Nestling sex and behaviour determine the host preference of insect vectors in avian nests.

Sexual differences in pathogen prevalence in wildlife often arise from varying susceptibility influenced by factors such as sex hormones and exposure to pathogens. In the case of vector-borne pathogens, host selection by insect vectors determines the exposure of hosts to infections, largely affecting the transmission of these infectious diseases. We identify the blood-feeding patterns of insect vectors in Blue Tit (Cyanistes caeruleus) nestlings in a 3-year study. Blood from both nestlings and insect vectors (Culicoides spp. and Simuliidae) captured inside nest-boxes were used to molecularly determine the sex of the host. We then compared the sex-ratios of the nestlings that had been bitten and those of the complete brood in each nest. We found that males were bitten more frequently than females in 2021, when males weighed less in comparison to other years. Additionally, we molecularly identified bitten nestlings individually by genotyping the DNA of blood obtained from both, the vector's abdomen and nestlings of each brood in 2022. Nestlings more frequently bitten by vectors were males, weighed less and were closest to the nest entrance. To our knowledge this is the first study identifying the nestling selection by insect vectors in bird nests under natural conditions. These results contribute to understanding the mechanisms of host selection by insect vectors, shedding light on pathogen transmission and offering insights into the observed sex-biased infections in wildlife populations.

Ratio changes in blood-feeding and voltinism in black flies (Diptera: Simuliidae) over a latitudinal gradient in North America north of Mexico.

We explored how the ratio of blood-feeding behaviour-nonfeeding, bird feeding (ornithophily) and mammal feeding (mammalophily)-and voltinism (univoltine and multivoltine) vary over a latitudinal gradient from Alaska to Florida. These two fixed species traits were divided into five mutually exclusive combinations of trait states-nonfeeding/univoltine, ornithophilic/univoltine, mammalophilic/univoltine, ornithophilic/multivoltine and mammalophilic/multivoltine-within each of three datasets (north, east and west). We found a significant association between location (north, east and west) and trait state, which was driven by the large percentage of nonfeeding females in the north. When this trait state was removed, no significant differences were found for the remaining trait states and locations. Although the distribution of trait states did not differ between east and west datasets, the distribution with relation to 1° changes in latitude within each of these datasets showed distinct differences. In the east, both ornithophilic/univoltine and mammalophilic/univoltine species significantly increased with latitude, in proportion to the total species present. In contrast, the proportion of mammalophilic/multivoltine species decreased as latitude increased. Ornithophilic/multivoltine species in the east and the trait states in the west did not show any significant relationship to latitude.

The possible role of haematophagous flies in the incidence of bovine teat papillomatosis.

The relationship between the incidence of bovine teat papillomatosis and the activity of haematophagous flies was investigated in Japan. A total of 15,737 flies consisting of 33 species were collected by dry ice-baited mosquito net (DMN) trap and a sweep net from udders of cattle. Simulium aokii (Takahasi) of Simuliidae (black flies) was the predominant species, followed by S. tobetsuense Ono and S. iwatense (Shiraki). Simulium aokii had the highest peak in October, followed by September. Numbers of blood spots from the bites per teat in nulliparous cattle were significantly correlated with numbers of S. aokii collected by DMN trap. Numbers of teats with warts and spots of blood from the bites per teat were significantly more abundant in anterior teats than posterior teats. The average incidence of teat papillomatosis in nulliparous cattle was significantly higher than that in parous cattle, and the highest incidence by month was in May, followed by April. Although bovine papillomavirus (BPV) DNA was not detected in flies examined, the presence of black flies and blood spots from their bites were associated with subsequent high incidence of growing warts. In particular, it would pay to give attention to species such as S. aokii that severely attack udders in the present locality. Further investigations for the detection of BPV DNA from flies parasitizing on teats are needed.

Environmental drivers of breeding sites in blackfly species of medical and veterinary importance in eastern Spain.

Geographical distribution and abundance of the pupae of six blackfly species of medical and veterinary concern were studied in eastern Spain according to three different sets of explanatory variables including in-stream variables, both (i) abiotic (i.e., physicochemical) and (ii) biotic (i.e., richness and abundance of either taxonomically or ecologically close related taxa), as well as (iii) meteorological and landscape variables. The results showed specific habitat requirements for pupation in Simulium (Boophthora) erythrocephalum (De Geer, 1776) and Simulium (Wilhelmia) equinum (Linnaeus, 1758), two of the six species studied regarding elevation and temperature. While the rest of the species showed a certain degree of ecological overlap, co-occurrence was in general low, which suggested that antagonistic biotic factors may be important in structuring blackfly assemblages. In effect, biotic predictors explained a high proportion (50%-70%) of the variability in the abundance of the pupae of the most generalist blackfly species, although further studies are needed to disentangle the sign of interspecific interactions. At the landscape level, S. (W.) equinum and S. (W.) pseudequinum Séguy, 1921 breeding habitats were associated with the presence of pig farms, and S. (Simulium) reptans (Linnaeus, 1758) and S. (B.) erythrocephalum with the presence of cattle.

The general architecture of black fly-parasite interactions: Parasitism in lotic systems at a continental scale.

We examined the general architecture of interactions between stream-dwelling larval black flies (Diptera: Simuliidae) and their common parasites in 1736 collections across North America. Mermithid nematodes (family Mermithidae), microsporidia (phylum Microsporidia), and the fungus Coelomycidium simulii Debaisieux (phylum Blastocladiomycota) infected larval black flies. We found similar continental distributions for these three parasite taxa across North America. At least one of these taxa was represented in 42.2% of all black fly collections. Species interactions in ecological networks typically imply that each link between species is equally important. By employing quantitative measures of host susceptibilities and parasite dependencies, we provide a more complete structure for host-parasite networks. The distribution of parasite dependencies and host susceptibilities were right-skewed, with low values indicating that most dependencies (parasites) and susceptibilities (hosts) were weak. Although regression analysis between host frequency and parasite incidence were highly significant, frequency analysis suggested that the distributions of parasites differ significantly among the four most common and closely related (same subgenus) species of hosts. A highly significant pattern of nestedness in our bipartite host-parasite network indicated that specialized parasites (i.e., those that interact with few host species) tend to occur as subsets of the most common hosts.

Effects of forest structure on the interaction between avian hosts, dipteran vectors and haemosporidian parasites.

BACKGROUND: Forest habitats are important biodiversity refuges for a wide variety of bird species. Parasitism may modulate host species presence and abundance, and parasite effects can change according to forest management practices. Such processes are not well studied in vector-borne avian haemosporidians. We analyzed the effects of forest management on bird-dipteran-haemosporidian interactions, using seven common bird species in managed and unmanaged beech forest habitats in northeastern Germany. We assumed that forest structural heterogeneity affects parasite population parameters in avian hosts (i.e., prevalence and parasitemia), through its effect on the condition of the avian host but also through varying vector abundances. RESULTS: Parasite prevalence was high (about 80%) and homogeneous across different beech forest categories (i.e., young, old, unmanaged) and for all bird species, except Erithacus rubecula (35%). Parasitemia varied across bird species but not across forest categories within each avian species (lowest parasitemia were found in E. rubecula, Turdus merula, and Turdus philomelos). In our study system, we found that vector abundance was not the main driver of parasite dynamics. We found that forest structure affects parasite infection probability directly and potentially host condition via available resources that have to be used either to combat infections (i.e., high parasitemia) or to maintain a good body condition. CONCLUSIONS: The effects of each of the predictors were bird species-specific, and we found that Diptera vectors were not the foremost influence in our host-vector-parasite system. Effects of forest habitat variables indicated that for most bird species in this study, habitat regulation of infection probability was more likely (i.e., E. rubecula, Fringilla coelebs, Sylvia atricapilla), whereas for Parus major habitat characteristics impacted first individuals' body condition and subsequently the probability of infection. Our findings emphasize the need of species-specific analyses and to use continuous forest structural parameters (e.g., the proportion of gap, south facing aspect) to better understand habitat and land use effects on host-vector-parasite dynamics.

DNA barcoding as an aid for species identification in austral black flies (Insecta: Diptera: Simuliidae).

In this paper, the utility of a partial sequence of the COI gene, the DNA barcoding region, for the identification of species of black flies in the austral region was assessed. Twenty-eight morphospecies were analyzed: eight of the genus Austrosimulium (four species in the subgenus Austrosimulium s. str., three species in the subgenus Novaustrosimulium, and one species unassigned to subgenus), two of the genus Cnesia, eight of Gigantodax, three of Paracnephia, one of Paraustrosimulium, and six of Simulium (subgenera Morops, Nevermannia, and Pternaspatha). The neighbour-joining tree derived from the DNA barcode sequences grouped most specimens according to species or species groups recognized by morphotaxonomic studies. Intraspecific sequence divergences within morphologically distinct species ranged from 0% to 1.8%, while higher divergences (2%-4.2%) in certain species suggested the presence of cryptic diversity. The existence of well-defined groups within S. simile revealed the likely inclusion of cryptic diversity. DNA barcodes also showed that specimens identified as C. dissimilis, C. nr. pussilla, and C. ornata might be conspecific, suggesting possible synonymy. DNA barcoding combined with a sound morphotaxonomic framework would provide an effective approach for the identification of black flies in the region.

Estimating Diversity of Black Flies in the Simulium ignescens and Simulium tunja Complexes in Colombia: Chromosomal Rearrangements as the Core of Integrative Taxonomy.

Black flies (Diptera: Simuliidae) are distributed throughout the world, with more than 2200 formally described species. The family is renowned for its high frequency of cryptic species, offering an opportunity for integrative taxonomy, based on morphological, chromosomal, and molecular approaches. The biodiversity within Simulium (Psilopelmia) ignescens and S. (Psilopelmia) tunja in Colombia was estimated from the larval stage; 10 morphoforms were recognized based on 7 structural characters. This remarkable morphological variation was evaluated through 23 markers on the polytene chromosomes. We established 1 new cytoform in each nominal species. The congruence of the morphological and chromosomal assignments was evaluated using the mitochondrial marker Cytochrome Oxidase subunit I (COI) for each morphoform. The molecular data supported the chromosomal recognition of cytoforms (i.e., cryptic species). We also established the suitability of the COI marker for linking the pupal stage with each cytoform. Our results reveal the presence of hidden biodiversity in S. ignescens and S. tunja and demonstrate the power of polytene chromosomes as a tool for evaluating simuliid diversity, while illustrating the importance of integrated analyses in modern taxonomy.

Identification of semiochemicals attractive to Simulium vittatum (IS-7).

Many blackfly species (Diptera: Simuliidae) are economically important insect pests, both as nuisance biters and as vectors of pathogens of medical and veterinary relevance. Among the important blackfly pest species in North America is Simulium vittatum Zetterstedt sensu lato. The objective of this study was to identify compounds excreted by mammalian hosts that are attractive to host-seeking S. vittatum females. The attractiveness of putative compounds to colonized S. vittatum was tested through electrophysiological (electroantennography; n = 58 compounds) and behavioural (Y-tube assays; n = 7 compounds in three concentrations) bioassays. Five compounds were significantly attractive to host-seeking S. vittatum females: 1-octen-3-ol; 2-heptanone; acetophenone; 1-octanol, and naphthalene. These candidate compounds might be useful as attractants in traps that could be developed for use in alternative or complementary management tactics in programmes to suppress nuisance blackfly populations, or for the collection of samples in which to study the transmission ecology of pathogens transmitted by blackflies of the S. vittatum complex.

Population genetic structure and demographic history of the black fly vector, Simulium nodosum in Thailand.

An understanding of the genetic structure and diversity of vector species is crucial for effective control and management. In this study, mitochondrial DNA sequences were used to examine the genetic structure, diversity and demographic history of a black fly vector, Simulium nodosum Puri (Diptera: Simuliidae), in Thailand. A total of 145 sequences were obtained from 10 sampling locations collected across geographical ranges in the country. Low genetic diversity was found in populations of S. nodosum that could be explained by the recent population history of this species. Demographic history analysis revealed a signature of demographic expansion dating back to only 2600-5200 years ago. Recent population expansion in S. nodosum possibly followed an increase in agriculture that enabled its hosts', humans and domestic animals, densities to increase. Alternatively, the Thai populations could be a derivative of an older expansion event in the more northern populations. Mitochondrial DNA genealogy revealed no genetically divergent lineages, which agrees with the previous cytogenetic study. Genetic structure analyses found that only 27% of the pairwise comparisons were significantly different. The most likely explanation for the pattern of genetic structuring is the effect of genetic drift because of recent colonization.

Cytogenetic and Molecular Evidence of Additional Cryptic Diversity in High Elevation Black fly Simulium feuerborni (Diptera: Simuliidae) Populations in Southeast Asia.

Simulium feuerborni Edwards is geographically widespread in Southeast Asia. Previous cytogenetic study in Thailand revealed that this species is a species complex composed of two cytoforms (A and B). In this study, we cytologically examined specimens obtained from the Cameron Highlands, Malaysia, and Puncak, Java, Indonesia. The results revealed two additional cytoforms (C and D) of S. feuerborni. Specimens from Malaysia represent cytoform C, differentiated from other cytoforms by a fixed chromosome inversion on the long arm of chromosome III (IIIL-5). High frequencies of the B chromosome (33-83%) were also observed in this cytoform. Specimens from Indonesia represent the cytoform D. This cytoform is differentiated from others by a fixed chromosome inversion difference on the long arm of chromosome II (IIL-4). Mitochondrial DNA sequences support genetic differentiation among cytoforms A, B, and C. The pairwise F(ST) values among these cytoforms were highly significantly consistent with the divergent lineages of the cytoforms in a median-joining haplotype network. However, a lack of the sympatric populations prevented us from testing the species status of the cytoforms.

Mortality Patterns of Simulium vittatum Larvae (Diptera: Simuliidae) Following Exposure to Insecticidal Proteins Produced by Bacillus thuringiensis var. israelensis.

Products containing insecticidal crystalline proteins (ICPs) produced by Bacillus thuringiensis var. israelensis (Bti ICPs) are used to suppress vector and nuisance populations of black flies. The efficacy of an application of these products is often determined by a posttreatment evaluation of larval mortality. Larvae are typically removed from the substrate at some point in time after application of the product and mortality is determined. The time necessary for the effects of Bti ICPs to cause morality in exposed larvae can vary, and there is little consensus on how long operators should wait before evaluating larval mortality. This study was conducted to provide more information to larvicide applicators when performing posttreatment evaluations. Simulium vittatum larvae were exposed to Bti ICPs under controlled conditions and the mortality was monitored over time. Larvae exposed to operational concentrations of ICPs exhibited maximum mortality, approximately 87%, after 4 h. Exposure of larvae to 1/3 of that concentration resulted in similar mortality; however, the maximum mortality was not reached until 8 h postexposure. Additional experiments revealed that maximum mortality and time to maximum mortality can also be affected by components in the larval medium. Larval mortality was compared between larvae exposed to Bti ICPs in moderately hard water, medium containing 50 parts per million (ppm) of kaolinite, and medium containing 50 ppm of cellulose. The clay material had no significant effect on larval mortality or time to achieve maximum mortality. When cellulose was present in the medium, the time to maximum mortality was increased 50% and overall mortality was reduced by more than 40%.

Molecular systematics of the Simulium jenningsi species group (Diptera: Simuliidae), with three new fast-evolving nuclear genes for phylogenetic inference.

A molecular phylogeny was inferred for the 22 nominal species of black flies in the Simulium jenningsi species group, which includes major pests of humans and livestock in North America. Females are structurally monomorphic, presenting a problem for identification of the pests. For each species, we sequenced approximately two kilobases from the mitochondrial genome (ND2, Cox I, proximal one-half of Cox II) and about six kilobases from the nuclear genome (ca. 2 kilobases each from 3 rapidly evolving nuclear genes: big zinc finger [BZF], "5-intron gene" [5intG], and elongation complex protein 1 [ECP1]) and analyzed them phylogenetically using maximum likelihood and Bayesian methods. The three nuclear loci have not previously been used in phylogenetic studies. The mitochondrial region recovered 6 group members as monophyletic. BZF, 5intG, and ECP1 sequences each permitted identification of 13 species and recovered the S. fibrinflatum and S. taxodium subgroups. Simulium aranti Stone and Snoddy and S. luggeri Nicholson and Mickel were consistently recovered at the base of the group. Simulium ozarkense Moulton and Adler, S. dixiense Stone and Snoddy, S. krebsorum Moulton and Adler, and S. haysi Stone and Snoddy branched off before two well-supported sister groups of the remaining species. This remainder consisted of species occupying slow, sandy lowland streams-S. definitum Moulton and Adler, S. jonesi Stone and Snoddy, and the S. taxodium subgroup (S. taxodium Snoddy and Beshear, S. chlorum Moulton and Adler, S. confusum Moulton and Adler, and S. lakei Snoddy)-as sister to two clades of species inhabiting swift, rocky upland streams-the S. fibrinflatum subgroup (S. fibrinflatum Twinn, S. notiale Stone and Snoddy, and S. snowi Stone and Snoddy) and a clade comprised of S. anchistinum Moulton and Adler, S. jenningsi Malloch, and S. nyssa Stone and Snoddy, plus species having cocoons without anterolateral apertures (S. infenestrum Moulton and Adler, S. podostemi Snoddy, S. penobscotense Snoddy and Bauer, and S. remissum Moulton and Adler). Simulium snowi Stone and Snoddy is here considered a synonym of S. notiale Stone and Snoddy. Trees inferred from BZF and 5intG were largely concordant with those from ECP1, but slightly less resolved. Combining mitochondrial and nuclear data sets did not greatly improve the performance of the ECP1 data set alone. We, therefore, propose ECP1 as the gold standard for identification of members of the S. jenningsi group. Maximum likelihood analysis of combined sequences from all three nuclear genes, with three morphological constraints imposed, yielded a tree proposed as the best hypothesis of relationships among group members, based on all available data.

Phylogeography of the black fly Simulium aureohirtum (Diptera: Simuliidae) in Thailand.

The black fly Simulium aureohirtum Brunetti (Diptera: Simuliidae) is geographically widespread and utilizes diverse habitats. Previous studies revealed high genetic diversity, suggesting that this species could be a species complex. In this study, we used mitochondrial cytochrome c oxidase II sequences to examine genetic structure and demographic history of S. aureohirtum in Thailand. High level of genetic variation was observed due to the existence of genetically divergent lineages (A, B, and C). Lineages A and C were geographically widespread, while lineage B was geographically restricted to the eastern part of Thailand. The geographic localization of lineage B suggested limitations in gene flow, which is most likely a result of ecologically different habitats. Large genetic differences between individuals of lineages A and C, but geographically sympatric distributions of the members of these lineages, are considered to represent an admixture of the populations that have evolved allopatrically. Historical environmental change during the Pleistocene glaciations is possibly the factor that drove the lineage divergence. Population demographic history analyses revealed recent population expansions in the three lineages dating back to the last glaciations. These observations further highlight the significance of the Pleistocene climatic change on current genetic structure and diversity of living organisms of the Southeast Asian mainland.

Validation of the trichomycete Paramoebidium chattoni (Amoebidiales, Mesomycetozoea), a common and cosmopolitan black fly endosymbiont.

Paramoebidium, along with Amoebidium, constitute the Amoebidiales, which is phylogenetically embedded within the protist clade Ichthyosporea (Mesomycetozoea). However, the order is conventionally included within the trichomycetes, an ecological and polyphyletic group of arthropod-gut endosymbionts. Paramoebidium chattoni (Léger and Duboscq) Duboscq et al. is regarded as nomen nudum because the species was incorrectly published, and its taxonomic situation has never been addressed. Thus, P. chattoni is validated here with a description and neotypification to formalize the species and to guarantee the maintenance and correct use of its name. This common species has a wide geographical range and inhabits the digestive system of aquatic black fly larvae, where it frequently appears together with other gut endosymbionts, including P. curvum.

Insights from common buzzard broods on the interaction between Leucocytozoon infection, watercourse habitats and simuliid blackfly vectors.

Blood parasites of the genus Leucocytozoon commonly infect many bird species worldwide and are particularly prevalent in birds of prey. As a vector-borne parasitic disease, the infection occurrence overlaps with that of the dominant vectors: blackflies (Diptera, Simuliidae). These blood-sucking insects are dependent on habitats with flowing freshwaters for the development of their larval stages. We investigated the correlation between the proximity to flowing waters and Leucocytozoon infection probability in common buzzard (Buteo buteo) broods, as well as the occurrence of adult blackflies directly at the nests. In addition, we investigated the survival of captured simuliids in relation to host infection intensity. In total in 2019, we examined 112 different nests, including 297 common buzzard nestlings, with a Leucocytozoon prevalence of 56.6% among the nestlings and of 80.3% at brood level. We found no significant association of Leucocytozoon infection probability with nestling age, the distance to the nearest stream and the sum of the length of streams within a radius of 200 and 1000 m around each nest. The number of blackflies caught around the nest showed a tentative correlation with the probability of Leucocyozoon infection of the nestlings. Among the subsample of 218 blackfly individuals that survived day one after capture, survival averaged 6.2 days. Our results suggest that Leucocytozoon transmission is complex and requires consideration of many factors, related to habitat and vector prevalence, especially given their temporal variation.

Morphological description and genetic analysis of a new black fly species (Diptera: Simuliidae) in the subgenus Asiosimulium from central Thailand.

BACKGROUND: Black flies are among the most medically and veterinary important insects, as adult females of certain species are the sole vector of Onchocerca volvulus. Here, a new black fly species belonging to the subgenus Asiosimulium Takaoka & Choochote, 2005, is described and formally named as Simulium (Asiosimulium) kittipati sp. nov. METHODS: Pupae and larvae of black flies were collected from available substrates in the stream from central Thailand. Pupae were individually separated in plastic tubes and maintained until adult flies emerged. The emerged adult flies associated with their pupal exuviae and cocoon as well as mature larvae preserved in 85% ethanol were used to describe the new species based on an integrated approach of morphological examination and molecular analysis of the COI gene. RESULTS: The new species is characterized in the female by the medium-long sensory vesicle with a medium-sized opening apically, scutum with three faint longitudinal vittae, and the ellipsoidal spermatheca; in the male by the number of upper-eye (large) facets in 20 vertical columns and 21 horizontal rows, hind basitarsus slender, nearly parallel-sided, and median sclerite much wider and upturned apically; in the pupa by the head and thoracic integument densely covered with tiny tubercles, and the pupal gill of arborescent type with 28-30 filaments; and in the larva by the postgenal cleft deep, nearly reaching the posterior margin of the hypostoma, and dark pigmented sheath of the subesophageal ganglion. The DNA barcode successfully differentiated the new species from its congeners with an interspecific genetic divergence of 1.74-18.72%, confirming the morphological identification that the species is a new member of the subgenus Asiosimulium. Phylogenetic analyses also indicated that the new species is genetically closely related to Simulium phurueaense Tangkawanit, Wongpakam & Pramual, 2018, further supporting its morphological classification. CONCLUSIONS: This is the ninth species assigned to the subgenus Asiosimulium within the genus Simulium Latreille, 1802. Taxonomic notes and identification keys are given to distinguish this new species from the eight known species members in its same subgenus. Additionally, a distribution map of all species members in this subgenus occurring in Thailand and other countries is provided.

Ecologically and medically important black flies of the genus Simulium: Identification of biogeographical groups according to similar larval niches.

The black fly genus Simulium includes medically and ecologically important species, characterized by a wide variation of ecological niches largely determining their distributional patterns. In a rapidly changing environment, species-specific niche characteristics determine whether a species benefits or not. With aquatic egg, larval and pupal stages followed by a terrestrial adult phase, their spatial arrangements depend upon the interplay of aquatic conditions and climatic-landscape parameters in the terrestrial realm. The aim of this study was to enhance the understanding of the distributional patterns among Simulium species and their ecological drivers. In an ecological niche modelling approach, we focused on 12 common black fly species with different ecological requirements. Our modelling was based on available distribution data along with five stream variables describing the climatic, land-cover, and topographic conditions of river catchments. The modelled freshwater habitat suitability was spatially interpolated to derive an estimate of the adult black flies' probability of occurrence. Based on similarities in the spatial patterns of modelled habitat suitability we were able to identify three biogeographical groups, which allows us to confirm old assessments with current occurrence data: (A) montane species, (B) broad range species and (C) lowland species. The five veterinary and human medical relevant species Simulium equinum, S. erythrocephalum, S. lineatum, S. ornatum and S. reptans are mainly classified in the lowland species group. In the course of climatic changes, it is expected that biocoenosis will slightly shift towards upstream regions, so that the lowland group will presumably emerge as the winner. This is mainly explained by wider ecological niches, including a higher temperature tolerance and tolerance to various pollutants. In conclusion, these findings have significant implications for human and animal health. As exposure to relevant Simulium species increases, it becomes imperative to remain vigilant, particularly in investigating the potential transmission of pathogens.

Community composition of black flies during and after the 2020 vesicular stomatitis virus outbreak in Southern New Mexico, USA.

BACKGROUND: Vesicular stomatitis virus (VSV), a vector-borne pathogen of livestock, emerges periodically in the western US. In New Mexico (NM), US, most cases occur close to the Rio Grande River, implicating black flies (Simulium spp.) as a possible vector. In 2020, VS cases were reported in NM from April to May, although total black fly abundance remained high until September. We investigated the hypothesis that transience of local VSV transmission results from transient abundance of key, competent black fly species. Additionally, we investigated whether irrigation canals in southern NM support a different community of black flies than the main river. Lastly, to gain insight into the source of local black flies, in 2023 we collected black fly larvae prior to the release of water into the Rio Grande River channel. METHODS: We randomly sub-sampled adult black flies collected along the Rio Grande during and after the 2020 VSV outbreak. We also collected black fly adults along the river in 2021 and 2022 and at southern NM farms and irrigation canals in 2022. Black fly larvae were collected from dams in the area in 2023. All collections were counted, and individual specimens were subjected to molecular barcoding for species identification. RESULTS: DNA barcoding of adult black flies detected four species in 2020: Simulium meridionale (N = 158), S. mediovittatum (N = 83), S. robynae (N = 26) and S. griseum/notatum (N = 1). Simulium robynae was only detected during the VSV outbreak period, S. meridionale showed higher relative abundance, but lower absolute abundance, during the outbreak than post-outbreak period, and S. mediovittatum was rare during the outbreak period but predominated later in the summer. In 2022, relative abundance of black fly species did not differ significantly between the Rio Grande sites and farm and irrigation canals. Intriguingly, 63 larval black flies comprised 56% Simulium vittatum, 43% S. argus and 1% S. encisoi species that were either extremely rare or not detected in previous adult collections. CONCLUSIONS: Our results suggest that S. robynae and S. meridionale could be shaping patterns of VSV transmission in southern NM. Thus, field studies of the source of these species as well as vector competence studies are warranted.

Descriptions of two new species of the Simulium (Simulium) striatum species-group (Diptera: Simuliidae) from Taiwan and Japan, and a revised description of S. (S.) quinquestriatum (Shiraki).

Species in the Simulium (Simulium) striatum species-group (Diptera: Simuliidae) in Taiwan and Japan are morphologically reevaluated. Simulium (S.) yanpingense sp. nov. is described as the third member in this species-group from Taiwan and a revised description of S. (S.) quinquestriatum (Shiraki) is provided. The species previously regarded as S. (S.) quinquestriatum in Japan is described as a new species, S. (S.) tanegashimaense. Simulium (S.) yanpingense sp. nov. is similar to S. (S.) pingtungense Huang & Takaoka from Taiwan, in many characteristics including the haired basal portion of the female radius, dark leg color, and male scutum with brassy hairs, but it is distinguished from the latter species by the number of male upper-eye (large) facets, which are in 17 (rarely 18) vertical columns and 17 or 18 horizontal rows in this new species but in 19 vertical columns and 20 horizontal rows in S. (S.) pingtungense. Simulium (S.) tanegashimaense sp. nov. is similar to S. (S.) quinquestriatum originally described from Taiwan by having the male scutum with yellow fine hairs, but is distinguished from the latter species by the number of male upper-eye (large) facets, which are in 17 (rarely 16) vertical columns and 17 horizontal rows in this new species but in 19 or 20 vertical columns and 19 or 20 horizontal rows in S. (S.) quinquestriatum. The morphological differences between these two new species and their related species from India, Malaysia, Thailand and Vietnam are noted.