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Hedtke SM, Post RJ, Feleke SM, Gebretsadik FS, Boakye DA, Krueger A, Grant WN, Wilding CS. Cytotaxonomic characterization and estimation of migration patterns of onchocerciasis vectors (Simulium damnosum sensu lato) in northwestern Ethiopia based on RADSeq data. PLoS Negl Trop Dis 2024; 18:e0011868. [PMID: 38175836 DOI: 10.1371/journal.pntd.0011868] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Revised: 01/17/2024] [Accepted: 12/17/2023] [Indexed: 01/06/2024] Open
Abstract
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.
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Affiliation(s)
- Shannon M Hedtke
- Department of Environment and Genetics, School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, Victoria, Australia
| | - Rory J Post
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
- Disease Control Department, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | - Fikre Seife Gebretsadik
- Neglected Tropical Disease Prevention and Control Program, Federal Ministry of Health, Addis Ababa, Ethiopia
| | - Daniel A Boakye
- Parasitology Department, Noguchi Memorial Institute for Medical Research, Accra, Ghana
| | - Andreas Krueger
- Military Hospital Hamburg, Department Tropical Medicine, Hamburg, Germany
| | - Warwick N Grant
- Department of Environment and Genetics, School of Agriculture, Biomedicine and Environment, La Trobe University, Bundoora, Victoria, Australia
| | - Craig S Wilding
- School of Biological and Environmental Sciences, Liverpool John Moores University, Liverpool, United Kingdom
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Kamtsap P, Archile P, Flore N, Njiokou F, Renz A. Testing the susceptibility of larval stages of Simulium to temephos and Bacillus thuringiensis var israelensis in Germany and Northern Cameroon. MEDICAL AND VETERINARY ENTOMOLOGY 2023; 37:286-299. [PMID: 36571295 DOI: 10.1111/mve.12630] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/09/2022] [Accepted: 11/21/2022] [Indexed: 05/18/2023]
Abstract
Assays to evaluate the susceptibility of Simulium larvae to temephos and Bacillus thuringiensis var israelensis (Bti) were carried out by setting-up an in vitro laboratory test ('bio assay') and a semi-natural test ('système de goutières') to assess the LC50/LC90 values. Larvae of Simulium species in Cameroon (S. damnosum s.l., S. hargreavesi, S. vorax and S. cervicornutum) and (S. (Odagmia) ornatum and S. latipes) in Germany were identified and tested. In the bio-assay, 50 larvae were exposed for 10 min to concentrations from 0.01 to 10 ppm. For the Simulium from Germany, the LC50 (LC90) values after 3 and 6 h were 3.1 (27.9) and 0.14 (1.26) ppm for temephos and for Bti 7.8 (70.2) and 1.7 (15.3) ppm, respectively. For Cameroonian species, the values of LC50 (LC90) were lower, that is, 0.42 (8.04), 0.14 (2.70) and 0.073 (1.38) ppm, respectively, after 3, 6 and 12 h for temephos. In a semi natural condition, the LC50 of 10 min of application of temephos was 0.84 ppm after 3 h and a working solution (2.6 L) of Bti killed 50% after 6 h. To detect an upcoming of any resistance as it happened in Ivory Coast, a study of the occurrence resistance genes should be implemented.
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Affiliation(s)
- Pierre Kamtsap
- Department of Comparative Zoology, Institute of Evolution and Ecology, University of Tübingen, Tübingen, Germany
- Faculty of Science, Department of Cellular and Molecular Parasitology, University of Buea, Buea, Cameroon
- Programme Onchocercoses field station, University of Tübingen, Ngaoundéré, Cameroon
| | - Paguem Archile
- Programme Onchocercoses field station, University of Tübingen, Ngaoundéré, Cameroon
- Faculty of Agriculture and Veterinary Medicine, Department Veterinary Medicine, University of Buea, Buea, Cameroon
| | - Nguemaïm Flore
- Faculty of Health Sciences, University of Bamenda, Bambili, Cameroon
| | - Flobert Njiokou
- Laboratoire de Biologie Générale, Université de Yaoundé I, Yaoundé, Cameroon
| | - Alfons Renz
- Department of Comparative Zoology, Institute of Evolution and Ecology, University of Tübingen, Tübingen, Germany
- Programme Onchocercoses field station, University of Tübingen, Ngaoundéré, Cameroon
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Hedtke SM, Kuesel AC, Crawford KE, Graves PM, Boussinesq M, Lau CL, Boakye DA, Grant WN. Genomic Epidemiology in Filarial Nematodes: Transforming the Basis for Elimination Program Decisions. Front Genet 2020; 10:1282. [PMID: 31998356 PMCID: PMC6964045 DOI: 10.3389/fgene.2019.01282] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Accepted: 11/21/2019] [Indexed: 11/25/2022] Open
Abstract
Onchocerciasis and lymphatic filariasis are targeted for elimination, primarily using mass drug administration at the country and community levels. Elimination of transmission is the onchocerciasis target and global elimination as a public health problem is the end point for lymphatic filariasis. Where program duration, treatment coverage, and compliance are sufficiently high, elimination is achievable for both parasites within defined geographic areas. However, transmission has re-emerged after apparent elimination in some areas, and in others has continued despite years of mass drug treatment. A critical question is whether this re-emergence and/or persistence of transmission is due to persistence of local parasites-i.e., the result of insufficient duration or drug coverage, poor parasite response to the drugs, or inadequate methods of assessment and/or criteria for determining when to stop treatment-or due to re-introduction of parasites via human or vector movement from another endemic area. We review recent genetics-based research exploring these questions in Onchocerca volvulus, the filarial nematode that causes onchocerciasis, and Wuchereria bancrofti, the major pathogen for lymphatic filariasis. We focus in particular on the combination of genomic epidemiology and genome-wide associations to delineate transmission zones and distinguish between local and introduced parasites as the source of resurgence or continuing transmission, and to identify genetic markers associated with parasite response to chemotherapy. Our ultimate goal is to assist elimination efforts by developing easy-to-use tools that incorporate genetic information about transmission and drug response for more effective mass drug distribution, surveillance strategies, and decisions on when to stop interventions to improve sustainability of elimination.
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Affiliation(s)
- Shannon M. Hedtke
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
| | - Annette C. Kuesel
- Unicef/UNDP/World Bank/World Health Organization Special Programme for Research and Training in Tropical Diseases (TDR), World Health Organization, Geneva, Switzerland
| | - Katie E. Crawford
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
| | - Patricia M. Graves
- College of Public Health, Medical and Veterinary Sciences, James Cook University, Cairns, QLD, Australia
| | - Michel Boussinesq
- Unité Mixte Internationale 233 "TransVIHMI", Institut de Recherche pour le Développement (IRD), INSERM U1175, University of Montpellier, Montpellier, France
| | - Colleen L. Lau
- Department of Global Health, Research School of Population Health, Australian National University, Acton, ACT, Australia
| | - Daniel A. Boakye
- Parasitology Department, Noguchi Memorial Institute for Medical Research, Accra, Ghana
| | - Warwick N. Grant
- Department of Physiology, Anatomy and Microbiology, La Trobe University, Bundoora, VIC, Australia
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Gomard Y, Cornuault J, Licciardi S, Lagadec E, Belqat B, Dsouli N, Mavingui P, Tortosa P. Evidence of multiple colonizations as a driver of black fly diversification in an oceanic island. PLoS One 2018; 13:e0202015. [PMID: 30096163 PMCID: PMC6086440 DOI: 10.1371/journal.pone.0202015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2017] [Accepted: 07/26/2018] [Indexed: 11/19/2022] Open
Abstract
True oceanic islands typically host reduced species diversity together with high levels of endemism, which make these environmental set-ups ideal for the exploration of species diversification drivers. In the present study, we used black fly species (Diptera: Simuliidae) from Reunion Island as a model to highlight the main drivers of insect species diversification in this young and remote volcanic island located in the Southwestern Indian Ocean. Using local and regional (Comoros and Seychelles archipelagos) samples as well as specimens from continental Africa, we tested the likelihood of two distinct scenarios, i.e. multiple colonizations vs. in-situ diversification. For this, posterior odds were used to test whether species from Reunion did form a monophyletic group and we estimated divergence times between species. Three out of the four previously described Reunion black fly species could be sampled, namely Simulium ruficorne, Simulium borbonense and Simulium triplex. The phylogenies based on nuclear and mitochondrial markers showed that S. ruficorne and S. borbonense are the most closely related species. Interestingly, we report a probable mitochondrial introgression between these two species although they diverged almost six million years ago. Finally, we showed that the three Reunion species did not form a monophyletic group, and, combined with the molecular datation, the results indicated that Reunion black fly diversity resulted from multiple colonization events. Thus, multiple colonizations, rather than in-situ diversification, are likely responsible for an important part of black fly diversity found on this young Darwinian island.
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Affiliation(s)
- Yann Gomard
- Université de La Réunion, UMR PIMIT (Processus Infectieux en Milieu Insulaire Tropical), INSERM 1187, CNRS 9192, IRD 249, Plateforme Technologique CYROI, Sainte-Clotilde, La Réunion, France
- * E-mail:
| | - Josselin Cornuault
- Department of Biodiversity and Conservation, Real Jardín Botánico, RJB-CSIC, Madrid, Spain
| | - Séverine Licciardi
- CIRAD, UMR ASTRE, Sainte-Clotilde, La Réunion, France
- ASTRE, Univ Montpellier, CIRAD, INRA, Montpellier, France
- Groupement d’Intérêt Public Cyclotron Reunion Océan Indien (GIP CYROI), Sainte-Clotilde, La Réunion, France
| | - Erwan Lagadec
- Université de La Réunion, UMR PIMIT (Processus Infectieux en Milieu Insulaire Tropical), INSERM 1187, CNRS 9192, IRD 249, Plateforme Technologique CYROI, Sainte-Clotilde, La Réunion, France
| | - Boutaïna Belqat
- Department of Biology, Faculty of Sciences, University Abdelmalek Essaâdi, Tétouan, Morocco
| | - Najla Dsouli
- Centre de Recherche et de Veille sur les maladies émergentes dans l’Océan Indien (CRVOI), Plateforme Technologique CYROI, Sainte-Clotilde, La Réunion, France
| | - Patrick Mavingui
- Université de La Réunion, UMR PIMIT (Processus Infectieux en Milieu Insulaire Tropical), INSERM 1187, CNRS 9192, IRD 249, Plateforme Technologique CYROI, Sainte-Clotilde, La Réunion, France
- Université de Lyon, Lyon, France; Université Lyon 1, Villeurbanne, France; CNRS, UMR 5557, Ecologie Microbienne, Villeurbanne, France; INRA, UMR1418, Villeurbanne, France
| | - Pablo Tortosa
- Université de La Réunion, UMR PIMIT (Processus Infectieux en Milieu Insulaire Tropical), INSERM 1187, CNRS 9192, IRD 249, Plateforme Technologique CYROI, Sainte-Clotilde, La Réunion, France
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Hendy A, Krüger A, Pfarr K, De Witte J, Kibweja A, Mwingira U, Dujardin JC, Post R, Colebunders R, O’Neill S, Kalinga A. The blackfly vectors and transmission of Onchocerca volvulus in Mahenge, south eastern Tanzania. Acta Trop 2018; 181:50-59. [PMID: 29410302 DOI: 10.1016/j.actatropica.2018.01.009] [Citation(s) in RCA: 25] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2017] [Revised: 12/15/2017] [Accepted: 01/19/2018] [Indexed: 10/18/2022]
Abstract
The Mahenge Mountains onchocerciasis focus in south eastern Tanzania was historically one of the most heavily infected areas in the country. The vectors of Onchocerca volvulus are mainly Simulium damnosum complex blackflies, but a species of the Simulium neavei group may also contribute to transmission in some areas. The only detailed studies of parasite transmission in Mahenge were conducted in the late 1960s. The taxonomy of the S. damnosum complex has since been revised and onchocerciasis control through annual community directed treatment with ivermectin (CDTI) commenced in 1997. This study aimed to provide a cytogenetic and molecular update of the S. damnosum complex cytoforms present in Mahenge, and to evaluate the current status of O. volvulus transmission by blackflies following 19 years of annual CDTI. Rivers were surveyed to identify sites of S. damnosum s.l. breeding among the eastern slopes of the mountains, and human landing collections of adult female blackflies were made close to breeding sites. Identification of S. damnosum complex cytoforms was by cytotaxonomy of late-instar larvae and ITS1 amplicon size polymorphisms of larvae and adults. Adult blackflies were pool screened for O. volvulus infection using a triplex real-time PCR. The cytoforms 'Nkusi', Simulium kilibanum and 'Turiani' were found breeding in perennial rivers. 'Nkusi' and S. kilibanum were collected on human bait at 7/7 catch sites and possessed ITS1 profiles most closely resembling the molecular forms 'Nkusi J' and S. kilibanum 'T'. Whereas 'Turiani' was present in rivers, it was not collected on human bait and appears to be zoophilic. Simulium nyasalandicum was collected in low numbers on human bait at 3/7 catch sites. In total, 12,452 S. damnosum s.l. were pool screened and O. volvulus infection was detected in 97/104 pools of bodies and 51/104 pools of heads. The estimated percentage of S. damnosum s.l. carrying infective L3 stage parasites was 0.57% (95% CI 0.43%-0.74%). Onchocerca volvulus transmission by S. damnosum s.l. is continuing in the Mahenge Mountains after 19 years of annual CDTI. Infection rates appear similar to those reported in the 1960s, but a more detailed study is required to fully understand the epidemiological significance of the ongoing transmission. These results provide further evidence that annual CDTI may be insufficient to eliminate the parasite in formerly hyperendemic foci.
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Norice-Tra CT, Ribeiro J, Bennuru S, Fay MP, Tyagi R, Mitreva M, Nutman TB. Insights Into Onchocerca volvulus Population Biology Through Multilocus Immunophenotyping. J Infect Dis 2017; 216:736-743. [PMID: 28934436 DOI: 10.1093/infdis/jix394] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Accepted: 08/03/2017] [Indexed: 11/13/2022] Open
Abstract
We have developed a serologically based immunophenotyping approach to study Onchocerca volvulus (Ov) population diversity. Using genomic sequence data and polymerase chain reaction-based genotyping, we identified nonsynonymous single-nucleotide polymorphisms (SNPs) in the genes of 16 major immunogenic Ov proteins: Ov-CHI-1/Ov-CHI-2, Ov16, Ov-FAR-1, Ov-CPI-1, Ov-B20, Ov-ASP-1, Ov-TMY-1, OvSOD1, OvGST1, Ov-CAL-1, M3/M4, Ov-RAL-1, Ov-RAL-2, Ov-ALT-1, Ov-FBA-1, and Ov-B8. We assessed the immunoreactivity of onchocerciasis patient sera (n = 152) from the Americas, West Africa, Central Africa, and East Africa against peptides derived from 10 of these proteins containing SNPs. Statistically significant variation in immunoreactivity among the regions was seen in SNP-containing peptides derived from 8 of 10 proteins tested: OVOC1192(1-15), OVOC9988(28-42), OVOC9225(320-334), OVOC7453(22-36), OVOC11517(14-28), OVOC3177(283-297), OVOC7911(594-608), and OVOC12628(174-188). Our data show that differences in immunoreactivity to variant antigenic peptides may be used to characterize Ov populations, thereby elucidating features of Ov population biology previously inaccessible because of the limited availability of parasite material.
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Affiliation(s)
| | | | | | - Michael P Fay
- Biostatistics Research Branch, Division of Clinical Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland
| | | | - Makedonka Mitreva
- McDonnell Genome Institute.,Division of Infectious Diseases, Department of Medicine, Washington University School of Medicine, St Louis, Missouri
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Colorado-Garzón FA, Adler PH, García LF, Muñoz de Hoyos P, Bueno ML, Matta NE. Estimating Diversity of Black Flies in theSimulium ignescensandSimulium tunjaComplexes in Colombia: Chromosomal Rearrangements as the Core of Integrative Taxonomy. J Hered 2016; 108:12-24. [DOI: 10.1093/jhered/esw063] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Accepted: 10/03/2016] [Indexed: 11/13/2022] Open
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Dijkstra KDB, Monaghan MT, Pauls SU. Freshwater biodiversity and aquatic insect diversification. ANNUAL REVIEW OF ENTOMOLOGY 2014; 59:143-63. [PMID: 24160433 PMCID: PMC4816856 DOI: 10.1146/annurev-ento-011613-161958] [Citation(s) in RCA: 82] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Inland waters cover less than 1% of Earth's surface but harbor more than 6% of all insect species: Nearly 100,000 species from 12 orders spend one or more life stages in freshwater. Little is known about how this remarkable diversity arose, although allopatric speciation and ecological adaptation are thought to be primary mechanisms. Freshwater habitats are highly susceptible to environmental change and exhibit marked ecological gradients. Standing waters appear to harbor more dispersive species than running waters, but there is little understanding of how this fundamental ecological difference has affected diversification. In contrast to the lack of evolutionary studies, the ecology and habitat preferences of aquatic insects have been intensively studied, in part because of their widespread use as bioindicators. The combination of phylogenetics with the extensive ecological data provides a promising avenue for future research, making aquatic insects highly suitable models for the study of ecological diversification.
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Affiliation(s)
- Klaas-Douwe B. Dijkstra
- Naturalis Biodiversity Center, P.O. Box 9517, 2300 RA, Leiden, The
Netherlands, and University Museum of Zoology, Cambridge, CB2 3EJ, United Kingdom
| | - Michael T. Monaghan
- Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB),
12587 Berlin, Germany;
| | - Steffen U. Pauls
- Biodiversity and Climate Research Centre, Frankfurt, Germany and
Senckenberg Research Institute and Natural History Museum Frankfurt, Frankfurt,
Germany;
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Krüger A, Strüven L, Post RJ, Faulde M. The sandflies (Diptera: Psychodidae, Phlebotominae) in military camps in northern Afghanistan (2007-2009), as identified by morphology and DNA 'barcoding'. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2011; 105:163-76. [PMID: 21396252 PMCID: PMC4084661 DOI: 10.1179/136485911x12899838683241] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2010] [Revised: 12/03/2010] [Accepted: 12/10/2010] [Indexed: 12/28/2022]
Abstract
As part of a continuous, standardized programme of monitoring the Leishmania vectors in German military camps in northern Afghanistan between 2007 and 2009, a detailed taxonomic analysis of the endemic sandfly fauna, as sampled using light and odour-baited traps, was conducted. Of the 10 sandfly species that were recorded, six may serve as enzootic and/or zooanthroponotic vectors of parasites causing human leishmaniasis. The use of a simple DNA-'barcoding' technique based on the mitochondrial cyt b gene, to identify the collected sandflies to species level, revealed (1) a clear discrimination between the potential vector species, (2) clustering of species within most subgenera, and (3) particularly high heterogeneity within the subgenus Paraphlebotomus (Phlebotomus alexandri being grouped with Ph. papatasi rather than with other Paraphlebotomus species). The data also indicate a high level of genetic heterogeneity within the subgenus Sergentomyia but close similarity between Sergentomyia sintoni and Sergentomyia murgabiensis. The morphological similarity of many medically important sandflies can make species identification difficult, if not impossible. The new DNA-barcoding techniques may provide powerful discriminatory tools in the future.
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Affiliation(s)
- A Krüger
- Bundeswehr Hospital Hamburg, Tropical Medicine Branch, Bernhard Nocht Institute for Tropical Medicine, Germany.
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Maegga BTA, Kalinga AK, Kabula B, Post RJ, Krueger A. Investigations into the isolation of the Tukuyu focus of onchocerciasis (Tanzania) from S. damnosum s.l. vector re-invasion. Acta Trop 2011; 117:86-96. [PMID: 21029718 DOI: 10.1016/j.actatropica.2010.10.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2010] [Revised: 10/07/2010] [Accepted: 10/07/2010] [Indexed: 11/29/2022]
Abstract
As part of the feasibility study for an onchocerciasis vector elimination project we investigated the isolation of the Tukuyu focus in Tanzania from possible vector re-invasion. This was achieved by examining the distribution of the Simulium damnosum complex vector cytospecies outside the focus to look for potential sources of re-invasion. Besides cytotaxonomic identifications of the aquatic stages, we applied morphotaxonomic and molecular techniques to identify S. thyolense and confirm it as the anthropophilic species in both the Tukuyu and the neighbouring Ruvuma foci. We detected significant differences in chromosome inversion frequencies between the Tukuyu populations and those breeding to the southwest in the adjacent Songwe river basin and in northern Malawi (where there is no man-biting and no onchocerciasis), suggesting that there is not normally a great deal of migration in either direction. By contrast, populations of S. thyolense from the Tukuyu and Ruvuma foci (150km southeast of Tukuyu) were much more similar in terms of their chromosomal polymorphisms, indicating a higher possibility of re-invasion, although migration is still restricted to some extent, as indicated by some differences in chromosome polymorphisms between the two foci. Future migratory events which might be associated with vector control operations can be monitored by vector cytospecies identification, the frequency of polymorphic inversions which characterise the different vector populations, and the identification of accompanying non-vector cytospecies (e.g. S. plumbeum and cytotype Kasyabone occur exclusively in the two foci, and hence their re-appearance in Tukuyu could have only one outside source). The morphology of the scutal pattern of neonate males may act as a quick test for vector species identification where chromosome squashes are unavailable.
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Affiliation(s)
- B T A Maegga
- National Institute for Medical Research, PO Box 9653, Dar es Salaam, Tanzania
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Adler PH, Cheke RA, Post RJ. Evolution, epidemiology, and population genetics of black flies (Diptera: Simuliidae). INFECTION GENETICS AND EVOLUTION 2010; 10:846-65. [DOI: 10.1016/j.meegid.2010.07.003] [Citation(s) in RCA: 86] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2010] [Revised: 07/02/2010] [Accepted: 07/02/2010] [Indexed: 10/19/2022]
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Construction and characterisation of a BAC library made from field specimens of the onchocerciasis vector Simulium squamosum (Diptera: Simuliidae). Genomics 2010; 96:251-7. [PMID: 20603211 DOI: 10.1016/j.ygeno.2010.06.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2010] [Revised: 06/25/2010] [Accepted: 06/28/2010] [Indexed: 12/21/2022]
Abstract
A Bacterial Artificial Chromosome (BAC) library was made from wild-caught Simulium squamosum, which is an important vector of human onchocerciasis. The library is composed of 12,288 BACs, with an average insert size of 128 kb, and is expected to contain ~1.54 GB of cloned DNA. Random BAC-end sequencing generated over 95 kb of DNA sequence data from which putative S. squamosum gene sequences and novel repetitive DNA families were identified, including DNA transposons, retrotransposons and simple sequence repeats (SSRs). The sequence survey also provided evidence of DNA of microbial origin, and dissection of sample blackflies indicated that some of those used to prepare the library were likely to be parasitized by the mermithid Isomermis lairdi. Hybridisations with a set of three independent blackfly single-copy genes and two Wolbachia genes suggest that the library provides around 13-fold coverage of the S. squamosum genome and about 12-fold coverage of its Wolbachia endosymbiont.
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Garros C, Mathieu B, Balenghien T, Cêtre-Sossah C, Delécolle JC. Suggesting synonymies? Comments on Kiehl et al. (2009) "the European vectors of Bluetongue virus: are there species complexes, single species or races in Culicoides obsoletus and C. pulicaris detectable by sequencing ITS-1, ITS-2 and 18S-rDNA?". Parasitol Res 2010; 107:731-4. [PMID: 20512587 DOI: 10.1007/s00436-010-1921-z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Accepted: 05/07/2010] [Indexed: 10/19/2022]
Abstract
Species recognition and identification are crucial in any biological studies, especially when dealing with insect species involved in pathogen transmission. In recent years, molecular approaches have helped the clarification of systematic schemes and taxonomic status. Kiehl et al. (Parasitol Res 105:331-336, 2009) used molecular data to discuss the taxonomic status of biting midge species in the Palaearctic region. In the present work, the statements that "[Thus] there is no molecular support for the existence of a separate species C. montanus" and "[Therefore] probably C. scoticus should be considered only as a race of C. obsoletus" are discussed.
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Affiliation(s)
- Claire Garros
- UMR CMAEE CIRAD-INRA, Contrôle des maladies animales exotiques et émergentes, Campus International de Baillarguet TA-A15/A, bureau A210, Montpellier Cedex 5, France.
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14
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Phylogenetic relationships among the black fly species (Diptera: Simuliidae) of Thailand based on multiple gene sequences. Genetica 2010; 138:633-48. [DOI: 10.1007/s10709-010-9437-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2009] [Accepted: 01/13/2010] [Indexed: 11/26/2022]
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15
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Morales-Hojas R, Krueger A. The species delimitation problem in the Simulium damnosum complex, blackfly vectors of onchocerciasis. MEDICAL AND VETERINARY ENTOMOLOGY 2009; 23:257-268. [PMID: 19712156 DOI: 10.1111/j.1365-2915.2009.00816.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The Simulium damnosum Theobald complex (Diptera: Simuliidae) comprises 57 cytoforms grouped into six subcomplexes. Previous phylogenetic studies using gene sequences have not completely resolved the evolutionary relationships of the cytoforms. The present study investigated the systematics of the complex using a phylogeographic approach. The differentiation between eastern and western forms observed in the phylogenetic studies is confirmed in the estimated haplotype networks. However, haplotypes tend to group in geographical clades and not according to cytoforms. Spatial analyses of the molecular variance also resulted in optimal groupings of sequences that did not correspond to cytoform boundaries. Moreover, Mantel tests showed significant correlations, although not strong, between genetic and geographical distances. This suggests an isolation-by-distance model of differentiation. Furthermore, there are instances in which genetic differentiation between cytoforms is low and not significant. These results indicate a lack of clear genetic differentiation between the cytoforms, which may be explained either by a separation of the taxa recent enough to allow the accumulation of few genetic differences or by recombination between the genomes of the cytoforms, which may be the result of hybridization with introgression or of non-independent evolutionary lineages. The results also emphasize the need for further sampling and for the use of more variable markers in order to clarify the evolutionary history of the group.
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Affiliation(s)
- R Morales-Hojas
- Laboratório de Evolução Molecular, Instituto de Biologia Molecular e Celular (IBMC), Universidade do Porto, Porto, Portugal.
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16
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Day JC, Goodall TI, Post RJ. Confirmation of the species status of the blackfly Simulium galeratum in Britain using molecular taxonomy. MEDICAL AND VETERINARY ENTOMOLOGY 2008; 22:55-61. [PMID: 18380654 DOI: 10.1111/j.1365-2915.2008.00719.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Since 1920 Simulium reptans (Linnaeus) (Diptera: Simuliidae) has been reported as exhibiting two different larval morphotypes, a typical S. reptans and an atypical S. reptans var. galeratum, which differ in the markings of the larval head capsule. Inconsistent variation in adults and no apparent variation in the pupae have led taxonomists to conclude that these types in Britain are a single species. We investigated populations in Britain where either the typical form or var. galeratum is found, and one population where the two exist sympatrically. A phylogenetic study based upon a region of the mitochondrial cytochrome c oxidase 1 gene (DNA barcoding) produced a tree that delineated the morphotypes into two distinct monophyletic clades. The average Kimura-2-parameter distances within each clade (i.e. within each morphotype) were very low (0.67% and 0.78%), with the distances between morphotypes being 9-10-fold greater (mean 7.06%). This is concordant with differences within and between species in other taxa; based upon the strict correlation between the molecular variation and the morphotypes, we propose the re-instatement of S. galeratum to species status.
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Affiliation(s)
- J C Day
- Centre for Ecology and Hydrology (CEH) Oxford, Oxford, UK.
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17
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Post RJ, Mustapha M, Krueger A. Taxonomy and inventory of the cytospecies and cytotypes of the Simulium damnosum complex (Diptera: Simuliidae) in relation to onchocerciasis. Trop Med Int Health 2008; 12:1342-53. [PMID: 18045261 DOI: 10.1111/j.1365-3156.2007.01921.x] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We provide an inventory of all named cytoforms of the Simulium damnosum complex (including those which are now considered invalid), along with all inversions that have been recorded (including synonyms and homonyms). There are 55 valid and distinct cytoforms known from the S. damnosum complex making it the largest sibling species complex of any vectors, and probably of any insect or other animal. All cytoforms are listed along with their fixed and diagnostic inversions and country distribution. There are 183 inversions known from the complex as a whole, of which 49% are fixed and/or diagnostic between cytoforms, and the fixed/diagnostic inversions seem to occur disproportionately on chromosome arm 2L.
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Affiliation(s)
- R J Post
- The Natural History Museum London and London School of Hygiene & Tropical Medicine, UK.
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18
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Mansiangi P, Kiyombo G, Mulumba P, Josens G, Krueger A. Molecular systematics of Simulium squamosum, the vector in the Kinsuka onchocerciasis focus (Kinshasa, Democratic Republic of Congo). ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 2007; 101:275-9. [PMID: 17362602 DOI: 10.1179/136485907x157013] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Affiliation(s)
- P Mansiangi
- Ecole de Santé Publique/Faculté de Médecine, Université de Kinshasa, Kinshasa, Democratic Republic of the Congo
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Krueger A, Kalinga AK, Kibweja AM, Mwaikonyole A, Maegga BTA. Cytogenetic and PCR-based identification of S. damnosum'Nkusi J' as the anthropophilic blackfly in the Uluguru onchocerciasis focus in Tanzania. Trop Med Int Health 2006; 11:1066-74. [PMID: 16827707 DOI: 10.1111/j.1365-3156.2006.01662.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A combined molecular and cytogenetic analysis was used to identify the local blackfly vectors of onchocerciasis in the Uluguru Mts. focus, Morogoro region, central Tanzania. Cytotaxonomic identification revealed the occurrence of three cytospecies of the Simulium damnosum complex, along altitudinal gradients. The cytoform "Nkusi" was found breeding at low to mid-altitudes (100-500 m), while S. kilibanum was found at mid- and high altitudes (300-1260 m), being sympatric with "Sebwe" only in the highlands. The analyses further revealed the cytoform "Nkusi" from the nearby Kilosa focus. Simulium kilibanum and "Nkusi" are potential vectors of onchocerciasis, while the "Sebwe" form is considered non-anthropophilic and therefore not a vector. By means of molecular typing of wild-caught females, "Nkusi" was incriminated as the man-biting fly at all catching sites, and consequently, is the assumed vector of onchocerciasis over the full altitude range. In the high altitude zones, however, S. neavei group species may act as secondary vectors at the edge of the forest reserve, if transmission actually occurs there at all. Our results also suggest that vector control could be feasible because of the vector species breeding in the foothills below 500 m in relatively accessible open country.
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Affiliation(s)
- A Krueger
- Department of Molecular Parasitology, Bernhard Nocht Institute for Tropical Medicine, Bernhard-Nocht-Strasse 74, 20259 Hamburg, Germany.
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