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Georgiades M, Alampounti A, Somers J, Su MP, Ellis DA, Bagi J, Terrazas-Duque D, Tytheridge S, Ntabaliba W, Moore S, Albert JT, Andrés M. Hearing of malaria mosquitoes is modulated by a beta-adrenergic-like octopamine receptor which serves as insecticide target. Nat Commun 2023; 14:4338. [PMID: 37468470 PMCID: PMC10356864 DOI: 10.1038/s41467-023-40029-y] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [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: 10/11/2022] [Accepted: 07/06/2023] [Indexed: 07/21/2023] Open
Abstract
Malaria mosquitoes acoustically detect their mating partners within large swarms that form transiently at dusk. Indeed, male malaria mosquitoes preferably respond to female flight tones during swarm time. This phenomenon implies a sophisticated context- and time-dependent modulation of mosquito audition, the mechanisms of which are largely unknown. Using transcriptomics, we identify a complex network of candidate neuromodulators regulating mosquito hearing in the species Anopheles gambiae. Among them, octopamine stands out as an auditory modulator during swarm time. In-depth analysis of octopamine auditory function shows that it affects the mosquito ear on multiple levels: it modulates the tuning and stiffness of the flagellar sound receiver and controls the erection of antennal fibrillae. We show that two α- and β-adrenergic-like octopamine receptors drive octopamine's auditory roles and demonstrate that the octopaminergic auditory control system can be targeted by insecticides. Our findings highlight octopamine as key for mosquito hearing and mating partner detection and as a potential novel target for mosquito control.
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Affiliation(s)
- Marcos Georgiades
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Alexandros Alampounti
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Jason Somers
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Matthew P Su
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
- Graduate School of Science, Nagoya University, Nagoya, Aichi, 464-8602, Japan
- Institute for Advanced Research, Nagoya University, Nagoya, Aichi, 464-8601, Japan
| | - David A Ellis
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Judit Bagi
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | | | - Scott Tytheridge
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK
| | - Watson Ntabaliba
- Vector Control Product Testing Unit (VCPTU), Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
| | - Sarah Moore
- Vector Control Product Testing Unit (VCPTU), Environmental Health and Ecological Sciences, Ifakara Health Institute, P.O. Box 74, Bagamoyo, Tanzania
- Swiss Tropical and Public Health Institute, Socinstrasse 57, PO Box, CH-4002, Basel, Switzerland
- University of Basel, Petersplatz 1, CH-4001, Basel, Switzerland
- The Nelson Mandela African Institution of Science and Technology (NM-AIST), P.O. Box 447, Tengeru, Arusha, Tanzania
| | - Joerg T Albert
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK.
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
- Cluster of Excellence Hearing4all, Sensory Physiology & Behaviour Group, Department for Neuroscience, School of Medicine and Health Sciences, Carl Von Ossietzky University Oldenburg, Carl Von Ossietzky Str. 9-11, 26111, Oldenburg, Germany.
| | - Marta Andrés
- Ear Institute, University College London, 332 Gray's Inn Road, London, WC1X 8EE, UK.
- The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
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Su MP, Andrés M, Georgiades M, Bagi J, Albert JT. Acoustic Physiology in Mosquitoes. Cold Spring Harb Protoc 2023; 2023:107685-pdb.top. [PMID: 36223985 DOI: 10.1101/pdb.top107685] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
The acoustic physiology of mosquitoes is perhaps the most complex within the entire insect class. Past research has uncovered several of its-sometimes stunningly unconventional-principles, but many mysteries remain. Their solution necessitates a concerted transdisciplinary effort to successfully link the neuroanatomical and biophysical properties of mosquito flagellar ears to the behavioral ecology of entire mosquito populations. Neuroanatomically, mosquito ears can rival those of humans in both complexity and sheer size. The approximately 16,000 auditory hair cells within the human organ of Corti, for example, are matched by the approximately 16,000 auditory neurons in the Johnston's organ of a male Anopheles mosquito. Both human and mosquito ears receive very extensive efferent innervation, which modulates their function in ways that are as yet poorly understood. Different populations of neuronal and nonneuronal cell types divide the labor of the mosquito ear amongst themselves. Yet, what exactly this labor is, and how it is achieved, is at best vaguely known. For the majority of mosquitoes, biologically relevant sounds are inextricably linked to their flight tones. Either these flight tones are (directly) the sounds of interest or they contribute (indirectly) to the production of audible sound through a process called nonlinear distortion. Finally, male ears can generate tones themselves: The generation of an internal "phantom copy" of a female flight tone (or self-sustained oscillation) is believed to aid the male hearing process. Here, we introduce protocols that target the mosquitoes' auditory neuroanatomy, electrophysiology, and behavior to help shed light on some of these issues.
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Affiliation(s)
- Matthew P Su
- Graduate School of Science, Nagoya University, Nagoya 464-8602, Japan
- Institute for Advanced Research, Nagoya University, Nagoya 464-8602, Japan
| | - Marta Andrés
- Ear Institute, University College London, London WC1X 8EE, United Kingdom
- The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Marcos Georgiades
- Ear Institute, University College London, London WC1X 8EE, United Kingdom
- The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Judit Bagi
- Ear Institute, University College London, London WC1X 8EE, United Kingdom
- The Francis Crick Institute, London NW1 1AT, United Kingdom
| | - Joerg T Albert
- Ear Institute, University College London, London WC1X 8EE, United Kingdom
- The Francis Crick Institute, London NW1 1AT, United Kingdom
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Andrés M, Bagi J, Albert JT. Immunohistochemical Staining of the Mosquito Ear. Cold Spring Harb Protoc 2022; 2023:108008-pdb.prot. [PMID: 36223991 DOI: 10.1101/pdb.prot108008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Immunohistochemistry has played a major role in improving our understanding of the anatomy and function of the nervous system. The use of fluorescent dyes that label different antigens reveals how biological tissues are built and how interactions between cells take place. Obtaining this information is particularly important in the case of the mosquito ear given its highly complex anatomy. This protocol describes an immunohistochemical technique to stain the mosquito ear. The first steps of the procedure include the embedding of the tissue in albumin-gelatin and its sectioning into thin slices to allow antibody penetration. The immunohistochemical procedure can be exploited to detect protein expression and localization by using antibodies specifically raised against the protein of interest or that recognize epitope tags fused to proteins using genome editing methods.
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Somers J, Georgiades M, Su MP, Bagi J, Andrés M, Alampounti A, Mills G, Ntabaliba W, Moore SJ, Spaccapelo R, Albert JT. Hitting the right note at the right time: Circadian control of audibility in Anopheles mosquito mating swarms is mediated by flight tones. Sci Adv 2022; 8:eabl4844. [PMID: 35020428 PMCID: PMC8754303 DOI: 10.1126/sciadv.abl4844] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2021] [Accepted: 11/12/2021] [Indexed: 05/20/2023]
Abstract
Mating swarms of malaria mosquitoes form every day at sunset throughout the tropical world. They typically last less than 30 minutes. Activity must thus be highly synchronized between the sexes. Moreover, males must identify the few sporadically entering females by detecting the females’ faint flight tones. We show that the Anopheles circadian clock not only ensures a tight synchrony of male and female activity but also helps sharpen the males’ acoustic detection system: By raising their flight tones to 1.5 times the female flight tone, males enhance the audibility of females, specifically at swarm time. Previously reported “harmonic convergence” events are only a random by-product of the mosquitoes’ flight tone variance and not a signature of acoustic interaction between males and females. The flight tones of individual mosquitoes occupy narrow, partly non-overlapping frequency ranges, suggesting that the audibility of individual females varies across males.
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Affiliation(s)
- Jason Somers
- Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK
- Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Marcos Georgiades
- Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK
- Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Matthew P. Su
- Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK
- Division of Biological Science, Nagoya University, Nagoya, Aichi 464-8602, Japan
- Institute for Advanced Research, Nagoya University, Nagoya, Aichi 464-8601, Japan
| | - Judit Bagi
- Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK
- Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Marta Andrés
- Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK
- Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Alexandros Alampounti
- Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK
- Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
| | - Gordon Mills
- Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK
| | - Watson Ntabaliba
- Vector Control Product Testing Unit, Ifakara Health Institute, Ifakara, Tanzania
| | - Sarah J. Moore
- Vector Control Product Testing Unit, Ifakara Health Institute, Ifakara, Tanzania
- Epidemiology and Public Health Department, Swiss Tropical and Public Health Institute, Socinstrasse 57, Basel 4051, Switzerland
| | - Roberta Spaccapelo
- Department of Medicine and Surgery, Centro Universitario di Ricerca sulla Genomica Funzionale (C.U.R.Ge.F), University of Perugia, Perugia, Italy
- Consorzio Interuniversitario Biotecnologie (CIB) Trieste, Italy
| | - Joerg T. Albert
- Ear Institute, University College London, 332 Grays Inn Road, London WC1X 8EE, UK
- Francis Crick Institute, 1 Midland Road, London NW1 1AT, UK
- Corresponding author.
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Su MP, Georgiades M, Bagi J, Kyrou K, Crisanti A, Albert JT. Assessing the acoustic behaviour of Anopheles gambiae (s.l.) dsxF mutants: implications for vector control. Parasit Vectors 2020; 13:507. [PMID: 33028410 PMCID: PMC7539510 DOI: 10.1186/s13071-020-04382-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [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: 07/14/2020] [Accepted: 09/28/2020] [Indexed: 12/29/2022] Open
Abstract
BACKGROUND Release of gene-drive mutants to suppress Anopheles mosquito reproduction is a promising method of malaria control. However, many scientific, regulatory and ethical questions remain before transgenic mosquitoes can be utilised in the field. At a behavioural level, gene-drive carrying mutants should be at least as sexually attractive as the wildtype populations they compete against, with a key element of Anopheles copulation being acoustic courtship. We analysed sound emissions and acoustic preference in a doublesex mutant previously used to collapse Anopheles gambiae (s.l.) cages. METHODS Anopheles rely on flight tones produced by the beating of their wings for acoustic mating communication. We assessed the impact of disrupting a female-specific isoform of the doublesex gene (dsxF) on the wing beat frequency (WBF; measured as flight tone) of males (XY) and females (XX) in homozygous dsxF- mutants (dsxF-/-), heterozygous dsxF- carriers (dsxF+/-) and G3 dsxF+ controls (dsxF+/+). To exclude non-genetic influences, we controlled for temperature and wing length. We used a phonotaxis assay to test the acoustic preferences of mutant and control mosquitoes. RESULTS A previous study showed an altered phenotype only for dsxF-/- females, who appear intersex, suggesting that the female-specific dsxF allele is haplosufficient. We identified significant, dose-dependent increases in the WBF of both dsxF-/- and dsxF+/- females compared to dsxF+/+ females. All female WBFs remained significantly lower than male equivalents, though. Males showed stronger phonotactic responses to the WBFs of control dsxF+/+ females than to those of dsxF+/- and dsxF-/- females. We found no evidence of phonotaxis in any female genotype. No male genotypes displayed any deviations from controls. CONCLUSIONS A prerequisite for anopheline copulation is the phonotactic attraction of males towards female flight tones within mating swarms. Reductions in mutant acoustic attractiveness diminish their mating efficiency and thus the efficacy of population control efforts. Caged population assessments may not successfully reproduce natural mating scenarios. We propose to amend existing testing protocols to better reflect competition between mutants and target populations. Our findings confirm that dsxF disruption has no effect on males; for some phenotypic traits, such as female WBFs, the effects of dsxF appear dose-dependent rather than haplosufficient.
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Affiliation(s)
- Matthew P Su
- Ear Institute, University College London, 332 Grays Inn Road, London, WC1X 8EE, UK.,The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.,Division of Biological Science, Nagoya University, Nagoya, 464-8602, Japan
| | - Marcos Georgiades
- Ear Institute, University College London, 332 Grays Inn Road, London, WC1X 8EE, UK.,The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Judit Bagi
- Ear Institute, University College London, 332 Grays Inn Road, London, WC1X 8EE, UK.,The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK
| | - Kyros Kyrou
- Department of Life Sciences, Imperial College London, London, UK
| | - Andrea Crisanti
- Department of Life Sciences, Imperial College London, London, UK
| | - Joerg T Albert
- Ear Institute, University College London, 332 Grays Inn Road, London, WC1X 8EE, UK. .,The Francis Crick Institute, 1 Midland Road, London, NW1 1AT, UK.
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Abstract
Supplemental feeding of wildlife populations can locally increase the density of individuals, which may in turn impact disease dynamics. Flower strips are a widely used intervention in intensive agricultural systems to nutritionally support pollinators such as bees. Using a controlled experimental semi-field design, we asked how density impacts transmission of a virus and a trypanosome parasite in bumblebees. We manipulated bumblebee density by using different numbers of colonies within the same area of floral resource. In high-density compartments, slow bee paralysis virus was transmitted more quickly, resulting in higher prevalence and level of infection in bumblebee hosts. By contrast, there was no impact of density on the transmission of the trypanosome Crithidia bombi, which may reflect the ease with which this parasite is transmitted. These results suggest that agri-environment schemes such as flower strips, which are known to enhance the nutrition and survival of bumblebees, may also have negative impacts on pollinators through enhanced disease transmission. Future studies should assess how changing the design of these schemes could minimize disease transmission and thus maximise their health benefits to wild pollinators.
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Affiliation(s)
- Emily J Bailes
- Department of Biological Sciences, Royal Holloway University of London, Bourne Building, Egham TW20 0EX, UK.,Department of Molecular Biology and Biotechnology, University of Sheffield, Firth Court, Sheffield S10 2TN, UK
| | - Judit Bagi
- Department of Biological Sciences, Royal Holloway University of London, Bourne Building, Egham TW20 0EX, UK.,Ear Institute, University College London, 332 Gray's Inn Road, London WC1X 8EE, UK
| | - Jake Coltman
- Expedia Group, Angel Building, 407 St John Street, London EC1V 4AD, UK
| | | | - Lena Wilfert
- Institute of Evolutionary Ecology and Conservation Genomics, University of Ulm, 89069 Ulm, Germany
| | - Mark J F Brown
- Department of Biological Sciences, Royal Holloway University of London, Bourne Building, Egham TW20 0EX, UK
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Bailes EJ, Deutsch KR, Bagi J, Rondissone L, Brown MJF, Lewis OT. First detection of bee viruses in hoverfly (syrphid) pollinators. Biol Lett 2018; 14:rsbl.2018.0001. [PMID: 29491032 PMCID: PMC5830674 DOI: 10.1098/rsbl.2018.0001] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [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: 01/01/2018] [Accepted: 02/02/2018] [Indexed: 12/24/2022] Open
Abstract
Global declines of insect pollinators jeopardize the delivery of pollination services in both agricultural and natural ecosystems. The importance of infectious diseases has been documented in honeybees, but there is little information on the extent to which these diseases are shared with other pollinator orders. Here, we establish for the first time the presence of three important bee viruses in hoverfly pollinators (Diptera: Syrphidae): black queen cell virus (BQCV), sacbrood virus (SBV) and deformed wing virus strain B (DWV-B). These viruses were detected in two Eristalis species, which are behavioural and morphological bee mimics and share a foraging niche with honeybees. Nucleotide sequences of viruses isolated from the Eristalis species and Apis mellifera were up to 99 and 100% identical for the two viruses, suggesting that these pathogens are being shared freely between bees and hoverflies. Interestingly, while replicative intermediates (negative strand virus) were not detected in the hoverflies, viral titres of SBV were similar to those found in A. mellifera. These results suggest that syrphid pollinators may play an important but previously unexplored role in pollinator disease dynamics.
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Affiliation(s)
- Emily J Bailes
- School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK
| | - Kaitlin R Deutsch
- School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK.,School of Geography and the Environment, University of Oxford, South Parks Road, Oxford OX1 3QY, UK.,Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK.,Department of Entomology, Cornell University, Ithaca, NY 14853, USA
| | - Judit Bagi
- School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK
| | - Lucila Rondissone
- School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK
| | - Mark J F Brown
- School of Biological Sciences, Royal Holloway University of London, Egham TW20 0EX, UK
| | - Owen T Lewis
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
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Haji KA, Thawer NG, Khatib BO, Mcha JH, Rashid A, Ali AS, Jones C, Bagi J, Magesa SM, Ramsan MM, Garimo I, Greer G, Reithinger R, Ngondi JM. Efficacy, persistence and vector susceptibility to pirimiphos-methyl (Actellic 300CS) insecticide for indoor residual spraying in Zanzibar. Parasit Vectors 2015; 8:628. [PMID: 26652708 PMCID: PMC4674920 DOI: 10.1186/s13071-015-1239-x] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [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: 08/10/2015] [Accepted: 12/03/2015] [Indexed: 11/10/2022] Open
Abstract
Background Indoor residual spraying (IRS) of households with insecticide is a principal malaria vector control intervention in Zanzibar. In 2006, IRS using the pyrethroid lambda-cyhalothrine was introduced in Zanzibar. Following detection of pyrethroid resistance in 2010, an insecticide resistance management plan was proposed, and IRS using bendiocarb was started in 2011. In 2014, bendiocarb was replaced by pirimiphos methyl. This study investigated the residual efficacy of pirimiphos methyl (Actellic® 300CS) sprayed on common surfaces of human dwellings in Zanzibar. Methods The residual activity of Actellic 300CS was determined over 9 months through bioassay tests that measured the mortality of female Anopheles mosquitoes, exposed to sprayed surfaces under a WHO cone. The wall surfaces included; mud wall, oil or water painted walls, lime washed wall, un-plastered cement block wall and stone blocks. Insecticide susceptibility testing was done to investigate the resistance status of local malaria vectors against Actellic 300CS using WHO protocols; Anopheline species were identified using PCR methods. Results Baseline tests conducted one-day post-IRS revealed 100 % mortality on all sprayed surfaces. The residual efficacy of Actellic 300CS was maintained on all sprayed surfaces up to 8 months post-IRS. However, the bioassay test conducted 9 months post-IRS showed the 24 h mortality rate to be ≤80 % for lime wash, mud wall, water paint and stone block surfaces. Only oil paint surface retained the recommended residual efficacy beyond 9 months post-IRS, with mortality maintained at ≥97 %. Results of susceptibility tests showed that malaria vectors in Zanzibar were fully (100 %) susceptible to Actellic 300CS. The predominant mosquito vector species was An. arabiensis (76.0 %) in Pemba and An. gambiae (83.5 %) in Unguja. Conclusion The microencapsulated formulation of pirimiphos methyl (Actellic 300CS) is a highly effective and appropriate insecticide for IRS use in Zanzibar as it showed a relatively prolonged residual activity compared to other products used for the same purpose. The insecticide extends the residual effect of IRS thereby making it possible to effectively protect communities with a single annual spray round reducing overall costs. The insecticide proved to be a useful alternative in insecticide resistance management plans.
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Affiliation(s)
- Khamis A Haji
- Zanzibar Malaria Elimination Programme, Zanzibar, Tanzania.
| | | | | | - Juma H Mcha
- Zanzibar Malaria Elimination Programme, Zanzibar, Tanzania.
| | | | - Abdullah S Ali
- Zanzibar Malaria Elimination Programme, Zanzibar, Tanzania.
| | | | - Judit Bagi
- Liverpool School of Tropical Medicine, Liverpool, UK.
| | | | | | | | - George Greer
- President's Malaria Initiative/United States Agency for International Development, Dar es Salaam, Tanzania.
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Bagi J, Grisales N, Corkill R, Morgan JC, N'Falé S, Brogdon WG, Ranson H. When a discriminating dose assay is not enough: measuring the intensity of insecticide resistance in malaria vectors. Malar J 2015; 14:210. [PMID: 25985896 PMCID: PMC4455279 DOI: 10.1186/s12936-015-0721-4] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [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: 01/19/2015] [Accepted: 05/05/2015] [Indexed: 11/12/2022] Open
Abstract
Background Guidelines from the World Health Organization for monitoring insecticide resistance in disease vectors recommend exposing insects to a predetermined discriminating dose of insecticide and recording the percentage mortality in the population. This standardized methodology has been widely adopted for malaria vectors and has provided valuable data on the spread and prevalence of resistance. However, understanding the potential impact of this resistance on malaria control requires a more quantitative measure of the strength or intensity of this resistance. Methods Bioassays were adapted to quantify the level of resistance to permethrin in laboratory colonies and field populations of Anopheles gambiae sensu lato. WHO susceptibility tube assays were used to produce data on mortality versus exposure time and CDC bottle bioassays were used to generate dose response data sets. A modified version of the CDC bottle bioassay, known as the Resistance Intensity Rapid Diagnostic Test (I-RDT), was also used to measure the knockdown and mortality after exposure to different multipliers of the diagnostic dose. Finally cone bioassays were used to assess mortality after exposure to insecticide treated nets. Results The time response assays were simple to perform but not suitable for highly resistant populations. After initial problems with stability of insecticide and bottle washing were resolved, the CDC bottle bioassay provided a reproducible, quantitative measure of resistance but there were challenges performing this under field conditions. The I-RDT was simple to perform and interpret although the end point selected (immediate knockdown versus 24 h mortality) could dramatically affect the interpretation of the data. The utility of the cone bioassays was dependent on net type and thus appropriate controls are needed to interpret the operational significance of these data sets. Conclusions Incorporating quantitative measures of resistance strength, and utilizing bioassays with field doses of insecticides, will help interpret the possible impact of resistance on vector control activities. Each method tested had different benefits and challenges and agreement on a common methodology would be beneficial so that data are generated in a standardized format. This type of quantitative data are an important prerequisite to linking resistance strength to epidemiological outcomes.
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Affiliation(s)
- Judit Bagi
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Nelson Grisales
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Rebecca Corkill
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - John C Morgan
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Sagnon N'Falé
- Centre National de Recherche et de la Formation sur Paludisme, Ouagadougou, 01BP2208, Burkina Faso.
| | - William G Brogdon
- Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control, Atlanta, GA, 30329, USA.
| | - Hilary Ranson
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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Jones CM, Haji KA, Khatib BO, Bagi J, Mcha J, Devine GJ, Daley M, Kabula B, Ali AS, Majambere S, Ranson H. The dynamics of pyrethroid resistance in Anopheles arabiensis from Zanzibar and an assessment of the underlying genetic basis. Parasit Vectors 2013; 6:343. [PMID: 24314005 PMCID: PMC3895773 DOI: 10.1186/1756-3305-6-343] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [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: 09/11/2013] [Accepted: 11/28/2013] [Indexed: 12/02/2022] Open
Abstract
Background The emergence of pyrethroid resistance in the malaria vector, Anopheles arabiensis, threatens to undermine the considerable gains made towards eliminating malaria on Zanzibar. Previously, resistance was restricted to the island of Pemba while mosquitoes from Unguja, the larger of the two islands of Zanzibar, were susceptible. Here, we characterised the mechanism(s) responsible for resistance on Zanzibar using a combination of gene expression and target-site mutation assays. Methods WHO resistance bioassays were conducted using 1-5d old adult Anopheles gambiae s.l. collected between 2011 and 2013 across the archipelago. Synergist assays with the P450 inhibitor piperonyl-butoxide were performed in 2013. Members of the An. gambiae complex were PCR-identified and screened for target-site mutations (kdr and Ace-1). Gene expression in pyrethroid resistant An. arabiensis from Pemba was analysed using whole-genome microarrays. Results Pyrethroid resistance is now present across the entire Zanzibar archipelago. Survival to the pyrethroid lambda-cyhalothrin in bioassays conducted in 2013 was 23.5-54.3% on Unguja and 32.9-81.7% on Pemba. We present evidence that resistance is mediated, in part at least, by elevated P450 monoxygenases. Whole-genome microarray scans showed that the most enriched gene terms in resistant An. arabiensis from Pemba were associated with P450 activity and synergist assays with PBO completely restored susceptibility to pyrethroids in both islands. CYP4G16 was the most consistently over-expressed gene in resistant mosquitoes compared with two susceptible strains from Unguja and Dar es Salaam. Expression of this P450 is enriched in the abdomen and it is thought to play a role in hydrocarbon synthesis. Microarray and qPCR detected several additional genes putatively involved in this pathway enriched in the Pemba pyrethroid resistant population and we hypothesise that resistance may be, in part, related to alterations in the structure of the mosquito cuticle. None of the kdr target-site mutations, associated with pyrethroid/DDT resistance in An. gambiae elsewhere in Africa, were found on the islands. Conclusion The consequences of this resistance phenotype are discussed in relation to future vector control strategies on Zanzibar to support the ongoing malaria elimination efforts on the islands.
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Affiliation(s)
| | | | | | | | | | | | | | | | | | | | - Hilary Ranson
- Department of Vector Biology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
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Abstract
A non-destructive method for assaying transuranic neutron sources was developed, using a combination of gamma-spectrometry and neutron correlation technique. Source strength or actinide content of a number of PuBe, AmBe, AmLi, (244)Cm, and (252)Cf sources was assessed, both as a safety issue and with respect to combating illicit trafficking. A passive neutron coincidence collar was designed with (3)He counters embedded in a polyethylene moderator (lined with Cd) surrounding the sources to be measured. The electronics consist of independent channels of pulse amplifiers and discriminators as well as a shift register for coincidence counting. The neutron output of the sources was determined by gross neutron counting, and the actinide content was found out by adopting specific spontaneous fission and (alpha,n) reaction yields of individual isotopes from the literature. Identification of an unknown source type and constituents can be made by gamma-spectrometry. The coincidences are due to spontaneous fission in the case of Cm and Cf sources, while they are mostly due to neutron-induced fission of the Pu isotopes (i.e. self-multiplication) and the (9)Be(n,2n)(8)Be reaction in Be-containing sources. Recording coincidence rate offers a potential for calibration, exploiting a correlation between the Pu amount and the coincidence-to-total ratio. The method and the equipment were tested in an in-field demonstration exercise, with participation of national public authorities and foreign observers. Seizure of the illicit transport of a PuBe source was simulated in the exercise, and the Pu content of the source was determined. It is expected that the method could be used for identification and assay of illicit, found, or not documented neutron sources.
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Affiliation(s)
- L Lakosi
- Institute of Isotopes, Chemical Research Centre of the Hungarian Academy of Sciences, P.O. Box 77, H-1525 Budapest, Hungary.
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