic analysis in which all trypanosomes from Thai black flies were resolved in the clade of T. avium. This is the first report for trypanosomes in Asian black flies and it is suspected that these insects are potential vectors of avian Trypanosoma.

Bloodmeal analysis in Culicoides midges collected near horses, donkeys and zebras in the Eastern Cape, South Africa

An upsurge in African horse sickness (AHS) in the Eastern Cape, South Africa, from 2006 led to an epidemiological reassessment of the disease there. Light trapping surveys carried out near horses, donkeys and zebras in 2014-2016 collected 39 species of Culicoides midge (Diptera: Ceratopogonidae) that are potential vectors of AHS. To establish if these midges fed on equids, DNA sequences were obtained from the gut contents of 52 female midges (35 freshly blood-fed, 13 gravid and four parous), representing 11 species collected across 11 sites. Culicoides leucostictus fed on all three equids. Culicoides bolitinos, Culicoides imicola and Culicoides magnus fed on both horses and donkeys. Culicoides onderstepoortensis fed on donkeys, and Culicoides similis and Culicoides pycnostictus fed on zebras. Bloodmeals from cows, pigs, warthogs, impalas and a domestic dog were also identified in various species, but none of the midges tested had fed on birds. These results contribute to knowledge of the vectorial capacity of several species of Culicoides with regard to AHS in the Eastern Cape and point to potential reservoir hosts, of which donkeys, zebras and domestic dogs have previously been found to harbour AHS. Blood-fed midges were also obtained throughout winter, indicating the potential for endemic AHS in the province.

Management of ecosystems alters vector dynamics and haemosporidian infections

The presence of insect vectors is a key prerequisite for transmission of vector-borne disease such as avian haemosporidians. In general, the effects of land use change on Diptera vectors are not well studied; the response of vectors to forest management depends on vector species, as has been shown previously for the birds. We tested if abundance of insects from different Diptera families and haemosporidian infection are affected through alteration of habitat structural variables (measured by LiDAR) and forest management intensities. We identified higher large-scale variation of female insect abundance in northeastern than in southwestern Germany. Unmanaged forest stands had higher Diptera insect abundances. We found that abundance of female Diptera increased with the amount of forest gaps but decreased in forest plots with more south facing aspect, higher habitat structural heterogeneity, temperature and humidity. We found that haemosporidian infections in Diptera insects increased with increased management intensity and more canopy structural diversity (e.g., amount of edge habitat), but decreased with a denser shrub layer, deeper leaf litter and higher humidity (characteristics for unmanaged forest stands). Although higher forest management intensity decreased vector abundance, the haemosporidian infections in the vectors increased, indicating a significant effect of forest management on disease dynamics.

DNA-aided identification of Culex mosquitoes (Diptera: Culicidae) reveals unexpected diversity in underground cavities in Austria

Subterranean cavities serve as resting places and hibernation shelters for mosquitoes. In Europe, members of the genus Culex are often the most abundant insects on cave walls. Culex pipiens L., the common house mosquito, exists in two physically very similar, yet genetically and ecologically distinct biotypes (or forms, 'f.'), namely Cx. pipiens f. pipiens and Cx. pipiens f. molestus. Autogeny and stenogamy of the latter form have been interpreted as adaptations to underground habitats. The epigean occurrence of the two biotypes and their hybrids was recently examined in Eastern Austria, but the hypogean distribution of the Cx. pipiens complex and morphologically similar non-members such as Cx. torrentium is unknown. Considering the key role of Culex mosquitoes in the epidemiology of certain zoonotic pathogens, the general paucity of data on species composition and relative abundance in subterranean shelters appears unfortunate.For a first pertinent investigation in Austria, we collected mosquitoes in four eastern federal states. Based on analyses of the ACE2 gene and the CQ11 microsatellite locus, 150 female and three male mosquitoes of the genus Culex, two females of the genus Culiseta and a single female of the genus Anopheles were determined to species level or below. In our catches, Cx. pipiens f. pipiens exceeded the apparent abundance of the purportedly cave-adapted Cx. pipiens f. molestus many times over. Records of Cx. hortensis and Cx. territans, two species rarely collected in Austria, lead us to infer that underground habitats host a higher diversity of culicine mosquitoes than previously thought.

Culicoides paolae and C. circumscriptus as potential vectors of avian haemosporidians in an arid ecosystem

BACKGROUND

Haemosporidians are the most important vector-borne parasites due to their cosmopolitan distribution and their wide range of hosts, including humans. Identification of their vectors is critical to highlight ecologically and epidemiologically relevant features such as host specificity or transmission routes. Biting midges of the genus Culicoides are considered the main vectors of Haemoproteus spp., yet important information on aspects such as vector feeding preferences or vector-host specificity involving haemosporidian parasites is frequently missing.

METHODS

We assessed the abundance of Culicoides circumscriptus and C. paolae and blood sources of the latter at the nests of cavity-nesting bird species (mainly the European roller Coracias garrulus) and in their surroundings. We also explored the prevalence and genetic diversity of avian haemosporidians in parous females of both species.

RESULTS

Both C. circumscriptus and C. paolae were abundant in the study area and common at European roller nests. Culicoides paolae had a diverse ornithophilic diet, feeding on at least seven bird species. Human DNA was also detected in the blood meal of some individuals. Four Haemoproteus lineages, including a new one reported here for the first time, were isolated from parous females of both biting midges.

CONCLUSIONS

Culicoides circumscriptus and C. paolae can play a locally important role in the transmission dynamics of Haemoproteus parasites in a community of cavity-nesting bird species in an arid ecosystem.

Vertical stratification of Culicoides biting midges at a Florida big game preserve

BACKGROUND

Many important vector arthropods are known to stratify vertically in forest environments, a phenomenon which has important implications for vector-borne disease transmission and vector control. Culicoides Latreille biting midges (Diptera: Ceratopogonidae) have been documented using the forest canopy; however, studies of this phenomenon are lacking for many Culicoides species found in great abundance in the state of Florida, USA, some of which have been implicated as suspected vectors of hemorrhagic diseases of white-tailed deer. The present study aimed to determine whether common Culicoides species in Florida stratify vertically and to determine whether strata used by midges corresponded to host use.

METHODS

Trapping was conducted at a big game preserve in Gadsden County, FL, USA. Over two summer field seasons in 2016 and 2017, CDC miniature light traps were set at two levels, one set at 1.37 m, designated as the ground trap, and a nearby trap in the forest canopy set at 6 m during 2016 and 9 m during 2017. Species abundance, physiological status, and blood-meal sources were analyzed and compared between trap heights.

RESULTS

Species abundances for C. haematopotus, C. stellifer and C. venustus were not significantly different between trap heights during the 2016 season; however, canopy traps were found to have significantly higher abundance of C. arboricola, C. biguttatus, C. debilipalpis, C. haematopotus, C. insignis and C. stellifer than ground traps in 2017. Greater numbers of blood-engorged midges were collected in the canopy compared with ground traps during both study years, and 98.6% and 98.7% of blood meals from canopy collected midges were taken from ground-dwelling mammals in 2016 and 2017, respectively.

CONCLUSIONS

Culicoides species in Florida, including species implicated as vectors of hemorrhagic disease viruses, are found in great abundance in the forest canopy. Many midges are feeding on host species that are known reservoirs of hemorrhagic disease and then moving into the forest canopy, which has implications for the calculation of vectorial capacity. These data contribute valuable ecological information on Culicoides species found in Florida and provide a framework for developing effective vector control strategies to target these species.

Spillover of avian haemosporidian parasites (Haemosporidia: Plasmodium) and death of captive psittacine species

CASE REPORT

During February 2014, a yellow-tailed black cockatoo (Calyptorhynchus funereus) and glossy black cockatoo (C. lathami) housed in aviaries on a property in Wamuran, Queensland, were submitted for postmortem. Histopathology and molecular diagnostics demonstrated the presence of Plasmodium sp. infection. The Plasmodium isolate identified has previously only been reported as infecting a healthy wild rufous fantail (Rhipidura rufifrons) in Australia.

CONCLUSION

To the authors' knowledge, these are the first reported cases of Plasmodium in Calyptorhynchus. We hypothesised that the maintenance of these two cockatoo species in ground level aviaries in a low-altitude geographic zone resulted in exposure of birds to mosquito vectors of endemic avian Plasmodium. Black cockatoos roost and forage in the mid to high canopy of forests in the wild, outside the likely spatiotemporal distribution of relevant haemosporidian vectors. It is therefore likely that these birds had immunological naivety and susceptibility to infection with Plasmodium circulating in wild passerines.

Host community heterogeneity and the expression of host specificity in avian haemosporidia in the Western Cape, South Africa

Similar patterns of parasite prevalence in animal communities may be driven by a range of different mechanisms. The influences of host heterogeneity and host-parasite interactions in host community assemblages are poorly understood. We sampled birds at 27 wetlands in South Africa to compare four hypotheses explaining how host community heterogeneity influences host specificity in avian haemosporidia communities: the host-neutral hypothesis, the super-spreader hypothesis, the host specialist hypothesis and the heterogeneity hypothesis. A total of 289 birds (29%) were infected with Plasmodium, Haemoproteus and/or Leucocytozoon lineages. Leucocytozoon was the most diverse and generalist parasite genus, and Plasmodium the most conservative. The host-neutral and host specialist hypotheses received the most support in explaining prevalence by lineage (Leucocytozoon) and genus (Plasmodium and Haemoproteus), respectively. We observed that haemosporidian prevalence was potentially amplified or reduced with variation in host and/or parasitic taxonomic levels of analysis. Our results show that Leucocytozoon host abundance and diversity was influential to parasite prevalence at varying taxonomic levels, particularly within heterogeneous host communities. Furthermore, we note that prevalent mechanisms of infection can potentially act as distinct roots for shaping communities of avian haemosporidia.

Evidence of exposure of laughing doves (Spilopelia senegalensis) to West Nile and Usutu viruses in southern Tunisian oases

It has previously been suggested that southern Tunisian oases may be suitable areas for the circulation of flaviviruses. In order to anticipate and prevent possible epidemiological spread of flaviviruses in humans and domestic animals, the ecology of their transmission in the oasis system needs to be better understood. Thus, the aim of this study was to assess the seroprevalence of anti-flavivirus antibodies in the laughing dove (Spilopelia senegalensis), an abundant resident bird in Tunisian oases. Anti-flavivirus antibodies were detected in 17% of sampled doves. Ten per cent of the total tested doves were West Nile virus (WNV) seropositive and 4% were Usutu virus (USUV) seropositive, which provides the first evidence of USUV circulation in Tunisian birds. We also found that the occurrence probability of anti-flavivirus antibodies in dove plasma increased with decreasing distance to coast, suggesting that doves inhabiting coastal oases were more exposed to flaviviruses compared with those inhabiting inland oases. We also found significantly higher antibody occurrence probability in adult doves compared with young doves, which underlines the effect of exposure time. Overall, our results suggest that the laughing dove may be used for WNV and USUV surveillance in southern Tunisia. They also stress the need for investigations combining data on birds and mosquitoes to better understand the ecological factors governing the circulation of flaviviruses in this area.

Survey of Haemosporidian Parasites in Resident and Migrant Game Birds of Illinois

Haemosporidian parasites are globally distributed in avian species, and are capable of leading to decreased reproductive success, weakness, and mortality. Bird conservation groups and organizations concerned with the health and immunological status of avian populations are interested in haemosporidian parasites that affect reproduction and population growth. Haemosporidian infection data are not yet always available for some avian species in specific regions. These data provide the starting points for researchers to evaluate geographical and temporal changes in the patterns of infection and prevalence across populations. We examined haemoparasite infections in four game bird species commonly hunted in Illinois. We calculated prevalence, mean intensity, median intensity, and mean abundance of haemosporidians, and evaluated the relation of these infection measures associated with age and sex of the avian hosts. Game species sampled (N = 237) included migrants such as mourning doves Zenaida macroura, wood ducks Aix sponsa, and Canada geese Branta canadensis, as well as resident birds such as wild turkeys Meleagris gallopavo. We identified only Haemoproteus, Plasmodium, and Leucocytozoon species. Haemoproteus was the most prevalent haemosporidian (46/237), followed by Plasmodium (11/237). Furthermore, Haemoproteus was the most persistent haemosporidian, as it was the only parasite genera that we found in all four avian species. We found coinfections in 55% of turkeys, but found no significant correlations between the genera of haemosporidinan coinfections and a host species. Moreover, no significant differences in the proportion of infected individuals (prevalence) and haemosporidian quantities (levels of intensity and abundance) were related to biotic factors such as age and sex of the host. However, parasite aggregation (distribution of parasites among hosts) was affected by age, as adult turkeys and juvenile doves showed the highest aggregation index (Poulin's index of discrepancy) for Haemoproteus spp. This study reveals patterns of infection and parasite aggregations that vary widely among different game bird species and provides baseline data on avian haemosporidians that, to the best of our knowledge, is not currently available in the state of Illinois for these avian species. Finally, wildlife biologists can use these patterns for management of landscape or host species to support conservation efforts.

Integrating phylogenetic and ecological distances reveals new insights into parasite host specificity

The range of hosts a pathogen infects (host specificity) is a key element of disease risk that may be influenced by both shared phylogenetic history and shared ecological attributes of prospective hosts. Phylospecificity indices quantify host specificity in terms of host relatedness, but can fail to capture ecological attributes that increase susceptibility. For instance, similarity in habitat niche may expose phylogenetically unrelated host species to similar pathogen assemblages. Using a recently proposed method that integrates multiple distances, we assess the relative contributions of host phylogenetic and functional distances to pathogen host specificity (functional-phylogenetic host specificity). We apply this index to a data set of avian malaria parasite (Plasmodium and Haemoproteus spp.) infections from Melanesian birds to show that multihost parasites generally use hosts that are closely related, not hosts with similar habitat niches. We also show that host community phylogenetic ß-diversity (Pßd) predicts parasite Pßd and that individual host species carry phylogenetically clustered Haemoproteus parasite assemblages. Our findings were robust to phylogenetic uncertainty, and suggest that phylogenetic ancestry of both hosts and parasites plays important roles in driving avian malaria host specificity and community assembly. However, restricting host specificity analyses to either recent or historical timescales identified notable exceptions, including a 'habitat specialist' parasite that infects a diversity of unrelated host species with similar habitat niches. This work highlights that integrating ecological and phylogenetic distances provides a powerful approach to better understand drivers of pathogen host specificity and community assembly.

Co-infections of haemosporidian and trypanosome parasites in a North American songbird

Hosts frequently harbour multiple parasite infections, yet patterns of parasite co-occurrence are poorly documented in nature. In this study, we asked whether two common avian blood parasites, one haemosporidian and one trypanosome, affect each other's occurrence in individuals of a single host species. We used molecular genotyping to survey protozoan parasites in the peripheral blood of yellow-breasted chats (Aves: Passeriformes [Parulidae]: Icteria virens) from the Ozarks of Southern Missouri. We also determined whether single and co-infections differently influence white blood cell and polychromatic erythrocyte counts, the latter being a measure of regenerative anaemia. We found a positive association between the haemosporidian and trypanosome parasites, such that infection by one increases the probability that an individual host is infected by the other. Adult individuals were more likely than juveniles to exhibit haemosporidian infection, but co-infections and single trypanosome infections were not age-related. We found evidence of pathogenicity of trypanosomes in that infected individuals exhibited similar levels of regenerative anaemia as birds infected with haemosporidian parasites of the genus Plasmodium. Counts of white blood cells did not differ with respect to infection status.

Culicoides Species Communities Associated with Wild Ruminant Ecosystems in Spain: Tracking the Way to Determine Potential Bridge Vectors for Arboviruses

The genus Culicoides Latreille 1809 is a well-known vector for protozoa, filarial worms and, above all, numerous viruses. The Bluetongue virus (BTV) and the recently emerged Schmallenberg virus (SBV) are responsible for important infectious, non-contagious, insect-borne viral diseases found in domestic ruminants and transmitted by Culicoides spp. Both of these diseases have been detected in wild ruminants, but their role as reservoirs during the vector-free season still remains relatively unknown. In fact, we tend to ignore the possibility of wild ruminants acting as a source of disease (BTV, SBV) and permitting its reintroduction to domestic ruminants during the following vector season. In this context, a knowledge of the composition of the Culicoides species communities that inhabit areas where there are wild ruminants is of major importance as the presence of a vector species is a prerequisite for disease transmission. In this study, samplings were conducted in areas inhabited by different wild ruminant species; samples were taken in both 2009 and 2010, on a monthly basis, during the peak season for midge activity (in summer and autumn). A total of 102,693 specimens of 40 different species of the genus Culicoides were trapped; these included major BTV and SBV vector species. The most abundant vector species were C. imicola and species of the Obsoletus group, which represented 15% and 11% of total numbers of specimens, respectively. At the local scale, the presence of major BTV and SBV vector species in areas with wild ruminants coincided with that of the nearest sentinel farms included in the Spanish Bluetongue Entomological Surveillance Programme, although their relative abundance varied. The data suggest that such species do not exhibit strong host specificity towards either domestic or wild ruminants and that they could consequently play a prominent role as bridge vectors for different pathogens between both types of ruminants. This finding would support the hypothesis that wild ruminants could act as reservoirs for such pathogens, and subsequently be involved in the reintroduction of disease to livestock on neighbouring farms.

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.

Host group formation decreases exposure to vector-borne disease: a field experiment in a 'hotspot' of West Nile virus transmission

Animals can decrease their individual risk of predation by forming groups. The encounter-dilution hypothesis extends the potential benefits of gregariousness to biting insects and vector-borne disease by predicting that the per capita number of insect bites should decrease within larger host groups. Although vector-borne diseases are common and can exert strong selective pressures on hosts, there have been few tests of the encounter-dilution effect in natural systems. We conducted an experimental test of the encounter-dilution hypothesis using the American robin (Turdus migratorius), a common host species for the West Nile virus (WNV), a mosquito-borne pathogen. By using sentinel hosts (house sparrows, Passer domesticus) caged in naturally occurring communal roosts in the suburbs of Chicago, we assessed sentinel host risk of WNV exposure inside and outside of roosts. We also estimated per capita host exposure to infected vectors inside roosts and outside of roosts. Sentinel birds caged inside roosts seroconverted to WNV more slowly than those outside of roosts, suggesting that social groups decrease per capita exposure to infected mosquitoes. These results therefore support the encounter-dilution hypothesis in a vector-borne disease system. Our results suggest that disease-related selective pressures on sociality may depend on the mode of disease transmission.

Fur or feather? Feeding preferences of species of Culicoides biting midges in Europe

Understanding the feeding preferences of haematophagous insects is critical to depicting the amplification and transmission networks of pathogens and identifying key vector species for surveillance programs. In the case of species from genus Culicoides, many of which are important vectors of pathogens causing animal diseases, information from molecular studies on the feeding habits of females is expanding but still limited for a significant fraction of competent vectors of Culicoides-borne pathogens. In spite of these limitations, recent studies highlight that most Culicoides species are able to feed on several vertebrate species, but present clear preferences for mammals or birds.

Mixed species flock, nest height, and elevation partially explain avian haemoparasite prevalence in Colombia

The high avian biodiversity present in the Neotropical region offers a great opportunity to explore the ecology of host-parasite relationships. We present a survey of avian haemoparasites in a megadiverse country and explore how parasite prevalences are related to physical and ecological host characteristics. Using light microscopy, we documented the presence of haemoparasites in over 2000 individuals belonging to 246 species of wild birds, from nine localities and several ecosystems of Colombia. We analysed the prevalence of six avian haemoparasite taxa in relation to elevation and the following host traits: nest height, nest type, foraging strata, primary diet, sociality, migratory behaviour, and participation in mixed species flocks. Our analyses indicate significant associations between both mixed species flocks and nest height and Haemoproteus and Leucocytozoon prevalence. The prevalence of Leucocytozoon increased with elevation, whereas the prevalence of Trypanosoma and microfilariae decreased. Plasmodium and Haemoproteus prevalence did not vary significantly with elevation; in fact, both parasites were found up to 3300m above sea level. The distribution of parasite prevalence across the phylogeny of bird species included in this study showed little host phylogenetic signal indicating that infection rates in this system are evolutionarily labile. Vector distribution as well as the biology of transmission and the maintenance of populations of avian haemoparasites deserve more detailed study in this system.

Mosquito communities with trap height and urban-rural gradient in Adelaide, South Australia: implications for disease vector surveillance

Understanding the factors influencing mosquito distribution is important for effective surveillance and control of nuisance and disease vector mosquitoes. The goal of this study was to determine how trap height and distance to the city center influenced the abundance and species of mosquitoes collected in Adelaide, South Australia. Mosquito communities were sampled at two heights (<2 m and ~10 m) along an urban-rural gradient. A total of 5,133 mosquitoes was identified over 176 trap nights. Aedes notoscriptus, Ae. vigilax, and Culex molestus were all more abundant in lower traps while Cx. quinquefasciatus (an ornithophilic species) was found to be more abundant in high traps. Distance to city center correlated strongly with the abundance of Ae. vigilax, Ae. camptorhynchus, Cx. globocoxitus, and Cx. molestus, all of which were most common at the sites farthest from the city and closest to the saltmarsh. Overall, the important disease vectors in South Australia (Ae. vigilax, Ae. camptorhynchus, Ae. notoscriptus, and Cx. annulirostris) were more abundant in low traps farthest from the city and closest to the saltmarsh. The current mosquito surveillance practice of setting traps within two meters of the ground is effective for sampling populations of the important disease vector species in South Australia.

Feeding behavior and spatial distribution of Culex mosquitoes (Diptera: Culicidae) in wetland areas of the Czech Republic

Mosquito feeding behavior determines the degree of vector-host contact and may have a serious impact on the risk of pathogen transmission, including that of the West Nile virus (WNV). To measure the role of Culex mosquitoes as WNV vectors, host-seeking females were collected using animal-baited traps containing live birds (quail) or mammals (rabbits) and CO2-baited Center for Disease Control and Prevention traps placed in several wetland areas in the Czech Republic. Culex pipiens (L.) and Culex modestus (F.) were the most frequently collected species. Although Cx. modestus did not distinguish between baits, Cx. pipiens was collected significantly more frequently in bird-baited traps. Based on mitochondrial DNA analysis of bloodmeals from engorged females collected by CO2-baited traps situated within reed beds, a diverse group of birds were the predominant hosts (93.7%), followed by mammals (4.2%) including humans, and amphibians (2.1%). Among birds, Anseriformes were fed upon most frequently by Cx. modestus, whereas Cx. pipiens fed most frequently on Passeriformes. To measure the infection risk and confirm the distribution of mosquito species in various biotopes, transects of CO2-baited CDC traps were operated from wetland reed beds into upland vegetated areas. Even though both Culex species occurred in all biotopes sampled and frequently dispersed hundreds of meters away from fishpond shore vegetation, the spatial distribution of Cx. modestus was significantly associated with reed beds at wetlands. The first detection of WNV (subtype RabV) in Cx. modestus in Bohemia and confirmation of WNV presence in Cx. pipiens in Moravia together with observed feeding behavior supports the presumed role of both Culex species in the avian-to-avian enzootic WNV cycle and in avian-to-mammal transmission in the Czech Republic.

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.

Spatial, temporal, molecular, and intraspecific differences of haemoparasite infection and relevant selected physiological parameters of wild birds in Georgia, USA

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Variable prevalences of different haemoparasite species noted among passerine hosts.

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Different foraging guilds associated with different haemoparasite infections.

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Prevalence of Haemoproteus, Plasmodium, and Trypanosoma higher in breeding season.

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PCV differences noted between bird species but no effect of haemoparasites on PCV or polychromasia.

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Novel haplotypes detected and new geographic and host associations noted for seven haplotypes.

The prevalence of five avian haemoparasite groups was examined for effects on health and associations with extrinsic factors. Overall, 786 samples were examined from six sites in two Georgia (USA) watersheds, during breeding and non-breeding periods in 2010 and 2011. Among the four most commonly infected species, Haemoproteus prevalence was significantly higher in Northern Cardinals (Cardinalis cardinalis) compared to Indigo Buntings (Passerina cyanea) and Tufted Titmice (Baeolophus bicolor) while prevalence in White-throated Sparrows (Zonotrichia albicollis) was significantly higher than in Indigo Buntings. Higher prevalence of Plasmodium was noted in Tufted Titmice and Northern Cardinals. While Leucocytozoon prevalence was highest in White-throated Sparrows, Trypanosoma prevalence was highest in Tufted Titmice. Interesting differences in infection probabilities were noted between foraging guilds with Haemoproteus associated with low-middle level strata and birds in the middle-upper strata were more likely to be infected with Plasmodium and Trypanosoma. In contrast, ground-foraging birds were more likely to be infected with Leucocytozoon. Breeding season was correlated with higher polychromasia counts and higher prevalence of Haemoproteus, Plasmodium and Trypanosoma. In addition, prevalence of infection with certain haemoparasite genera and packed cell volume (PCV) were different among host species. Body mass index was inversely correlated with prevalence of microfilaria infection but positively related to Haemoproteus infection. However, we found no relationship between PCV or polychromasia levels with haemoparasite infection. Molecular characterization of 61 samples revealed 19 unique Haemoproteus (n = 7) and Plasmodium (n = 12) haplotypes with numerous new host records. No differences were noted in haplotype diversity among birds with different migratory behaviors or foraging heights, thus additional studies are needed that incorporate molecular analysis, host biology, and vector biology into comprehensive models on parasite ecology. Detailed morphological examination of these parasites is also necessary to determine if closely related haplotypes represent single species or morphologically distinct, but closely related, haplotypes.

Comparative study of antennal and maxillary palp olfactory sensilla of female biting midges (Diptera: Ceratopogonidae: Culicoides) in the context of host preference and phylogeny

Culicoides biting midges (Diptera Ceratopogonidae) are vectors of disease, including bluetongue and African horse sickness. Host preference of these insects is primarily regulated by olfactory cues, detected by olfactory sensilla on the antennae and maxillary palps. In this study, we analyzed the sensillum repertoire of biting midge species with known host preferences. Five different morphological sensillum types, sensilla trichodea, s. chaetica, s. ampullacea, s. coeloconica, and grooved peg sensilla, were present on the antennae of all species. In addition sensilla basiconica were present on the maxillary palps. We found that the numbers of short blunt-tipped s. trichodea, s. coeloconica, and s. basiconica are significantly higher in the ornithophilic Culicoides festivipennis (Kieffer) compared with the mammalophilic Culicoides obsoletus (Meigen) and Culicoides chiopterus (Meigen). In contrast, we found that the mammalophilic Culicoides pulicaris (L.) and the opportunistic Culicoides punctatus (Meigen) have intermediate numbers of these sensillum types. Comparison with available data from other species strongly suggests that these differences in the number of specific sensillum types, in general, are a reflection of host preference and not of phylogeny. We discuss the putative function of the individual sensillum types in relation to host volatile detection.

Molecular identification of bloodmeals and species composition in Culicoides biting midges

Investigations of host preferences in haematophagous insects, including Culicoides biting midges (Diptera: Ceratopogonidae), are critical in order to assess transmission routes of vector-borne diseases. In this study, we collected and morphologically identified 164 blood-engorged Culicoides females caught in both light traps and permanent 12-m high suction traps during 2008-2010 in Sweden. Molecular analysis of the mitochondrial cytochrome c oxidase subunit I (COI) gene in the biting midges was performed to verify species classification, discern phylogenetic relationships and uncover possible cryptic species. Bloodmeal analysis using universal vertebrate cytochrome b primers revealed a clear distinction in host selection between mammalophilic and ornithophilic Culicoides species. Host sequences found matches in horse (n = 59), sheep (n = 39), cattle (n = 26), Eurasian elk (n = 1) and 10 different bird species (n = 18). We identified 15 Culicoides species previously recorded in Scandinavia and four additional species haplotypes that were distinctly different from the described species. All ornithophilic individuals (n = 23) were caught exclusively in the suction traps, as were, interestingly, almost all mammalophilic species (n = 41), indicating that many biting midge species may be able to cover long distances after completing a bloodmeal. These results add new information on the composition of Culicoides species and their host preferences and their potential long-distance dispersal while blood-engorged.

Avian haemosporidians in haematophagous insects in the Czech Republic

The degree to which avian haemosporidian parasites can exploit different vectors as a definitive host has ecological implications for their transmission and biogeography. Studies targeting haemosporidian parasites using precise molecular detection methods are almost lacking in Central Europe, however. Here, we utilized PCR-based molecular methods to detect avian haemosporidians in insect vectors in the Czech Republic. Nine lineages of parasites belonging to three genera, Haemoproteus, Plasmodium, and Leucocytozoon, were detected in pooled samples of insect individuals, of which three lineages had not yet been discovered in previous studies. All three Leucocytozoon lineages were found exclusively in black flies, while five Haemoproteus lineages were found in biting midges. The most abundant insect species Culicoides kibunensis harbored three Haemoproteus lineages, and the second-most numerous species Culicoides segnis even four. The positive mosquitoes of Culex pipiens complex hosted two parasite lineages, one Plasmodium and one Haemoproteus, the latter of which, however, could suggest the aberrant development of this parasite in an unusual invertebrate host. The co-occurrence of Haemoproteus ROFI1 and TURDUS2 lineages in both insects and birds at the same study plot suggests a transmission of these lineages during breeding season of birds.

Identity and diversity of blood meal hosts of biting midges (Diptera: Ceratopogonidae: Culicoides Latreille) in Denmark

BACKGROUND

Host preference studies in haematophagous insects e.g. Culicoides biting midges are pivotal to assess transmission routes of vector-borne diseases and critical for the development of veterinary contingency plans to identify which species should be included due to their risk potential. Species of Culicoides have been found in almost all parts of the world and known to live in a variety of habitats. Several parasites and viruses are transmitted by Culicoides biting midges including Bluetongue virus and Schmallenberg virus. The aim of the present study was to determine the identity and diversity of blood meals taken from vertebrate hosts in wild-caught Culicoides biting midges near livestock farms.

METHODS

Biting midges were collected at weekly intervals for 20 weeks from May to October 2009 using light traps at four collection sites on the island Sealand, Denmark. Blood-fed female biting midges were sorted and head and wings were removed for morphological species identification. The thoraxes and abdomens including the blood meals of the individual females were subsequently subjected to DNA isolation. The molecular marker cytochrome oxidase I (COI barcode) was applied to identify the species of the collected biting midges (GenBank accessions JQ683259-JQ683374). The blood meals were first screened with a species-specific cytochrome b primer pair for cow and if negative with a universal cytochrome b primer pair followed by sequencing to identify mammal or avian blood meal hosts.

RESULTS

Twenty-four species of biting midges were identified from the four study sites. A total of 111,356 Culicoides biting midges were collected, of which 2,164 were blood-fed. Specimens of twenty species were identified with blood in their abdomens. Blood meal sources were successfully identified by DNA sequencing from 242 (76%) out of 320 Culicoides specimens. Eight species of mammals and seven species of birds were identified as blood meal hosts. The most common host species was the cow, which constituted 77% of the identified blood meals. The second most numerous host species was the common wood pigeon, which constituted 6% of the identified blood meals.

CONCLUSIONS

Our results suggest that some Culicoides species are opportunistic and readily feed on a variety of mammals and birds, while others seems to be strictly mammalophilic or ornithophilic. Based on their number, dispersal potential and blood feeding behaviour, we conclude that Culicoides biting midges are potential vectors for many pathogens not yet introduced to Denmark.

High prevalence and lineage diversity of avian malaria in wild populations of great tits (Parus major) and mosquitoes (Culex pipiens)

Avian malaria studies have taken a prominent place in different aspects of evolutionary ecology. Despite a recent interest in the role of vectors within the complex interaction system of the malaria parasite, they have largely been ignored in most epidemiological studies. Epidemiology of the disease is however strongly related to the vector's ecology and behaviour, and there is a need for basic investigations to obtain a better picture of the natural associations between Plasmodium lineages, vector species and bird hosts.

The aim of the present study was to identify the mosquito species involved in the transmission of the haemosporidian parasites Plasmodium spp. in two wild populations of breeding great tits (Parus major) in western Switzerland. Additionally, we compared Plasmodium lineages, based on mitochondrial DNA cytochrome b sequences, between the vertebrate and dipteran hosts, and evaluated the prevalence of the parasite in the mosquito populations. Plasmodium spp. were detected in Culex pipiens only, with an overall 6.6% prevalence. Among the six cytochrome b lineages of Plasmodium identified in the mosquitoes, three were also present in great tits. The results provide evidence for the first time that C. pipiens can act as a natural vector of avian malaria in Europe and yield baseline data for future research on the epidemiology of avian malaria in European countries.

Biodiversity of avian trypanosomes

We have studied the biodiversity of trypanosomes from birds and bloodsucking Diptera on a large number of isolates. We used two molecular approaches, random amplification of polymorphic DNA (RAPD) method, and sequence analysis of the small subunit ribosomal RNA (SSU rRNA) gene. RAPD method divided the isolates into 11 separate lineages. Phylogenetic analysis of the SSU rRNA gene was congruent with the RAPD. Morphometric analysis of kinetoplast width and cell length was in agreement with molecular data. Avian trypanosomes appeared polyphyletic on SSU rDNA tree; thus, they do not represent a taxonomic group. We propose that all lineages recovered by SSU analysis probably represent distinct species of avian trypanosomes. We discuss possible transmission ways and geographical distribution of new avian trypanosome lineages. Finally, we recommend methods that should be used for species determination of avian trypanosomes.

Trypanosoma culicavium sp. nov., an avian trypanosome transmitted by Culex mosquitoes

A novel avian trypanosome, Trypanosoma culicavium sp. nov., isolated from Culex mosquitoes, is described on the basis of naturally and experimentally infected vectors and bird hosts, localization in the vector, morphological characters and molecular data. This study provides the first comprehensive description of a trypanosome species transmitted by mosquitoes, in which parasites form plugs and rosettes on the stomodeal valve. Trypanosomes occurred as long epimastigotes and short trypomastigotes in vectors and culture and as long trypomastigotes in birds. Transmission of parasites to bird hosts was achieved exclusively by ingestion of experimentally infected Culex mosquito females by canaries (Serinus canaria), but not by Japanese quails (Coturnix japonica), nor by the bite of infected vectors, nor by ingestion of parasites from laboratory cultures. Transmission experiments and the identity of isolates from collared flycatchers (Ficedula albicollis) and Culex mosquitoes suggests that the natural hosts of T. culicavium are insectivorous songbirds (Passeriformes). Phylogenetic analyses of small-subunit rRNA and glycosomal glyceraldehyde-3-phosphate dehydrogenase gene sequences demonstrated that T. culicavium sp. nov. is more related to Trypanosoma corvi than to other avian trypanosomes (e.g. Trypanosoma avium and Trypanosoma bennetti).