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Champer SE, Kim IK, Clark AG, Messer PW, Champer J. Anopheles homing suppression drive candidates exhibit unexpected performance differences in simulations with spatial structure. eLife 2022; 11:e79121. [PMID: 36239372 PMCID: PMC9596161 DOI: 10.7554/elife.79121] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2022] [Accepted: 10/14/2022] [Indexed: 11/16/2022] Open
Abstract
Recent experiments have produced several Anopheles gambiae homing gene drives that disrupt female fertility genes, thereby eventually inducing population collapse. Such drives may be highly effective tools to combat malaria. One such homing drive, based on the zpg promoter driving CRISPR/Cas9, was able to eliminate a cage population of mosquitoes. A second version, purportedly improved upon the first by incorporating an X-shredder element (which biases inheritance towards male offspring), was similarly successful. Here, we analyze experimental data from each of these gene drives to extract their characteristics and performance parameters and compare these to previous interpretations of their experimental performance. We assess each suppression drive within an individual-based simulation framework that models mosquito population dynamics in continuous space. We find that the combined homing/X-shredder drive is actually less effective at population suppression within the context of our mosquito population model. In particular, the combined drive often fails to completely suppress the population, instead resulting in an unstable equilibrium between drive and wild-type alleles. By contrast, otherwise similar drives based on the nos promoter may prove to be more promising candidates for future development than originally thought.
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Affiliation(s)
- Samuel E Champer
- Department of Computational Biology, Cornell UniversityIthacaUnited States
| | - Isabel K Kim
- Department of Computational Biology, Cornell UniversityIthacaUnited States
| | - Andrew G Clark
- Department of Computational Biology, Cornell UniversityIthacaUnited States
- Department of Molecular Biology and Genetics, Cornell UniversityIthacaUnited States
| | - Philipp W Messer
- Department of Computational Biology, Cornell UniversityIthacaUnited States
| | - Jackson Champer
- Center for Bioinformatics, School of Life Sciences, Peking-Tsinghua Center for Life Sciences, Peking UniversityBeijingChina
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2
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Thabet HS, TagEldin RA, Fahmy NT, Diclaro JW, Alaribe AA, Ezedinachi E, Nwachuku NS, Odey FO, Arimoto H. Spatial Distribution of PCR-Identified Species of Anopheles gambiae senu lato (Diptera: Culicidae) Across Three Eco-Vegetational Zones in Cross River State, Nigeria. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:576-584. [PMID: 35064267 DOI: 10.1093/jme/tjab221] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/02/2021] [Indexed: 06/14/2023]
Abstract
Anopheles gambiae sensu lato complex (An. gambiae s.l.) describes a group of nine morphologically indistinguishable members that vary in their distribution, ability to transmit malaria, and susceptibility to pyrethroids. Here, we recorded the spatial patterns of PCR-identified An. gambiae s.l. complex species collected from four sites in Cross River State, Nigeria that represented three different ecological zones. Trapping was conducted between October 2015 and June 2016. Anopheles gambiae s.l. complex species identification was performed using species-specific primers followed by An. gambiae and An. coluzzii differentiation using the restriction fragment length polymorphism (RFLP) method. Bivariate and multivariate logistic regression models were used to identify ecological and seasonal variables closely associated with An. coluzzii and An. gambiae distribution. Out of 1,388 An. gambiae s.l. successfully amplified, 1,074 (77.4%) were An. coluzzii, 278 (20%) were An. gambiae, and 25 (1.8%) were hybrids (An. coluzzii/An. gambiae). A very small number of An. arabiensis (0.8%, n = 11) were also collected. Statistical analysis indicated that An. coluzzii is predominant in Guinea-savannah and tropical rainforest, and is highly associated with rainy seasons, while, An. gambiae is prevalent in mangrove swamp forest during dry seasons. Only 13 An. gambiae s.l. females were infected with Plasmodium falciparum (P. falciparum). The sporozoite infection rate was higher in mangrove swamp forest (53.8%, n = 7) than in rain forest (38.5%, n = 5) followed by Guinea-savannah (7.7%, n = 1) ecological zones. These results provide important insights for strategic planning of malaria control programs in Nigeria.
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Affiliation(s)
- H S Thabet
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
| | - R A TagEldin
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
| | - N T Fahmy
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
| | - J W Diclaro
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
- Navy Entomology Center of Excellence (NECE), Jacksonville, FL, USA
| | - A A Alaribe
- Calabar Institute of Tropical Diseases Research and Prevention (CITDRP), University of Calabar, Cross River State, Nigeria
| | - E Ezedinachi
- Calabar Institute of Tropical Diseases Research and Prevention (CITDRP), University of Calabar, Cross River State, Nigeria
| | - N S Nwachuku
- Calabar Institute of Tropical Diseases Research and Prevention (CITDRP), University of Calabar, Cross River State, Nigeria
| | - F O Odey
- Calabar Institute of Tropical Diseases Research and Prevention (CITDRP), University of Calabar, Cross River State, Nigeria
| | - H Arimoto
- U.S. Naval Medical Research Unit No. 3 (NAMRU-3), Cairo Detachment, Egypt
- Navy Environmental and Preventive Medicine Unit Five, San Diego, CA, USA
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3
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Nørgaard LS, Álvarez-Noriega M, McGraw E, White CR, Marshall DJ. Predicting the response of disease vectors to global change: The importance of allometric scaling. GLOBAL CHANGE BIOLOGY 2022; 28:390-402. [PMID: 34674354 DOI: 10.1111/gcb.15950] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/06/2021] [Accepted: 10/09/2021] [Indexed: 06/13/2023]
Abstract
The distribution of disease vectors such as mosquitoes is changing. Climate change, invasions and vector control strategies all alter the distribution and abundance of mosquitoes. When disease vectors undergo a range shift, so do disease burdens. Predicting such shifts is a priority to adequately prepare for disease control. Accurate predictions of distributional changes depend on how factors such as temperature and competition affect mosquito life-history traits, particularly body size and reproduction. Direct estimates of both body size and reproduction in mosquitoes are logistically challenging and time-consuming, so the field has long relied upon linear (isometric) conversions between wing length (a convenient proxy of size) and reproductive output. These linear transformations underlie most models projecting species' distributions and competitive interactions between native and invasive disease vectors. Using a series of meta-analyses, we show that the relationship between wing length and fecundity are nonlinear (hyperallometric) for most mosquito species. We show that whilst most models ignore reproductive hyperallometry (with respect to wing length), doing so introduces systematic biases into estimates of population growth. In particular, failing to account for reproductive hyperallometry overestimates the effects of temperature and underestimates the effects of competition. Assuming isometry also increases the potential to misestimate the efficacy of vector control strategies by underestimating the contribution of larger females in population replenishment. Finally, failing to account for reproductive hyperallometry and variation in body size can lead to qualitative errors via the counter-intuitive effects of Jensen's inequality. For example, if mean sizes decrease, but variance increases, then reproductive outputs may actually increase. We suggest that future disease vector models incorporate hyperallometric relationships to more accurately predict changes in mosquito distribution in response to global change.
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Affiliation(s)
- Louise S Nørgaard
- School of Biological Sciences & Centre for Geometric Biology, Monash University, Melbourne, Victoria, Australia
| | - Mariana Álvarez-Noriega
- School of Biological Sciences & Centre for Geometric Biology, Monash University, Melbourne, Victoria, Australia
| | - Elizabeth McGraw
- Center for Infectious Disease Dynamics, The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, Pennsylvania, USA
- Biology Department, The Pennsylvania State University, University Park, Pennsylvania, USA
- Entomology Department, The Pennsylvania State University, University Park, Pennsylvania, USA
| | - Craig R White
- School of Biological Sciences & Centre for Geometric Biology, Monash University, Melbourne, Victoria, Australia
| | - Dustin J Marshall
- School of Biological Sciences & Centre for Geometric Biology, Monash University, Melbourne, Victoria, Australia
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4
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Pesticides and the evolution of the genetic structure of Anopheles coluzzii populations in some localities in Benin (West Africa). Malar J 2019; 18:407. [PMID: 31805939 PMCID: PMC6896764 DOI: 10.1186/s12936-019-3036-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Accepted: 11/26/2019] [Indexed: 01/25/2023] Open
Abstract
Background Changes in the natural habitats of insect groups are determined the genetic polymorphisms between individuals. The objective of this study was to establish the genetic structure of the Anopheles coluzzii populations in four localities of Benin. Methods Insecticide surveys and larval sampling were conducted on 4 study localities, including Cotonou, Ketou, Zagnanado, and Sô-Ava. Molecular characterizations were performed on the Anopheles mosquitoes collected with the allelic and genotypic frequencies of kdr gene determined. The multiple comparison Chi square test for proportions was performed with R version 3.3.3. Next, the observed heterozygosity, expected heterozygosity, and indices of fixation, and genetic differentiation were estimated. Finally, the Hardy–Weinberg equilibrium (EHW) was determined to assess whether panmixia exists in the different populations of mosquitoes of the agroecological zones under study. Results Carbamates, pyrethroids, organophosphorus and organochlorines use have been reported in all localities except Sô-Ava. Anopheles coluzzii was strongly represented across all study localities. The L1014F allele was observed in the localities of Kétou, Cotonou and Zagnanado. Likewise, insecticide selection pressure of homozygous resistant individuals (L1014F/L1014F) was significantly higher in Kétou, Cotonou and Zagnanado (p value < 0.05). Surprisingly in Sô-Ava, a relatively high frequency of the L1014F allele despite the reported absence of pesticide use was observed. All mosquito populations were found to be deficient in heterozygosity across the study sites (FIS< 0). No genetic differentiation (FST< 0) was observed in the localities of Zagnanado and Kétou. Conclusion The survey on the use of insecticides showed that insecticide selection pressures differ across the investigated localities. It would be desirable to rotate or apply formulations of combined products with different modes of action. Doing so would enable a better management of resistant homozygous individuals, and mitigate the resistance effect of commonly used insecticides.
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Noble C, Adlam B, Church GM, Esvelt KM, Nowak MA. Current CRISPR gene drive systems are likely to be highly invasive in wild populations. eLife 2018; 7:33423. [PMID: 29916367 PMCID: PMC6014726 DOI: 10.7554/elife.33423] [Citation(s) in RCA: 92] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2017] [Accepted: 05/15/2018] [Indexed: 12/25/2022] Open
Abstract
Recent reports have suggested that self-propagating CRISPR-based gene drive systems are unlikely to efficiently invade wild populations due to drive-resistant alleles that prevent cutting. Here we develop mathematical models based on existing empirical data to explicitly test this assumption for population alteration drives. Our models show that although resistance prevents spread to fixation in large populations, even the least effective drive systems reported to date are likely to be highly invasive. Releasing a small number of organisms will often cause invasion of the local population, followed by invasion of additional populations connected by very low rates of gene flow. Hence, initiating contained field trials as tentatively endorsed by the National Academies report on gene drive could potentially result in unintended spread to additional populations. Our mathematical results suggest that self-propagating gene drive is best suited to applications such as malaria prevention that seek to affect all wild populations of the target species.
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Affiliation(s)
- Charleston Noble
- Program for Evolutionary Dynamics, Harvard University, Cambridge, United States.,Department of Genetics, Harvard Medical School, Harvard University, Boston, United States.,Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston MA, United States
| | - Ben Adlam
- Program for Evolutionary Dynamics, Harvard University, Cambridge, United States.,School of Engineering and Applied Science, Harvard University, Cambridge, United States
| | - George M Church
- Department of Genetics, Harvard Medical School, Harvard University, Boston, United States.,Wyss Institute for Biologically Inspired Engineering, Harvard University, Boston MA, United States
| | - Kevin M Esvelt
- Massachusetts Institute of Technology Media Lab, Cambridge, United States
| | - Martin A Nowak
- Program for Evolutionary Dynamics, Harvard University, Cambridge, United States.,Department of Mathematics, Harvard University, Cambridge, United States.,Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, United States
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Mitchell SN, Catteruccia F. Anopheline Reproductive Biology: Impacts on Vectorial Capacity and Potential Avenues for Malaria Control. Cold Spring Harb Perspect Med 2017; 7:a025593. [PMID: 28389513 PMCID: PMC5710097 DOI: 10.1101/cshperspect.a025593] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Vectorial capacity is a mathematical approximation of the efficiency of vector-borne disease transmission, measured as the number of new infections disseminated per case per day by an insect vector. Multiple elements of mosquito biology govern their vectorial capacity, including survival, population densities, feeding preferences, and vector competence. Intriguingly, biological pathways essential to mosquito reproductive fitness directly or indirectly influence a number of these elements. Here, we explore this complex interaction, focusing on how the interplay between mating and blood feeding in female Anopheles not only shapes their reproductive success but also influences their ability to sustain Plasmodium parasite development. Central to malaria transmission, mosquito reproductive biology has recently become the focus of research strategies aimed at malaria control, and we discuss promising new methods based on the manipulation of key reproductive steps. In light of widespread resistance to all public health-approved insecticides targeting mosquito reproduction may prove crucial to the success of malaria-eradication campaigns.
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Affiliation(s)
- Sara N Mitchell
- Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Diseases, Boston, Massachusetts 02115
| | - Flaminia Catteruccia
- Harvard T.H. Chan School of Public Health, Department of Immunology and Infectious Diseases, Boston, Massachusetts 02115
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7
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Ranford-Cartwright LC, McGeechan S, Inch D, Smart G, Richterová L, Mwangi JM. Characterisation of Species and Diversity of Anopheles gambiae Keele Colony. PLoS One 2016; 11:e0168999. [PMID: 28033418 PMCID: PMC5199079 DOI: 10.1371/journal.pone.0168999] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Accepted: 12/09/2016] [Indexed: 11/18/2022] Open
Abstract
Anopheles gambiae sensu stricto was recently reclassified as two species, An. coluzzii and An. gambiae s.s., in wild-caught mosquitoes, on the basis of the molecular form, denoted M or S, of a marker on the X chromosome. The An. gambiae Keele line is an outbred laboratory colony strain that was developed around 12 years ago by crosses between mosquitoes from 4 existing An. gambiae colonies. Laboratory colonies of mosquitoes often have limited genetic diversity because of small starting populations (founder effect) and subsequent fluctuations in colony size. Here we describe the characterisation of the chromosomal form(s) present in the Keele line, and investigate the diversity present in the colony using microsatellite markers on chromosome 3. We also characterise the large 2La inversion on chromosome 2. The results indicate that only the M-form of the chromosome X marker is present in the Keele colony, which was unexpected given that 3 of the 4 parent colonies were probably S-form. Levels of diversity were relatively high, as indicated by a mean number of microsatellite alleles of 6.25 across 4 microsatellites, in at least 25 mosquitoes. Both karyotypes of the inversion on chromosome 2 (2La/2L+a) were found to be present at approximately equal proportions. The Keele colony has a mixed M- and S-form origin, and in common with the PEST strain, we propose continuing to denote it as an An. gambiae s.s. line.
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Affiliation(s)
- Lisa C Ranford-Cartwright
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Sion McGeechan
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Donald Inch
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Graeme Smart
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Lenka Richterová
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
| | - Jonathan M Mwangi
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, Glasgow, Scotland, United Kingdom
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Arcaz AC, Huestis DL, Dao A, Yaro AS, Diallo M, Andersen J, Blomquist GJ, Lehmann T. Desiccation tolerance in Anopheles coluzzii: the effects of spiracle size and cuticular hydrocarbons. ACTA ACUST UNITED AC 2016; 219:1675-88. [PMID: 27207644 PMCID: PMC4920233 DOI: 10.1242/jeb.135665] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2015] [Accepted: 03/09/2016] [Indexed: 01/08/2023]
Abstract
The African malaria mosquitoes Anopheles gambiae and Anopheles coluzzii range over forests and arid areas, where they withstand dry spells and months-long dry seasons, suggesting variation in their desiccation tolerance. We subjected a laboratory colony (G3) and wild Sahelian mosquitoes during the rainy and dry seasons to desiccation assays. The thoracic spiracles and amount and composition of cuticular hydrocarbons (CHCs) of individual mosquitoes were measured to determine the effects of these traits on desiccation tolerance. The relative humidity of the assay, body water available, rate of water loss and water content at death accounted for 88% of the variation in desiccation tolerance. Spiracle size did not affect the rate of water loss or desiccation tolerance of the colony mosquitoes, as was the case for the total CHCs. However, six CHCs accounted for 71% of the variation in desiccation tolerance and three accounted for 72% of the variation in the rate of water loss. Wild A. coluzzii exhibited elevated desiccation tolerance during the dry season. During that time, relative thorax and spiracle sizes were smaller than during the rainy season. A smaller spiracle size appeared to increase A. coluzzii's desiccation tolerance, but was not statistically significant. Seasonal changes in CHC composition were detected in Sahelian A. coluzzii Stepwise regression models suggested the effect of particular CHCs on desiccation tolerance. In conclusion, the combination of particular CHCs along with the total amount of CHCs is a primary mechanism conferring desiccation tolerance in A. coluzzii, while variation in spiracle size might be a secondary mechanism.
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Affiliation(s)
- Arthur C Arcaz
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD 20852, USA
| | - Diana L Huestis
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD 20852, USA
| | - Adama Dao
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, Bamako, BP 1805, Mali
| | - Alpha S Yaro
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, Bamako, BP 1805, Mali
| | - Moussa Diallo
- Malaria Research and Training Center (MRTC)/Faculty of Medicine, Pharmacy and Odonto-stomatology, Bamako, BP 1805, Mali
| | - John Andersen
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD 20852, USA
| | - Gary J Blomquist
- Department of Biochemistry and Molecular Biology, University of Nevada, Reno, NV 89557, USA
| | - Tovi Lehmann
- Laboratory of Malaria and Vector Research, NIAID, NIH, Rockville, MD 20852, USA
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Lunde TM, Korecha D, Loha E, Sorteberg A, Lindtjørn B. A dynamic model of some malaria-transmitting anopheline mosquitoes of the Afrotropical region. I. Model description and sensitivity analysis. Malar J 2013; 12:28. [PMID: 23342980 PMCID: PMC3664083 DOI: 10.1186/1475-2875-12-28] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2012] [Accepted: 01/07/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Most of the current biophysical models designed to address the large-scale distribution of malaria assume that transmission of the disease is independent of the vector involved. Another common assumption in these type of model is that the mortality rate of mosquitoes is constant over their life span and that their dispersion is negligible. Mosquito models are important in the prediction of malaria and hence there is a need for a realistic representation of the vectors involved. RESULTS We construct a biophysical model including two competing species, Anopheles gambiae s.s. and Anopheles arabiensis. Sensitivity analysis highlight the importance of relative humidity and mosquito size, the initial conditions and dispersion, and a rarely used parameter, the probability of finding blood. We also show that the assumption of exponential mortality of adult mosquitoes does not match the observed data, and suggest that an age dimension can overcome this problem. CONCLUSIONS This study highlights some of the assumptions commonly used when constructing mosquito-malaria models and presents a realistic model of An. gambiae s.s. and An. arabiensis and their interaction. This new mosquito model, OMaWa, can improve our understanding of the dynamics of these vectors, which in turn can be used to understand the dynamics of malaria.
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Affiliation(s)
- Torleif Markussen Lunde
- Centre for International Health, University of Bergen, Bergen, Norway
- Bjerknes Centre for Climate Research, University of Bergen/Uni Research, Bergen, Norway
- Geophysical Institute, University of Bergen, Bergen, Norway
| | - Diriba Korecha
- National Meteorological Agency of Ethiopia, Addis Ababa, Ethiopia
- Geophysical Institute, University of Bergen, Bergen, Norway
| | | | - Asgeir Sorteberg
- Bjerknes Centre for Climate Research, University of Bergen/Uni Research, Bergen, Norway
- Geophysical Institute, University of Bergen, Bergen, Norway
| | - Bernt Lindtjørn
- Centre for International Health, University of Bergen, Bergen, Norway
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10
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Sangare I, Michalakis Y, Yameogo B, Dabire R, Morlais I, Cohuet A. Studying fitness cost of Plasmodium falciparum infection in malaria vectors: validation of an appropriate negative control. Malar J 2013; 12:2. [PMID: 23282172 PMCID: PMC3543248 DOI: 10.1186/1475-2875-12-2] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2012] [Accepted: 12/29/2012] [Indexed: 12/13/2022] Open
Abstract
Background The question whether Plasmodium falciparum infection affects the fitness of mosquito vectors remains open. A hurdle for resolving this question is the lack of appropriate control, non-infected mosquitoes that can be compared to the infected ones. It was shown recently that heating P. falciparum gametocyte-infected blood before feeding by malaria vectors inhibits the infection. Therefore, the same source of gametocyte-infected blood could be divided in two parts, one heated, serving as the control, the other unheated, allowing the comparison of infected and uninfected mosquitoes which fed on exactly the same blood otherwise. However, before using this method for characterizing the cost of infection to mosquitoes, it is necessary to establish whether feeding on previously heated blood affects the survival and fecundity of mosquito females. Methods Anopheles gambiae M molecular form females were exposed to heated versus non-heated, parasite-free human blood to mimic blood meal on non-infectious versus infectious gametocyte-containing blood. Life history traits of mosquito females fed on blood that was heat-treated or not were then compared. Results The results reveal that heat treatment of the blood did not affect the survival and fecundity of mosquito females. Consistently, blood heat treatment did not affect the quantity of blood ingested. Conclusions The study indicates that heat inactivation of gametocyte-infected blood will only inhibit mosquito infection and that this method is suitable for quantifying the fitness cost incurred by mosquitoes upon infection by P. falciparum.
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Affiliation(s)
- Ibrahim Sangare
- Institut de Recherche en Sciences de la Santé-Direction Régionale de l'Ouest, Bobo Dioulasso, Burkina Faso
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11
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Dieter KL, Huestis DL, Lehmann T. The effects of oviposition-site deprivation on Anopheles gambiae reproduction. Parasit Vectors 2012; 5:235. [PMID: 23072301 PMCID: PMC3514158 DOI: 10.1186/1756-3305-5-235] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2012] [Accepted: 09/23/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The African malaria mosquito, Anopheles gambiae, depends on availability of suitable surface water for oviposition. Short and long dry spells occur throughout the year in many parts of its range that limit its access to oviposition sites. Although not well understood, oviposition-site deprivation has been found to rapidly reduce egg batch size and hatch rate of several mosquito species. We conducted laboratory experiments to assess these effects of oviposition-site deprivation on An. gambiae and to evaluate the role of nutrition and sperm viability as mediators of these effects. METHODS Anopheles gambiae adults (1-2 d old) from the G3 laboratory colony were assigned to the following treatment groups: oviposition-deprived (fed once and then deprived of oviposition site for 7 or 14 d), multiple-fed control (fed regularly once a week and allowed to lay eggs without delay), and age matched blood-deprived control (fed once, three days before water for oviposition was provided). Egg batch size and hatch rate were measured. In the second experiment two additional treatment groups were included: oviposition-deprived females that received either a second (supplemental) blood meal or virgin males (supplemental mating) 4 days prior to receiving water for oviposition. RESULTS An. gambiae was highly sensitive to oviposition-site deprivation. Egg batch size dropped sharply to 0-3.5 egg/female within 14 days, due to reduced oviposition rate rather than a reduced number of eggs/batch. Egg hatch rate also fell dramatically to 0-2% within 7 days. The frequency of brown eggs that fail to tan was elevated. A supplemental blood meal, but not 'supplemental insemination,' recovered the oviposition rate of females subjected to oviposition-site deprivation. Similarly, a supplemental blood meal, but not 'supplemental insemination,' partly recovered hatch rate, but this increase was marginally significant (P < 0.069). CONCLUSIONS Even a short dry spell resulting in oviposition-site deprivation for several days may result in a dramatic decline of An. gambiae populations via reduced fecundity and fertility. However, females taking supplemental blood meals regain at least some reproductive success. If mosquitoes subjected to oviposition-site deprivation increase the frequency of blood feeding, malaria transmission may even increase during a short dry spell. The relevance of oviposition-site deprivation as a cue to alter the physiology of An. gambiae during the long dry season is not evident from these results because no reduction in hatch rate was evident in wild M-form An. gambiae collected in the dry season in the Sahel by previous studies.
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Affiliation(s)
- Kathryne L Dieter
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 12735 Twinbrook Parkway, Room 2W-09-C, Rockville, MD 20852, USA
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12
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Mollahosseini A, Rossignol M, Pennetier C, Cohuet A, Anjos AD, Chandre F, Shahbazkia HR. A user-friendly software to easily count Anopheles egg batches. Parasit Vectors 2012; 5:122. [PMID: 22713553 PMCID: PMC3464736 DOI: 10.1186/1756-3305-5-122] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2012] [Accepted: 05/10/2012] [Indexed: 11/12/2022] Open
Abstract
Background Studies on malaria vector ecology and development/evaluation of vector control strategies often require measures of mosquito life history traits. Assessing the fecundity of malaria vectors can be carried out by counting eggs laid by Anopheles females. However, manually counting the eggs is time consuming, tedious, and error prone. Methods In this paper we present a newly developed software for high precision automatic egg counting. The software written in the Java programming language proposes a user-friendly interface and a complete online manual. It allows the inspection of results by the operator and includes proper tools for manual corrections. The user can in fact correct any details on the acquired results by a mouse click. Time saving is significant and errors due to loss of concentration are avoided. Results The software was tested over 16 randomly chosen images from 2 different experiments. The results show that the proposed automatic method produces results that are close to the ground truth. Conclusions The proposed approaches demonstrated a very high level of robustness. The adoption of the proposed software package will save many hours of labor to the bench scientist. The software needs no particular configuration and is freely available for download on: http://w3.ualg.pt/∼hshah/eggcounter/.
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Affiliation(s)
- Ali Mollahosseini
- Departamento de Engenharia Eletrónica e Informática, Universidade do Algarve, 8008-139 Faro, Portugal
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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] [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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14
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DAO ADAMA, KASSOGUE YAYA, ADAMOU ABDOULAYE, DIALLO MOUSSA, YARO ALPHASEYDOU, TRAORE SEKOUF, LEHMANN TOVI. Reproduction-longevity trade-off in Anopheles gambiae (Diptera: Culicidae). JOURNAL OF MEDICAL ENTOMOLOGY 2010; 47:769-777. [PMID: 20939369 PMCID: PMC2965199 DOI: 10.1603/me10052] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Reduced survival and future reproduction due to of current reproduction is a trade-off known as the cost of reproduction. Surprisingly, only a few studies have assessed the cost of reproduction in arthropod disease vectors, despite its effect on longevity, and thus on vectorial capacity. We evaluated the cost of reproduction on survival of Anopheles gambiae Giles by comparing mosquitoes that were denied exposure to the other sex, hereafter named virgins, and those that were allowed exposure to the other sex and mating, hereafter named mated. Merely 6 d of exposure to females with mating activity reduced male survival from a median of 17 d in virgins to 15 d in mated, indicating that male mating cost is substantial. The increase in mortality of mated males began several days after the exposure to females ended, indicating that mating is not associated with immediate mortality risk. Notably, body size was negatively correlated with male mortality in mated males, but not in virgins. The rate of insemination declined after 4 d of exposure to females, indicating that male mating capacity is limited and further supporting the hypothesis that mating is costly for males. Consistent with previous studies, female survival on sugar alone (median=16 d) was shorter than on blood and sugar (median=19 d), regardless if she was mated or virgin. Overall, survival of mated females was lower than that of virgins on a diet of blood and sugar, but no difference was found on a diet of sugar only. However, the cost of reproduction in females remains ambiguous because the difference in survival between virgin and mated females was driven by the difference between virgin (median=19 d) and uninseminated females exposed to males (median=17 d), rather than between virgin and inseminated females (median=19 d). Accordingly, sperm and seminal fluid, egg development, and oviposition have negligible cost in terms of female survival. Only exposure to males without insemination decreased female survival. Nonetheless, if exposure to males under natural conditions is also associated with reduced survival, it might explain why females remain monogamous.
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Affiliation(s)
- ADAMA DAO
- Malaria Research and Training Center, University of Mali, Bamako, Mali
| | - YAYA KASSOGUE
- Malaria Research and Training Center, University of Mali, Bamako, Mali
| | - ABDOULAYE ADAMOU
- Malaria Research and Training Center, University of Mali, Bamako, Mali
| | - MOUSSA DIALLO
- Malaria Research and Training Center, University of Mali, Bamako, Mali
| | - ALPHA SEYDOU YARO
- Malaria Research and Training Center, University of Mali, Bamako, Mali
| | - SEKOU F. TRAORE
- Malaria Research and Training Center, University of Mali, Bamako, Mali
| | - TOVI LEHMANN
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD 20852
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15
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Lehmann T, Diabate A. The molecular forms of Anopheles gambiae: a phenotypic perspective. INFECTION GENETICS AND EVOLUTION 2008; 8:737-46. [PMID: 18640289 DOI: 10.1016/j.meegid.2008.06.003] [Citation(s) in RCA: 124] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/13/2008] [Revised: 06/11/2008] [Accepted: 06/12/2008] [Indexed: 11/18/2022]
Abstract
The African malaria mosquito Anopheles gambiae is undergoing speciation, being split into the M and S molecular forms. Speciation is the main process promoting biological diversity, thus, new vector species might complicate disease transmission. Genetic differentiation between the molecular forms has been extensively studied, but phenotypic differences between them, the evolutionary forces that generated divergence, and the mechanisms that maintain their genetic isolation have only recently been addressed. Here, we review recent studies suggesting that selection mediated by larval predation and competition promoted divergence between temporary and permanent freshwater habitats. These differences explain the sharp discontinuity in distribution of the molecular forms between rice fields and surrounding savanna, but they can also explain the concurrent cline between humid and arid environments due to the dependence on permanent habitats in the latter. Although less pronounced, differences in adult body size, reproductive output, and longevity also suggest that the molecular forms have adapted to distinct niches. Reproductive isolation between the molecular forms is achieved by spatial swarm segregation, although within-swarm mate recognition appears to play a role in certain locations. The implications of these results to disease transmission and control are discussed and many of the gaps in our understanding are highlighted.
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Affiliation(s)
- Tovi Lehmann
- Laboratory of Malaria and Vector Research, NIAID, NIH, MS 8132, 12735 Twinbrook Parkway, Rockville, MD, USA.
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16
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Diabaté A, Dabiré RK, Heidenberger K, Crawford J, Lamp WO, Culler LE, Lehmann T. Evidence for divergent selection between the molecular forms of Anopheles gambiae: role of predation. BMC Evol Biol 2008; 8:5. [PMID: 18190719 PMCID: PMC2217532 DOI: 10.1186/1471-2148-8-5] [Citation(s) in RCA: 76] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2007] [Accepted: 01/11/2008] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND The molecular forms of Anopheles gambiae are undergoing speciation. They are characterized by a strong assortative mating and they display partial habitat segregation. The M form is mostly found in flooded/irrigated areas whereas the S form dominates in the surrounding areas, but the ecological factors that shape this habitat segregation are not known. Resource competition has been demonstrated between species undergoing divergent selection, but resource competition is not the only factor that can lead to divergence. RESULTS In a field experiment using transplantation of first instar larvae, we evaluated the role of larval predators in mediating habitat segregation between the forms. We found a significant difference in the ability of the molecular forms to exploit the different larval sites conditioned on the presence of predators. In absence of predation, the molecular forms outcompeted each other in their respective natural habitats however, the developmental success of the M form was significantly higher than that of the S form in both habitats under predator pressure. CONCLUSION Our results provide the first empirical evidence for specific adaptive differences between the molecular forms and stress the role of larval predation as one of the mechanisms contributing to their divergence.
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Affiliation(s)
- Abdoulaye Diabaté
- Laboratory of Malaria and Vector Research, NIAID, National Institute of Health, 12735 Twinbrook Parkway, Room 2W13A, Rockville MD 20852 USA
- IRSS/Centre Muraz, Laboratoire de Parasitologie/Entomologie BP 390 Bobo Dioulasso, Burkina Faso
| | - Roch K Dabiré
- IRSS/Centre Muraz, Laboratoire de Parasitologie/Entomologie BP 390 Bobo Dioulasso, Burkina Faso
| | - Kyle Heidenberger
- Laboratory of Malaria and Vector Research, NIAID, National Institute of Health, 12735 Twinbrook Parkway, Room 2W13A, Rockville MD 20852 USA
| | - Jacob Crawford
- Laboratory of Malaria and Vector Research, NIAID, National Institute of Health, 12735 Twinbrook Parkway, Room 2W13A, Rockville MD 20852 USA
| | - William O Lamp
- Department of Entomology University of Maryland College Park, MD 20742-4454 USA
| | - Lauren E Culler
- Department of Entomology University of Maryland College Park, MD 20742-4454 USA
| | - Tovi Lehmann
- Laboratory of Malaria and Vector Research, NIAID, National Institute of Health, 12735 Twinbrook Parkway, Room 2W13A, Rockville MD 20852 USA
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