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Insects May 2024Two species of black flies (Simuliidae) in Thailand, Takaoka and Kuvangkadilok, 2000, and Takaoka, Srisuka & Saeung, 2022, are potent vectors of avian blood protozoa...
Two species of black flies (Simuliidae) in Thailand, Takaoka and Kuvangkadilok, 2000, and Takaoka, Srisuka & Saeung, 2022, are potent vectors of avian blood protozoa of the genera and and are pests of domestic avian species. Although the adults are abundant throughout Thailand, information on their breeding habitats is limited, and the immature stages of are unknown. We collected the larvae and pupae of from the Mekong River, the first-ever record of Simuliidae from this large continental river. Mitochondrial cytochrome c oxidase I and internal transcribed spacer 2 were used to associate the larvae and pupae with known adults. Both genetic markers strongly supported their identity as . The larvae and pupa of are described. The pupal gill filaments, larval abdominal protuberances, and setae distinguish this species from other members of the species group. The immature stages of inhabit a wide variety of flowing waters, from small streams (3 m wide) to enormous continental rivers (400 m wide); thus, is a habitat generalist. In contrast, was found only in the large Mekong River and is, therefore, a habitat specialist. Both species can exploit their principal habitats and produce abundant adult populations.
PubMed: 38786902
DOI: 10.3390/insects15050346 -
Parasites & Vectors May 2024The main vectors of onchocerciasis in Africa are Simulium damnosum sensu lato, which transmit the causative agent Onchocerca volvulus. The force of transmission is...
BACKGROUND
The main vectors of onchocerciasis in Africa are Simulium damnosum sensu lato, which transmit the causative agent Onchocerca volvulus. The force of transmission is driven by the vector density, hence influencing the disease prevalence and intensity. Onchocerciasis is currently targeted for elimination using mass drug administration (MDA) of ivermectin, a potent microfilaricide. MDA in Cameroon began in 1987 in the Vina Valley, an endemic cross-border area with Chad, known for high vector densities and precontrol endemicity. Evaluations in 2008-2010 in this area showed ongoing transmission, while border areas in Chad were close to interrupting transmission. This study aimed to evaluate transmission in this area after several rounds of MDA since the last evaluation surveys.
METHODS
Black flies were collected by human landing catches at seven border sites in Cameroon, twice a week, from August 2021 to March 2022. A fraction of the flies was dissected for parity assessment and identification of Onchocerca larval stages. The transmission indices were estimated. Black fly larvae were also collected from the breeding sites at the fly catching sites and identified to species level by cytotaxonomy.
RESULTS
A total of 14,303 female flies were collected, and 6918 were dissected. Of these, 4421 (64.0%) were parous. The total biting rates were high, reaching up to 16,407 bites/person/study period, and transmission potential (third-stage larvae (L3) from head/all L3) were 367/702, 146/506, 51/55, 20/32, 0/3, 0/0, and 0/0 infective larvae/person, respectively, for Mbere-Tchad, Babidan, Hajam/V5, Gor, Djeing, Touboro, and Koinderi. Infectivity rates (L3 from head) were 16.00, 12.75, 5.15, and 4.07 infective females (L3H)/1000 parous flies for Haijam, Mbere-Tchad, Babidan, and Gor, respectively. These values exceed the World Health Organization (WHO) thresholds of ≤ 20 annual transmission potential (ATP) or < 1 infective female/1000 parous females. The major vectors identified were Simulium damnosum sensu stricto, S. squamosum, and for the first time in the area, S. yahense.
CONCLUSIONS
More than 20 years of MDA has not eliminated onchocerciasis in the study area; hence, this area is a potential source of reintroduction of onchocerciasis in Chad and would require alternative treatment strategies. Many factors such as MDA efficiency, effectiveness of ivermectin, and cytospecies composition may be contributing to transmission persistence.
Topics: Onchocerciasis; Animals; Cameroon; Ivermectin; Simuliidae; Humans; Onchocerca volvulus; Insect Vectors; Female; Mass Drug Administration; Chad; Larva; Filaricides; Male
PubMed: 38741212
DOI: 10.1186/s13071-024-06284-8 -
Waste Management (New York, N.Y.) May 2024The interest in mass-rearing black soldier fly (Hermetia illucens) larvae for food and feed is rapidly increasing. This is partly sparked by the ability of the larvae to...
The interest in mass-rearing black soldier fly (Hermetia illucens) larvae for food and feed is rapidly increasing. This is partly sparked by the ability of the larvae to efficiently valorise a wide range of organic waste and by-products. Primarily, research has focused on the larval stage, hence underprioritizing aspects of the adult biology, and knowledge on reproduction-related traits such as egg production is needed. We investigated the impact of different organic waste and by-products as larval diets on various life-history traits of adult black soldier flies in a large-scale experimental setup. We reared larvae on four different diets: spent Brewer's grain, ground carrots, Gainesville diet, and ground oranges. Traits assessed were development time to pupa and adult life-stages, adult body mass, female lifespan, egg production, and egg hatch. Larval diet significantly impacted development time to pupa and adult, lifespan, body size, and egg production. In general, flies reared on Brewer's grain developed up to 4.7 d faster, lived up to 2.3 d longer, and produced up to 57% more eggs compared to flies reared on oranges on which they performed worst for these traits. There was no effect of diet type on egg hatch, suggesting that low-nutritious diets, i.e. carrots and oranges, do not reduce the quality but merely the quantity of eggs. Our results demonstrate the importance of larval diet on reproductive output and other adult traits, all important for an efficient valorisation of organic waste and by-products, which is important for a sustainable insect-based food and feed production.
Topics: Animals; Larva; Reproduction; Female; Life History Traits; Diet; Diptera; Waste Products; Male; Simuliidae
PubMed: 38608528
DOI: 10.1016/j.wasman.2024.04.010 -
Insects Feb 2024Discoveries of endemic species highlight areas of biogeographic and conservation interest. Endemic species, however, are often morphologically disguised as more common...
Discoveries of endemic species highlight areas of biogeographic and conservation interest. Endemic species, however, are often morphologically disguised as more common and widespread species. The larval polytene chromosomes revealed a new species of black fly, , from the Djurdjura Mountains of northern Algeria, and its female, male, pupa, and larva are described. The species is chromosomally unique; none of its 11 chromosomal rearrangements are shared with other species. Although the new species structurally resembles (Meigen) with which it previously has been confused, it can be distinguished from all other known species of in the Western Palearctic based on at least one character in each described life stage. Symbiotic organisms included two species of microsporidia, at least one of which is probably undescribed, one unknown protozoan pathogen novel in simuliids, and the trichomycete fungus Léger and Duboscq. Associated simuliid species included at least one new species of the genus . The new species of is tentatively considered endemic to the mountains of northern Algeria but might be expected in the mountains of eastern Morocco and northern Tunisia and perhaps in Sicily. If its endemic status holds, it would be the only nominal species of black fly unique to Algeria.
PubMed: 38535346
DOI: 10.3390/insects15030150 -
Parasites & Vectors Feb 2024Vesicular 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...
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.
Topics: Animals; Simuliidae; Vesicular Stomatitis; New Mexico; Insect Vectors; Vesiculovirus; Larva; Disease Outbreaks
PubMed: 38414030
DOI: 10.1186/s13071-024-06127-6 -
Insects Jan 2024The Huangshui River, a vital tributary in the upper reaches of the Yellow River within the eastern Qinghai-Tibet Plateau, is home to the endemic black fly species . In...
Comparative Study of Potential Habitats for (Diptera: Simuliidae) in the Huangshui River Basin, Qinghai-Tibet Plateau: An Analysis Using Four Ecological Niche Models and Optimized Approaches.
The Huangshui River, a vital tributary in the upper reaches of the Yellow River within the eastern Qinghai-Tibet Plateau, is home to the endemic black fly species . In this study, we conducted a systematic survey of the distribution of the species in the Huangshui River basin, revealing its predominant presence along the river's main stem. Based on four ecological niche models-MaxEnt with parameter optimization; GARP; BIOCLIM; and DOMAIN-we conduct a comparative analysis; evaluating the accuracy of AUC and Kappa values. Our findings indicate that optimizing parameters significantly improves the MaxEnt model's predictive accuracy by reducing complexity and overfitting. Furthermore, all four models exhibit higher accuracy compared to a random model, with MaxEnt demonstrating the highest AUC and Kappa values (0.9756 and 0.8118, respectively), showcasing significant superiority over the other models ( < 0.05). Evaluation of predictions from the four models elucidates that potential areas of in the Huangshui River basin are primarily concentrated in the central and southern areas, with precipitation exerting a predominant influence. Building upon these results, we utilized the MaxEnt model to forecast changes in suitable areas and distribution centers during the Last Interglacial (LIG), Mid-Holocene (MH), and future periods under three climate scenarios. The results indicate significantly smaller suitable areas during LIG and MH compared to the present, with the center of distribution shifting southeastward from the Qilian Mountains to the central part of the basin. In the future, suitable areas under different climate scenarios are expected to contract, with the center of distribution shifting southeastward. These findings provide important theoretical references for monitoring, early warning, and control measures for in the region, contributing to ecological health assessment.
PubMed: 38392501
DOI: 10.3390/insects15020081 -
The Science of the Total Environment Mar 2024The black fly genus Simulium includes medically and ecologically important species, characterized by a wide variation of ecological niches largely determining their...
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.
Topics: Humans; Animals; Simuliidae; Larva; Ecosystem; Rivers
PubMed: 38290683
DOI: 10.1016/j.scitotenv.2024.170454 -
Insects Jan 2024Understanding the factors associated with the species diversity and distribution of insect vectors is critically important for disease epidemiology. Black flies...
Understanding the factors associated with the species diversity and distribution of insect vectors is critically important for disease epidemiology. Black flies (Diptera: Simuliidae) are significant hematophagous insects, as many species are pests and vectors that transmit pathogens to humans and other animals. Ecological factors associated with black fly species distribution have been extensively examined for the immature stages but are far less well explored for the adult stage. In this study, we collected a total of 7706 adult black fly specimens from various locations in forests, villages and animal shelters in Thailand. The integration of morphology and DNA barcoding revealed 16 black fly taxa, including , a species first found in Vietnam, which is a new record for Thailand. The most abundant species was the complex ( = 5739, 74%), followed by Takaoka and Kuvangkadilok (n = 1232, 16%). The complex was dominant in forest (3786 of 4456; 85%) and village (1774 of 2077; 85%) habitats, while predominated (857 of 1175; 73%) in animal shelter areas. The complex and Summers, which are significant pests and vectors in Thailand, occurred at a wide range of elevations, although the latter species was found mainly in high (>1000 m) mountain areas. , Puri and the Takaoka and Suzuki complex occurred predominately in low (<800 m)-elevation areas. Takaoka and Srisuka; Tangkawanit, Wongpakam and Pramual; and nr were only found in high (>1000 m) mountain areas. A host blood meal analysis revealed that the ; Takaoka and Suzuki; ; ; and the species group were biting humans. This is the first report of the latter two species biting humans. We also found that was biting turkeys, and was biting chickens, which are new host blood sources recorded for these species. In addition, we found that the Edwards complex was biting water buffalo, which is the first report on the biting habits of this species.
PubMed: 38276823
DOI: 10.3390/insects15010074 -
PLoS Neglected Tropical Diseases Jan 2024While much progress has been made in the control and elimination of onchocerciasis across Africa, the extent to which vector migration might confound progress towards...
Cytotaxonomic characterization and estimation of migration patterns of onchocerciasis vectors (Simulium damnosum sensu lato) in northwestern Ethiopia based on RADSeq data.
BACKGROUND
While much progress has been made in the control and elimination of onchocerciasis across Africa, the extent to which vector migration might confound progress towards elimination or result in re-establishment of endemism in areas where transmission has been eliminated remains unclear. In Northern Ethiopia, Metema and Metekel-two foci located near the Sudan border-exhibit continuing transmission. While progress towards elimination has been faster in Metema, there remains a problematic hotspot of transmission. Whether migration from Metekel contributes to this is currently unknown.
METHODOLOGY/PRINCIPLE FINDINGS
To assess the role of vector migration from Metekel into Metema, we present a population genomics study of 151 adult female vectors using 47,638 RADseq markers and mtDNA CoI sequencing. From additional cytotaxonomy data we identified a new cytoform in Metema, closely related to S. damnosum s.str, here called the Gondar form. RADseq data strongly indicate the existence of two distinctly differentiated clusters within S. damnosum s.l.: one genotypic cluster found only in Metema, and the second found predominantly in Metekel. Because blackflies from both clusters were found in sympatry (in all four collection sites in Metema), but hybrid genotypes were not detected, there may be reproductive barriers preventing interbreeding. The dominant genotype in Metema was not found in Metekel while the dominant genotype in Metekel was found in Metema, indicating that (at the time of sampling) migration is primarily unidirectional, with flies moving from Metekel to Metema. There was strong differentiation between clusters but little genetic differentiation within clusters, suggesting migration and gene flow of flies within the same genetic cluster are sufficient to prevent genetic divergence between sites.
CONCLUSIONS/SIGNIFICANCE
Our results confirm that Metekel and Metema represent different transmission foci, but also indicate a northward movement of vectors between foci that may have epidemiological importance, although its significance requires further study.
Topics: Animals; Female; Onchocerciasis; Simuliidae; Ethiopia; Insect Vectors; Chromosomes
PubMed: 38175836
DOI: 10.1371/journal.pntd.0011868 -
Scientific Reports Jan 2024The effectiveness of the "Slash and Clear" method in reducing blackfly populations in low transmission areas is established, but its impact in high transmission settings...
The effectiveness of the "Slash and Clear" method in reducing blackfly populations in low transmission areas is established, but its impact in high transmission settings with large rivers and dense vectors is yet to be proven. A community-based intervention study was conducted in the Mbam Valley, Centre Cameroon, involving two sites: Bayomen (control) and Biatsota (intervention). In each arm, baseline blackfly densities were collected over one year using the human landing method. The intervention consisted of destroying the trailing vegetation where blackflies breed. Blackfly densities were collected post-intervention to assess the impact of the intervention. Post-intervention data showed a 50.8% reduction in blackfly density in Biatsota (mean number of collected blackflies from 1936 to 953), while a reduction of 26.7% was observed in Bayomen (mean number of collected blackflies from 2418 to 1774). The reduction rate attributable to the intervention was 32.9%. Statistical analysis confirmed that the reduction in blackfly density was significantly greater in the intervention site. This study demonstrates the feasibility and significant impact of the "Slash and Clear" method in high transmission areas. However, further research is required to assess its long-term effects and determine how this strategy can be scaled up and sustained until onchocerciasis elimination is achieved.
Topics: Animals; Humans; Onchocerciasis; Simuliidae; Insect Vectors; Cameroon; Rivers
PubMed: 38172522
DOI: 10.1038/s41598-023-50747-4