Genetic diversity of Culicoides species within the Pulicaris complex (Diptera: Ceratopogonidae) in Turkey inferred from mitochondrial COI gene sequences

The investigation of Culicoides (Diptera: Ceratopogonidae) species and Bluetongue virus and Schmallenberg virus in Northwest Türkiye

Culicoides biting midges (Diptera: Ceratopogonidae) act as mechanical and biological vectors of arboviruses and are crucial in the global spread of these viruses. This study investigated the diversity of distribution of Culicoides species and the presence of Bluetongue virus (BTV) and Schmallenberg virus (SBV) in Tekirdağ province in Northwest Türkiye. The fourteen Culicoides species, such as Culicoides newsteadi, Culicoides schultzei, Culicoides nubeculosus comp., Culicoides punctatus, Culicoides circumscriptus, Culicoides obsoletus comp., Culicoides gejgelensis, Culicoides festivipennis, Culicoides longipennis, Culicoides spp., Culicoides pulicaris, Culicoides picturatus, Culicoides odiatus, Culicoides kurensis, and Culicoides flavipulicaris, were detected. Culicoides newsteadi, C. odiatus, and C. pulicaris were the most abundant species. Phylogenetic analyses of Culicoides species' ITS-1 gene region were performed. A pool of C. festivipennis was positive for SBV RNA, while the BTV genomic materials was not found in the qPCR analysis. This is the first report of the presence/detection of SBV in Culicoides species in Türkiye. The survey of bioecological and epizootiological aspects of vector species is essential in implementing effective control measures for arboviral infections.

Assigning Culicoides larvae to species using DNA barcoding of adult females and phylogenetic associations

Background

Orbivirus-induced hemorrhagic diseases cause high mortality in wild and captive white-tailed deer in North America. The role of different Culicoides species in Orbivirus transmission outside of areas of intensive animal production has not been established. At our study location, bluetongue virus (BTV) RNA-positive female Culicoides debilipalpis pools have been detected annually since 2012 when BTV transmission was noted in a captive deer herd. Identifying specific larval habitats of suspected vectors at active transmission sites is crucial both for identifying the source of the vectors and for subsequently planning intervention actions. Since C. debilipalpis larvae are known to develop in tree holes, this study was designed to use DNA barcoding to identify larvae collected from tree holes.

Methods

Adult female Culicoides were collected using light or emergence traps and morphologically identified to 11 species. Culicoides sonorensis were also obtained from a laboratory colony. Substrate was collected from tree holes and flooded with water to harvest floating larvae. Total DNA from three to seven adult females per species and 19 larvae was extracted. Two loci of the nuclear 18S ribosomal RNA (rRNA) gene, one locus each of the mitochondrial cytochrome oxidase subunit I (COI) gene and the nuclear 28S rRNA gene were amplified using loci-specific primers.

Results

All 61 adults were sequenced at each of the four loci under study. Since no single locus delineated all putative species and the COI locus yielded unreliable pseudogenes for two individuals of C. arboricola, sequences of all four loci were concatenated to maximize species separation and allow for larval association with identified adults. Sixteen larvae were clearly assigned to species based on DNA barcoding and phylogenetic results. Multiple larvae were assigned to each of the C. debilipalpis clade, the C. villosipennis clade, the C. arboricola clade and the C. nanus clade.

Conclusions

Of the approximately 62 species described in the southeast USA, 21 have now been barcoded and sequences are publicly available. In this study, we constructed a database composed of species-specific sequences of adult Culicoides and then identified larvae to species by matching their corresponding sequences with adults. Since Culicoides larvae are difficult to identify, using DNA barcoding to facilitate larval habitat surveys can be a valuable tool.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05479-1.

Development of microsatellite markers for population genetics of biting midges and a potential tool for species identification of Culicoides sonorensis Wirth & Jones

Background

Proper vector surveillance relies on the ability to identify species of interest accurately and efficiently, though this can be difficult in groups containing cryptic species. Culicoides Latreille is a genus of small biting flies responsible for the transmission of numerous pathogens to a multitude of vertebrates. Regarding pathogen transmission, the C. variipennis species complex is of particular interest in North America. Of the six species within this group, only C. sonorensis Wirth & Jones is a proven vector of bluetongue virus and epizootic hemorrhagic disease virus. Unfortunately, subtle morphological differences, cryptic species, and mitonuclear discordance make species identification in the C. variipennis complex challenging. Recently, single-nucleotide polymorphism (SNP) analysis enabled discrimination between the species of this group; however, this demanding approach is not practical for vector surveillance.

Methods

The aim of the current study was to develop a reliable and affordable way of distinguishing between the species within the C. variipennis complex, especially C. sonorensis. Twenty-five putative microsatellite markers were identified using the C. sonorensis genome and tested for amplification within five species of the C. variipennis complex. Machine learning was then used to determine which markers best explain the genetic differentiation between species. This led to the development of a subset of four and seven markers, which were also tested for species differentiation.

Results

A total of 21 microsatellite markers were successfully amplified in the species tested. Clustering analyses of all of these markers recovered the same species-level identification as the previous SNP data. Additionally, the subset of seven markers was equally capable of accurately distinguishing between the members of the C. variipennis complex as the 21 microsatellite markers. Finally, one microsatellite marker (C508) was found to be species-specific, only amplifying in the vector species C. sonorensis among the samples tested.

Conclusions

These microsatellites provide an affordable way to distinguish between the sibling species of the C. variipennis complex and could lead to a better understanding of the species dynamics within this group. Additionally, after further testing, marker C508 may allow for the identification of C. sonorensis with a single-tube assay, potentially providing a powerful new tool for vector surveillance in North America.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05189-8.

A Review of the Vector Status of North American Culicoides (Diptera: Ceratopogonidae) for Bluetongue Virus, Epizootic Hemorrhagic Disease Virus, and Other Arboviruses of Concern

Purpose of Review

Culicoides biting midges transmit several pathogens of veterinary importance in North America, but the vector status of many midge species is unresolved. Additionally, the available evidence of vector competence in these species is scattered and variable. The purpose of this review is to summarize current knowledge on confirmed and putative North American Culicoides arbovirus vectors.

Recent Findings

While the vector status of Culicoides sonorensis (EHDV, BTV, VSV) and Culicoides insignis (BTV) are well established, several other potential vector species have been recently identified. Frequently, these species are implicated based primarily on host-feeding, abundance, and/or detection of arboviruses from field-collected insects, and often lack laboratory infection and transmission data necessary to fully confirm their vector status. Recent genetic studies have also indicated that some wide-ranging species likely represent several cryptic species, further complicating our understanding of their vector status.

Summary

In most cases, laboratory evidence needed to fully understand the vector status of the putative Culicoides vectors is absent; however, it appears that several species are likely contributing to the transmission of arboviruses in North America.

Updated checklist of Culicoides Latreille (Diptera: Ceratopogonidae) of Turkey with ten new records

We investigated the Culicoides fauna in Turkey during the years 2016-2019 in the process of entomological surveillance for arboviral diseases. The entomological survey was conducted at 104 sampling stations in 51 provinces in Turkey during four consecutive years. There were approximately 450,000 specimens and 59 identified species collected during the surveillance. Ten species were newly recorded for Turkey: C. chiopterus, C. grisescens, C. paradoxalis, C. santonicus, C. poperinghensis, C. sergenti, C. tbilisicus, C. comosioculatus, C. haranti, and C. univittatus. Identification of C. chiopterus and C. grisescens was confirmed using species-specific PCR and DNA sequencing. With our recent findings, previous data were critically reviewed and updated, and the number of Culicoides species has been increased to 71 for Turkey. The presence of C. chiopterus has particular importance due to its potential vector status for bluetongue virus (BTV) and Schmallenberg virus (SBV). This study presents result of the first large-scale integrated faunistic survey on Culicoides species in Turkey.

Prevalence and genetic diversity of avian haemosporidian parasites at an intersection point of bird migration routes: Sultan Marshes National Park, Turkey

Avian haemosporidians (Haemosporida) represent a globally distributed, species-rich multiparasite-multihost host-parasite system. Each year, many of these parasite lineages are carried between temperate and tropical regions by migratory birds. While several factors can limit the transmission of avian haemosporidians to new areas, recent studies have shown that some abundant parasites can sometimes disperse and be transmitted in new areas to become emerging infectious diseases. In this study, we investigated the prevalence and diversity of avian haemosporidian parasites in Sultan Marshes National Park (SMNP), a major stopover site in the eastern Mediterranean flyway, and we evaluated the potential for avian haemosporidians in SMNP to be transmitted to areas outside of their known distributions. We sampled a total of 565 migratory and resident birds belonging to 39 species and 23 families. We applied both molecular and microscopic methods to detect and identify avian haemosporidian infections and also quantified the frequency of potential abortive infections. We identified a total of 52 different mitochondrial cytochrome b (cyt b) parasite lineages belonging to the genera Plasmodium (N = 12), Haemoproteus (N = 31), and Leucocytozoon (N = 9) in 193 (34.2%) infected birds. Ten of the lineages were reported for the first time. Our findings show that numerous parasite lineages are actively transmitted among resident bird species of SMNP. Our findings also revealed new parasite-host interactions while considering the role of possible abortive infections. The relatively high frequency of presumed abortive infections suggests that analyses of datasets generated only by PCR-based methods should be interpreted with caution. We also compared the prevalence and distribution of avian haemosporidian infections in both resident and migratory bird species and showed that haemosporidian prevalence was related to bird migratory behavior. The results of this study contribute to a better understanding of the ecological and genetic adaptations associated with changes in transmission areas of avian haemosporidian parasites.

Barcoding of the Genus Culicoides (Diptera: Ceratopogonidae) in Austria-An Update of the Species Inventory Including the First Records of Three Species in Austria

Ceratopogonidae are small nematoceran Diptera with a worldwide distribution, consisting of more than 5400 described species, divided into 125 genera. The genus Culicoides is known to comprise hematophagous vectors of medical and veterinary importance. Diseases transmitted by Culicoides spp. Such as African horse sickness virus, Bluetongue virus, equine encephalitis virus (Reoviridae) and Schmallenberg virus (Bunyaviridae) affect large parts of Europe and are strongly linked to the spread and abundance of its vectors. However, Culicoides surveillance measures are not implemented regularly nor in the whole of Austria. In this study, 142 morphologically identified individuals were chosen for molecular analyses (barcoding) of the mitochondrial cytochrome c oxidase subunit I gene (mt COI). Molecular analyses mostly supported previous morphologic identification. Mismatches between results of molecular and morphologic analysis revealed three new Culicoides species in Austria, Culicoidesgornostaevae Mirzaeva, 1984, which is a member of the Obsoletus group, C. griseidorsum Kieffer, 1918 and C. pallidicornis Kieffer, 1919 as well as possible cryptic species. We present here the first Austrian barcodes of the mt COI region of 26 Culicoides species and conclude that barcoding is a reliable tool with which to support morphologic analysis, especially with regard to the difficult to identify females of the medically and economically important genus Culicoides.