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Montanez-Gonzalez R, Pichler V, Calzetta M, Love RR, Vallera A, Schaecher L, Caputo B, Pombi M, Petrarca V, Della Torre A, Besansky NJ. Highly specific PCR-RFLP assays for karyotyping the widespread 2Rb inversion in malaria vectors of the Anopheles gambiae complex. Parasit Vectors 2020; 13:16. [PMID: 31924251 PMCID: PMC6954590 DOI: 10.1186/s13071-019-3877-x] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2019] [Accepted: 12/30/2019] [Indexed: 01/29/2023] Open
Abstract
Background Chromosomal inversion polymorphisms play a role in adaptation to heterogeneous environments. Inversion polymorphisms are implicated in the very high ecological flexibility of the three main malaria vector species of the Afrotropical Anopheles gambiae complex, facilitating the exploitation of anthropogenic environmental modifications and promoting a strong association with humans. In addition to extending the species’ spatial and temporal distribution, inversions are associated with epidemiologically relevant mosquito behavior and physiology, underscoring their medical importance. We here present novel PCR-RFLP based assays strongly predictive of genotype for the cosmopolitan 2Rb inversion in An. coluzzii and An. gambiae, a development which overcomes the numerous constraints inherent to traditional cytological karyotyping. Methods We designed PCR-RFLP genotyping assays based on tag SNPs previously computationally identified as strongly predictive (> 95%) of 2Rb genotype. We targeted those tags whose alternative allelic states destroyed or created the recognition site of a commercially available restriction enzyme, and designed assays with distinctive cleavage profiles for each inversion genotype. The assays were validated on 251 An. coluzzii and 451 An. gambiae cytologically karyotyped specimens from nine countries across Africa and one An. coluzzii laboratory colony. Results For three tag SNPs, PCR-RFLP assays (denoted DraIII, MspAI, and TatI) reliably produced robust amplicons and clearly distinguishable electrophoretic profiles for all three inversion genotypes. Results obtained with the DraIII assay are ≥ 95% concordant with cytogenetic assignments in both species, while MspAI and TatI assays produce patterns highly concordant with cytogenetic assignments only in An. coluzzii or An. gambiae, respectively. Joint application of species-appropriate pairs of assays increased the concordance levels to > 99% in An. coluzzii and 98% in An. gambiae. Potential sources of discordance (e.g. imperfect association between tag and inversion, allelic dropout, additional polymorphisms in the restriction target site, incomplete or failed restriction digestion) are discussed. Conclusions The availability of highly specific, cost effective and accessible molecular assays for genotyping 2Rb in An. gambiae and An. coluzzii allows karyotyping of both sexes and all developmental stages. These novel tools will accelerate deeper investigations into the role of this ecologically and epidemiologically important chromosomal inversion in vector biology.![]()
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Affiliation(s)
- Raquel Montanez-Gonzalez
- Eck Institute for Global Health, & Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Verena Pichler
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università "La Sapienza", Istituto Pasteur-Fondazione Cenci-Bolognetti, 00185, Rome, Italy
| | - Maria Calzetta
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università "La Sapienza", Istituto Pasteur-Fondazione Cenci-Bolognetti, 00185, Rome, Italy
| | - Rachel R Love
- Eck Institute for Global Health, & Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Alexandra Vallera
- Eck Institute for Global Health, & Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Lydia Schaecher
- Eck Institute for Global Health, & Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA
| | - Beniamino Caputo
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università "La Sapienza", Istituto Pasteur-Fondazione Cenci-Bolognetti, 00185, Rome, Italy
| | - Marco Pombi
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università "La Sapienza", Istituto Pasteur-Fondazione Cenci-Bolognetti, 00185, Rome, Italy
| | - Vincenzo Petrarca
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università "La Sapienza", Istituto Pasteur-Fondazione Cenci-Bolognetti, 00185, Rome, Italy
| | - Alessandra Della Torre
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università "La Sapienza", Istituto Pasteur-Fondazione Cenci-Bolognetti, 00185, Rome, Italy.
| | - Nora J Besansky
- Eck Institute for Global Health, & Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, 46556, USA.
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Corbett-Detig RB, Said I, Calzetta M, Genetti M, McBroome J, Maurer NW, Petrarca V, Della Torre A, Besansky NJ. Fine-Mapping Complex Inversion Breakpoints and Investigating Somatic Pairing in the Anopheles gambiae Species Complex Using Proximity-Ligation Sequencing. Genetics 2019; 213:1495-1511. [PMID: 31666292 PMCID: PMC6893396 DOI: 10.1534/genetics.119.302385] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Accepted: 10/21/2019] [Indexed: 11/18/2022] Open
Abstract
Chromosomal inversions are fundamental drivers of genome evolution. In the main Afrotropical malaria vector species, belonging to the Anopheles gambiae species complex, inversions play an important role in local adaptation and have a rich history of cytological study. Despite the importance and ubiquity of some chromosomal inversions across the species complex, inversion breakpoints are often challenging to map molecularly due to the presence of large repetitive regions. Here, we develop an approach that uses Hi-C sequencing data to molecularly fine-map the breakpoints of inversions. We demonstrate that this approach is robust and likely to be widely applicable for both identification and fine-mapping inversion breakpoints in species whose inversions have heretofore been challenging to characterize. We apply our method to interrogate the previously unknown inversion breakpoints of 2Rbc and 2Rd in An. coluzzii We found that inversion breakpoints occur in large repetitive regions, and, strikingly, among three inversions analyzed, two breakpoints appear to be reused in two separate inversions. These breakpoint-adjacent regions are strongly enriched for the presence of a 30 bp satellite repeat sequence. Because low frequency inversion breakpoints are not correlated with genomic regions containing this satellite, we suggest that interrupting this particular repeat may result in arrangements with higher relative fitness. Additionally, we use heterozygous individuals to quantitatively investigate the impacts of somatic pairing in the regions immediately surrounding inversion breakpoints. Finally, we discuss important considerations for possible applications of this approach for inversion breakpoint identification in a range of organisms.
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Affiliation(s)
- Russell B Corbett-Detig
- Department of Biomolecular Engineering, University of California Santa Cruz, California 95064
- Genomics Institute, University of California Santa Cruz, California 95064
| | - Iskander Said
- Department of Biomolecular Engineering, University of California Santa Cruz, California 95064
| | - Maria Calzetta
- Dipartimento di Sanità Pubblica e Malattie Infettive and Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Università di Roma "La Sapienza", 00185 Rome, Italy
| | - Max Genetti
- Department of Biomolecular Engineering, University of California Santa Cruz, California 95064
| | - Jakob McBroome
- Department of Biomolecular Engineering, University of California Santa Cruz, California 95064
| | - Nicholas W Maurer
- Department of Biomolecular Engineering, University of California Santa Cruz, California 95064
| | - Vincenzo Petrarca
- Dipartimento di Sanità Pubblica e Malattie Infettive and Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Università di Roma "La Sapienza", 00185 Rome, Italy
| | - Alessandra Della Torre
- Dipartimento di Sanità Pubblica e Malattie Infettive and Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Università di Roma "La Sapienza", 00185 Rome, Italy
| | - Nora J Besansky
- Eck Institute for Global Health and Department of Biological Sciences, University of Notre Dame, Indiana 46556
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3
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Love RR, Redmond SN, Pombi M, Caputo B, Petrarca V, Della Torre A, Besansky NJ. In Silico Karyotyping of Chromosomally Polymorphic Malaria Mosquitoes in the Anopheles gambiae Complex. G3 (Bethesda) 2019; 9:3249-3262. [PMID: 31391198 PMCID: PMC6778791 DOI: 10.1534/g3.119.400445] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/13/2019] [Accepted: 07/30/2019] [Indexed: 01/13/2023]
Abstract
Chromosomal inversion polymorphisms play an important role in adaptation to environmental heterogeneities. For mosquito species in the Anopheles gambiae complex that are significant vectors of human malaria, paracentric inversion polymorphisms are abundant and are associated with ecologically and epidemiologically important phenotypes. Improved understanding of these traits relies on determining mosquito karyotype, which currently depends upon laborious cytogenetic methods whose application is limited both by the requirement for specialized expertise and for properly preserved adult females at specific gonotrophic stages. To overcome this limitation, we developed sets of tag single nucleotide polymorphisms (SNPs) inside inversions whose biallelic genotype is strongly correlated with inversion genotype. We leveraged 1,347 fully sequenced An. gambiae and Anopheles coluzzii genomes in the Ag1000G database of natural variation. Beginning with principal components analysis (PCA) of population samples, applied to windows of the genome containing individual chromosomal rearrangements, we classified samples into three inversion genotypes, distinguishing homozygous inverted and homozygous uninverted groups by inclusion of the small subset of specimens in Ag1000G that are associated with cytogenetic metadata. We then assessed the correlation between candidate tag SNP genotypes and PCA-based inversion genotypes in our training sets, selecting those candidates with >80% agreement. Our initial tests both in held-back validation samples from Ag1000G and in data independent of Ag1000G suggest that when used for in silico inversion genotyping of sequenced mosquitoes, these tags perform better than traditional cytogenetics, even for specimens where only a small subset of the tag SNPs can be successfully ascertained.
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Affiliation(s)
- R Rebecca Love
- Eck Institute for Global Health & Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556
| | - Seth N Redmond
- Infectious Disease and Microbiome Program, Broad Institute, Cambridge, MA 02142
| | - Marco Pombi
- Dipartimento di Sanità Pubblica e Malattie Infettive, Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Università di Roma "La Sapienza," Piazzale Aldo Moro, 5, 00185 Rome, Italy
| | - Beniamino Caputo
- Dipartimento di Sanità Pubblica e Malattie Infettive, Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Università di Roma "La Sapienza," Piazzale Aldo Moro, 5, 00185 Rome, Italy
| | - Vincenzo Petrarca
- Dipartimento di Sanità Pubblica e Malattie Infettive, Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Università di Roma "La Sapienza," Piazzale Aldo Moro, 5, 00185 Rome, Italy
| | - Alessandra Della Torre
- Dipartimento di Sanità Pubblica e Malattie Infettive, Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Università di Roma "La Sapienza," Piazzale Aldo Moro, 5, 00185 Rome, Italy
| | - Nora J Besansky
- Eck Institute for Global Health & Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556
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Pichler V, Malandruccolo C, Serini P, Bellini R, Severini F, Toma L, Di Luca M, Montarsi F, Ballardini M, Manica M, Petrarca V, Vontas J, Kasai S, Della Torre A, Caputo B. Phenotypic and genotypic pyrethroid resistance of Aedes albopictus, with focus on the 2017 chikungunya outbreak in Italy. Pest Manag Sci 2019; 75:2642-2651. [PMID: 30729706 DOI: 10.1002/ps.5369] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Revised: 12/31/2018] [Accepted: 02/02/2019] [Indexed: 06/09/2023]
Abstract
BACKGROUND The highly invasive mosquito species Aedes albopictus has become a major health concern in temperate areas due to its role as vector of exotic arboviruses. Pyrethroid insecticides represent the main tools for limiting the circulation of such mosquito-borne viruses. The present work aim to extend previous reports on phenotypic pyrethroid-resistance in European Ae. albopictus, to identify its genetic basis and to monitor the geographical distribution of resistant genotypes, with a particular focus on sites experiencing the 2017 chikungunya outbreak in Italy. RESULTS Bioassays, performed according to World Health Organization protocols, showed full susceptibility to deltamethrin (concentration = 0.05%) and varying levels of resistance to permethrin (0.75%) and/or α-cypermethrin (0.05%) across Italy, with highest levels in the core of the 2017 chikungunya outbreak. Partial genotyping of the VSSC gene revealed widespread distribution of V1016G mutation and confirmed its association with pyrethroid resistance. CONCLUSION The results obtained show that the condition for the spread of pyrethroid resistance in Ae. albopictus in Europe exists under strong selective pressure due to intensive insecticide spraying to control exotic arbovirus outbreak or high levels of nuisance. The results draw attention to the need for an evidence-based implementation of mosquito nuisance control, taking insecticide resistance management into consideration. © 2019 Society of Chemical Industry.
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Affiliation(s)
- Verena Pichler
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università Sapienza, Rome, Italy
| | - Chiara Malandruccolo
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università Sapienza, Rome, Italy
| | - Paola Serini
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università Sapienza, Rome, Italy
| | - Romeo Bellini
- Centro Agricoltura Ambiente "G.Nicoli", Crevalcore, Italy
| | - Francesco Severini
- Dipartimento di Malattie Infettive, Istituto Superiore di Sanità, Rome, Italy
| | - Luciano Toma
- Dipartimento di Malattie Infettive, Istituto Superiore di Sanità, Rome, Italy
| | - Marco Di Luca
- Dipartimento di Malattie Infettive, Istituto Superiore di Sanità, Rome, Italy
| | | | - Marco Ballardini
- Istituto Zooprofilattico Sperimentale del Piemonte, Liguria e Valle d'Aosta, Torino, Italy
| | - Mattia Manica
- Department of Biodiversity and Molecular Ecology, Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy
| | - Vincenzo Petrarca
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università Sapienza, Rome, Italy
| | - John Vontas
- Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology Hellas, Heraklion, Greece
- Agricultural University of Athens, Athens, Greece
| | - Shinji Kasai
- Department of Medical Entomology, National Institute of Infectious Diseases, Tokyo, Japan
| | | | - Beniamino Caputo
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università Sapienza, Rome, Italy
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5
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Pombi M, Kengne P, Gimonneau G, Tene-Fossog B, Ayala D, Kamdem C, Santolamazza F, Guelbeogo WM, Sagnon N, Petrarca V, Fontenille D, Besansky NJ, Antonio-Nkondjio C, Dabiré RK, Della Torre A, Simard F, Costantini C. Dissecting functional components of reproductive isolation among closely related sympatric species of the Anopheles gambiae complex. Evol Appl 2017; 10:1102-1120. [PMID: 29151864 PMCID: PMC5680640 DOI: 10.1111/eva.12517] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Accepted: 07/10/2017] [Indexed: 01/10/2023] Open
Abstract
Explaining how and why reproductive isolation evolves and determining which forms of reproductive isolation have the largest impact on the process of population divergence are major goals in the study of speciation. By studying recent adaptive radiations in incompletely isolated taxa, it is possible to identify barriers involved at early divergence before other confounding barriers emerge after speciation is complete. Sibling species of the Anopheles gambiae complex offer opportunities to provide insights into speciation mechanisms. Here, we studied patterns of reproductive isolation among three taxa, Anopheles coluzzii, An. gambiae s.s. and Anopheles arabiensis, to compare its strength at different spatial scales, to dissect the relative contribution of pre‐ versus postmating isolation, and to infer the involvement of ecological divergence on hybridization. Because F1 hybrids are viable, fertile and not uncommon, understanding the dynamics of hybridization in this trio of major malaria vectors has important implications for how adaptations arise and spread across the group, and in planning studies of the safety and efficacy of gene drive as a means of malaria control. We first performed a systematic review and meta‐analysis of published surveys reporting on hybrid prevalence, showing strong reproductive isolation at a continental scale despite geographically restricted exceptions. Second, we exploited our own extensive field data sets collected at a regional scale in two contrasting environmental settings, to assess: (i) levels of premating isolation; (ii) spatio/temporal and frequency‐dependent dynamics of hybridization, (iii) relationship between reproductive isolation and ecological divergence and (iv) hybrid viability penalty. Results are in accordance with ecological speciation theory predicting a positive association between the strength of reproductive isolation and degree of ecological divergence, and indicate that postmating isolation does contribute to reproductive isolation among these species. Specifically, only postmating isolation was positively associated with ecological divergence, whereas premating isolation was correlated with phylogenetic distance.
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Affiliation(s)
- Marco Pombi
- Dipartimento di Sanità Pubblica e Malattie InfettiveUniversità di Roma "Sapienza"RomeItaly.,Istituto Pasteur Italia-Fondazione Cenci-Bolognetti Rome Italy
| | - Pierre Kengne
- Institut de Recherche pour le Développement (IRD) UMR MIVEGEC (University of Montpellier, CNRS 5290 IRD 224) Centre IRD de Montpellier Montpellier France.,Organisation de Coordination pour la lutte contre les Endemies en Afrique Centrale (OCEAC) Yaoundé Cameroon
| | | | - Billy Tene-Fossog
- Institut de Recherche pour le Développement (IRD) UMR MIVEGEC (University of Montpellier, CNRS 5290 IRD 224) Centre IRD de Montpellier Montpellier France.,Organisation de Coordination pour la lutte contre les Endemies en Afrique Centrale (OCEAC) Yaoundé Cameroon
| | - Diego Ayala
- Institut de Recherche pour le Développement (IRD) UMR MIVEGEC (University of Montpellier, CNRS 5290 IRD 224) Centre IRD de Montpellier Montpellier France.,Centre International de Recherches Médicales de Franceville Franceville Gabon
| | - Colince Kamdem
- Department of Entomology University of California Riverside CA USA
| | - Federica Santolamazza
- Dipartimento di Sanità Pubblica e Malattie InfettiveUniversità di Roma "Sapienza"RomeItaly.,Istituto Pasteur Italia-Fondazione Cenci-Bolognetti Rome Italy
| | | | - N'Falé Sagnon
- Centre National de Recherche et Formation sur le Paludisme (CNRFP) Ouagadougou Burkina Faso
| | - Vincenzo Petrarca
- Dipartimento di Sanità Pubblica e Malattie InfettiveUniversità di Roma "Sapienza"RomeItaly.,Istituto Pasteur Italia-Fondazione Cenci-Bolognetti Rome Italy
| | - Didier Fontenille
- Institut de Recherche pour le Développement (IRD) UMR MIVEGEC (University of Montpellier, CNRS 5290 IRD 224) Centre IRD de Montpellier Montpellier France.,Institut Pasteur du Cambodge Phnom Penh Cambodia
| | - Nora J Besansky
- Eck Institute for Global Health & Department of Biological Sciences University of Notre Dame Notre Dame IN USA
| | | | - Roch Kounbobr Dabiré
- Institut de Recherche en Sciences de la Santé (IRSS) Bobo-Dioulasso Burkina Faso
| | - Alessandra Della Torre
- Dipartimento di Sanità Pubblica e Malattie InfettiveUniversità di Roma "Sapienza"RomeItaly.,Istituto Pasteur Italia-Fondazione Cenci-Bolognetti Rome Italy
| | - Frédéric Simard
- Institut de Recherche pour le Développement (IRD) UMR MIVEGEC (University of Montpellier, CNRS 5290 IRD 224) Centre IRD de Montpellier Montpellier France.,Organisation de Coordination pour la lutte contre les Endemies en Afrique Centrale (OCEAC) Yaoundé Cameroon.,Institut de Recherche en Sciences de la Santé (IRSS) Bobo-Dioulasso Burkina Faso
| | - Carlo Costantini
- Institut de Recherche pour le Développement (IRD) UMR MIVEGEC (University of Montpellier, CNRS 5290 IRD 224) Centre IRD de Montpellier Montpellier France.,Organisation de Coordination pour la lutte contre les Endemies en Afrique Centrale (OCEAC) Yaoundé Cameroon.,Institut de Recherche en Sciences de la Santé (IRSS) Bobo-Dioulasso Burkina Faso
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6
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Vicente JL, Clarkson CS, Caputo B, Gomes B, Pombi M, Sousa CA, Antao T, Dinis J, Bottà G, Mancini E, Petrarca V, Mead D, Drury E, Stalker J, Miles A, Kwiatkowski DP, Donnelly MJ, Rodrigues A, Torre AD, Weetman D, Pinto J. Massive introgression drives species radiation at the range limit of Anopheles gambiae. Sci Rep 2017; 7:46451. [PMID: 28417969 PMCID: PMC5394460 DOI: 10.1038/srep46451] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Accepted: 03/17/2017] [Indexed: 12/30/2022] Open
Abstract
Impacts of introgressive hybridisation may range from genomic erosion and species collapse to rapid adaptation and speciation but opportunities to study these dynamics are rare. We investigated the extent, causes and consequences of a hybrid zone between Anopheles coluzzii and Anopheles gambiae in Guinea-Bissau, where high hybridisation rates appear to be stable at least since the 1990s. Anopheles gambiae was genetically partitioned into inland and coastal subpopulations, separated by a central region dominated by A. coluzzii. Surprisingly, whole genome sequencing revealed that the coastal region harbours a hybrid form characterised by an A. gambiae-like sex chromosome and massive introgression of A. coluzzii autosomal alleles. Local selection on chromosomal inversions may play a role in this process, suggesting potential for spatiotemporal stability of the coastal hybrid form and providing resilience against introgression of medically-important loci and traits, found to be more prevalent in inland A. gambiae.
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Affiliation(s)
- José L Vicente
- Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Lisbon, Portugal
| | - Christopher S Clarkson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Beniamino Caputo
- Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy
| | - Bruno Gomes
- Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Lisbon, Portugal
| | - Marco Pombi
- Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy
| | - Carla A Sousa
- Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Lisbon, Portugal
| | - Tiago Antao
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - João Dinis
- Instituto Nacional de Saúde Pública, Ministério da Saúde Pública, Bissau, Guiné-Bissau
| | - Giordano Bottà
- Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy.,Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom
| | - Emiliano Mancini
- Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy
| | - Vincenzo Petrarca
- Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy.,Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Dipartimento di Biologia e Biotecnologie "Charles Darwin", Università di Roma "Sapienza", Rome, Italy
| | - Daniel Mead
- Wellcome Trust Sanger Institute, Hinxton, UK
| | | | | | - Alistair Miles
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom.,Medical Research Council Centre for Genomics and Global Health, University of Oxford, Oxford, UK
| | - Dominic P Kwiatkowski
- Wellcome Trust Centre for Human Genetics, University of Oxford, Oxford, United Kingdom.,Wellcome Trust Sanger Institute, Hinxton, UK.,Medical Research Council Centre for Genomics and Global Health, University of Oxford, Oxford, UK
| | - Martin J Donnelly
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Amabélia Rodrigues
- Instituto Nacional de Saúde Pública, Ministério da Saúde Pública, Bissau, Guiné-Bissau
| | - Alessandra Della Torre
- Istituto Pasteur Italia-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy
| | - David Weetman
- Department of Vector Biology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - João Pinto
- Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Lisbon, Portugal
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7
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Caputo B, Pichler V, Mancini E, Pombi M, Vicente JL, Dinis J, Steen K, Petrarca V, Rodrigues A, Pinto J, Della Torre A, Weetman D. The last bastion? X chromosome genotyping of Anopheles gambiae species pair males from a hybrid zone reveals complex recombination within the major candidate 'genomic island of speciation'. Mol Ecol 2016; 25:5719-5731. [PMID: 27661465 DOI: 10.1111/mec.13840] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2015] [Revised: 07/19/2016] [Accepted: 09/01/2016] [Indexed: 01/19/2023]
Abstract
Speciation with gene flow may be aided by reduced recombination helping to build linkage between genes involved in the early stages of reproductive isolation. Reduced recombination on chromosome X has been implicated in speciation within the Anopheles gambiae complex, species of which represent the major Afrotropical malaria vectors. The most recently diverged, morphologically indistinguishable, species pair, A. gambiae and Anopheles coluzzii, ubiquitously displays a 'genomic island of divergence' spanning over 4 Mb from chromosome X centromere, which represents a particularly promising candidate region for reproductive isolation genes, in addition to containing the diagnostic markers used to distinguish the species. Very low recombination makes the island intractable for experimental recombination studies, but an extreme hybrid zone in Guinea Bissau offers the opportunity for natural investigation of X-island recombination. SNP analysis of chromosome X hemizygous males revealed: (i) strong divergence in the X-island despite a lack of autosomal divergence; (ii) individuals with multiple-recombinant genotypes, including likely double crossovers and localized gene conversion; (iii) recombination-driven discontinuity both within and between the molecular species markers, suggesting that the utility of the diagnostics is undermined under high hybridization. The largely, but incompletely protected nature of the X centromeric genomic island is consistent with a primary candidate area for accumulation of adaptive variants driving speciation with gene flow, while permitting some selective shuffling and removal of genetic variation.
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Affiliation(s)
- Beniamino Caputo
- Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università 'Sapienza', Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - Verena Pichler
- Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università 'Sapienza', Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - Emiliano Mancini
- Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università 'Sapienza', Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - Marco Pombi
- Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università 'Sapienza', Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - José L Vicente
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua daJunqueira, 100, 1349-008, Lisboa, Portugal
| | - Joao Dinis
- Instituto Nacional de Saúde Pública, Ministério da Saúde Pública, Avenida Combatentes da Liberdade da Pátria, Apartado 861, 1004, Bissau Codex, Guinea Bissau
| | - Keith Steen
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Pl, Liverpool, Merseyside, L3 5QA, UK
| | - Vincenzo Petrarca
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Biologia e Biotecnologie Charles Darwin, Università 'Sapienza', Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - Amabelia Rodrigues
- Instituto Nacional de Saúde Pública, Ministério da Saúde Pública, Avenida Combatentes da Liberdade da Pátria, Apartado 861, 1004, Bissau Codex, Guinea Bissau
| | - Joao Pinto
- Global Health and Tropical Medicine, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua daJunqueira, 100, 1349-008, Lisboa, Portugal
| | - Alessandra Della Torre
- Istituto Pasteur Italia - Fondazione Cenci Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università 'Sapienza', Piazzale Aldo Moro 5, 00185, Rome, Italy
| | - David Weetman
- Vector Biology Department, Liverpool School of Tropical Medicine, Pembroke Pl, Liverpool, Merseyside, L3 5QA, UK
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Robert V, Petrarca V, Carnevale P, Ovazza L, Coluzzi M. Analyse cytogénétique du complexeAnopheles gambiaedans la région de Bobo-Dioulasso (Burkina Faso). ACTA ACUST UNITED AC 2016. [DOI: 10.1051/parasite/1989644290] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022]
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Pombi M, Guelbeogo WM, Calzetta M, Sagnon N, Petrarca V, La Gioia V, della Torre A. Evaluation of a protocol for remote identification of mosquito vector species reveals BG-Sentinel trap as an efficient tool for Anopheles gambiae outdoor collection in Burkina Faso. Malar J 2015; 14:161. [PMID: 25888896 PMCID: PMC4406007 DOI: 10.1186/s12936-015-0674-7] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/03/2014] [Accepted: 04/04/2015] [Indexed: 01/22/2023] Open
Abstract
Background Feasibility and costs of monitoring efforts aimed to monitor mosquito species are strictly dependent on the presence of skilled entomologists directly in the field. However, in several contexts this is not possible or easy to organize, thus limiting the possibility to obtain crucial information on presence/abundance of potential disease vectors and of new invasive species. Digital imaging approaches could be extremely useful in the frame of medical entomology to overcome this limit. This work describes a surveillance approach to collect and morphologically identify host-seeking malaria vectors based on remote transmission of digital images of specimens collected with ad hoc modified traps. Methods CDC light trap (CDC) and the BG-Sentinel trap (BG), both baited with BG-lure and CO2, were modified in order to have collected mosquitoes immobilized on a bi-dimensional surface. The performance of the two traps in the field was comparatively tested by Latin-square experiments in two villages of Burkina Faso under low and high mosquito densities. The efficiency of identifications based the inspection of digital images versus microscopic identifications of collected specimens was compared. Results A total of 1,519 mosquitoes belonging to 16 species were collected, of which 88.5% were microscopically identified as Anopheles gambiae s.l. (mainly Anopheles coluzzii, 85.7%). During dry season BG collected 15 times more females than CDC outdoors, whereas indoors the BG collected 0.4 times less than CDC. During rainy season the ratio BG/CDC was 6.4 and 0.7 outdoors and indoors, respectively. The efficiency of digital images versus microscopic identifications of collected specimens was 97.9%, 95.6% and 81.5% for Culicidae, Anophelinae and An. gambiae s.l., respectively. Conclusions Results strongly encourage the use of BG-trap for collecting host-seeking An. gambiae particularly in the outdoor environment, providing new perspectives to the challenge of collecting this fraction of the biting population, whose epidemiological relevance is increasing due to the success of large-scale implementation of indoor malaria vector control strategies. Moreover, results show that the transmission of digital images of specimens collected by the ad hoc modified host-seeking traps efficiently allows identification of malaria vectors, thus opening the perspective to easily carry out mosquito monitoring also in the absence of entomologists directly in the field. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0674-7) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Marco Pombi
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy.
| | - Wamdaogo M Guelbeogo
- Centre National de Recherche et Formation sur le Paludisme, Ouagadougou, Burkina Faso.
| | - Maria Calzetta
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy.
| | - N'Fale Sagnon
- Centre National de Recherche et Formation sur le Paludisme, Ouagadougou, Burkina Faso.
| | - Vincenzo Petrarca
- Dipartimento di Biologia e Biotecnologie, Università di Roma "Sapienza", Rome, Italy.
| | | | - Alessandra della Torre
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Rome, Italy.
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Caputo B, Ienco A, Manica M, Petrarca V, Rosà R, della Torre A. New adhesive traps to monitor urban mosquitoes with a case study to assess the efficacy of insecticide control strategies in temperate areas. Parasit Vectors 2015; 8:134. [PMID: 25880935 PMCID: PMC4378381 DOI: 10.1186/s13071-015-0734-4] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2015] [Accepted: 02/12/2015] [Indexed: 02/02/2023] Open
Abstract
BACKGROUND Urban mosquitoes in temperate regions may represent a high nuisance and are associated with the risk of arbovirus transmission. Common practices to reduce this burden, at least in Italian highly infested urban areas, imply calendar-based larvicide treatments of street catch basins - which represent the main non-removable urban breeding site - and/or insecticide ground spraying. The planning of these interventions, as well as the evaluation of their effectiveness, rarely benefit of adequate monitoring of the mosquito abundance and dynamics. We propose the use of adhesive traps to monitor Aedes albopictus and Culex pipiens adults and to evaluate the efficacy of insecticide-based control strategies. METHODS We designed two novel types of adhesive traps to collect adult mosquitoes visiting and/or emerging from catch basins. The Mosquito Emerging Trap (MET) was exploited to assess the efficacy of larvicide treatments. The Catch Basin Trap (CBT) was exploited together with the Sticky Trap (ST, commonly used to collect ovipositing/resting females) to monitor adults abundance in the campus of the University of Rome "Sapienza" - where catch basins were treated with Insect Growth Regulators (IGR) bi-monthly and Low-Volume insecticide spraying were carried out before sunset - and in a nearby control area. RESULTS Results obtained by MET showed that, although all monitored diflubenzuron-treated catch basins were repeatedly visited by Ae. albopictus and Cx. pipiens, adult emergence was inhibited in most basins. Results obtained by ST and CBT showed a significant lower adult abundance in the treated area than in the untreated one after the second adulticide spraying, which was carried out during the major phase of Ae. albopictus population expansion in Rome. Spatial heterogeneities in the effect of the treatments were also revealed. CONCLUSIONS The results support the potential of the three adhesive traps tested in passively monitoring urban mosquito adult abundance and seasonal dynamics and in assessing the efficacy of control measures. ST showed higher specificity for Ae. albopictus and CBT for Cx. pipiens. The results also provide a preliminary indication on the effectiveness of common mosquito control strategies carried out against urban mosquito in European urban areas.
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Affiliation(s)
- Beniamino Caputo
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Piazzale Aldo Moro 5, 00185, Rome, Italy.
| | - Annamaria Ienco
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Piazzale Aldo Moro 5, 00185, Rome, Italy.
| | - Mattia Manica
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Piazzale Aldo Moro 5, 00185, Rome, Italy.
| | - Vincenzo Petrarca
- Dipartimento di Biologia e Biotecnologie, Università di Roma " Sapienza", Piazzale Aldo Moro 5, 00185, Rome, Italy.
| | - Roberto Rosà
- Dipartimento di Biodiversità ed Ecologia Molecolare, Centro Ricerca e Innovazione, Fondazione Edmund Mach, San Michele all'Adige, TN, Italia.
| | - Alessandra della Torre
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma "Sapienza", Piazzale Aldo Moro 5, 00185, Rome, Italy.
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Santolamazza F, Caputo B, Nwakanma DC, Fanello C, Petrarca V, Conway DJ, Weetman D, Pinto J, Mancini E, della Torre A. Remarkable diversity of intron-1 of the para voltage-gated sodium channel gene in an Anopheles gambiae/Anopheles coluzzii hybrid zone. Malar J 2015; 14:9. [PMID: 25604888 PMCID: PMC4308935 DOI: 10.1186/s12936-014-0522-1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2014] [Accepted: 12/20/2014] [Indexed: 11/26/2022] Open
Abstract
Background Genomic differentiation between Anopheles gambiae and Anopheles coluzzii - the major malaria vectors in sub-Saharan Africa - is localized into large “islands” toward the centromeres of chromosome-X and the two autosomes. Linkage disequilibrium between these genomic islands was first detected between species-specific polymorphisms within ribosomal DNA genes (IGS-rDNA) on the X-chromosome and a single variant at position 702 of intron 1 (Int-1702) of the para Voltage-Gated Sodium Channel (VGSC) gene on chromosome arm 2 L. Intron-1 sequence data from West and Central Africa revealed two clearly distinct and species-specific haplogroups, each characterized by very low polymorphism, which has been attributed to a selective sweep. The aim of this study was to analyse Int-1 sequence diversity in A. gambiae and A. coluzzii populations from the Far-West of their range, in order to assess whether this selective-sweep signature could persist in a zone of high interspecific hybridization. Methods A 531 bp region of VGSC Int-1 was sequenced in 21 A. coluzzii, 31 A. gambiae, and 12 hybrids from The Gambia and Guinea Bissau, located within the Far-West geographical region, and in 53 A. gambiae s.l. samples from the rest of the range. Results Far-West samples exhibit dramatic Int-1 polymorphism, far higher within each country than observed throughout the rest of the species range. Moreover, patterning of haplotypes within A. coluzzii confirms previous evidence of a macro-geographic subdivision into a West and a Central African genetic cluster, and reveals a possible genetic distinction of A. coluzzii populations from the Far-West. Conclusions The results suggest a relaxation of selective pressures acting across the VGSC gene region in the hybrid zone. Genetic differentiation in the Far-West could be attributable to a founder effect within A. coluzzii, with subsequent extensive gene flow with secondarily-colonizing A. gambiae, potentially yielding a novel insight on the dynamic processes impacting genetic divergence of these key malaria vectors. Electronic supplementary material The online version of this article (doi:10.1186/s12936-014-0522-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Emiliano Mancini
- Dipartimento di Sanità Pubblica e Malattie Infettive, Istituto Pasteur-Fondazione Cenci-Bolognetti, Università "Sapienza", Piazzale Aldo Moro 5, Rome, 00185, Italy.
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Caputo B, Nwakanma D, Caputo FP, Jawara M, Oriero EC, Hamid-Adiamoh M, Dia I, Konate L, Petrarca V, Pinto J, Conway DJ, Della Torre A. Prominent intraspecific genetic divergence within Anopheles gambiae sibling species triggered by habitat discontinuities across a riverine landscape. Mol Ecol 2014; 23:4574-89. [PMID: 25040079 DOI: 10.1111/mec.12866] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2014] [Revised: 07/09/2014] [Accepted: 07/16/2014] [Indexed: 01/09/2023]
Abstract
The Anopheles gambiae complex of mosquitoes includes malaria vectors at different stages of speciation, whose study enables a better understanding of how adaptation to divergent environmental conditions leads to evolution of reproductive isolation. We investigated the population genetic structure of closely related sympatric taxa that have recently been proposed as separate species (An. coluzzii and An. gambiae), sampled from diverse habitats along the Gambia river in West Africa. We characterized putatively neutral microsatellite loci as well as chromosomal inversion polymorphisms known to be associated with ecological adaptation. The results revealed strong ecologically associated population subdivisions within both species. Microsatellite loci on chromosome-3L revealed clear differentiation between coastal and inland populations, which in An. coluzzii is reinforced by a unusual inversion polymorphism pattern, supporting the hypothesis of genetic divergence driven by adaptation to the coastal habitat. A strong reduction of gene flow was observed between An. gambiae populations west and east of an extensively rice-cultivated region apparently colonized exclusively by An. coluzzii. Notably, this 'intraspecific' differentiation is higher than that observed between the two species and involves also the centromeric region of chromosome-X which has previously been considered a marker of speciation within this complex, possibly suggesting that the two populations may be at an advanced stage of differentiation triggered by human-made habitat fragmentation. These results confirm ongoing ecological speciation within these most important Afro-tropical malaria vectors and raise new questions on the possible effect of this process in malaria transmission.
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Affiliation(s)
- B Caputo
- Dipartimento di Sanità Pubblica e Malattie Infettive, Istituto Pasteur-Fondazione Cenci-Bolognetti, Università 'Sapienza', Piazzale Aldo Moro 5, 00185, Rome, Italy
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Affiliation(s)
- Jeffrey R Powell
- Department of Ecology and Evolutionary Biology, Yale University, New Haven, CT 06520, USA
| | - Nora J Besansky
- Eck Institute for Global Health & Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Alessandra della Torre
- Department of Public Health and Infectious Diseases, Università di Roma “La Sapienza”, Rome 00185, Italy
| | - Vincenzo Petrarca
- Department of Biology and Biotechnology “Charles Darwin”, Università di Roma “La Sapienza”, Rome 00185 Italy
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Deitz KC, Athrey G, Reddy MR, Overgaard HJ, Matias A, Jawara M, Torre AD, Petrarca V, Pinto J, Kiszewski AE, Kengne P, Costantini C, Caccone A, Slotman MA. Genetic isolation within the malaria mosquito Anopheles melas. Mol Ecol 2013. [DOI: 10.1111/mec.12402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Caputo B, Ienco A, Cianci D, Pombi M, Petrarca V, Baseggio A, Devine GJ, della Torre A. The "auto-dissemination" approach: a novel concept to fight Aedes albopictus in urban areas. PLoS Negl Trop Dis 2012; 6:e1793. [PMID: 22953015 PMCID: PMC3429402 DOI: 10.1371/journal.pntd.0001793] [Citation(s) in RCA: 102] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2012] [Accepted: 07/11/2012] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND The main constraint to the fight against container-breeding mosquito vectors of human arboviruses is the difficulty in targeting the multiplicity of larval sources, mostly represented by small man-made water containers. The aim of this work is to assess the feasibility of the "auto-dissemination" approach, already tested for Aedes aegypti, as a possible alternative to traditional, inefficient control tools, against Ae. albopictus in urban areas. The approach is based on the possibility that wild adult females, exposed to artificial resting sites contaminated with pyriproxyfen, can disseminate this juvenile hormone analogue to larval habitats, thus interfering with adult emergence. METHODOLOGY We carried out four field experiments in two areas of Rome that are typically highly infested with Ae. albopictus, i.e. the main cemetery and a small green area within a highly urbanised neighbourhood. In each area we used 10 pyriproxyfen "dissemination" stations, 10 "sentinel" sites and 10 covered, control sites. The sentinel and control sites each contained 25 Ae. albopictus larvae. These were monitored for development and adult emergence. PRINCIPAL FINDINGS When a 5% pyriproxyfen powder was used to contaminate the dissemination sites, we observed significantly higher mortality at the pupal stage in the sentinel sites (50-70%) than in the controls (<2%), showing that pyriproxyfen was transferred by mosquitoes into sentinel sites and that it had a lethal effect. CONCLUSIONS The results support the potential feasibility of the auto-dissemination approach to control Ae. albopictus in urban areas. Further studies will be carried out to optimize the method and provide an effective tool to reduce the biting nuisance caused by this aggressive species and the transmission risk of diseases such as Dengue and Chikungunya. These arboviruses pose an increasing threat in Europe as Ae. albopictus expands its range.
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Affiliation(s)
- Beniamino Caputo
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma “Sapienza”, Rome, Italy
| | - Annamaria Ienco
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma “Sapienza”, Rome, Italy
| | - Daniela Cianci
- Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Marco Pombi
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma “Sapienza”, Rome, Italy
| | - Vincenzo Petrarca
- Dipartimento di Biologia e Biotecnologie “Charles Darwin”, Università di Roma “Sapienza”, Rome, Italy
| | | | - Gregor J. Devine
- Cairns Public Health Unit, Tropical Regional Services, Queensland Health, Cairns, Australia
| | - Alessandra della Torre
- Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma “Sapienza”, Rome, Italy
- * E-mail:
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Deitz KC, Athrey G, Reddy MR, Overgaard HJ, Matias A, Jawara M, Della Torre A, Petrarca V, Pinto J, Kiszewski AE, Kengne P, Costantini C, Caccone A, Slotman MA. Genetic isolation within the malaria mosquito Anopheles melas. Mol Ecol 2012; 21:4498-513. [PMID: 22882458 DOI: 10.1111/j.1365-294x.2012.05724.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Revised: 06/05/2012] [Accepted: 06/08/2012] [Indexed: 11/29/2022]
Abstract
Anopheles melas is a brackish water-breeding member of the Anopheles gambiae complex that is distributed along the coast of West Africa and is a major malaria vector within its range. Because little is known about the population structure of this species, we analysed 15 microsatellite markers and 1161 bp of mtDNA in 11 A. melas populations collected throughout its range. Compared with its sibling species A. gambiae, A. melas populations have a high level of genetic differentiation between them, representing its patchy distribution due to its fragmented larval habitat that is associated with mangroves and salt marsh grass. Populations clustered into three distinct groups representing Western Africa, Southern Africa and Bioko Island populations that appear to be mostly isolated. Fixed differences in the mtDNA are present between all three clusters, and a Bayesian clustering analysis of the microsatellite data found no evidence for migration from mainland to Bioko Island populations, and little migration was evident between the Southern to the Western cluster. Surprisingly, mtDNA divergence between the three A. melas clusters is on par with levels of divergence between other species of the A. gambiae complex, and no support for monophyly was observed in a maximum-likelihood phylogenetic analysis. Finally, an approximate Bayesian analysis of microsatellite data indicates that Bioko Island A. melas populations were connected to the mainland populations in the past, but became isolated, presumably when sea levels rose after the last glaciation period (≥10 000-11 000 bp). This study has exposed species-level genetic divergence within A. melas and also has implications for control of this malaria vector.
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Affiliation(s)
- Kevin C Deitz
- Department of Entomology, Texas A&M University, 2475 TAMU, College Station, TX, USA
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Santolamazza F, Caputo B, Calzetta M, Vicente JL, Mancini E, Petrarca V, Pinto J, della Torre A. Comparative analyses reveal discrepancies among results of commonly used methods for Anopheles gambiaemolecular form identification. Malar J 2011; 10:215. [PMID: 21810255 PMCID: PMC3170251 DOI: 10.1186/1475-2875-10-215] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2011] [Accepted: 08/02/2011] [Indexed: 01/05/2023] Open
Abstract
BACKGROUND Anopheles gambiae M and S molecular forms, the major malaria vectors in the Afro-tropical region, are ongoing a process of ecological diversification and adaptive lineage splitting, which is affecting malaria transmission and vector control strategies in West Africa. These two incipient species are defined on the basis of single nucleotide differences in the IGS and ITS regions of multicopy rDNA located on the X-chromosome. A number of PCR and PCR-RFLP approaches based on form-specific SNPs in the IGS region are used for M and S identification. Moreover, a PCR-method to detect the M-specific insertion of a short interspersed transposable element (SINE200) has recently been introduced as an alternative identification approach. However, a large-scale comparative analysis of four widely used PCR or PCR-RFLP genotyping methods for M and S identification was never carried out to evaluate whether they could be used interchangeably, as commonly assumed. RESULTS The genotyping of more than 400 A. gambiae specimens from nine African countries, and the sequencing of the IGS-amplicon of 115 of them, highlighted discrepancies among results obtained by the different approaches due to different kinds of biases, which may result in an overestimation of MS putative hybrids, as follows: i) incorrect match of M and S specific primers used in the allele specific-PCR approach; ii) presence of polymorphisms in the recognition sequence of restriction enzymes used in the PCR-RFLP approaches; iii) incomplete cleavage during the restriction reactions; iv) presence of different copy numbers of M and S-specific IGS-arrays in single individuals in areas of secondary contact between the two forms. CONCLUSIONS The results reveal that the PCR and PCR-RFLP approaches most commonly utilized to identify A. gambiae M and S forms are not fully interchangeable as usually assumed, and highlight limits of the actual definition of the two molecular forms, which might not fully correspond to the two A. gambiae incipient species in their entire geographical range. These limits are discussed and operational suggestions on the choice of the most convenient method for large-scale M- and S-form identification are provided, also taking into consideration technical aspects related to the epidemiological characteristics of different study areas.
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Affiliation(s)
- Federica Santolamazza
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università SAPIENZA, Piazzale Aldo Moro 5, 00185, Rome, Italy
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Rizzo C, Ronca R, Fiorentino G, Mangano VD, Sirima SB, Nèbiè I, Petrarca V, Modiano D, Arcà B. Wide cross-reactivity between Anopheles gambiae and Anopheles funestus SG6 salivary proteins supports exploitation of gSG6 as a marker of human exposure to major malaria vectors in tropical Africa. Malar J 2011; 10:206. [PMID: 21794142 PMCID: PMC3160432 DOI: 10.1186/1475-2875-10-206] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2011] [Accepted: 07/27/2011] [Indexed: 11/21/2022] Open
Abstract
Background The Anopheles gambiae gSG6 is an anopheline-specific salivary protein which helps female mosquitoes to efficiently feed on blood. Besides its role in haematophagy, gSG6 is immunogenic and elicits in exposed individuals an IgG response, which may be used as indicator of exposure to the main African malaria vector A. gambiae. However, malaria transmission in tropical Africa is sustained by three main vectors (A. gambiae, Anopheles arabiensis and Anopheles funestus) and a general marker, reflecting exposure to at least these three species, would be especially valuable. The SG6 protein is highly conserved within the A. gambiae species complex whereas the A. funestus homologue, fSG6, is more divergent (80% identity with gSG6). The aim of this study was to evaluate cross-reactivity of human sera to gSG6 and fSG6. Methods The A. funestus SG6 protein was expressed/purified and the humoral response to gSG6, fSG6 and a combination of the two antigens was compared in a population from a malaria hyperendemic area of Burkina Faso where both vectors were present, although with a large A. gambiae prevalence (>75%). Sera collected at the beginning and at the end of the high transmission/rainy season, as well as during the following low transmission/dry season, were analysed. Results According to previous observations, both anti-SG6 IgG level and prevalence decreased during the low transmission/dry season and showed a typical age-dependent pattern. No significant difference in the response to the two antigens was found, although their combined use yielded in most cases higher IgG level. Conclusions Comparative analysis of gSG6 and fSG6 immunogenicity to humans suggests the occurrence of a wide cross-reactivity, even though the two proteins carry species-specific epitopes. This study supports the use of gSG6 as reliable indicator of exposure to the three main African malaria vectors, a marker which may be useful to monitor malaria transmission and evaluate vector control measures, especially in conditions of low malaria transmission and/or reduced vector density. The Anopheles stephensi SG6 protein also shares 80% identity with gSG6, suggesting the attractive possibility that the A. gambiae protein may also be useful to assess human exposure to several Asian malaria vectors.
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Affiliation(s)
- Cinzia Rizzo
- Department of Public Health and Infectious Diseases, Sapienza University, P.le Aldo Moro 5, 00185 Rome, Italy
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Rizzo C, Ronca R, Fiorentino G, Verra F, Mangano V, Poinsignon A, Sirima SB, Nèbiè I, Lombardo F, Remoue F, Coluzzi M, Petrarca V, Modiano D, Arcà B. Humoral response to the Anopheles gambiae salivary protein gSG6: a serological indicator of exposure to Afrotropical malaria vectors. PLoS One 2011; 6:e17980. [PMID: 21437289 PMCID: PMC3060095 DOI: 10.1371/journal.pone.0017980] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2010] [Accepted: 02/17/2011] [Indexed: 11/19/2022] Open
Abstract
Salivary proteins injected by blood feeding arthropods into their hosts evoke a saliva-specific humoral response which can be useful to evaluate exposure to bites of disease vectors. However, saliva of hematophagous arthropods is a complex cocktail of bioactive factors and its use in immunoassays can be misleading because of potential cross-reactivity to other antigens. Toward the development of a serological marker of exposure to Afrotropical malaria vectors we expressed the Anopheles gambiae gSG6, a small anopheline-specific salivary protein, and we measured the anti-gSG6 IgG response in individuals from a malaria hyperendemic area of Burkina Faso, West Africa. The gSG6 protein was immunogenic and anti-gSG6 IgG levels and/or prevalence increased in exposed individuals during the malaria transmission/rainy season. Moreover, this response dropped during the intervening low transmission/dry season, suggesting it is sensitive enough to detect variation in vector density. Members of the Fulani ethnic group showed higher anti-gSG6 IgG response as compared to Mossi, a result consistent with the stronger immune reactivity reported in this group. Remarkably, anti-gSG6 IgG levels among responders were high in children and gradually declined with age. This unusual pattern, opposite to the one observed with Plasmodium antigens, is compatible with a progressive desensitization to mosquito saliva and may be linked to the continued exposure to bites of anopheline mosquitoes. Overall, the humoral anti-gSG6 IgG response appears a reliable serological indicator of exposure to bites of the main African malaria vectors (An. gambiae, Anopheles arabiensis and, possibly, Anopheles funestus) and it may be exploited for malaria epidemiological studies, development of risk maps and evaluation of anti-vector measures. In addition, the gSG6 protein may represent a powerful model system to get a deeper understanding of molecular and cellular mechanisms underlying the immune tolerance and progressive desensitization to insect salivary allergens.
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Affiliation(s)
- Cinzia Rizzo
- Department of Public Health and Infectious Diseases, “Sapienza” University, Rome, Italy
- Istituto Pasteur - Fondazione Cenci Bolognetti, Sapienza University, Rome, Italy
| | - Raffaele Ronca
- Department of Structural and Functional Biology, “Federico II” University, Naples, Italy
| | - Gabriella Fiorentino
- Department of Structural and Functional Biology, “Federico II” University, Naples, Italy
| | - Federica Verra
- Department of Public Health and Infectious Diseases, “Sapienza” University, Rome, Italy
| | - Valentina Mangano
- Department of Public Health and Infectious Diseases, “Sapienza” University, Rome, Italy
| | - Anne Poinsignon
- UR016 Biology and Control of Vectors, Institut de Recherche pour le Développement, Montpellier, France
| | | | - Issa Nèbiè
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Fabrizio Lombardo
- Department of Public Health and Infectious Diseases, “Sapienza” University, Rome, Italy
| | - Franck Remoue
- UR016 Biology and Control of Vectors, Institut de Recherche pour le Développement, Montpellier, France
| | - Mario Coluzzi
- Department of Public Health and Infectious Diseases, “Sapienza” University, Rome, Italy
| | - Vincenzo Petrarca
- Istituto Pasteur - Fondazione Cenci Bolognetti, Sapienza University, Rome, Italy
- Department of Biology and Biotechnology “Charles Darwin”, Sapienza University, Rome, Italy
| | - David Modiano
- Department of Public Health and Infectious Diseases, “Sapienza” University, Rome, Italy
- Istituto Pasteur - Fondazione Cenci Bolognetti, Sapienza University, Rome, Italy
| | - Bruno Arcà
- Department of Structural and Functional Biology, “Federico II” University, Naples, Italy
- * E-mail:
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Caputo B, Santolamazza F, Vicente JL, Nwakanma DC, Jawara M, Palsson K, Jaenson T, White BJ, Mancini E, Petrarca V, Conway DJ, Besansky NJ, Pinto J, Torre AD. The "far-west" of Anopheles gambiae molecular forms. PLoS One 2011; 6:e16415. [PMID: 21347223 PMCID: PMC3039643 DOI: 10.1371/journal.pone.0016415] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Accepted: 12/15/2010] [Indexed: 11/18/2022] Open
Abstract
The main Afrotropical malaria vector, Anopheles gambiae sensu stricto, is undergoing a process of sympatric ecological diversification leading to at least two incipient species (the M and S molecular forms) showing heterogeneous levels of divergence across the genome. The physically unlinked centromeric regions on all three chromosomes of these closely related taxa contain fixed nucleotide differences which have been found in nearly complete linkage disequilibrium in geographic areas of no or low M-S hybridization. Assays diagnostic for SNP and structural differences between M and S forms in the three centromeric regions were applied in samples from the western extreme of their range of sympatry, the only area where high frequencies of putative M/S hybrids have been reported. The results reveal a level of admixture not observed in the rest of the range. In particular, we found: i) heterozygous genotypes at each marker, although at frequencies lower than expected under panmixia; ii) virtually all possible genotypic combinations between markers on different chromosomes, although genetic association was nevertheless detected; iii) discordant M and S genotypes at two X-linked markers near the centromere, suggestive of introgression and inter-locus recombination. These results could be indicative either of a secondary contact zone between M and S, or of the maintenance of ancestral polymorphisms. This issue and the perspectives opened by these results in the study of the M and S incipient speciation process are discussed.
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Affiliation(s)
- Beniamino Caputo
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma “Sapienza”, Rome, Italy
| | - Federica Santolamazza
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma “Sapienza”, Rome, Italy
| | - José L. Vicente
- Centro de Malária e outras Doenças Tropicais, UEI Malária and UEI Entomologia Médica, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisbon, Portugal
| | | | - Musa Jawara
- Medical Research Council Laboratories, Banjul, The Gambia
| | - Katinka Palsson
- Medical Entomology Unit, Department of Systematic Biology, Uppsala University, Uppsala, Sweden
| | - Thomas Jaenson
- Medical Entomology Unit, Department of Systematic Biology, Uppsala University, Uppsala, Sweden
| | - Bradley J. White
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - Emiliano Mancini
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma “Sapienza”, Rome, Italy
| | - Vincenzo Petrarca
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Biologia e Biotecnologie “Charles Darwin”, Università di Roma “Sapienza”, Rome, Italy
| | | | - Nora J. Besansky
- Eck Institute for Global Health, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana, United States of America
| | - João Pinto
- Centro de Malária e outras Doenças Tropicais, UEI Malária and UEI Entomologia Médica, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Lisbon, Portugal
| | - Alessandra della Torre
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Sanità Pubblica e Malattie Infettive, Università di Roma “Sapienza”, Rome, Italy
- * E-mail:
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23
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Lulli P, Mangano VD, Onori A, Batini C, Luoni G, Sirima BS, Nebie I, Chessa L, Petrarca V, Modiano D. HLA-DRB1 and -DQB1 loci in three west African ethnic groups: genetic relationship with sub-Saharan African and European populations. Hum Immunol 2009; 70:903-9. [PMID: 19664674 DOI: 10.1016/j.humimm.2009.07.025] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2009] [Revised: 07/20/2009] [Accepted: 07/30/2009] [Indexed: 11/18/2022]
Abstract
The Fulani of west Africa have been shown to be less susceptible to malaria and to mount a stronger immune response to malaria than sympatric ethnic groups. The analysis of HLA diversity is useful for the assessment of the genetic distance between the Fulani and sympatric populations, which represents the necessary theoretical background for the investigation of genetic determinants of susceptibility to malaria. We assessed the polymorphism of HLA-DRB1 and -DQB1 loci and analyzed the distribution of alleles/haplotypes in Fulani, Mossi, and Rimaibé from Burkina Faso. We then investigated the genetic relationship of these three ethnic groups with other sub-Saharan African populations as well as with Europeans. We confirmed that the Fulani from Burkina Faso are genetically distinct from sympatric Mossi and Rimaibé. Furthermore the Fulani from Burkina Faso are close to those from The Gambia and, intriguingly, share the distribution of specific alleles with east African populations (Amhara and Oromo). It is noteworthy that the HLA-DRB1*04 and -DQB1*02 alleles, which are implicated in the development of several autoimmune diseases, are present at high frequency in the Fulani, suggesting their potential involvement in the enhanced immune reactivity observed in this population.
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Affiliation(s)
- Patrizia Lulli
- Department of Experimental Medicine, Sapienza University of Rome, Italy
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Lombardo F, Ronca R, Rizzo C, Mestres-Simòn M, Lanfrancotti A, Currà C, Fiorentino G, Bourgouin C, Ribeiro JM, Petrarca V, Ponzi M, Coluzzi M, Arcà B. The Anopheles gambiae salivary protein gSG6: an anopheline-specific protein with a blood-feeding role. Insect Biochem Mol Biol 2009; 39:457-66. [PMID: 19442731 PMCID: PMC3740408 DOI: 10.1016/j.ibmb.2009.04.006] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/05/2009] [Revised: 04/23/2009] [Accepted: 04/27/2009] [Indexed: 05/25/2023]
Abstract
The Anopheles gambiae salivary gland protein 6 (gSG6) is a small protein specifically found in the salivary glands of adult female mosquitoes. We report here the expression of a recombinant form of the protein and we show that in vivo gSG6 is expressed in distal-lateral lobes and is secreted with the saliva while the female mosquito probes for feeding. Injection of gSG6 dsRNA into adult A. gambiae females results in decreased gSG6 protein levels, increased probing time and reduced blood feeding ability. gSG6 orthologs have been found so far only in the salivary glands of Anopheles stephensi and Anopheles funestus, both members of the Cellia subgenus. We report here the gSG6 sequence from five additional anophelines, four species of the A. gambiae complex and Anopheles freeborni, a member of the subgenus Anopheles. We conclude that gSG6 plays some essential blood feeding role and was recruited in the anopheline subfamily most probably after the separation of the lineage which gave origin to Cellia and Anopheles subgenera.
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Affiliation(s)
- Fabrizio Lombardo
- Dipartimento di Scienze di Sanità Pubblica, Sezione di Parassitologia, Università “La Sapienza” - Piazzale Aldo Moro 5, 00185 Roma, Italy
| | - Raffaele Ronca
- Dipartimento di Biologia Strutturale e Funzionale, Università “Federico II” - Via Cinthia, 80126 Napoli, Italy
| | - Cinzia Rizzo
- Dipartimento di Scienze di Sanità Pubblica, Sezione di Parassitologia, Università “La Sapienza” - Piazzale Aldo Moro 5, 00185 Roma, Italy
| | - Montserrat Mestres-Simòn
- Dipartimento di Scienze di Sanità Pubblica, Sezione di Parassitologia, Università “La Sapienza” - Piazzale Aldo Moro 5, 00185 Roma, Italy
| | - Alessandra Lanfrancotti
- Dipartimento di Scienze di Sanità Pubblica, Sezione di Parassitologia, Università “La Sapienza” - Piazzale Aldo Moro 5, 00185 Roma, Italy
| | - Chiara Currà
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate Istituto superiore di Sanità, Viale Regina Elena 299, 00161 Roma, Italy
| | - Gabriella Fiorentino
- Dipartimento di Biologia Strutturale e Funzionale, Università “Federico II” - Via Cinthia, 80126 Napoli, Italy
| | - Catherine Bourgouin
- Institut Pasteur, Centre de Production et d’Infection des Anophèles, 28 rue du Docteur Roux, 75724 Paris Cedex 15, France
| | - Josè M.C. Ribeiro
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, Twinbrook III, 12735 Twinbrook Parkway, National Institute of Health, Rockville, MD 20852, USA
| | - Vincenzo Petrarca
- Dipartimento di Genetica e Biologia Moleculare, Università “La Sapienza” - Piazzale Aldo Moro 5, 00185 Roma, Italy
| | - Marta Ponzi
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate Istituto superiore di Sanità, Viale Regina Elena 299, 00161 Roma, Italy
| | - Mario Coluzzi
- Dipartimento di Scienze di Sanità Pubblica, Sezione di Parassitologia, Università “La Sapienza” - Piazzale Aldo Moro 5, 00185 Roma, Italy
| | - Bruno Arcà
- Dipartimento di Scienze di Sanità Pubblica, Sezione di Parassitologia, Università “La Sapienza” - Piazzale Aldo Moro 5, 00185 Roma, Italy
- Dipartimento di Biologia Strutturale e Funzionale, Università “Federico II” - Via Cinthia, 80126 Napoli, Italy
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Pombi M, Caputo B, Simard F, Di Deco MA, Coluzzi M, della Torre A, Costantini C, Besansky NJ, Petrarca V. Chromosomal plasticity and evolutionary potential in the malaria vector Anopheles gambiae sensu stricto: insights from three decades of rare paracentric inversions. BMC Evol Biol 2008; 8:309. [PMID: 19000304 PMCID: PMC2654565 DOI: 10.1186/1471-2148-8-309] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2008] [Accepted: 11/10/2008] [Indexed: 12/27/2022] Open
Abstract
Background In the Anopheles gambiae complex, paracentric chromosomal inversions are non-randomly distributed along the complement: 18/31 (58%) of common polymorphic inversions are on chromosome arm 2R, which represents only ~30% of the complement. Moreover, in An. gambiae sensu stricto, 6/7 common polymorphic inversions occur on 2R. Most of these inversions are considered markers of ecological adaptation that increase the fitness of the carriers of alternative karyotypes in contrasting habitats. However, little is known about the evolutionary forces responsible for their origin and subsequent establishment in field populations. Results Here, we present data on 82 previously undescribed rare chromosomal inversions (RCIs) recorded during extensive field sampling in 16 African countries over a 30 year period, which may shed light on the dynamics of chromosomal plasticity in An. gambiae. We analyzed breakpoint distribution, length, and geographic distribution of RCIs, and compared these measures to those of the common inversions. We found that RCIs, like common inversions, are disproportionately clustered on 2R, which may indicate that this arm is especially prone to breakages. However, contrasting patterns were observed between the geographic distribution of common inversions and RCIs. RCIs were equally frequent across biomes and on both sides of the Great Rift Valley (GRV), whereas common inversions predominated in arid ecological settings and west of the GRV. Moreover, the distribution of RCI lengths followed a random pattern while common inversions were significantly less frequent at shorter lengths. Conclusion Because 17/82 (21%) RCIs were found repeatedly at very low frequencies – at the same sampling location in different years and/or in different sampling locations – we suggest that RCIs are subject mainly to drift under unperturbed ecological conditions. Nevertheless, RCIs may represent an important reservoir of genetic variation for An. gambiae in response to environmental changes, further testifying to the considerable evolutionary potential hidden within this pan-African malaria vector.
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Affiliation(s)
- Marco Pombi
- Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, Università di Roma Sapienza, P. Aldo Moro 5, 00185 Roma, Italy.
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Caputo B, Nwakanma D, Jawara M, Adiamoh M, Dia I, Konate L, Petrarca V, Conway DJ, della Torre A. Anopheles gambiae complex along The Gambia river, with particular reference to the molecular forms of An. gambiae s.s. Malar J 2008; 7:182. [PMID: 18803885 PMCID: PMC2569043 DOI: 10.1186/1475-2875-7-182] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2008] [Accepted: 09/22/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The geographic and temporal distribution of M and S molecular forms of the major Afrotropical malaria vector species Anopheles gambiae s.s. at the western extreme of their range of distribution has never been investigated in detail. MATERIALS AND METHODS Collections of indoor-resting An. gambiae s.l. females were carried out along a ca. 400 km west to east transect following the River Gambia from the western coastal region of The Gambia to south-eastern Senegal during 2005 end of rainy season/early dry season and the 2006 rainy season. Specimens were identified to species and molecular forms by PCR-RFLP and the origin of blood-meal of fed females was determined by ELISA test. RESULTS Over 4,000 An. gambiae s.l. adult females were collected and identified, 1,041 and 3,038 in 2005 and 2006, respectively. M-form was mainly found in sympatry with Anopheles melas and S-form in the western part of the transect, and with Anopheles arabiensis in the central part. S-form was found to prevail in rural Sudan-Guinean savannah areas of Eastern Senegal, in sympatry with An. arabiensis. Anopheles melas and An. arabiensis relative frequencies were generally lower in the rainy season samples, when An. gambiae s.s. was prevailing. No large seasonal fluctuations were observed for M and S-forms. In areas where both M and S were recorded, the frequency of hybrids between them ranged from to 0.6% to 7%. DISCUSSION The observed pattern of taxa distribution supports the hypothesis of a better adaptation of M-form to areas characterized by water-retaining alluvial deposits along the Gambia River, characterized by marshy vegetation, mangrove woods and rice cultivations. In contrast, the S-form seems to be better adapted to free-draining soil, covered with open woodland savannah or farmland, rich in temporary larval breeding sites characterizing mainly the eastern part of the transect, where the environmental impact of the Gambia River is much less profound and agricultural activities are mainly rain-dependent. Very interestingly, the observed frequency of hybridization between the molecular forms along the whole transect was much higher than has been reported so far for other areas. CONCLUSION The results support a bionomic divergence between the M and S-forms, and suggest that the western extreme of An. gambiae s.s. geographical distribution may represent an area of higher-than-expected hybridization between the two molecular forms.
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Affiliation(s)
- Beniamino Caputo
- Istituto Pasteur-Fondazione Cenci-Bolognetti, Dipartimento di Scienze di Sanità Pubblica, Università La Sapienza, Piazzale Aldo Moro 5, 00185, Rome, Italy.
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della Torre A, Arca B, Favia G, Petrarca V, Coluzzi M. The role of research in molecular entomology in the fight against malaria vectors. Parassitologia 2008; 50:137-140. [PMID: 18693580] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
The text summarizes the principal current fields of investigation and the recent achievements of the research groups presently contributing to the Molecular Entomology Cluster of the Italian Malaria Network. Particular emphasis is given to the researches with a more direct impact on the fight against malaria vectors.
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Affiliation(s)
- A della Torre
- Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, Università "La Sapienza", Rome, Italy.
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Santolamazza F, Calzetta M, Etang J, Barrese E, Dia I, Caccone A, Donnelly MJ, Petrarca V, Simard F, Pinto J, della Torre A. Distribution of knock-down resistance mutations in Anopheles gambiae molecular forms in west and west-central Africa. Malar J 2008; 7:74. [PMID: 18445265 PMCID: PMC2405802 DOI: 10.1186/1475-2875-7-74] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2008] [Accepted: 04/29/2008] [Indexed: 11/10/2022] Open
Abstract
Background Knock-down resistance (kdr) to DDT and pyrethroids in the major Afrotropical vector species, Anopheles gambiae sensu stricto, is associated with two alternative point mutations at amino acid position 1014 of the voltage-gated sodium channel gene, resulting in either a leucine-phenylalanine (L1014F), or a leucine-serine (L1014S) substitution. In An. gambiae S-form populations, the former mutation appears to be widespread in west Africa and has been recently reported from Uganda, while the latter, originally recorded in Kenya, has been recently found in Gabon, Cameroon and Equatorial Guinea. In M-form populations surveyed to date, only the L1014F mutation has been found, although less widespread and at lower frequencies than in sympatric S-form populations. Methods Anopheles gambiae M- and S-form specimens from 19 sites from 11 west and west-central African countries were identified to molecular form and genotyped at the kdr locus either by Hot Oligonucleotide Ligation Assay (HOLA) or allele-specific PCR (AS-PCR). Results The kdr genotype was determined for about 1,000 An. gambiae specimens. The L1014F allele was found at frequencies ranging from 6% to 100% in all S-form samples (N = 628), with the exception of two samples from Angola, where it was absent, and coexisted with the L1014S allele in samples from Cameroon, Gabon and north-western Angola. The L1014F allele was present in M-form samples (N = 354) from Benin, Nigeria, and Cameroon, where both M- and S-forms were sympatric. Conclusion The results represent the most comprehensive effort to analyse the overall distribution of the L1014F and L1014S mutations in An. gambiae molecular forms, and will serve as baseline data for resistance monitoring. The overall picture shows that the emergence and spread of kdr alleles in An. gambiae is a dynamic process and that there is marked intra- and inter-form heterogeneity in resistance allele frequencies. Further studies are needed to determine: i) the importance of selection pressure exerted by both agricultural and public health use of pyrethroid insecticides, ii) the phenotypic effects, particularly when the two mutations co-occur; and iii) the epidemiological importance of kdr for both pyrethroid- and DDT-based malaria control operations, particularly if/when the two insecticides are to be used in concert.
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Calzetta M, Santolamazza F, Carrara GC, Cani PJ, Fortes F, Di Deco MA, della Torre A, Petrarca V. Distribution and chromosomal characterization of the Anopheles gambiae complex in Angola. Am J Trop Med Hyg 2008; 78:169-175. [PMID: 18187801] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023] Open
Abstract
Mosquitoes of the Anopheles gambiae complex (N = 1,336) were sampled (2001-2005) across Angola to identify taxa, study inversion polymorphisms, and detect the circumsporozoite protein of Plasmodium falciparum. Anopheles gambiae s.s. was found in all sites; it was characterized as M-form in localities of the tropical dry and semi-desertic belts, whereas the S-form was predominant in comparatively more humid and less anthropized sites. Both forms were characterized by low degrees of chromosomal polymorphism based solely on the 2La inversion, a pattern usually associated with An. gambiae populations from forested, humid, and derived savanna areas. Unexpectedly, this pattern was also observed in M-form populations collected in dry/pre-desertic areas, where this form largely predominates over An. arabiensis, which was also detected in central/inland sites. Anopheles melas was found in northern coastal sites. Three of 534 An. gambiae s.s. were positive for P. falciparum CS-protein, whereas none of the 105 An. melas were positive.
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Affiliation(s)
- Maria Calzetta
- Dipartimento di Scienze di Sanità Pubblica, Sezione de Parassitologia, Università degli Studi di Roma La Sapienza, Piazzale Aldo Moro 5, Rome, Italy.
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Calzetta M, Cani PJ, Di Deco MA, Santolamazza F, Torre AD, Carrara GC, Petrarca V, Fortes F. Distribution and Chromosomal Characterization of the Anopheles gambiae Complex in Angola. Am J Trop Med Hyg 2008. [DOI: 10.4269/ajtmh.2008.78.169] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
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Coulibaly MB, Pombi M, Caputo B, Nwakanma D, Jawara M, Konate L, Dia I, Fofana A, Kern M, Simard F, Conway DJ, Petrarca V, Torre AD, Traoré S, Besansky NJ. PCR-based karyotyping of Anopheles gambiae inversion 2Rj identifies the BAMAKO chromosomal form. Malar J 2007; 6:133. [PMID: 17908310 PMCID: PMC2134931 DOI: 10.1186/1475-2875-6-133] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2007] [Accepted: 10/01/2007] [Indexed: 11/10/2022] Open
Abstract
Background The malaria vector Anopheles gambiae is polymorphic for chromosomal inversions on the right arm of chromosome 2 that segregate nonrandomly between assortatively mating populations in West Africa. One such inversion, 2Rj, is associated with the BAMAKO chromosomal form endemic to southern Mali and northern Guinea Conakry near the Niger River. Although it exploits a unique ecology and both molecular and chromosomal data suggest reduced gene flow between BAMAKO and other A. gambiae populations, no molecular markers exist to identify this form. Methods To facilitate study of the BAMAKO form, a PCR assay for molecular karyotyping of 2Rj was developed based on sequences at the breakpoint junctions. The assay was extensively validated using more than 700 field specimens whose karyotypes were determined in parallel by cytogenetic and molecular methods. As inversion 2Rj also occurs in SAVANNA populations outside the geographic range of BAMAKO, samples were tested from Senegal, Cameroon and western Guinea Conakry as well as from Mali. Results In southern Mali, where 2Rj polymorphism in SAVANNA populations was very low and most of the 2Rj homozygotes were found in BAMAKO karyotypes, the molecular and cytogenetic methods were almost perfectly congruent. Elsewhere agreement between the methods was much poorer, as the molecular assay frequently misclassified 2Rj heterozygotes as 2R+j standard homozygotes. Conclusion Molecular karyotyping of 2Rj is robust and accurate on 2R+j standard and 2Rj inverted homozygotes. Therefore, the proposed approach overcomes the lack of a rapid tool for identifying the BAMAKO form across developmental stages and sexes, and opens new perspectives for the study of BAMAKO ecology and behaviour. On the other hand, the method should not be applied for molecular karyotyping of j-carriers within the SAVANNA chromosomal form.
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Affiliation(s)
- Mamadou B Coulibaly
- Center for Global Health and Infectious Diseases, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Marco Pombi
- Istituto Pasteur-Fondazione Cenci Bolognetti and Dipartimento di Scienze di Sanità Pubblica, Università di Roma "La Sapienza", Rome, Italy
| | - Beniamino Caputo
- Istituto Pasteur-Fondazione Cenci Bolognetti and Dipartimento di Scienze di Sanità Pubblica, Università di Roma "La Sapienza", Rome, Italy
| | - Davis Nwakanma
- Medical Research Council Laboratories, Fajara, Banjul, The Gambia
| | - Musa Jawara
- Medical Research Council Laboratories, Fajara, Banjul, The Gambia
| | - Lassana Konate
- Département de Biologie Animale, Faculté des Sciences et Techniques, Université de Dakar, Senegal
| | - Ibrahima Dia
- Medical Entomology Unit, Pasteur Institute, Dakar, Senegal
| | - Abdrahamane Fofana
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Marcia Kern
- Center for Global Health and Infectious Diseases, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
| | - Frédéric Simard
- Organisation de Coordination pour la Lutte contre les Endémies en Afrique Centrale, Yaoundé, Cameroon
- Institut de Recherche pour le Développement, Unité de Recherche 016, Yaoundé, Cameroon
| | - David J Conway
- Medical Research Council Laboratories, Fajara, Banjul, The Gambia
| | - Vincenzo Petrarca
- Istituto Pasteur-Fondazione Cenci Bolognetti and Dipartimento di Genetica e Biologia Molecolare, Università di Roma "La Sapienza", Rome, Italy
| | - Alessandra della Torre
- Istituto Pasteur-Fondazione Cenci Bolognetti and Dipartimento di Scienze di Sanità Pubblica, Università di Roma "La Sapienza", Rome, Italy
| | - Sékou Traoré
- Malaria Research and Training Center, University of Bamako, Bamako, Mali
| | - Nora J Besansky
- Center for Global Health and Infectious Diseases, Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, USA
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Caputo B, Dani FR, Horne GL, N'Fale S, Diabate A, Turillazzi S, Coluzzi M, Costantini C, Priestman AA, Petrarca V, della Torre A. Comparative analysis of epicuticular lipid profiles of sympatric and allopatric field populations of Anopheles gambiae s.s. molecular forms and An. arabiensis from Burkina Faso (West Africa). Insect Biochem Mol Biol 2007; 37:389-98. [PMID: 17368202 DOI: 10.1016/j.ibmb.2007.01.002] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2006] [Revised: 01/12/2007] [Accepted: 01/12/2007] [Indexed: 05/14/2023]
Abstract
We analysed by gas chromatography-mass spectrometry (GC-MS) and Gas Chromatography-Flame Ionization Detector (GC-FID) the epicuticular lipid profiles of field females of the major Afro-tropical malaria vector, Anopheles gambiae. The samples were collected in three villages in Burkina Faso (West Africa), where An. gambiae M and S molecular forms and An. arabiensis live sympatrically. The aim was to compare the cuticular hydrocarbon (CHC) composition of individual field specimens of these three taxa, to highlight possible differences among them. All the samples analysed by GC-MS (55 individuals and eight pools) were characterized by the same 48 CHCs and 10 oxygenated compounds. The 19 most abundant CHCs were quantified in 174 specimens by GC-FID: quantitative intra-taxon differences were found between allopatric populations of both An. arabiensis and S-form. Inter-taxa quantitative differences in the relative abundances of some hydrocarbons between pairs of sympatric taxa were also found, which appear to be mainly linked to local situations, with the possible exception of diMeC(35) between An. arabiensis and S-form. Moreover, MeC(29) shows some degree of differentiation between S- and M-form in all three villages. Possible causes of these differences are discussed.
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Affiliation(s)
- B Caputo
- Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, Università di Roma "La Sapienza", Piazzale Aldo Moro 5, 00185, Rome, Italy
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White BJ, Santolamazza F, Kamau L, Pombi M, Grushko O, Mouline K, Brengues C, Guelbeogo W, Coulibaly M, Kayondo JK, Sharakhov I, Simard F, Petrarca V, Della Torre A, Besansky NJ. Molecular karyotyping of the 2La inversion in Anopheles gambiae. Am J Trop Med Hyg 2007; 76:334-9. [PMID: 17297045] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/13/2023] Open
Abstract
The African malaria vector Anopheles gambiae is polymorphic for alternative arrangements on the left arm of chromosome 2 (2La and 2L+(a)) that are non-randomly distributed with respect to degree of aridity. Detailed studies on the ecological role of inversion 2La have been hindered by the technical demands of traditional karyotype analysis and by sex- and stage-specific limitations on the availability of polytene chromosomes favorable for analysis. Recent molecular characterization of both inversion breakpoints presented the opportunity to develop a polymerase chain reaction (PCR)-based method for karyotype analysis. Here we report the development of this molecular diagnostic assay and the results of extensive field validation. When tested on 765 An. gambiae specimens sampled across Africa, the molecular approach compared favorably with traditional cytologic methods, correctly scoring > 94% of these specimens. By providing ready access to the 2La karyotype, this tool lays groundwork for future studies of the ecological genomics of this medically important species.
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Affiliation(s)
- Bradley J White
- Center for Global Health and Infectious Diseases, Department of Biological Sciences, University of Notre Dame, Notre Dame, Indiana 46556, USA.
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Caputo B, Dani FR, Horne GL, Petrarca V, Turillazzi S, Coluzzi M, Priestman AA, della Torre A. Identification and composition of cuticular hydrocarbons of the major Afrotropical malaria vector Anopheles gambiae s.s. (Diptera: Culicidae): analysis of sexual dimorphism and age-related changes. J Mass Spectrom 2005; 40:1595-604. [PMID: 16320293 DOI: 10.1002/jms.961] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
Forty-eight cuticular hydrocarbons (CHCs) were characterized by gas chromatography-mass spectrometry from the epicuticular surface of the major Afrotropical malaria vector Anopheles gambiae. The hydrocarbons identified were 14 n-alkanes, 16 monomethyl alkanes, 13 dimethyl alkanes, 5 alkenes, with main-chain lengths ranging from C(17) to C(47), and the results are consistent with those from other Culicidae species. Qualitative differences were not observed between laboratory pools of three females and males, between different age-groups (0-16 days) and between single field specimens, whereas quantitative differences in CHC profiles were observed. Differences between sexes were more marked in individuals aged 0-2 days than in older ones. Both sexes undergo strong CHC profile changes with age, and individuals aged 0-2 days differ remarkably from the older ones. The possibility of exploiting these changes for estimating the age of mosquito was explored through multivariate analyses of the relative abundance of the compounds, using either the whole CHC profile or a subset of CHCs. Such a method allows us to assign more than 85% of females and 75% of males to the correct age-group. Although preliminary, these results show that the method is promising, as it has already been shown in Aedes aegypti and An. stephensi. The correct determination of the vector age (particularly in the case of the An. gambiae complex of sibling species) provides valuable information in malaria epidemiology and in evaluation of the effectiveness of vector control strategies. Further efforts will be made to validate this method on single specimens reared in seminatural conditions before being proposed to medical entomologists working in the Afrotropical region.
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Affiliation(s)
- Beniamino Caputo
- Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, Università La Sapienza, Roma, Italy
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35
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Wondji C, Frédéric S, Petrarca V, Etang J, Santolamazza F, Della Torre A, Fontenille D. Species and populations of the Anopheles gambiae complex in Cameroon with special emphasis on chromosomal and molecular forms of Anopheles gambiae s.s. J Med Entomol 2005; 42:998-1005. [PMID: 16465741 DOI: 10.1093/jmedent/42.6.998] [Citation(s) in RCA: 83] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
We studied the geographical distribution of species, chromosomal, and molecular forms of the Anopheles gambiae Giles (Diptera: Culicidae) complex in 23 sites in Cameroon, Central Africa. Almost all the specimens collected in the four northern-most arid sites were Anopheles arabiensis. Anopheles melas was found in a rural locality surrounded by mangrove swamps, on the Atlantic Coast. In total, 1,525 An. gambiae s.s. females were identified down to their molecular form, and inversion polymorphisms on polytene chromosomes were scored from 186 half-gravid females. The Forest chromosomal form, with standard arrangements almost fixed on both arms of chromosome-2, was the only one observed in the southern, more humid localities. Karyotypes typical of Savanna and Mopti were recorded northwards, in the humid savannas of the Adamawa Province. The molecular forms M and S were widespread throughout Cameroon, and assort independently from the chromosomal forms. S-form populations were characterized by karyotypes typical of Forest and Savanna chromosomal forms, and M-form populations were characterized by karyotypes typical of Forest, Savanna, and Mopti. No M/S hybrid patterns were detected, although M and S mosquitoes were sympatric in 15 sites, providing further evidence for positive assortative mating within molecular forms. The observed ecogeographical distribution of M and S was peculiar: the ecological parameters involved in this distribution still need to be clarified as well as the possible role of competitive exclusion between chromosomally homosequential molecular forms. No difference was observed in host preference or in Plasmodium falciparum infection rates between sympatric M and S populations.
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Affiliation(s)
- Charles Wondji
- Organisation de Coordination pour lalutte contre les Endémies en Afrique Centrale, Yaoundé, Cameroon.
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36
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della Torre A, Tu Z, Petrarca V. On the distribution and genetic differentiation of Anopheles gambiae s.s. molecular forms. Insect Biochem Mol Biol 2005; 35:755-69. [PMID: 15894192 DOI: 10.1016/j.ibmb.2005.02.006] [Citation(s) in RCA: 179] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/11/2005] [Indexed: 05/02/2023]
Abstract
This paper summarises published and unpublished data on the spatial and temporal distribution, and on the genetic characterisation of molecular forms M and S of Anopheles gambiae s.s. The two forms are characterised by a high level of gene-flow restriction, by a largely overlapping geographical and temporal distribution, and by a low degree of genetic differentiation. Floating paracentric inversions on chromosome-2 are shown to be shared by the two forms, although with very different frequencies of alternative arrangements, confirming that these inversions are most probably involved in ecotypic adaptation, rather than in the building of reproductive barriers. Further studies and tools are needed to throw light on the genetic and biological differentiation of M and S to improve the knowledge of the real composition of the vector system, of its demography, population genetics and dynamics, also in view of the possible consequences on the transmission of human pathogens in sub-Saharan Africa. Preliminary results and perspectives of the use of transposable element insertion sites as markers of genetic differentiation and tools for population genetic studies are discussed.
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Affiliation(s)
- Alessandra della Torre
- Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, Università di Roma La Sapienza, Piazzale Aldo Moro 5, 00185 Roma, Italy.
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Aranda C, Aponte JJ, Saute F, Casimiro S, Pinto J, Sousa C, Rosario VD, Petrarca V, Dgedge M, Alonso P. Entomological characteristics of malaria transmission in Manhiça, a rural area in southern Mozambique. J Med Entomol 2005; 42:180-186. [PMID: 15799528 DOI: 10.1093/jmedent/42.2.180] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
From October 1997 to September 1998, an entomological survey was carried out in Manhiça, Mozambique, to describe the anopheline population and intensity of malaria transmission. Ten different huts were randomly selected for entomological surveillance throughout the year. CDC light trap collections were conducted during three nights each month. Additional knockdown spraying catches were carried out in the morning, after the last catch. A total of 17,245 Culicinae and 1,251 Anophelinae were collected during the study. There was substantial house to house variation and seasonality in the distribution of Anophelinae population, with a peak in April towards the end of the warm and rainy season. Four species of genus Anopheles (Diptera: Culicidae) were described: Anopheles funestus Giles, Anopheles tenebrosus Dönitz, Anopheles arabiensis Patton, and Anopheles merus Dönitz. An. funestus constitutes 72.3% of the anopheline population. The estimated sporozoite rate was 1.2% and the average entomological inoculation rate for the area was 15 infective bites per person per year.
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Affiliation(s)
- C Aranda
- Centro de Investigação em Saúde da Manhiça, Instituto Nacional de Saúde, Ministerio de Saúde, Manhiça, Mozambique
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38
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Gentile G, Santolamazza F, Fanello C, Petrarca V, Caccone A, della Torre A. Variation in an intron sequence of the voltage-gated sodium channel gene correlates with genetic differentiation between Anopheles gambiae s.s. molecular forms. Insect Mol Biol 2004; 13:371-377. [PMID: 15271209 DOI: 10.1111/j.0962-1075.2004.00494.x] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
We present the results of a geographical survey of genetic variation in Anopheles gambiae M and S molecular forms from ten African countries at Intron I of the voltage-gated sodium channel gene. We found two major haplotypes separated by a single mutational step, which cosegregate almost completely with the rDNA sites that identify M and S, consistent with previous estimates of strong reductions of gene flow between the two forms. We also report ten additional haplotypes stemming from the two major haplotypes, mostly present in single localities. The low levels of genetic variation found in this intronic region are discussed in light of a possible selective sweep. These findings offer additional elements to the ongoing debate on the amount of genetic differentiation and isolation between the two molecular forms and on their taxonomic status.
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Affiliation(s)
- G Gentile
- Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, Rome, Italy
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39
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Pinto J, Donnelly MJ, Sousa CA, Malta-Vacas J, Gil V, Ferreira C, Petrarca V, do Rosário VE, Charlwood JD. An island within an island: genetic differentiation of Anopheles gambiae in São Tomé, West Africa, and its relevance to malaria vector control. Heredity (Edinb) 2004; 91:407-14. [PMID: 14512957 DOI: 10.1038/sj.hdy.6800348] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Islands are choice settings for experimental studies of vector control strategies based on transgenic insects. Before considering this approach, knowledge of the population structure of the vector is essential. Genetic variation at 12 microsatellite loci was therefore studied in samples of the malaria vector Anopheles gambiae s.s., collected from six localities of São Tomé island (West Africa). The objectives were (i) to assess the demographic stability and effective population size of A. gambiae from these sites, (ii) to determine population differentiation and (iii) to relate the observed patterns of population structure with geographic, ecological and historical aspects of the vector on the island. Significant population differentiation, revealed by FST and RST statistics, was found between the southernmost site, Porto Alegre, and northern localities. The observed patterns of population substructure are probably a result of restrictions to gene flow in the less inhabited, more densely forested and mountainous south. In all localities surveyed, A. gambiae appeared to be experiencing a demographic expansion, consistent with a relatively recent (ca. 500 years) founder effect. The results are discussed with respect to current and future prospects of malaria vector control.
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Affiliation(s)
- J Pinto
- Centro de Malária e outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, Lisbon 1349-008, Portugal
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40
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Mariniello L, Ortis M, D'Amelio S, Petrarca V. Morphometric variability between and within species of Ligophorus Euzet & Suriano, 1977 (Monogenea: Ancyrocephalidae) in the Mediterranean Sea. Syst Parasitol 2004; 57:183-90. [PMID: 15010592 DOI: 10.1023/b:sypa.0000019080.43784.06] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Monogeneans belonging to the genus Ligophorus Euzet & Suriano, 1977 are parasitic on the gills of several fish species of the family Mugilidae (mullets). At present, 12 species belonging to this genus have been described in the Mediterranean Sea and each host species is infected by a number of Ligophorus species that are not found on other mullets. A multivariate study using principal component and canonical variate analyses was carried out, with the aim of investigating the extent of morphometric variability within and between the 12 Mediterranean species of Ligophorus. Significant intraspecific morphometric variation was detected between two allopatric populations of L. angustus Euzet & Suriano, 1977 parasitic on Chelon labrosus from Sardinia; however, the existence of a new species of Ligophorus needs further evidence. Analysis of interspecific variation confirms the validity of the morphological keys used at present for the identification of Ligophorus at the species level and provides a picture of the relationships between species, indicating that the two species parasitising Mugil cephalus, L. chabaudi Euzet & Suriano, 1977 and L. mugilinus (Hargis, 1955) are the most differentiated. The hypothesis that strict host-parasite ecological relationships may be the result of co-speciation processes is briefly discussed.
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Affiliation(s)
- Loredana Mariniello
- Sezione di Parassitologia, Dipartimento di Scienze di Sanità Pubblica, P. le Aldo Moro, 5, Università di Roma 'La Sapienza', 00185 Rome, Italy
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Fanello C, Petrarca V, della Torre A, Santolamazza F, Dolo G, Coulibaly M, Alloueche A, Curtis CF, Touré YT, Coluzzi M. The pyrethroid knock-down resistance gene in the Anopheles gambiae complex in Mali and further indication of incipient speciation within An. gambiae s.s. Insect Mol Biol 2003; 12:241-245. [PMID: 12752657 DOI: 10.1046/j.1365-2583.2003.00407.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
In Mali the Anopheles gambiae complex consists of An. arabiensis and Mopti, Savanna and Bamako chromosomal forms of An. gambiae s.s. Previous chromosomal data suggests a complete reproductive isolation among these forms. Sequence analysis of rDNA regions led to the characterization of two molecular forms of An. gambiae, named M-form and S-form, which in Mali correspond to Mopti and to Savanna/Bamako, respectively, while it has failed so far to show any molecular difference between Savanna and Bamako. The population structure of An. gambiae s.l. was analysed in three villages in the Bamako and Sikasso areas of Mali and the frequency of pyrethroid resistance of the knock-down resistance (kdr) type was calculated. The results show that the kdr allele is associated only with the Savanna form populations and absent in sympatric and synchronous populations of Bamako, Mopti and An. arabiensis. This is the first molecular indication of barriers to gene flow between the Bamako and Savanna chromosomal forms. Moreover, analyses of specimens collected in the Bamako area in 1987 show that the kdr allele was already present in the Savanna population at that time, and that the frequency of this allele has gradually increased since then.
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Affiliation(s)
- C Fanello
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London, UK.
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42
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Zardi EM, Iori A, Picardi A, Costantino S, Petrarca V. Myiasis of a perineal fistula. Parassitologia 2002; 44:201-2. [PMID: 12701384] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 03/01/2023]
Abstract
We report a case of myiasis of a rectocutaneous fistula in a subject suffering from bone metastases after surgical resection of a neoplastic bladder. The fistula was infested by maggots identified as third-instar larvae of flies belonging to the family Sarcophagidae, genus Sarcophaga. The infestation was neither intestinal nor pseudointestinal; it was probably caused by a fly ovipositing on the fistula of the patient while having wound care at home, even though the possibility that the infestation might have occurred during hospitalization cannot be ruled out.
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Affiliation(s)
- E M Zardi
- Interdisciplinary Center for Biomedical Research (CIR), Laboratory of Internal Medicine and Hepatology, University Campus Bio-Medico, Via Emilio Longoni 83, 00155 Roma, Italy.
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Abstract
Field-collected specimens of all known taxa in the Anopheles gambiae complex were analyzed on the basis of chromosome inversions with reference to a standard polytene chromosome map. The phylogenetic relationships among the seven described species in the complex could be inferred from the distribution of fixed inversions. Nonrandom patterns of inversion distribution were observed and, particularly on chromosome arm 2R, provided evidence for genetically distinct populations in A. gambiae, A. arabiensis, and A. melas. In A. gambiae from Mali, stable genetic differentiation was observed even in populations living in the same region, suggesting a process of incipient speciation which is being confirmed by studies with molecular markers. The possible role of chromosome differentiation in speciation of the A. gambiae complex and in the emergence of distinct chromosomal forms within the nominal species is discussed in relation to human malaria.
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Affiliation(s)
- Mario Coluzzi
- Dipartimento di Scienze di Sanità Pubblica and Istituto Pasteur-Cenci Bolognetti, Università "La Sapienza," Rome, Italy.
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Abstract
Restrictions to gene flow among molecular forms of the mosquito Anopheles gambiae sensu stricto reveal an ongoing speciation process affecting the epidemiology of malaria in sub-Saharan Africa.
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Affiliation(s)
- A della Torre
- Parasitology Unit, Department of Public Health, University of Rome "La Sapienza," P.le Aldo Moro 5, 00185 Rome, Italy.
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Berzosa PJ, Cano J, Roche J, Rubio JM, García L, Moyano E, Guerra A, Mateos JC, Petrarca V, Rosario VD, Benito A. Malaria vectors in Bioko Island (Equatorial Guinea): PCR determination of the members of Anopheles gambiae Giles complex (Diptera: Culicidae) and pyrethroid knockdown resistance (kdr) in An. gambiae sensu stricto. J Vector Ecol 2002; 27:102-106. [PMID: 12125862] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Anopheles gambiae sensu lato Giles, 1902 and Anophelesfunestus Giles, 1900 are the main malaria vectors on the island of Bioko (Equatorial Guinea). This study was carried out to determine: a) members of the An. gambiae complex that may be present on the island of Bioko and, b) the sensitivity of An. gambiae sensu stricto to pyrethroids. The analysis by PCR detected the presence of An. gambiae s.s. as the major vector of the complex and the "forest chromosomal form" was demonstrated by cytogenetic analysis. The presence of Anopheles melas in the southwest, north and southeast of the island justifies its study as a vector. The molecular characterization of pyrethroid knockdown resistance (kdr) showed that the populations of An. gambiae s.s. were sensitive and no mutations were found. This fact justifies the implementation on a large scale of pyrethroid-impregnated bednets within the framework of the Malaria Control Program of Equatorial Guinea.
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Affiliation(s)
- P J Berzosa
- Laboratorio de Malaria, Servicio de Parasitología, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain
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Charlwood JD, Qassim M, Elnsur EI, Donnelly M, Petrarca V, Billingsley PF, Pinto J, Smith T. The impact of indoor residual spraying with malathion on malaria in refugee camps in eastern Sudan. Acta Trop 2001; 80:1-8. [PMID: 11495638 DOI: 10.1016/s0001-706x(01)00152-8] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
An exploratory trial of the efficacy of indoor spraying with malathion on morbidity and mortality in refugee camps in eastern Sudan was conducted during the rainy season of 1997. The interior walls of houses from a randomly selected group of five camps were sprayed with malathion in mid-September and morbidity and mortality rates in the camps for the months October to December compared with rates in five controls. Pyrethrum spray collection and human landing catches were performed in two collection rounds. An exophagic but endophilic population of Anopheles arabiensis was the most common mosquito collected. The mean human blood index of 242 mosquitoes from eight camps was 0.51. Only two of 1040 mosquitoes examined harboured sporozoites. Blood samples of 83 putative malaria patients were examined for parasites by PCR. Mortality rates in the 3 months following spraying were significantly lower in sprayed camps although differences in clinical malaria incidence between sprayed and non-sprayed camps were not significant.
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Affiliation(s)
- J D Charlwood
- Centro de Malaria e Outros Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Rua da Junqueira 96, 1300, Lisboa, Portugal.
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Modiano D, Luoni G, Sirima BS, Lanfrancotti A, Petrarca V, Cruciani F, Simporé J, Ciminelli BM, Foglietta E, Grisanti P, Bianco I, Modiano G, Coluzzi M. The lower susceptibility to Plasmodium falciparum malaria of Fulani of Burkina Faso (west Africa) is associated with low frequencies of classic malaria-resistance genes. Trans R Soc Trop Med Hyg 2001; 95:149-52. [PMID: 11355545 DOI: 10.1016/s0035-9203(01)90141-5] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
Abstract
The gene frequencies in 1993-94 for haemoglobin S, haemoglobin C, alpha-3.7 deletional thalassaemia, G6PDA-, HLAB*5301 were estimated in Fulani, Mossi and Rimaibé ethnic groups of Burkina Faso, West Africa. The aim of the study was to verify whether the previously reported Fulani lower susceptibility to Plasmodium falciparum malaria was associated with any of these malaria-resistance genes. Similar frequencies for haemoglobin S were recorded in the 3 ethnic groups (0.024 +/- 0.008, 0.030 +/- 0.011, 0.022 +/- 0.013; in Mossi, Rimaibé and Fulani, respectively). The Mossi and Rimaibé showed higher frequencies when compared to Fulani for haemoglobin C (0.117 +/- 0.018, 0.127 +/- 0.020, 0.059 +/- 0.020), alpha-3.7 deletional thalassaemia (0.227 +/- 0.040, 0.134 +/- 0.032, 0.103 +/- 0.028), G6PDA- (0.196 +/- 0.025, 0.187 +/- 0.044, 0.069 +/- 0.025) and HLA B*5301 (0.189 +/- 0.038, 0.202 +/- 0.041, 0.061 +/- 0.024). Among Fulani the proportion of individuals not having any of these protective alleles was more than 3-fold greater than in the Mossi-Rimaibé group (56.8% vs 16.7%; P < 0.001). These findings exclude the involvement of these genetic factors of resistance to P. falciparum in the lower susceptibility to malaria of Fulani. This evidence, in association with the previously reported higher immune reactivity to malaria of Fulani, further supports the existence in this ethnic group of unknown genetic factor(s) of resistance to malaria probably involved in the regulation of humoral immune responses.
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Affiliation(s)
- D Modiano
- Dipartimento di Biologia Molecolare, Cellulare e Animale, Università di Camerino, Italy.
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della Torre A, Fanello C, Akogbeto M, Dossou-yovo J, Favia G, Petrarca V, Coluzzi M. Molecular evidence of incipient speciation within Anopheles gambiae s.s. in West Africa. Insect Mol Biol 2001; 10:9-18. [PMID: 11240632 DOI: 10.1046/j.1365-2583.2001.00235.x] [Citation(s) in RCA: 235] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
We karyotyped and identified by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP) analysis Anopheles gambiae s.s. samples collected in several African countries. The data show the existence of two non-panmictic molecular forms, named S and M, whose distribution extended from forest to savannahs. Mosquitoes of the S and M forms are homosequential standard for chromosome-2 inversions in forest areas. In dry savannahs, S is characterized mainly by inversion polymorphisms typical of Savanna and Bamako chromosomal forms, while M shows chromosome-2 arrangements typical of Mopti and/or Savanna and/or Bissau, depending on its geographical origin. Chromosome-2 inversions therefore seem to be involved in ecotypic adaptation rather than in mate-recognition systems. Strong support for the reproductive isolation of S and M in Ivory Coast comes from the observation that the kdr allele is found at high frequencies in S specimens and not at all in chromosomal identical M specimens. However, the kdr allele does not segregate with molecular forms in Benin.
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Affiliation(s)
- A della Torre
- Istituto di Parassitologia, Fondazione Pasteur - Cenci Bolognetti, Università di Roma La Sapienza, Piazzale Aldo Moro 5, 00185, Rome, Italy.
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Modiano D, Luoni G, Petrarca V, Sodiomon Sirima B, De Luca M, Simporé J, Coluzzi M, Bodmer JG, Modiano G. HLA class I in three West African ethnic groups: genetic distances from sub-Saharan and Caucasoid populations. Tissue Antigens 2001; 57:128-37. [PMID: 11260507 DOI: 10.1034/j.1399-0039.2001.057002128.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Fulani of Burkina Faso (West Africa) are a particularly interesting ethnic group because of their lower susceptibility to Plasmodium falciparum malaria as compared to sympatric populations, Mossi and Rimaibé. Moreover, the occurrence of a Caucasoid component in their genetic make-up has been suggested on the basis of their physical traits and cultural traditions even though this view was not supported by genetic studies. A total of 149 unrelated subjects (53 Mossi, 47 Rimaibé and 49 Fulani) have been typed for 97 HLA class I alleles with the amplification refractory mutation system/polymerase chain reaction (ARMS/PCR) technique. Mossi and Rimaibé data were pooled since none of the 42 statistically testable alleles exhibited a significant heterogeneity. These pooled gene frequencies were found to be very different from those of Fulani: a certain (P<0.001) or a likely (0.001 <P<0.01) difference was found for 5 and 12 alleles, respectively. Four alleles (A*24, A*29, B*27, B*3701) appeared to be essentially "private" Fulani alleles with respect to the other two populations but their presence was not associated with higher resistance to P. falciparum. Our data have then been compared using chord distances (CD) with those from the literature on Africans (including Gambian Fulani) and Caucasoids. The Burkina Faso and Gambian Fulani turned out to be very different (CD=2.191). Moreover, Burkina Faso Fulani were very distant from sympatric Mossi and Rimaibé (CDs=1.912 and 1.884), whereas Gambian Fulani were similar to sympatric Mandinka and Wolof (CDs=0.412 and 0.388) to an extent comparable to that found between Mossi and Rimaibé (CD=0.555). Our study does not suggest the involvement of HLA I in the higher resistance to malaria of Fulani, and confirms a low, if any, Caucasoid component in their gene pool.
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Affiliation(s)
- D Modiano
- Istituto di Parassitologia, W.H.O. Collaborating Centre for Malaria Epidemiology, Università di Roma "La Sapienza", Rome, Italy
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Pinto J, Sousa CA, Gil V, Ferreira C, Gonçalves L, Lopes D, Petrarca V, Charlwood JD, do Rosário VE. Malaria in São Tomé and Príncipe: parasite prevalences and vector densities. Acta Trop 2000; 76:185-93. [PMID: 10936578 DOI: 10.1016/s0001-706x(00)00100-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
A cross-sectional survey was carried out in 16 localities on the island of São Tomé and three on the island of Príncipe, at the end of the rainy season of 1997, to determine malaria prevalence and vector densities. Blood samples from 664 inhabitants of all ages were examined by optical microscopy (OM) and PCR. Mosquito collections were made by outdoor landing captures from 21:00-23:00 h. Great differences were found between OM and PCR readings. OM had a sensitivity of 66%, a specificity of 79% and failed to reveal any mixed-infections. Overall prevalence, determined by PCR, was higher in São Tomé (53%) than in Príncipe (35%). It was highest in children below 16 years-old. All four human Plasmodium species occurred in São Tomé but P. ovale was not detected in Príncipe. The human population was largely asymptomatic. Bednet users had lower prevalence than did non-users. The FOREST form of Anopheles gambiae s.s., identified by PCR and cytogenetics, was the only vector on the islands. The sporozoite rate in São Tomé, assessed by ELISA, was 0.5%. Parasite prevalence and vector densities were positively correlated in São Tomé, where malaria transmission must occur predominantly in the more populated coastal areas.
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Affiliation(s)
- J Pinto
- Centro de Malária e outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisbon, Portugal
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