Biodiversity of the Simuliidae family

Simuliidae belong to the order Diptera, suborder Nematocera, Infraorder Culicomorpha, Superfamily Chironomoidea, and Family Simuliidae. They are known as “borrachudo” or “pium” in Brazil and as “black flies” in English-speaking countries. This study objective to report the characteristics of the Family Simuliidae. The research was carried out in studies related to quantitative aspects of the Family, Subfamily and Species (taxonomic groups) and conceptual aspects such as: biology, geographical distribution, species, life cycle, damage, economic importance, medicinal importance, biological aspects, and reproduction. A literature search was carried out containing articles published from 1950 to 2021. The mini-review was prepared in Goiânia, Goiás, from September to October 2021, through the Portal of Scientific Journals in Health Sciences, Pubmed, Online Scientific Library (Scielo), internet, ResearchGate, Academia.edu, Frontiers, Biological Abstract, Publons, Qeios, Dialnet, World, Wide Science, Springer, RefSeek, Microsoft Academic, Science, ERIC, Science Research.com, SEEK education, Periodicals CAPES, Google Academic, Bioline International and VADLO.

Onchocerca volvulus transmission in the Mbam valley of Cameroon following 16 years of annual community-directed treatment with ivermectin, and the description of a new cytotype of Simulium squamosum

Background The onchocerciasis focus surrounding the lower Mbam and Sanaga rivers, where Onchocerca volvulus is transmitted by Simulium damnosum s.l. (Diptera: Simuliidae), was historically the largest in the southern regions of Cameroon. Annual community-directed treatment with ivermectin (CDTI) has been taking place since 2000, but recent studies have shown that new infections are occurring in children. We aimed to investigate blackfly biting and O. volvulus transmission rates along the lower Mbam river 16 years after the formal onset of annual CDTI. Methods Black flies were collected for three consecutive days each month between July 2016 and June 2017 at two riverside villages and two inland sites situated 4.9 km and 7.9 km from the riverside. Specimens collected at each site were dissected on one of the three collection days each month to estimate parity rates and O. volvulus infection rates, while the remaining samples were preserved for pool screening. Results In total, 93,573 S. damnosum s.l. black flies were recorded biting humans and 9281 were dissected. Annual biting rates of up to 606,370 were estimated at the riverside, decreasing to 20,540 at 7.9 km, while, based on dissections, annual transmission potentials of up to 4488 were estimated at the riverside, decreasing to 102 and 0 at 4.9 km and 7.9 km, respectively. However, pool screening showed evidence of infection in black flies at the furthest distance from the river. Results of both methods demonstrated the percentage of infective flies to be relatively low (0.10–0.36%), but above the WHO threshold for interruption of transmission. In addition, a small number of larvae collected during the dry season revealed the presence of Simulium squamosum E. This is the first time S. squamosum E has been found east of Lake Volta in Ghana, but our material was chromosomally distinctive, and we call it S. squamosum E2. Conclusions Relatively low O. volvulus infection rates appear to be offset by extremely high densities of biting black flies which are sustaining transmission along the banks of the lower Mbam river. Graphical Abstract

The efficiency of methods for catching insects - vectors of vector-borne diseases of animals and their species composition

The article provides the results of study of the effectiveness of collection methods and the taxonomic identification of insects in the regions of Russia. During the research three methods of collecting insects were used: a UV trap, fly strips and a liquid gadfly trap (“death puddle”). The following blood-sucking insects play a key role in the epizootology of transmissible infections - houseflies (Muscidae), black flies (Simuliidae), mosquitoes (Culicidae), biting midges (Ceratopogonidae), gadflies (Tabanidae). There has been obtained new information on the species, territorial and temporal dynamics of the distribution of vectors of lumpy skin disease in cattle in the subjects of the Russian Federation. Data collection of the spatial and temporal spread of the disease visualized using GIS-technologies have been generated on the basis of the statistical reports. As the result of the research, it has been established that in the Nizhny Novgorod region representatives of the Psychodidae family, the percentage of which was 40.9 %, predominate in the nocturnal entomological complex. They are followed by mosquitoes (genus Culex) - 21.6 %, biting midges - 16.4 % manure flies - 7.0 % and black flies - 3.0 %, respectively. In the Saratov region, the nocturnal entomological complex was represented by manure flies (family Sphaeroceridae), black flies (family Simuliidae) and mosquitoes (genus Culex), the percentages were 56,0, 32,0 and 12,0 %, respectively. At the same time, in the Saratov region there were collected 239 times less mosquitoes than in the Nizhny Novgorod region, which was due to an increase in temperature in the conditions of the southern regions. This caused the water bodies to dry out and reduced the pool of insects whose developmental cycle is related to water. It has been established that all-year keeping of cattle in winter cow yards provides the diversity and rise in the number of insect vectors, which increases the risk of lumpy skin disease as compared to the grazing system of cattle keeping. For collection daytime insect vectors, it is recommended to use fly strips covered with rosin and mineral oil. For collection insects of the nocturnal entomocomplex, which are the main transmitters of the lumpy skin disease virus, one should use ultraviolet traps.

“Slash and Clear”, a Community-Based Vector Control Method to Reduce Onchocerciasis Transmission by Simulium sirbanum in Maridi, South Sudan: A Prospective Study

Background: High ongoing Onchocerca volvulus transmission was recently documented in Maridi County, South Sudan. To complement community-directed treatment with ivermectin (CDTI) as the main onchocerciasis control strategy, we initiated a community-based vector control method “slash and clear” at the Maridi dam, a Simulium damnosum s.l. breeding site, to reduce O. volvulus transmission. Methods: Simulium damnosum s.l. biting rates were collected before and during the twenty months following the “slash and clear” intervention using the human landing catches. Black flies were dissected to measure parity rates before and twelve months after the intervention. Larvae and pupae of S. damnosum s.l. were collected from the dam for morphological and chromosomal characterization to identify the cytospecies involved. Results: Biting rates of S. damnosum s.l. close to the Maridi dam spillway decreased by >90% post-“slash and clear” for more than six months. Twelve months after the “slash and clear” intervention, the reduction in biting rates was still at <50% (p = 0.0007). Parity rates reduced from 13% pre-“slash and clear” (November 2019) to 5.6% post-“slash and clear” (November 2020). Larvae collected from the dam were identified as Simulium sirbanum. Conclusion: The “slash and clear” method was found to be an effective and cheap community-based method to reduce black fly biting rates caused by S. sirbanum. When repeated at least annually together with a high CDTI coverage, this intervention has the potential to considerably accelerate onchocerciasis elimination.

Fungi of entomopathogenic potential in Chytridiomycota and Blastocladiomycota, and in fungal allies of the Oomycota and Microsporidia

The relationship between entomopathogenic fungi and their insect hosts is a classic example of the co-evolutionary arms race between pathogen and target host. The present review describes the entomopathogenic potential of Chytridiomycota and Blastocladiomycota fungi, and two groups of fungal allies: Oomycota and Microsporidia. The Oomycota (water moulds) are considered as a model biological control agent of mosquito larvae. Due to their shared ecological and morphological similarities, they had long been considered a part of the fungal kingdom; however, phylogenetic studies have since placed this group within the Straminipila. The Microsporidia are parasites of economically-important insects, including grasshoppers, lady beetles, bumblebees, colorado potato beetles and honeybees. They have been found to display some fungal characteristics, and phylogenetic studies suggest that they are related to fungi, either as a basal branch or sister group. The Blastocladiomycota and Chytridiomycota, named the lower fungi, historically were described together; however, molecular phylogenetic and ultrastructural research has classified them in their own phylum. They are considered parasites of ants, and of the larval stages of black flies, mosquitoes and scale insects.

Surveillance along the Rio Grande during the 2020 Vesicular Stomatitis Outbreak Reveals Spatio-Temporal Dynamics of and Viral RNA Detection in Black Flies

Vesicular stomatitis virus (VSV) emerges periodically from its focus of endemic transmission in southern Mexico to cause epizootics in livestock in the US. The ecology of VSV involves a diverse, but largely undefined, repertoire of potential reservoir hosts and invertebrate vectors. As part of a larger program to decipher VSV transmission, we conducted a study of the spatiotemporal dynamics of Simulium black flies, a known vector of VSV, along the Rio Grande in southern New Mexico, USA from March to December 2020. Serendipitously, the index case of VSV-Indiana (VSIV) in the USA in 2020 occurred at a central point of our study. Black flies appeared soon after the release of the Rio Grande’s water from an upstream dam in March 2020. Two-month and one-year lagged precipitation, maximum temperature, and vegetation greenness, measured as Normalized Difference Vegetation Index (NDVI), were associated with increased black fly abundance. We detected VSIV RNA in 11 pools comprising five black fly species using rRT-PCR; five pools yielded a VSIV sequence. To our knowledge, this is the first detection of VSV in the western US from vectors that were not collected on premises with infected domestic animals.

Cytogenetics of the Simulium arcticum complex (Diptera: Simuliidae)

Descriptions of chromosomal rearrangements, geographic distributions and frequencies of nine siblings and 28 cytotypes of the Simulium arcticum Malloch complex are presented. Findings are based on six data sets that include approximately 21,000 chromosomally analyzed larvae from throughout the known geographic range of S. arcticum. This is the largest chromosomal data set for any North American complex of black flies. This summary emphasizes the need to chromosomally analyze taxa of black flies since this type of analysis can result in, not only, a better understanding of the number of taxa in a complex and their relationships but also, it may help to understand the initial stages of reproductive isolation within otherwise morphologically identical groups. Geographically, the streams of eastern Alaska, the entire province of the Yukon and northern Mexico should be sampled. Taxonomically the many cytotypes should be tested for reproductive status when they occur in sympatry with other siblings and cytotypes of the complex. Finally, comparative multi-omic research would be useful.

Presence of a cryptic Onchocerca species in black flies of northern California, USA

Background Black flies (Diptera: Simuliidae) serve as arthropod vectors for various species of Onchocerca (Nematoda: Onchocercidae) that may be associated with disease in humans, domestic animals, and wildlife. The emergence of zoonotic Onchocerca lupi in North America and reports of cervid-associated zoonotic onchocerciasis by Onchocerca jakutensis highlight the need for increased entomological surveillance. In addition, there is mounting evidence that Onchocerca diversity in North America is far greater than previously thought, currently regarded as Onchocerca cervipedis species complex. This study reports new geographic records and black fly vector associations of an uncharacterized Onchocerca species. Methods To better understand the biodiversity and geographic distribution of Onchocerca, 485 female black flies (2015: 150, 2016: 335) were collected using CO2-baited traps from February to October 2015–2016 in Lake County, northern California, USA. Individual flies were morphologically identified and pooled (≤ 10 individuals) by species, collection date, and trap location. Black fly pools were processed for DNA extraction, and subsequent PCR and sequencing targeting of the NADH dehydrogenase subunit 5 gene of filarioids. Results Among the pools of black flies, there were 158 individuals of Simulium tescorum (2015: 57, 2016: 101), 302 individuals of Simulium vittatum (sensu lato [s.l.]) (2015: 82, 2016: 220), 16 individuals of Simulium clarum “black” phenotype (2015: 5, 2016: 11), and 13 individuals of S. clarum “orange” phenotype (2015: 6, 2016: 7). PCR analysis revealed the percentage of filarioid-positive pools were 7.50% (n = 3) for S. tescorum, 3.75% (n = 3) for S. vittatum (s.l., likely S. tribulatum), 7.69% (n = 1) for S. clarum “black” phenotype, and no positives for S. clarum “orange” phenotype. Genetic distance and phylogenetic analyses suggest that the northern California Onchocerca isolates belong to the same species reported in black flies from southern California (average pairwise comparison: 0.32%), and seem closely related to Onchocerca isolates of white-tailed deer from upstate New York (average pairwise comparison: 2.31%). Conclusion A cryptic Onchocerca species was found in Lake County, California, and may be a part of a larger, continentally distributed species complex rather than a single described species of North America. In addition, there are at least three putative vectors of black flies (S. clarum, S. tescorum, S. vittatum) associated with this cryptic Onchocerca species. A comprehensive reassessment of North American Onchocerca biodiversity, host, and geographic range is necessary. Graphical abstract