Tabanids as vectors of disease agents

Hemopathogens in naturally infected bovine fetuses in Brazil

The transplacental transmission of parasites and hemoparasites is crucial for understanding the epidemiology of diseases. This study aimed to assess the prevalence of hemopathogens in bovine fetuses at various gestational periods. Samples were obtained from a slaughterhouse in the state of Minas Gerais, Brazil, and a total of 236 fetuses were collected. DNA extracted from blood samples (145) and organ samples (a pool of brain and spleen) (236) underwent a nested PCR (nPCR) assay to detect Babesia spp., Theileria spp., Trypanosoma vivax, Anaplasma marginale, Anaplasma bovis, Anaplasma phagocytophilum, Ehrlichia minasensis, and hemotropic Mycoplasma spp. Additionally, serological analysis of 145 plasma samples was conducted using the indirect fluorescent antibody test-IFAT to detect IgG against Babesia bovis, Babesia bigemina, A. marginale, and Trypanosoma vivax. The observed prevalence of transplacental transmission was 19.3 %, 6.2 %, 42.7 % and 2.7 %, for A. marginale, B. bigemina, 'Candidatus M. haemobos', and Mycoplasma wenyonii, respectively. The prevalence of A. marginale by gestational trimester was 16 % (13/81) in the second trimester and 23 % (14/60) in the third trimester, with no positive samples in the first trimester. Regarding the species B. bovis and B. bigemina, all evaluated animals tested negative by nPCR, and no serological evidence for B. bovis was found by the IFAT. Babesia bigemina demonstrated an overall seroprevalence of 6.2 % (9/145), with 4.8 % (7/145) in the last trimester and 1.3 % (2/145) in the second trimester of pregnancy. In total, 42.7 % (62/145) of blood samples were positive for 'Candidatus M. haemobos', with 42 % (34/81) in the middle trimester, and 43 % (26/60) in the final trimester of pregnancy. Mycoplasma wenyonni was detected in 2.7 % (4/145) blood samples, all in coinfection with 'C. M. haemobos'. The prevalence by pregnancy trimester was 25 % (1/4) in the first trimester; 1.2 % (1/81) in the second trimester and 3.3 % (2/60) in the third trimester of pregnancy. Hemopathogen DNA was detected in fetus blood samples but not the brain or spleen samples. All the samples were negative for T. vivax, Theileria spp., Anaplasma spp. and Ehrlichia spp. Overall, in this study, approximately 70 % of fetuses were positive for one or more of the studied parasites. No significant associations were observed between pairs of pathogens, except 'C. M. haemobos' and A. marginale.

Molecular evidence of pathogens and endosymbionts in the black horse fly Osca lata (Diptera: Tabanidae) in Southern Chile

Little is known about the role of horse flies in potential pathogen transmission in Chile. This study provides evidence of the molecular detection of microorganisms in southern Chile. In the present study, adult Osca lata horse flies were trapped from Punucapa (39°45'06"S/73°16'08"W, Región de Los Ríos) and Puyehue (40°39'10"S/72°10'57"W, Región de Los Lagos), Chile. Among the 95 samples analyzed by PCR using specific primers, microorganisms were detected in 23.2% (n = 22) of the samples. Rickettsia spp. DNA was detected in 15.8% (n = 15) of the samples, Trypanosomatidae DNA in 5.3% (n = 5) of the samples, and filarial DNA in 2.1% (n = 2) of the samples. This study found that horse flies in the region are capable of carrying a variety of both parasites and endosymbionts. Further research is needed to understand the specific impact of horse flies as mechanical or biological vectors and develop effective control measures to prevent the spread of any microorganisms associated with disease.

Diversity and seasonality of horse flies (Diptera: Tabanidae) in Amazon Forest fragments of Monte Negro, Rondônia, Western Amazon

Tabanidae are considered a nuisance to humans, wild animals, and livestock due to their painful, annoying, and insistent biting. Tabanids transmit some pathogens and parasites biologically and mechanically. In humans, there are relatively few pathogens transmitted regularly. Still, tabanids serve as vectors of a number of disease agents of animals, including viruses, bacteria, protozoans, and nematodes. They are more abundant in tropical and humid regions, and their seasonal patterns are affected by habitat changes such as deforestation and fragmentation. Here, we analyze the tabanid fauna in Monte Negro, a central municipality of Rondônia, Brazil, comparing abundance, richness, and diversity in forest and pasture habitats. Traps were set for 5 days a month for 12 consecutive months. We also examined how abiotic factors (humidity, temperature, and rainfall) affected the abundance, diversity, and richness and the effectiveness of Malaise and Nzi traps as sample methods. The influence of climatic variables on the richness and abundance of the species was tested using generalized linear models, and we used non-parametric dimensional scaling (nMDS) for analysis of species composition and diversity in different traps and environments. We collect 1032 specimens of 25 species. The most abundant species were Tabanus antarcticus, Dichelacera tetradelta, Tabanus mucronatus, and Leucotabanus albovarius. Forest habitats had the highest number of tabanids, followed by pasture and the anthropized area, and there was no significant difference regarding the effectiveness of the Malaise and Nzi traps. The study provides new information on the distribution and ecology of tabanids in Brazil.

Molecular Detection and Analysis of Trypanosoma (Megatrypanum) spp. Diversity in Tabanidae (Diptera) Collected in Lithuania

Trypanosomatids from the Tabanidae family have not been studied in Lithuania in any detail. In this study, a nested PCR amplifying the DNA fragment coding the SSU rRNA was used to determine the Trypanosoma spp. prevalence and diversity in the Tabanidae family collected in Lithuania in 2018-2019. In total, 101 Tabanidae individuals were investigated from six areas in Lithuania, and 14 different species were identified. The overall positivity of Trypanosoma spp. DNA in tabanids was 50.5% (51/101). Tabanus maculicornis was the most abundant species and yielded the highest prevalence of trypanosomatids (84.62%, 22/26), while Hybomitra nitidifrons showed a high prevalence as well, reaching 77.8% (14/18). In flies of some species (Hybomitra lapponica and Hybomitra lurida), Trypanosoma was detected for the first time. Nine different haplotypes were detected as being distributed in different tabanid species. Analysis showed that most sequences obtained during our study were identical or extremely close to two major T. theileri subclades: TthI and TthII. Our data analysis suggests the presence of different Trypanosoma genotypes in the same tabanid species, meaning that different lineages of Trypanosoma could be more related to the vertebrate host and not the fly species. This is the first study of trypanosomatid parasites in tabanids from Lithuania, and our results are valuable in providing data on the diversity of these parasites in different Tabanidae species.

Tabanidae (Diptera) collected on horses in a Cerrado biome in the state of Tocantins, Brazil

Tabanidae (Diptera), popularly known as horse flies, is an important vector group. This is the first study to ascertain the abundance and diversity of horse flies in horses at the cerrado biome of the state of Tocantins, Brazil. Collecting took place in typical Cerrado, and sampling occurred in the dry and rainy seasons. The horseflies were collected from horses using an entomological net. A total of 249 individuals were collected and spread over 25 species. The prevalent species were Stypommisa aripuana (25.8%) and Catachlorops rufescens (6.4%), in the dry period, and Fidena lissorhina (22.5%), Tabanus occidentalis var. dorsovittatus (10%) and Poeciloderas quadripunctatus (6.4%), in the rainy season. The results suggest that tabanids attack horses throughout the dry and rainy seasons, posing a constant threat to their health in the Cerrado of Tocantins.

Characterization of complete mitochondrial genome of three Horse flies of the genus Tabanus (Diptera: Tabanidae): comparative analysis

BACKGROUND

Tabanidae (Horse-Flies or Deer-Flies) are one of the most economically important as well as medically significant haematophagous insect family within the order Diptera. Members of this group are also responsible for the mortality of substantial number of live-stock every year. Due to their pathogen transmission potential and vector competencies makes them an important insect group to study. Till now, mitochondrial genome of 18 species of tabanids were available.

METHODS AND RESULTS

The complete mitogenome of three species T. diversifrons (15,809 bp), T. rubidus (15,878 bp) and T. tenens (15,872 bp) were generated by Next generation sequencing method. They consist 37 genes, with a positive AT skew and a negative GC skew. The gene order of these three species is similar to the typical gene arrangement of infra-order Tabanomorpha. Most of the tRNAs showed typical clover-leaf secondary structure except trnS1, which lacks the DHU arm. The sliding window analysis showed that the nad4L is the most conserved while atp8, and nad6 are the most variable genes. Moreover, the ratios of non-synonymous to synonymous substitution rates indicated that all PCGs under the purifying selection. Phylogeny revealed Chrysops and Haematopota are monophyletic while species of Hybomitra are nested within the polyphyletic clade of Tabanus. T. diversifrons exhibits sister relationship with Atylotus miser. Two morphologically divergent species T. rubidus and T. tenens are found to be genetically similar and indistinguishable by mitochondrial genome.

CONCLUSIONS

The hypervariable genes like atp8 and nad6 can be used as molecular markers for the identification of recently diverged lineages of family Tabanidae. Further, to address uncertainties arising from the two morphological divergent species, it is imperative to obtain data from nuclear gene markers.

Epidemiology and Transmission of Theileria orientalis in Australasia

Oriental theileriosis, a disease primarily impacting cattle is caused by an apicomplexan hemoprotozoan parasite, Theileria orientalis. It has now become established in the Australasia region. The organism was long considered a benign cause of persistent infections; however, an increase in clinical outbreaks since 2006 in the eastern Australian states and New Zealand was associated with the identification of the pathogenic Ikeda (Type 2) and Chitose (Type 1) genotypes. Unlike the pathogenic T. parva and T. annulate, which target leucocytes, clinical manifestation with T. orientalis is due to its effects on erythrocytes, with the infection sometimes designated as Theileria associated bovine anemia (TABA). In Australia and New Zealand, the tick Haemaphysalis longicornis is the principal vector, though other Haemaphysalis species are also likely vectors. The endemic status of infection with pathogenic genotypes in areas with low or absent tick populations is an apparent paradox that may be attributable to alternative modes of transmission, such as mechanical transmission by hematophagous insects (lice, mosquitoes, and biting flies), vertical transmission, and transmission via iatrogenic means. This review addresses the evidence for the different modes of transmission of T. orientalis with particular focus on the reported and potential vectors in Australasia.

Relevant Brachycera (Excluding Oestroidea) for Horses in Veterinary Medicine: A Systematic Review

In equine stables and their surroundings, a large number of insects are present that can be a nuisance to their equine hosts. Previous studies about dipterans transmitting infectious agents to Equidae have largely focused on Nematocera. For the preparation of this systematic review, the existing literature (until February 2022) was systematically screened for various infectious agents transmitted to Equidae via insects of the suborder Brachycera, including Tabanidae, Muscidae, Glossinidae and Hippoboscidae, acting as pests or potential vectors. The PRISMA statement 2020 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for systematic reviews were followed. The two concepts, Brachycera and Equidae, were combined for the search that was carried out in three languages (English, German and French) using four different search engines. In total, 38 articles investigating Brachycera as vectors for viral, bacterial and parasitic infections or as pests of equids were identified. Only 7 of the 14 investigated pathogens in the 38 reports extracted from the literature were shown to be transmitted by Brachycera. This review clearly shows that further studies are needed to investigate the role of Brachycera as vectors for pathogens relevant to equine health.

Pathology and pathogenesis of cutaneous lesions in beef cattle associated with buffalo fly infestation

Haematobia irritans exigua, commonly known as buffalo fly, is the major hematophagous ectoparasite of north Australian cattle herds. Lesions associated with buffalo fly infestation are generally alopecic, hyperkeratotic, or scab encrusted wounds with variable hemorrhagic ulceration. Buffalo flies can transmit a filarial nematode, Stephanofilaria sp., which has been implicated in the pathogenesis of buffalo fly lesions, but Stephanofilaria infection has not been detected in all lesions suggesting that other causal factors may be involved. This study characterized the pathology of buffalo fly lesions to identify the role of Stephanofilaria in lesion development, as well as to identify other potential agents. Lesion biopsies were collected from north and south Queensland and tested for the presence of Stephanofilaria by qPCR. Each lesion was scored grossly (0-4) for hemorrhage, ulceration, exudation, and alopecia. Lesions were also scored microscopically (0-4) for epidermal and dermal damage and inflammatory characters. Stephanofilaria infection was detected in 31% of lesion biopsies. Grossly, Stephanofilaria-infected lesions had significantly larger lesion area and higher scores for alopecia and hyperkeratosis than lesions where no nematodes were found (P < 0.05). Histologically, epidermal, dermal, and adnexal damage was significantly higher in Stephanofilaria infected lesions than lesions without nematodes. Eosinophils, macrophages, and lymphocytes were significantly more abundant in Stephanofilaria positive lesions as compared to negative lesions. This study also noted bacterial infection with colonies of coccoid bacteria, observed in skin sections from 19 lesions. Grossly, lesions with bacterial infection had significantly higher ulceration scores compared to Stephanofilaria positive lesions, and histologically epidermal disruption was significantly greater in bacteria-infected lesions. We found no evidence of bacteria or Stephanofilaria infection in 49% of the lesions assessed and tissue damage patterns and eosinophilic inflammation suggested hypersensitivity to buffalo fly feeding as a possible cause of these lesions. These findings suggest that although the presence of Stephanofilaria infection may increase the severity of lesion pathology, it is not essential for lesion development. These outcomes also suggest a potential role of bacteria and hypersensitivity in pathogenesis of some lesion. A better understanding of buffalo fly lesion etiology will contribute to the optimal treatment and control programmes.

Blood-seeking horseflies prefer vessel-imitating temperature gradients on host-mimicking targets: Experimental corroboration of a new explanation of the visual unattractiveness of zebras to tabanids

Several hypotheses tried to explain the advantages of zebra stripes. According to the most recent explanation, since the borderlines of sunlit white and black stripes can hamper thermal vessel detection by blood-seeking female horseflies, striped host animals are unattractive to these parasites which prefer hosts with a homogeneous coat, on which the temperature gradients above blood vessels can be detected more easily. This hypothesis has been tested in a field experiment with horseflies walking on a grey barrel with thin black stripes which were slightly warmer than their grey surroundings in sunshine, while in shade both areas had practically the same temperature. To eliminate the multiple (optical and thermal) cues of this test target, we repeated this experiment with improved test surfaces: we attracted horseflies by water- or host-imitating homogeneous black test surfaces, beneath which a heatable wire ran. When heated, this invisible and mechanically impalpable wire imitated thermally the slightly warmer subsurface blood vessels, otherwise it was thermally imperceptible. We measured the times spent by landed and walking horseflies on the test surface parts with and without underlying heated or unheated wire. We found that walking female and male horseflies had no preference for any (wired or wireless) area of the water-imitating horizontal plane test surface on the ground, independent of the temperature (heated or unheated) of the underlying wire. These horseflies looked for water, rather than a host. On the other hand, in the case of host-imitating test surfaces, female horseflies preferred the thin surface regions above the wire only if it was heated and thus warmer than its surroundings. This behaviour can be explained exclusively with the higher temperature of the wire given the lack of other sensorial cues. Our results prove the thermal vessel recognition of female horseflies and support the idea that sunlit zebra stripes impede the thermal detection of a host's vessels by blood-seeking horseflies, the consequence of which is the visual (non-thermal) unattractiveness of zebras to horseflies.

Molecular of Anaplasma marginale Theiler (Rickettsiales: Anaplasmataceae) in horseflies (Diptera: Tabanidae) in Uruguay

Anaplasma marginale is transmitted biologically by infected ticks or mechanically by biting flies and contaminated fomites. In tick-free areas, such as southern Uruguay, horseflies could be the principal vectors of this pathogen for bovines, causing anaplasmosis. The objective of this work was to detect the presence of A. marginale by MSP-5 PCR and Sanger sequencing in the most prevalent species of horseflies obtained using different collection methods in Colonia, Tacuarembó and Paysandú, Uruguay. Eight horsefly species were tested (Dasybasis missionum, Poeciloderas lindneri, Tabanus campestris, T. claripennis, T. fuscofasciatus, T. platensis, T. tacuaremboensis and T. triangulum); four species were found to be positive for A. marginale, with D. missionum and P. lindneri having the most frequent infections, while only one individual each of T. fuscofasciatus and T. tacuaremboensis was positive. Both D. missionum and P. lindneri were positive for A. marginale in tick-free areas, and the implications are discussed in this report.

Assays to evaluate the transovarial transmission of Anaplasma marginale by Rhipicephalus microplus

The aim of this study was to evaluate the vectorial competence of Rhipicephalus microplus to transmit Anaplasma marginale transovarially, by analyzing the results of three different but complementary assays. First, larvae of R. microplus were fed on a calf infected with the isolate S1P of A. marginale. The engorged females obtained were analyzed by PCR and incubated for oviposition. After hatching, larvae were analyzed by PCR and fed on susceptible splenectomized cattle. Although A. marginale was detected in the females, no A. marginale DNA was amplified from the larvae and transmission of A. marginale to cattle was not recorded. In the second experiment, R. microplus larvae were fed on cattle naturally infected with field isolates of A. marginale and experimentally infected with the isolate S1P of A. marginale. After detachment, engorged females were incubated for oviposition. The offspring were analyzed by PCR, with negative results. Finally, free-living larvae of R. microplus collected from pasture on farms with cattle infected with A. marginale were analyzed by PCR for Anaplasma infection. All samples analyzed were negative for A. marginale. The results of this work indicate that transovarial transmission of A. marginale by R. microplus is unlikely to occur.

First study on molecular detection of hemopathogens in tabanid flies (Diptera: Tabanidae) and cattle in Southern Thailand

Background and Aim:

Female tabanids play a key role in disease transmission as mechanical vectors for various hemopathogens, but only a limited number of studies have been conducted on them. This study aimed to investigate the occurrence of hemopathogens in tabanid flies compared to those found in nearby cattle hosts.

Materials and Methods:

Tabanids were collected using a Nzi trap for three consecutive days per month during the dry season (February–May 2021). Furthermore, blood samples were collected from 20 beef cattle (Bos taurus) raised in the same area where the flies were captured. Conventional polymerase chain reaction (PCR) was used to detect hemopathogenic DNA in flies and beef cattle.

Results:

In total, 279 female tabanids belonging to five species were collected: Tabanus megalops, Tabanus rubidus, Tabanus mesogaeus, Chrysops dispar, and Chrysops fuscomarginalis. Notably, T. megalops was the most abundant species, accounting for 89.2% of the flies collected (n = 249). PCR technique revealed that 76.6% of T. megalops carried at least one pathogen (Anaplasma, Ehrlichia, Babesia, or Theileria). In addition, all beef cattle had multiple hemopathogenic infections (Anaplasma marginale, Ehrlichia spp., Babesia bigemina, Babesia bovis, and Theileria spp.).

Conclusion:

Although T. megalops could carry many hemopathogens, it might not be an important vector due to the limited number of flies and parasitic load. Furthermore, T. megalops could be utilized to monitor the presence of hemopathogens in the study area, but not the disease occurrence in the individual host species. Knowing the presence of hemopathogens in flies could help manage the disease in this area.

Sunlit zebra stripes may confuse the thermal perception of blood vessels causing the visual unattractiveness of zebras to horseflies

Multiple hypotheses have been proposed for possible functions of zebra stripes. The most thoroughly experimentally supported advantage of zebra stripes is their visual unattractiveness to horseflies (tabanids) and tsetse flies. We propose here a plausible hypothesis why biting horseflies avoid host animals with striped pelages: in sunshine the temperature gradients of the skin above the slightly warmer blood vessels are difficult to distinguish from the temperature gradients induced by the hairs at the borderlines of warmer black and cooler white stripes. To test this hypothesis, we performed a field experiment with tabanids walking on a host-imitating grey test target with vessel-mimicking thin black stripes which were slightly warmer than their grey surroundings in sunshine, while under shady conditions both areas had practically the same temperature as demonstrated by thermography. We found that horseflies spend more time walking on thin black stripes than surrounding grey areas as expected by chance, but only when the substrate is sunlit. This is because the black stripes are warmer than the surrounding grey areas in the sun, but not in the shade. This is consistent with the flies' well-documented attraction to warmer temperatures and provides indirect support for the proposed hypothesis. The frequent false vessel locations at the numerous black-white borderlines, the subsequent painful bitings with unsuccessful blood-sucking attempts and the host's fly-repellent reactions enhance considerably the chance that horseflies cannot evade host responses and are swatted by them. To eliminate this risk, a good evolutionary strategy was the avoidance of striped (and spotted) host animals.

Phylogenetic Analysis of Mitochondrial Genome of Tabanidae (Diptera: Tabanidae) Reveals the Present Status of Tabanidae Classification

Simple Summary

Tabanidae suck the blood of humans and animals, are important biological vectors for the transmission of diseases, and are of considerable economic and medical significance. However, current knowledge about the mitochondrial genome of this family is limited. Therefore, six newly completed mitochondrial genomes of four genera of Tabanidae (Haematopota turkestanica, Chrysops vanderwulpi, Chrysops dissectus, Tabanus chrysurus, Tabanus pleskei, and Hybomitra sp. species) were sequenced and analyzed. The results show that the six newly mitochondrial genomes have quite similar structures and features. Phylogeny was inferred by analyzing the 13 amino acid sequences coded by mitochondrial genes of 22 mitogenomes (all available complete mitochondrial genomes of tabanidae). Bayesian inference, maximum likelihood trees, and maximum parsimony inference analyses all showed consistent results. This study supports the concept of monophyly of all groups, ratifies the current taxonomic classification, and provides useful genetic markers for studying the molecular ecology, systematics, and population genetics of Tabanidae.

Abstract

Tabanidae suck the blood of humans and animals, are important biological vectors for the transmission of diseases, and are of considerable economic and medical significance. However, current knowledge about the mitochondrial genome of this family is limited. More complete mitochondrial genomes of Tabanidae are essential for the identification and phylogeny. Therefore, this study sequenced and analyzed six complete mitochondrial (mt) genome sequences of four genera of Tabanidae for the first time. The complete mt genomes of the six new sequences are circular molecules ranging from 15,851 to 16,107 base pairs (bp) in size, with AT content ranging from 75.64 to 77.91%. The six complete mitochondrial genomes all consist of 13 protein-coding genes (PCGs), 2 ribosomal RNA genes (RRNA), 22 transfer RNA genes (tRNAs), and a control region, making a total of 37 functional subunits. ATT/ATG was the most common start codon, and the stop codon was TAA of all PCGS. All tRNA except tRNA Ser1 had a typical clover structure. Phylogeny was inferred by analyzing the 13 concatenated amino acid sequences of the 22 mt genomes. Bayesian inference, maximum-likelihood trees, and maximum-parsimony inference analyses all showed consistent results. This study supports the concept of monophyly of all genus, ratifies the current taxonomic classification, and provides effective genetic markers for molecular classification, systematics, and genetic studies of Tabanidae.

DNA barcoding of the horsefly fauna (Diptera, Tabanidae) of Croatia with notes on the morphology and taxonomy of selected species from Chrysopsinae and Tabaninae

In the Croatian fauna, horseflies (Tabanidae) are represented by 78 species belonging to two subfamilies, five tribes, and 10 genera. Identification of these species is based on morphological characteristics. In this study, 43 species of horseflies were analyzed. The highest number of species (19) belongs to the genus Tabanus, followed by the genera Hybomitra with seven species, Haematopota with six species, Chrysops with four species, Atylotus and Philipomyia with two species each, and the genera Silvius, Dasyrhamphis, and Heptatoma with one species each. The standard DNA barcoding region of the mitochondrial cytochrome c oxidase gene, subunit I (COI), was sequenced and compared to the Barcode of Life Database (BOLD). Our analyses confirmed our morphological identifications and added 16 new Barcode Index Numbers (BINs) for Tabanidae to BOLD. Potential problems in the systematics and taxonomy of this family are highlighted.

A need for null models in understanding disease transmission: the example of Mycobacterium ulcerans (Buruli ulcer disease)

Understanding the interactions of ecosystems, humans and pathogens is important for disease risk estimation. This is particularly true for neglected and newly emerging diseases where modes and efficiencies of transmission leading to epidemics are not well understood. Using a model for other emerging diseases, the neglected tropical skin disease Buruli ulcer (BU), we systematically review the literature on transmission of the etiologic agent, Mycobacterium ulcerans (MU), within a One Health/EcoHealth framework and against Hill's nine criteria and Koch's postulates for making strong inference in disease systems. Using this strong inference approach, we advocate a null hypothesis for MU transmission and other understudied disease systems. The null should be tested against alternative vector or host roles in pathogen transmission to better inform disease management. We propose a re-evaluation of what is necessary to identify and confirm hosts, reservoirs and vectors associated with environmental pathogen replication, dispersal and transmission; critically review alternative environmental sources of MU that may be important for transmission, including invertebrate and vertebrate species, plants and biofilms on aquatic substrates; and conclude with placing BU within the context of other neglected and emerging infectious diseases with intricate ecological relationships that lead to disease in humans, wildlife and domestic animals.

'A flying start': Wildlife trypanosomes in tissues of Australian tabanids (Diptera: Tabanidae)

Tabanids (syn. horse flies) are biting-flies of medical and veterinary significance because of their ability to transmit a range of pathogens including trypanosomes - some species of which carry a combined health and biosecurity risk. Invertebrate vectors responsible for transmitting species of Trypanosoma between Australian wildlife remains unknown, thus establishing the role of potential vector candidates such as tabanids is of utmost importance. The current study aimed to investigate the presence of indigenous trypanosomes in tabanids from an endemic area of south-west Australia. A total of 148 tabanids were collected, with morphological analysis revealing two subgenera: Scaptia (Pseudoscione) and S. (Scaptia) among collected flies. A parasitological survey using an HRM-qPCR and sequencing approach revealed a high (105/148; 71%) prevalence of trypanosomatid DNA within collected tabanids. Individual tissues - proboscis (labrum, labium and mandibles, hypopharynx), salivary glands, proventriculus, midgut, and hindgut and rectum - were also tested from a subset of 20 tabanids (n = 140 tissues), confirming the presence of Trypanosoma noyesi in 31% of screened tissues, accompanied by T. copemani (3%) and T. vegrandis/T.gilletti (5%). An unconfirmed trypanosomatid sp. was also detected (9%) within tissues. The difference between tissues infected with T. noyesi compared with tissues infected with other trypanosome species was statistically significant (p < 0.05), revealing T. noyesi as the more frequent species detected in the tabanids examined. Fluorescence in situ hybridisation (FISH) and scanning electron microscopy (SEM) confirmed intact parasites within salivary glands and the proboscis respectively, suggesting that both biological and mechanical modes of transmission could occur. This study reveals the presence of Australian Trypanosoma across tabanid tissues and confirms intact parasites within tabanid salivary glands and the proboscis for the first time. Further investigations are required to determine whether tabanids have the vectorial competence to transmit Australian trypanosomes between wildlife.

Greenhead (Tabanus nigrovittatus) Wolbachia and Its Microbiome: A Preliminary Study

Endosymbiotic Wolbachia bacteria are known to influence the host physiology, microbiota composition, and dissemination of pathogens. We surveyed a population of Tabanus nigrovittatus, commonly referred to as "greenheads," from Crane Beach (Ipswich, MA, USA) for the presence of the alphaproteobacterial symbiont Wolbachia. We studied the COI (mitochondrial cytochrome oxidase) marker gene to evaluate the phylogenetic diversity of the studied specimens. The DNA sequences show strong similarity (between 99.9 and 98%) among the collected specimens but lower similarity to closely related entries in the NCBI database (only between 96.3 and 94.7%), suggesting a more distant relatedness. Low levels of Wolbachia presence necessitated a nested PCR approach, and using 5 markers (ftsZ, fbpA, dnaA, coxA, and gatB), we determined that two recognized "supergroups" of Wolbachia species were represented in the studied specimens, members of clades A and B. Using next-generation sequencing, we also surveyed the insect gut microbiomes of a subset of flies, using Illumina and PacBio 16S rRNA gene sequencing with barcoded primers. The composition of Proteobacteria also varied from fly to fly, with components belonging to Gammaproteobacteria making up the largest percentage of organisms (30 to 70%) among the microbiome samples. Most of the samples showed the presence of Spiroplasma, a member of the phylum Mollicutes, although the frequency of its presence was variable, ranging from 2 to 57%. Another noteworthy bacterial phylum consistently identified was Firmicutes, though the read abundances were typically below 10%. Of interest is an association between Wolbachia presence and higher Alphaproteobacteria representation in the microbiomes, suggesting that the presence of Wolbachia affects the host microbiome. IMPORTANCE Tabanus nigrovittatus greenhead populations contain two supergroups of Wolbachia endosymbionts, members of supergroups A and B. Analysis of the greenhead microbiome using next-generation sequencing revealed that the majority of bacterial species detected belonged to Gammaproteobacteria, with most of the samples also showing the presence of Spiroplasma, a member of the Mollicutes phylum also known to infect insects. An association between Wolbachia presence and higher Alphaproteobacteria representation in the microbiomes suggests that Wolbachia presence affects the host microbiome composition.

Population genetics and phylogeography of Tabanus bromius (Diptera: Tabanidae)

Background

Tabanus bromius (Diptera: Tabanidae) is one of the most notable Tabanidae species of veterinary and medical importance distributed throughout the Palearctic region. In this study, we investigate the genetic diversity and the phylogeographic structure of T. bromius sampled from Turkey, Croatia, and Iran.

Methods

For this purpose, a 686-base-pair (bp) fragment of mitochondrial DNA cytochrome oxidase I gene (COI) and 1339 bp of the nuclear DNA internal transcribed spacer (ITS) were sequenced from 247 individuals representing 15 populations.

Results

The sequences generated 169 COI haplotypes and 90 ITS alleles. A higher haplotype/allele diversity (h = 0.9909 for the COI gene and Ad = 0.8193 for the ITS region) compared to a low nucleotide diversity (π = 0.020605 for COI gene and π = 0.013667 for the ITS region), present for a high number of singleton and private haplotypes/alleles imply population expansion in the past. The results of phylogenetic analysis led to the uncovering of geographically significant groupings of lineages with regard to the entrance of the species into Anatolia and the location of major geographic barriers. According to current data, the species appears to have entered Turkey from Caucasia and Iran. A molecular clock applied to the COI data suggests that T. bromius diverged from the outgroup species nearly 8.83 million years ago, around the end of the Miocene era.

Conclusions

The results of this study indicate remarkable genetic diversity across the studied range of the species. High haplotype/allele versus low nucleotide diversity and demographic analyses implied that the T. bromius populations have undergone a series of expansions and retreats in the past. Our current findings suggest that T. bromius split from outgroups around the Late Miocene. Subsequent diversification events during the climatic and environmental fluctuation times of the Late Pliocene and Early Pleistocene periods also significantly influenced the species, resulting in the formation of some major genetic lineages. The phylogenetic analyses indicate that T. bromius most likely entered Turkey from the Caucasus region and Iran.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04970-5.

The contribution of insects to African swine fever virus dispersal: data from domestic pig farms in Lithuania

Outbreaks of African Swine Fever (ASF) in domestic pig farms in Lithuania typically begin in June and are detected through October, suggesting that insects might be involved in the transmission of the virus. Entomological collecting was performed to obtain two data sets: from farms with ASF outbreaks, and from farms without ASF outbreaks but in an ASF-infected area. Target insects from the families Muscidae, Calliphoridae and Tabanidae were analysed for the presence of ASF Virus (ASFV) DNA. Musca domestica L., Calliphoridae flies and Stomoxys calcitrans (L.) collected by entomological net during ASF outbreaks were confirmed to be ASFV positive. Viral DNA detected in insects collected by Nzi traps from farms with no ASFV outbreaks indicate that Culex, Lucilia, M. domestica and S. calcitrans are likely to play a role in spreading the ASFV mechanically. This finding could suggest contamination from outside of the farms: from infected wild boar or their carcasses. The role of Stomoxys flies as mechanical vectors could be accidental, because we did not find a significant correlation between the activity of S. calcitrans and the number of ASF outbreaks in pig farms, whereas temperatures positively correlated to the number of ASF outbreaks during 2018-2019.

Differential Immune Response Following Intranasal and Intradermal Infection with Francisella tularensis: Implications for Vaccine Development

Francisella tularensis (Ft) is a Gram-negative, facultative intracellular coccobacillus that is the etiological agent of tularemia. Interestingly, the disease tularemia has variable clinical presentations that are dependent upon the route of infection with Ft. Two of the most likely routes of Ft infection include intranasal and intradermal, which result in pneumonic and ulceroglandular tularemia, respectively. While there are several differences between these two forms of tularemia, the most notable disparity is between mortality rates: the mortality rate following pneumonic tularemia is over ten times that of the ulceroglandular disease. Understanding the differences between intradermal and intranasal Ft infections is important not only for clinical diagnoses and treatment but also for the development of a safe and effective vaccine. However, the immune correlates of protection against Ft, especially within the context of infection by disparate routes, are not yet fully understood. Recent advances in different animal models have revealed new insights in the complex interplay of innate and adaptive immune responses, indicating dissimilar patterns in both responses following infection with Ft via different routes. Further investigation of these differences will be crucial to predicting disease outcomes and inducing protective immunity via vaccination or natural infection.

Tabanids as possible pathogen vectors in Senegal (West Africa)

BACKGROUND

Species of the Tabanidae are potent vectors of human and animal diseases, but they have not been thoroughly investigated to date. In Senegal (West Africa), little information is available on these dipterans. Our objective in this study was to investigate Senegalese tabanids and their diversity by using molecular and proteomics approaches, as well as their associated pathogens.

METHODS

A total of 171 female tabanids were collected, including 143 from Casamance and 28 from Niokolo-Koba. The samples were identified morphologically by PCR sequencing and by MALDI-TOF MS, and PCR analysis was employed for pathogen detection and blood-meal characterization.

RESULTS

The morphological identification revealed four species concordantly with the molecular identification: Atylotus fuscipes (79.5%), Tabanus guineensis (16.4%), Chrysops distinctipennis (3.5%) and Tabanus taeniola (0.6%) (not identified by PCR). The molecular investigation of pathogens revealed the presence of Trypanosoma theileri (6.6%), Leishmania donovani (6.6%), Setaria digitata (1.5%), Rickettsia spp. (5.1%) and Anaplasmataceae bacteria (0.7%) in A. fuscipes. Tabanus guineensis was positive for L. donovani (35.7%), S. digitata (3.6%) and Anaplasmataceae (17.8%). Leishmania donovani has been detected in 50% of C. distinctipennis specimens and the only T. taeniola specimen. No Piroplasmida, Mansonella spp. or Coxeilla burnetii DNA was detected. In addition to humans (96.43%), Chlorocebus sabeus, a non-human primate, has been identified as a host of (3.57%) analysed tabanids. MALDI-TOF MS enabled us to correctly identify all tabanid species that had good quality spectra and to create a database for future identification.

CONCLUSIONS

Tabanids in Senegal could be vectors of several pathogens threatening animal and public health. To fully characterize these dipterans, it is therefore necessary that researchers in entomology and infectiology employ molecular characterization and mass spectrometric techniques such as MALDI-TOF MS to analyse these dipterans in Senegal and West Africa.

Genetic diversity of Anaplasma marginale in calves with anaplasmosis on farms in Minas Gerais, Brazil

The objective of this study was to identify Anaplasma marginale strains in dairy heifers from farms with a history of anaplasmosis in the northwest region of the State of Minas Gerais, Brazil. Among the examined animals of the four farms, the overall prevalence total of A. marginale was 55.7 % for gene msp5 and 36.7 % for blood smear. Thirty DNA samples (from 24 asymptomatic and six symptomatic animals) positive for A. marginale msp1α were sequenced to study genotype and strain diversity. The majority (28/30) were the E genotype, followed by C (1/30) and G (1/30). Thirteen different strains were found: α-β-F-F-F (nine animals), 13-27-27 (three animals), τ-27-18 (three animals), α-β-β- BRA1-31 (three animals), α- 22-1318 (three animals), 80-F-F- F-F (three animals), and α -22-13-13, α-β-β-Г, M-φ-φ-φ-φ-F, 42-25- 25-31, Q-Q-Q-M, B-Q-B-Q-B-M, and 16-17-F-F (one animal each). A new structure repeated in tandem was described and named BRA 1 (TDSSSASGVLSQSGQASTSSQLG). The α-β-F-F-F strain was present in all animals with acute anaplasmosis and in three animals asymptomatic. Thus, although 13 strains were observed in the animals evaluated, only the α-β-F-F-F strain was identified during occurrence of acute disease and mortality, we suggest that this strain has important pathogenicity for calves in northeastern Minas Gerais.

Incompletely observed: niche estimation for six frequent European horsefly species (Diptera, Tabanoidea, Tabanidae)

Background

More than 170 species of tabanids are known in Europe, with many occurring only in limited areas or having become very rare in the last decades. They continue to spread various diseases in animals and are responsible for livestock losses in developing countries. The current monitoring and recording of horseflies is mainly conducted throughout central Europe, with varying degrees of frequency depending on the country. To the detriment of tabanid research, little cooperation exists between western European and Eurasian countries.

Methods

For these reasons, we have compiled available sources in order to generate as complete a dataset as possible of six horsefly species common in Europe. We chose Haematopota pluvialis, Chrysops relictus, C. caecutiens, Tabanus bromius, T. bovinus and T. sudeticus as ubiquitous and abundant species within Europe. The aim of this study is to estimate the distribution, land cover usage and niches of these species. We used a surface-range envelope (SRE) model in accordance with our hypothesis of an underestimated distribution based on Eurocentric monitoring regimes.

Results

Our results show that all six species have a wide range in Eurasia, have a broad climatic niche and can therefore be considered as widespread generalists. Areas with modelled habitat suitability cover the observed distribution and go far beyond these. This supports our assumption that the current state of tabanid monitoring and the recorded distribution significantly underestimates the actual distribution. Our results show that the species can withstand extreme weather and climatic conditions and can be found in areas with only a few frost-free months per year. Additionally, our results reveal that species prefer certain land-cover environments and avoid other land-cover types.

Conclusions

The SRE model is an effective tool to calculate the distribution of species that are well monitored in some areas but poorly in others. Our results support the hypothesis that the available distribution data underestimate the actual distribution of the surveyed species.

Putative Role of Arthropod Vectors in African Swine Fever Virus Transmission in Relation to Their Bio-Ecological Properties

African swine fever (ASF) is one of the most important diseases in Suidae due to its significant health and socioeconomic consequences and represents a major threat to the European pig industry, especially in the absence of any available treatment or vaccine. In fact, with its high mortality rate and the subsequent trade restrictions imposed on affected countries, ASF can dramatically disrupt the pig industry in afflicted countries. In September 2018, ASF was unexpectedly identified in wild boars from southern Belgium in the province of Luxembourg, not far from the Franco-Belgian border. The French authorities rapidly commissioned an expert opinion on the risk of ASF introduction and dissemination into metropolitan France. In Europe, the main transmission routes of the virus comprise direct contact between infected and susceptible animals and indirect transmission through contaminated material or feed. However, the seasonality of the disease in some pig farms in Baltic countries, including outbreaks in farms with high biosecurity levels, have led to questions on the possible involvement of arthropods in the transmission of the virus. This review explores the current body of knowledge on the most common arthropod families present in metropolitan France. We examine their potential role in spreading ASF-by active biological or mechanical transmission or by passive transport or ingestion-in relation to their bio-ecological properties. It also highlights the existence of significant gaps in our knowledge on vector ecology in domestic and wild boar environments and in vector competence for ASFV transmission. Filling these gaps is essential to further understanding ASF transmission in order to thus implement appropriate management measures.

Evaluation of the relative roles of the Tabanidae and Glossinidae in the transmission of trypanosomosis in drug resistance hotspots in Mozambique

BACKGROUND

Tsetse flies (Diptera: Glossinidae) and tabanids (Diptera: Tabanidae) are haematophagous insects of medical and veterinary importance due to their respective role in the biological and mechanical transmission of trypanosomes. Few studies on the distribution and relative abundance of both families have been conducted in Mozambique since the country's independence. Despite Nicoadala, Mozambique, being a multiple trypanocidal drug resistance hotspot no information regarding the distribution, seasonality or infection rates of fly-vectors are available. This is, however, crucial to understanding the epidemiology of trypanosomosis and to refine vector management.

METHODS

For 365 days, 55 traps (20 NGU traps, 20 horizontal traps and 15 Epsilon traps) were deployed in three grazing areas of Nicoadala District: Namitangurine (25 traps); Zalala (15 traps); and Botao (15 traps). Flies were collected weekly and preserved in 70% ethanol. Identification using morphological keys was followed by molecular confirmation using cytochrome c oxidase subunit 1 gene. Trap efficiency, species distribution and seasonal abundance were also assessed. To determine trypanosome infection rates, DNA was extracted from the captured flies, and submitted to 18S PCR-RFLP screening for the detection of Trypanosoma.

RESULTS

In total, 4379 tabanids (of 10 species) and 24 tsetse flies (of 3 species), were caught. NGU traps were more effective in capturing both the Tabanidae and Glossinidae. Higher abundance and species diversity were observed in Namitangurine followed by Zalala and Botao. Tabanid abundance was approximately double during the rainy season compared to the dry season. Trypanosoma congolense and T. theileri were detected in the flies with overall infection rates of 75% for tsetse flies and 13% for tabanids. Atylotus agrestis had the highest infection rate of the tabanid species. The only pathogenic trypanosome detected was T. congolense.

CONCLUSIONS

Despite the low numbers of tsetse flies captured, it can be assumed that they are still the cyclical vectors of trypanosomosis in the area. However, the high numbers of tabanids captured, associated to their demonstrated capacity of transmitting trypanosomes mechanically, suggest an important role in the epidemiology of trypanosomosis in the Nicoadala district. These results on the composition of tsetse and tabanid populations as well as the observed infection rates, should be considered when defining strategies to control the disease.

Study on the Fauna of Aquatic Insects in Northwestern Iran

Background:

Aquatic insects include groups of arthropods which at least one step of their life happens in water. Some of these insects play an important role in the transmission of various diseases to human and animals. Because there is a little information about the fauna of aquatic insects in Iran, this study was aimed to collect and identify aquatic insects in northwestern Iran.

Methods:

A descriptive cross sectional study was performed in July 2017 in Rivers of three villages of Osku County of East Azerbaijan Province, northwestern Iran. The specimens were collected using different methods including D frame net-collector, standard mosquito dipper, Sweep Netting and plastic pipette. The collected specimens were identified based on the systematic keys of aquatic insects.

Results:

Totally 285 samples were collected. Four orders including Diptera, Hemiptera, Ephemeroptera and Coleoptera were identified. Collected samples belonged to seven families of Tipulidae, Chironomidae, Corixidae, Culicidae, Hydrophilidae, Baetidae and Dytiscidae. The most predominant family was Culicidae belonging to order Diptera. Culiseta longiareolata was the most frequent species collected in the study area.

Conclusion:

Aquatic insects usually play an important role in the food chain of animals and some species of them act as predators and play an important role in the biological control of vectors. Therefore, more studies are required to carry out in the field of aquatic insects.

Diversity and seasonality of horse flies (Diptera: Tabanidae) in Uruguay

Horse flies (Diptera: Tabanidae) cause direct and indirect losses in livestock production and are important vectors of pathogens. The aim of this study was to determine the diversity and seasonality of horse fly species at an experimental farm in Tacuarembó and the diversity of species in different departments of Uruguay. For 20 months, systematic collections were performed in two different environments at the experimental farm using Nzi and Malaise traps. In addition, nonsystematic collections were performed at farms located in the departments of Paysandú, Tacuarembó and Colonia. A total of 3,666 horse flies were collected, and 16 species were identified. These species included three species that had not been previously recorded in Uruguay, namely, Dasybasis ornatissima (Brèthes), Dasybasis missionum (Macquart), and Tabanus aff. platensis Brèthes, and a species that had not been previously taxonomically described (Tabanus sp.1). Among the systematically captured samples, the most abundant species were Tabanus campestris Brèthes, T. aff. platensis and D. missionum, representing 77.6% of the collected specimens. The horse fly season in Tacuarembó started in September and ended in May. No horse flies were caught during winter. Variations in the prevalences of species in the different departments were observed, which indicates the need for new sampling efforts.

Shared species of crocodilian trypanosomes carried by tabanid flies in Africa and South America, including the description of a new species from caimans, Trypanosoma kaiowa n. sp

BACKGROUND

The genus Trypanosoma Gruby, 1843 is constituted by terrestrial and aquatic phylogenetic lineages both harboring understudied trypanosomes from reptiles including an increasing diversity of crocodilian trypanosomes. Trypanosoma clandestinus Teixeira & Camargo, 2016 of the aquatic lineage is transmitted by leeches to caimans. Trypanosoma grayi Novy, 1906 of the terrestrial lineage is transmitted by tsetse flies to crocodiles in Africa, but the vectors of Neotropical caiman trypanosomes nested in this lineage remain unknown.

RESULTS

Our phylogenetic analyses uncovered crocodilian trypanosomes in tabanids from South America and Africa, and trypanosomes other than T. grayi in tsetse flies. All trypanosomes found in tabanids clustered in the crocodilian clade (terrestrial lineage) forming six clades: Grayi (African trypanosomes from crocodiles and tsetse flies); Ralphi (trypanosomes from caimans, African and Brazilian tabanids and tsetse flies); Terena (caimans); Cay03 (caimans and Brazilian tabanids); and two new clades, Tab01 (Brazilian tabanid and tsetse flies) and Kaiowa. The clade Kaiowa comprises Trypanosoma kaiowa n. sp. and trypanosomes from African and Brazilian tabanids, caimans, tsetse flies and the African dwarf crocodile. Trypanosoma kaiowa n. sp. heavily colonises tabanid guts and differs remarkably in morphology from other caiman trypanosomes. This species multiplied predominantly as promastigotes on log-phase cultures showing scarce epimastigotes and exhibited very long flagellates in old cultures. Analyses of growth behavior revealed that insect cells allow the intracellular development of Trypanosoma kaiowa n. sp.

CONCLUSIONS

Prior to this description of Trypanosoma kaiowa n. sp., no crocodilian trypanosome parasitic in tabanid flies had been cultured, morphologically examined by light, scanning and transmission microscopy, and phylogenetically compared with other crocodilian trypanosomes. Additionally, trypanosomes thought to be restricted to caimans were identified in Brazilian and African tabanids, tsetse flies and the dwarf crocodile. Similar repertoires of trypanosomes found in South American caimans, African crocodiles and tabanids from both continents support the recent diversification of these transcontinental trypanosomes. Our findings are consistent with trypanosome host-switching likely mediated by tabanid flies between caimans and transoceanic migrant crocodiles co-inhabiting South American wetlands at the Miocene.

Molecular Detection of Anaplasma phagocytophilum in Blood-Sucking Flies (Diptera: Tabanidae) in Poland

Anaplasma phagocytophilum is a pathogen of veterinary and medical importance. It is the causative agent of tick-borne fever (TBF) in ruminants (also known as bovine or ovine granulocytic anaplasmosis), and of human granulocytic anaplasmosis (HGA) in humans. In Europe, A. phagocytophilum is transmitted by Ixodes ricinus (Linnaeus 1758) ticks. The aim of this study was to confirm the presence of A. phagocytophilum DNA in blood-sucking flies belonging to the Tabanidae family using molecular methods. It represents the first detection of this pathogen in Haematopota pluvialis (Linnaeus 1758), Tabanus bromius (Linnaeus 1758), and Tabanus distinguendus (Verrall 1909) in Europe.

Benefits of zebra stripes: Behaviour of tabanid flies around zebras and horses

Averting attack by biting flies is increasingly regarded as the evolutionary driver of zebra stripes, although the precise mechanism by which stripes ameliorate attack by ectoparasites is unknown. We examined the behaviour of tabanids (horse flies) in the vicinity of captive plains zebras and uniformly coloured domestic horses living on a horse farm in Britain. Observations showed that fewer tabanids landed on zebras than on horses per unit time, although rates of tabanid circling around or briefly touching zebra and horse pelage did not differ. In an experiment in which horses sequentially wore cloth coats of different colours, those wearing a striped pattern suffered far lower rates of tabanid touching and landing on coats than the same horses wearing black or white, yet there were no differences in attack rates to their naked heads. In separate, detailed video analyses, tabanids approached zebras faster and failed to decelerate before contacting zebras, and proportionately more tabanids simply touched rather than landed on zebra pelage in comparison to horses. Taken together, these findings indicate that, up close, striped surfaces prevented flies from making a controlled landing but did not influence tabanid behaviour at a distance. To counteract flies, zebras swished their tails and ran away from fly nuisance whereas horses showed higher rates of skin twitching. As a consequence of zebras’ striping, very few tabanids successfully landed on zebras and, as a result of zebras’ changeable behaviour, few stayed a long time, or probed for blood.

Striped bodypainting protects against horseflies

Bodypainting is widespread in African, Australian and Papua New Guinean indigenous communities. Many bodypaintings use white or bright yellow/grey/beige stripes on brown skin. Where the majority of people using bodypainting presently live, blood-sucking horseflies are abundant, and they frequently attack the naked brown regions of the human body surface with the risk of transmitting the pathogens of dangerous diseases. Since horseflies are deterred by the black and white stripes of zebras, we hypothesized that white-striped paintings on dark brown human bodies have a similar effect. In a field experiment in Hungary, we tested this hypothesis. We show that the attractiveness to horseflies of a dark brown human body model significantly decreases, if it is painted with the white stripes that are used in bodypaintings. Our brown human model was 10 times more attractive to horseflies than the white-striped brown model, and a beige model, which was used as a control, attracted two times more horseflies than the striped brown model. Thus, white-striped bodypaintings, such as those used by African and Australian people, may serve to deter horseflies, which is an advantageous byproduct of these bodypaintings that could lead to reduced irritation and disease transmission by these blood-sucking insects.

Specimens inventory of Tabanidae (Diptera) of Entomological Collection of National Museum of Natural History - Universidade Federal do Rio de Janeiro

Abstract: A checklist of tabanids of the Entomological Collection of National Museum of Natural History - Universidade Federal do Rio de Janeiro is provide. A total of 5,325 specimens was examined of which 2,916 were found identified, belonging to 341 species, 42 genera e four varieties, collected from all continents since 1902. The currently taxa names were provided when possible, also currently localities of collections.

Horse flies and their seasonal abundance in El Tarf Province of northeastern Algeria

The horse flies of El Tarf Province, northeastern Algeria comprise 15 species within two subfamilies (Chrysopsinae and Tabaninae) belonging to five genera (Atylotus, Chrysops, Dasyrhamphis, Haematopota, and Tabanus). The genera Chrysops, Dasyrhamphis, and Haematopota are represented by two species for each, while the genera Atylotus and Tabanus are represented by four and five species, respectively. Seasonal abundance was assessed from mid-March until the end of September, 2017 for the trapped species. Haematopota pluvialis and Tabanus autumnalis appeared in April and lasted until September with a peak in May. Atylotus agrestis appeared in May with the highest density and lasted until September. Atylotus fulvus, Atylotus kroberi, and Haematopota italica emerged in April with peaks in May, while Chrysops flavipes appeared in March, reaching its peak in May and June, declining in July, and disappearing thereafter. Atylotus flavoguttatus, Chrysops mauritanicus, and Dasyrhamphis tomentosus appeared in April with a peak in June, then disappearing in August. Tabanus nemoralis started to appear in April with a peak in May and disappearance after July. Dasyrhamphis algirus, Tabanus bromius, and Tabanus eggeri started to appear in May. Both Tabanus eggeri and Dasyrhamphis algirus peaked in June and July, whereas T. eggeri lasted until the end of September. Tabanus tinctus was observed in June with a peak in August and lasted until September.

Alighting and Feeding Behavior of Trypanosome-Transmitting Vectors on Cattle in Nigeria

Vector control is important to effectively prevent trypanosomiasis. Therefore, alighting and feeding responses of trypanosome-transmitting vectors were conducted in Nigeria. The aim of this study was to assess the landing preference, level of fly annoyance on cattle, and feeding behavior by direct observation of cows, bulls, and calves. The percentage of Glossina species, Tabanus species, and stomoxyine that fed on cattle blood after landing varied according to the age and sex of the cattle host. Although most flies left the cattle host before completing their meal because of host defensive behaviors, an average of 78, 19.6, and 10.2% of Glossina, Tabanus, and stomoxyines, respectively, were fully engorged. The longest mean feeding time was observed in Glossina. Over more than 90% of Glossina spp. landed on the belly and legs. Most Tabanus spp. (85%) also landed on the belly and legs while Tabanus par Walker (Diptera: Tabanidae) often landed on the back (45%). Half of Stomoxys species landed on the head and neck. Vector flies' feeding success varied according to cattle host age and was negatively correlated with defensive host behaviors and apparent fly density. Hence, fly defensive behaviors contribute to trypanosomiasis dynamics in a cattle herd, and expended energy from defensive behaviors could adversely affect productivity.

Dispersal capacity of Haematopota spp. and Stomoxys calcitrans using a mark-release-recapture approach in Belgium

The dispersion potential of mechanical vectors is an important factor in the dissemination of pathogens. A mark-release-recapture experiment was implemented using two groups (unfed and partially fed) of the Tabanidae (Diptera) (Haematopota spp.) and biting Muscidae (Diptera) (Stomoxys calcitrans) most frequently collected in Belgium in order to evaluate their dispersion potential. In total, 2104 specimens of Haematopota spp. were collected directly from horses and 5396 S. calcitrans were collected in a cattle farm using hand-nets. Some of these insects were partially fed in vitro and all were subsequently coloured. Overall, 67 specimens of S. calcitrans (1.2%) and 17 of Haematopota spp. (0.8%) were recaptured directly on horses. Stomoxys calcitrans flew maximum distances of 150 m and 300 m when partially fed and unfed, respectively. Haematopota spp. travelled maximum distances of 100 m and 200 m when partially fed and unfed, respectively. Segregation measures seem essential in order to reduce the risk for pathogen transmission. A distance of 150 m appears to be the minimum required for segregation to avoid the risk for mechanical transmission, but in areas of higher vector density, this should probably be increased.

Species identification of horse flies (Diptera: Tabanidae) in Thailand using DNA barcoding

Horse flies (Diptera: Tabanidae) are of medical and veterinary importance because they are known to transmit pathogens. Approximately 80 species of horse flies have been reported in Thailand. Monitoring the distribution of horse fly species is important to control the spread of diseases transmitted by them. Currently, the species identification of horse flies is based on their morphology; this requires considerable skills and taxonomic expertise, and it may be difficult to identify morphologically similar species. DNA-based identification methods are increasingly being developed for rapid and accurate identification of various insect species. In this study, we used mitochondrial cytochrome oxidase subunit I (COI) for species identification of horse flies in Thailand. A 658 bp fragment of COI was amplified from 145 adult horse flies belonging to 48 morphologically distinct species and sequenced. Sequence analysis revealed an intraspecific divergence of 0.0%-4.4% and an interspecific divergence of 0.0%-16.2%. Our results showed that COI barcodes were effective in discriminating a majority of horse flies in Thailand on the basis of the barcoding gap and phylogenetic analyses. However, COI barcodes were unable to distinguish among members of the Tabanus striatus complex and some species within the T. ceylonicus group.

An Investigation into the High Prevalence of Hepatitis B in a Rural Area of Kerala State, India: Hypothesis on Chrysops sp. (Diptera: Tabanidae) Transmission

Objective

Since 2005 there have been several reports of hepatitis B outbreak in the state of Kerala in southern India. Objective of this study was to analyze such outbreaks and to explore hypothesis pertaining the transmission mode.

Methods

Retrospective observational study involving cases of acute hepatitis B acquired between 1 January 2015 and 31 December 2015 and their family members residing in Mazhuvanoor village in Ernakulam district of Kerala State in southern India.

Results

59 houses were included in the survey. The number of patients diagnosed to have acute viral hepatitis B was 59. Majority (66.10%) were over 50 years old. There were no cases below the age of 15 years. All 59 patients claimed to have been bitten frequently by a fly which was identified as “deer fly” belonging to the genus Chrysops.

Conclusion

Given the current understanding of mechanical transmission of pathogens in both humans and animals by insects belonging to the Tabanidae family which also includes Chrysops, it is plausible that the same mechanism may hold true for hepatitis B also. However this needs to be proven in further studies both at the laboratory level and at field studies.

Two New Species and Seven New Records of Horse Fly (Diptera: Tabanidae) From Malaysia, Including a Description of New Species and Modified Keys

Horse flies (Diptera: Tabanidae) are of medical and veterinary importance, as their blood-sucking feeding habit enables them to transmit several disease-causing agents. In Malaysia, the family Tabanidae consists of 120 species belonging to eight genera. The current study describes two new species (Chrysops idlani sp. nov. and Tabanus ekor sp. nov.) and presents new records for seven species: Tabanus fontinalisSchuurmans Stekhoven, 1926; Tabanus fuscifronsSchuurmans Stekhoven, 1926, Tabanus latifasciesSchuurmans Stekhoven, 1926, Tabanus megalops (Walker, 1854), Tabanus rhinargusPhilip, 1962, Tabanus salvazai (Surcouf, 1922), and Tabanus tristisWulp, 1881. Complete descriptions and illustrations are provided for the new species, and species variations for the new records are discussed. Male Tabanus latifasciesSchuurmans Stekhoven, 1926 and Tabanus perakiensis Ricardo, 1911 are thoroughly described herein.

An Overview of Trypanosoma brucei Infections: An Intense Host-Parasite Interaction

Trypanosoma brucei rhodesiense and T. brucei gambiense, the causative agents of Human African Trypanosomiasis, are transmitted by tsetse flies. Within the vector, the parasite undergoes through transformations that prepares it to infect the human host. Sequentially these developmental stages are the replicative procyclic (in which the parasite surface is covered by procyclins) and trypo-epimastigote forms, as well as the non-replicative, infective, metacyclic form that develops in the vector salivary glands. As a pre-adaptation to their life in humans, metacyclic parasites begin to express and be densely covered by the Variant Surface Glycoprotein (VSG). Once the metacyclic form invades the human host the parasite develops into the bloodstream form. Herein the VSG triggers a humoral immune response. To avoid this humoral response, and essential for survival while in the bloodstream, the parasite changes its cover periodically and sheds into the surroundings the expressed VSG, thus evading the consequences of the immune system activation. Additionally, tools comparable to quorum sensing are used by the parasite for the successful parasite transmission from human to insect. On the other hand, the human host promotes clearance of the parasite triggering innate and adaptive immune responses and stimulating cytokine and chemokine secretion. All in all, the host–parasite interaction is extremely active and leads to responses that need multiple control sites to develop appropriately.

Seasonal patterns of horse fly richness and abundance in the Pampa biome of southern Brazil

Fluctuations in seasonal patterns of horse fly populations were examined in rainforests of tropical South America, where the climate is seasonal. These patterns were evaluated with robust analytical models rather than identifying the main factors that influenced the fluctuations. We examined the seasonality of populations of horse flies in fields and lowland areas of the Pampa biome of southern Brazil with generalized linear models. We also investigated the diversity of these flies and the sampling effort of Malaise traps in this biome over two years. All of the 29 species had clear seasonality with regard to occurrence and abundance, but only seven species were identified as being influenced by temperature and humidity. The sampling was sufficient and the estimated diversity was 10% more than observed. Seasonal trends were synchronized across species and the populations were most abundant between September and March and nearly zero in other months. While previous studies demonstrated that seasonal patterns in population fluctuations are correlated with climatic conditions in horse fly assemblages in South America rainforests, we show a clear effect of each factor on richness and abundance and the seasonality in the prevalence of horse fly assemblages in localities of the Pampa biome.

Description of Dichelacera (Dichelacera) walteri n. sp. (Diptera: Tabanidae) with a Key to Related Species in the Subgenus Dichelacera Macquart

Dichelacera (Dichelacera) walteri Guimarães, Gorayeb & Rodrigues-Guimarães n. sp. is described from female specimens collected in Marambaia Island, located in Mangaratiba County, state of Rio de Janeiro, Brazil. The characterization of the species was based in the following characters: a medium-sized species, more sclerotized than others in the subgenus Dichelacera Macquart, the second segment of palp with dark setae and longer than the third antennal segment, a brown scutum with pruinescence on the anterior half and posterior edges with white tonality, yellow dorsum of abdomen with the last three segments brown, white-yellowish venter with yellow setae, narrow frons with dark brown callus, extending just beyond a ridge in the middle of the frons, vertex with ocelli, hyaline wings with three large black bands, and tricolored legs.

Identification through DNA barcoding of Tabanidae (Diptera) vectors of surra disease in India

Horse flies and deer flies are common names applied to members of the family Tabanidae (Diptera). Tabanid flies are pestiferous and of veterinary and medical importance, with about 244 species in India. They are major vectors of Trypanosoma evansi that causes trypanosomiasis (surra disease). Lack of stable morphological characters, and scarcity of taxonomic expertise, is major impediments for accurate species identification of these important pest and disease vectors. Molecular data, especially DNA barcode data, has been widely used in the identification of Diptera of economic importance. We evaluated the utility of DNA barcode data to discriminate the vectors of surra disease (trypanosomiasis) from India. We used barcode gap and reciprocal monophyly (neighbor-joining and Bayesian tree) criteria to analyze barcode data. A total of 46 specimens belonging to 7 species under four genera in two subfamilies were used for this study. DNA barcode data was not available previously for these species. Analysis revealed that all morphologically identifiable species can be discriminated using DNA barcoding data. Further, our study clearly demonstrated the presence of cryptic species in Chrysops dispar. Moreover, we revealed that closely related species without stable taxonomic distinguishing characters in the "Tabanus striatus species complex" can be discriminated using DNA barcode data.

Seasonal Abundance of Deer and Horse Flies (Diptera: Tabanidae) in the Northern Part of Gyeonggi-do, Republic of Korea

The seasonal abundance of horse and deer flies (family Tabanidae) was analyzed using Mosquito Magnet^® traps at 5 sites located near/in the demilitarized zone, northern Gyeonggi-do, Republic of Korea from late April to early October for 4 consecutive years (2010-2013). A total of 2,999 horse and deer flies (tabanids) belonging to 5 genera and 20 species were collected. Chrysops mlokosiewiczi (90.9%) was the most frequently collected, followed by Haematopota koryoensis (4.8%) and C. suavis (1.0%). The remaining 17 species comprised only of 3.3% of all species collected. C. mlokosiewiczi demonstrated bimodal peak populations during mid-June and early August, while H. koryoensis demonstrated a unimodal peak during mid-July. Overall numbers of tabanids collected were influenced by the previous year’s winter temperatures and precipitation. Population abundance was influenced by habitat with most of tabanids collected from habitats near forested areas, followed by rice paddies, and a beef farm.