23 results found
O'Loughlin SM, Forster AJ, Fuchs S, et al., 2021, Ultra-conserved sequences in the genomes of highly diverse Anopheles mosquitoes, with implications for malaria vector control, G3-GENES GENOMES GENETICS, Vol: 11, ISSN: 2160-1836
Epopa PS, Millogo AA, Collins C, et al., 2020, Anopheles gambiae (s.l.) is found where few are looking: assessing mosquito diversity and density outside inhabited areas using diverse sampling methods, Parasites and Vectors, Vol: 13, ISSN: 1756-3305
BackgroundOne of the promising current approaches to curb malaria lies in genetic vector control, the implementation of which will require an improved understanding of the movement of genetic constructs among mosquito populations. To predict potential gene flow from one area to another, it is important to begin to understand mosquito dynamics outside of the commonly-sampled village areas, and thus how genes may move between villages. This study assessed the presence and relative abundance of mosquitoes in a 6-km corridor between two villages in western Burkina Faso.MethodsThe area surrounding the villages was mapped and the road between them was used as the basis of a transect along which to sample. Five collection points were placed along this transect. To investigate both larval and adult mosquito presence, multiple sampling approaches were used surrounding each point: searching for larval sites in an area of 500 m radius, swarm sampling, human landing catches (HLC), CDC light traps and backpack aspiration catches of potential resting sites. Sampling took place twice: in September and October 2015.ResultsAdult mosquitoes from six species of Anopheles and three other genera were found along the whole transect. Anopheles gambiae (s.l.) was the most abundant followed by Anopheles nili and Anopheles coustani. Larvae of Anopheles spp. were found in small pools of surface water along the whole transect, though their presence increased with human proximity. HLC and aspiration were the most efficient methods of collecting adult mosquitoes along the whole transect, indicating that there are both host-seeking and resting mosquitoes well away from core village areas. In contrast, swarms of male mosquitoes, thought to be the principle mating locations of Anopheles spp. mosquitoes in West Africa, were only found close to the core village areas.ConclusionsThis preliminary study indicates that Anopheles spp. mosquitoes are both present and breeding in low human-density areas alo
Clarkson CS, Miles A, Harding NJ, et al., 2020, Genome variation and population structure among 1142 mosquitoes of the African malaria vector species Anopheles gambiae and Anopheles coluzzii, GENOME RESEARCH, Vol: 30, Pages: 1533-1546, ISSN: 1088-9051
Miles A, Kwiatkowski D, Lawniczak M, et al., 2018, THE MALARIAGEN VECTOR OBSERVATORY: A NETWORK FOR THE GENOMIC SURVEILLANCE OF MALARIA VECTORS IN AFRICA AND SOUTHEAST ASIA, 67th Annual Meeting of the American-Society-of-Tropical-Medicine-and-Hygiene (ASTHM), Publisher: AMER SOC TROP MED & HYGIENE, Pages: 12-13, ISSN: 0002-9637
Miles A, Harding NJ, Botta G, et al., 2017, Genetic diversity of the African malaria vector Anopheles gambiae, Nature, Vol: 552, Pages: 96-100, ISSN: 0028-0836
The sustainability of malaria control in Africa is threatened by the rise of insecticide resistance in Anopheles mosquitoes, which transmit the disease1. To gain a deeper understanding of how mosquito populations are evolving, here we sequenced the genomes of 765 specimens of Anopheles gambiae and Anopheles coluzzii sampled from 15 locations across Africa, and identified over 50 million single nucleotide polymorphisms within the accessible genome. These data revealed complex population structure and patterns of gene flow, with evidence of ancient expansions, recent bottlenecks, and local variation in effective population size. Strong signals of recent selection were observed in insecticide-resistance genes, with several sweeps spreading over large geographical distances and between species. The design of new tools for mosquito control using gene-drive systems will need to take account of high levels of genetic diversity in natural mosquito populations.
Galizi R, Hammond A, Kyrou K, et al., 2016, A CRISPR-Cas9 sex-ratio distortion system for genetic control., Scientific Reports, Vol: 6, ISSN: 2045-2322
Genetic control aims to reduce the ability of insect pest populations to cause harm via the release of modified insects. One strategy is to bias the reproductive sex ratio towards males so that a population decreases in size or is eliminated altogether due to a lack of females. We have shown previously that sex ratio distortion can be generated synthetically in the main human malaria vector Anopheles gambiae, by selectively destroying the X-chromosome during spermatogenesis, through the activity of a naturally-occurring endonuclease that targets a repetitive rDNA sequence highly-conserved in a wide range of organisms. Here we describe a CRISPR-Cas9 sex distortion system that targets ribosomal sequences restricted to the member species of the Anopheles gambiae complex. Expression of Cas9 during spermatogenesis resulted in RNA-guided shredding of the X-chromosome during male meiosis and produced extreme male bias among progeny in the absence of any significant reduction in fertility. The flexibility of CRISPR-Cas9 combined with the availability of genomic data for a range of insects renders this strategy broadly applicable for the species-specific control of any pest or vector species with an XY sex-determination system by targeting sequences exclusive to the female sex chromosome.
O'Loughlin SM, Magesa SM, Mbogo C, et al., 2016, Genomic signatures of population decline in the malaria mosquito Anopheles gambiae, Malaria Journal, Vol: 15, ISSN: 1475-2875
BACKGROUND: Population genomic features such as nucleotide diversity and linkage disequilibrium are expected to be strongly shaped by changes in population size, and might therefore be useful for monitoring the success of a control campaign. In the Kilifi district of Kenya, there has been a marked decline in the abundance of the malaria vector Anopheles gambiae subsequent to the rollout of insecticide-treated bed nets. METHODS: To investigate whether this decline left a detectable population genomic signature, simulations were performed to compare the effect of population crashes on nucleotide diversity, Tajima's D, and linkage disequilibrium (as measured by the population recombination parameter ρ). Linkage disequilibrium and ρ were estimated for An. gambiae from Kilifi, and compared them to values for Anopheles arabiensis and Anopheles merus at the same location, and for An. gambiae in a location 200 km from Kilifi. RESULTS: In the first simulations ρ changed more rapidly after a population crash than the other statistics, and therefore is a more sensitive indicator of recent population decline. In the empirical data, linkage disequilibrium extends 100-1000 times further, and ρ is 100-1000 times smaller, for the Kilifi population of An. gambiae than for any of the other populations. There were also significant runs of homozygosity in many of the individual An. gambiae mosquitoes from Kilifi. CONCLUSIONS: These results support the hypothesis that the recent decline in An. gambiae was driven by the rollout of bed nets. Measuring population genomic parameters in a small sample of individuals before, during and after vector or pest control may be a valuable method of tracking the effectiveness of interventions.
Deredec A, O'Loughlin SM, Hui T-YJ, et al., 2016, Partitioning the contributions of alternative malaria vector species, Malaria Journal, Vol: 15, ISSN: 1475-2875
BackgroundIn many locations malaria is transmitted by more than one vector species. Some vector control interventions, in particular those using genetic approaches, are likely to be targeted against a single species or species complex, at least initially, and it would therefore be useful to be able to predict the epidemiological impact of controlling a single species when multiple vector species are present.MethodsTo address this issue, the classical Ross-McDonald model of malaria epidemiology is expanded to account for multiple vector species, giving expressions for the equilibrium prevalence, sporozoite rates and reproductive number. These allow one to predict when control of just one vector species will lead to elimination of the disease. Application of the model is illustrated using published data from a particularly extensive entomological and epidemiological survey before the rollout of bed nets in eastern Kenya, where Anopheles gambiae s.l. and An. funestus were vectors.ResultsMeta-analysis indicates that sporozoite rates were 38 % higher in An. gambiae s.l. than in An. funestus, and, according to the model, this difference could be due to An. gambiae s.l. having a higher frequency of feeding on humans, a higher human-to-mosquito transmission rate, a lower adult mortality rate, and/or a shorter incubation period. Further calculations suggest that An. gambiae s.l. would have been sufficient to maintain transmission by itself throughout the region, whereas An. funestus would not have been able to support transmission by itself in Malindi District.ConclusionsPartitioning the contributions of different vector species may allow us to predict whether malaria will persist after targeted vector control.
Redmond SN, Antao T, Besansky N, et al., 2015, AN ANALYSIS OF CHROMOSOMAL INVERSIONS WITHIN THE ANOPHELES 1000-GENOMES PROJECT - MARKERS OF POPULATION STRUCTURE IN DISEASE VECTORS FROM THE PAST TO THE FUTURE, Publisher: AMER SOC TROP MED & HYGIENE, Pages: 423-423, ISSN: 0002-9637
Neafsey DE, Waterhouse RM, Abai MR, et al., 2015, Highly evolvable malaria vectors: The genomes of 16 Anopheles mosquitoes, Science, Vol: 347
O'Loughlin SM, Magesa S, Mbogo C, et al., 2014, Genomic Analyses of Three Malaria Vectors Reveals Extensive Shared Polymorphism but Contrasting Population Histories, MOLECULAR BIOLOGY AND EVOLUTION, Vol: 31, Pages: 889-902, ISSN: 0737-4038
O'Loughlin S, Burt A, 2013, INFERRING DEMOGRAPHY AND SELECTION IN EAST AFRICAN ANOPHELES GAMBIAE SL FROM GENOME WIDE SNPS, PATHOGENS AND GLOBAL HEALTH, Vol: 107, Pages: 416-416, ISSN: 2047-7724
Sarma DK, Prakash A, O'Loughlin SM, et al., 2012, Genetic population structure of the malaria vector Anopheles baimaii in north-east India using mitochondrial DNA, MALARIA JOURNAL, Vol: 11
Morgan K, O'Loughlin SM, Chen B, et al., 2011, Comparative phylogeography reveals a shared impact of pleistocene environmental change in shaping genetic diversity within nine Anopheles mosquito species across the Indo-Burma biodiversity hotspot, MOLECULAR ECOLOGY, Vol: 20, Pages: 4533-4549, ISSN: 0962-1083
Morgan K, O'Loughlin SM, Mun-Yik F, et al., 2009, Molecular phylogenetics and biogeography of the Neocellia Series of Anopheles mosquitoes in the Oriental Region., Mol Phylogenet Evol, Vol: 52, Pages: 588-601
Molecular studies of population divergence and speciation across the Oriental Region are sparse, despite the region's high biodiversity and extensive Pliocene and Pleistocene environmental change. A molecular phylogenetic study of the Neocellia Series of Anopheles mosquitoes was undertaken to identify patterns of diversification across the Oriental Region and to infer the role of Pleistocene and Pliocene climatic change. A robust phylogeny was constructed using CO2 and ND5 mitochondrial genes and ITS2 and D3 nuclear ribosomal markers. Bayesian analysis of mitochondrial genes was used to date divergence events. The repeated contraction and expansion of forest habitat resulting from Pleistocene climatic fluctuations appears to have had a substantial impact on intraspecific diversification, but has not driven speciation within this group. Primarily early to mid Pliocene speciation was detected within the Annularis Group, whereas speciation within the Maculatus and Jamesii Groups occurred during the mid and late Pliocene. Both allopatric divergence driven by late Pliocene environmental changes and ecological adaptation, involving altitudinal replacement and seasonality, are likely to have influenced speciation in the Maculatus Group.
O'Loughlin SM, Okabayashi T, Honda M, et al., 2008, Complex population history of two Anopheles dirus mosquito species in Southeast Asia suggests the influence of Pleistocene climate change rather than human-mediated effects, JOURNAL OF EVOLUTIONARY BIOLOGY, Vol: 21, Pages: 1555-1569, ISSN: 1010-061X
Thongwat D, Morgan K, O'Loughlin SM, et al., 2008, Crossing experiments supporting the specific status of Anopheles maculatus chromosomal form K, JOURNAL OF THE AMERICAN MOSQUITO CONTROL ASSOCIATION, Vol: 24, Pages: 194-202, ISSN: 8756-971X
O'Loughlin SM, Somboon P, Walton C, 2007, High levels of population structure caused by habitat islands in the malarial vector Anopheles scanloni, HEREDITY, Vol: 99, Pages: 31-40, ISSN: 0018-067X
Walton C, Somboon P, Harbach RE, et al., 2007, Molecular identification of mosquito species in the Anopheles annularis group in southern Asia, MEDICAL AND VETERINARY ENTOMOLOGY, Vol: 21, Pages: 30-35, ISSN: 0269-283X
Walton C, Somboon P, O'Loughlin SM, et al., 2007, Genetic diversity and molecular identification of mosquito species in the Anopheles maculatus group using the ITS2 region of rDNA, INFECTION GENETICS AND EVOLUTION, Vol: 7, Pages: 93-102, ISSN: 1567-1348
Prakash A, Walton C, Bhattacharyya DR, et al., 2006, Molecular characterization and species identification of the Anopheles dirus and An. minimus complexes in north-east India using r-DNA ITS-2, ACTA TROPICA, Vol: 100, Pages: 156-161, ISSN: 0001-706X
Okabayashi T, Kitazoe Y, Kishino H, et al., 2006, Core set approach to reduce uncertainty of gene trees, BMC EVOLUTIONARY BIOLOGY, Vol: 6, ISSN: 1471-2148
Cawkwell L, Gray S, Murgatroyd H, et al., 1999, Choice of management strategy for colorectal cancer based on a diagnostic immunohistochemical test for defective mismatch repair, GUT, Vol: 45, Pages: 409-415, ISSN: 0017-5749
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