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Odero JO, Fillinger U, Rippon EJ, Masiga DK, Weetman D. Using sibship reconstructions to understand the relationship between larval habitat productivity and oviposition behaviour in Kenyan Anopheles arabiensis. Malar J 2019; 18:286. [PMID: 31443645 PMCID: PMC6708163 DOI: 10.1186/s12936-019-2917-5] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2019] [Accepted: 08/17/2019] [Indexed: 11/10/2022] Open
Abstract
Background Strategies for combatting residual malaria by targeting vectors outdoors are gaining importance as the limitations of primary indoor interventions are reached. Strategies to target ovipositing females or her offspring are broadly applicable because all mosquitoes require aquatic habitats for immature development irrespective of their biting or resting preferences. Oviposition site selection by gravid females is frequently studied by counting early instar larvae in habitats; an approach which is valid only if the number of larvae correlates with the number of females laying eggs. This hypothesis was tested against the alternative, that a higher abundance of larvae results from improved survival of a similar or fewer number of families. Methods In a controlled experiment, 20 outdoor artificial ponds were left uncovered for 4 days to allow oviposition by wild mosquitoes, then covered with netting and first and second instar larvae sampled daily. Natural Anopheles habitats of two different types were also identified, and all visible larvae sampled. All larvae were identified to species, and most samples of the predominant species, Anopheles arabiensis, were genotyped using microsatellites for sibling group reconstructions using two contrasting softwares, BAPS and COLONY. Results In the ponds, the number of families reconstructed by each software significantly predicted larval abundance (BAPS R2 = 0.318, p = 0.01; COLONY R2 = 0.476, p = 0.001), and suggested that around 50% of females spread larvae across multiple ponds (skip oviposition). From natural habitats, the mean family size again predicted larval abundance using BAPS (R2 = 0.829, p = 0.017) though not using COLONY (R2 = 0.218, p = 0.68), but both softwares once more suggested high rates of skip oviposition (in excess of 50%). Conclusion This study shows that, whether in closely-located artificial habitats or natural breeding sites, higher early instar larval densities result from more females laying eggs in these sites. These results provide empirical support for use of early instar larval abundance as an index for oviposition site preference. Furthermore, the sharing of habitats by multiple females and the high skip-oviposition rate in An. arabiensis suggest that larviciding by auto-dissemination of insecticide may be successful.
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Affiliation(s)
- Joel O Odero
- Human Health Theme, International Centre of Insect Physiology and Ecology, Nairobi, Kenya. .,Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK.
| | - Ulrike Fillinger
- Human Health Theme, International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | - Emily J Rippon
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
| | - Daniel K Masiga
- Human Health Theme, International Centre of Insect Physiology and Ecology, Nairobi, Kenya
| | - David Weetman
- Vector Biology Department, Liverpool School of Tropical Medicine, Liverpool, UK
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Salazar F, Angeles J, Sy AK, Inobaya MT, Aguila A, Toner T, Bangs MJ, Thomsen E, Paul RE. Efficacy of the In2Care® auto-dissemination device for reducing dengue transmission: study protocol for a parallel, two-armed cluster randomised trial in the Philippines. Trials 2019; 20:269. [PMID: 31088515 PMCID: PMC6518692 DOI: 10.1186/s13063-019-3376-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [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: 01/31/2019] [Accepted: 04/19/2019] [Indexed: 12/26/2022] Open
Abstract
Background Mosquito-borne viruses are imposing an ever increasing health burden worldwide. In addition to the recent Zika and chikungunya virus epidemics, dengue viruses have become the fastest growing problem with a 40-fold increase in the number of reported cases over the past five decades. Current mosquito control techniques involving larval source reduction, larviciding, and space spray of adulticides are costly, laborious, and of debatable efficacy. There remains an urgent need for the development of intervention methods that can be reasonably implemented in the context of modern day urbanisation. Auto-dissemination (AD) of insecticide by adult mosquitoes offers a potentially practical and useful tool in an integrated vector control programme. Recently, an immediately employable AD device, the In2Care® mosquito trap, has been commercialised and shows promise as an effective tool. However, there remains a lack of demonstration of epidemiological efficacy. Methods/design This trial aims to assess the extent to which implementation of In2Care® mosquito traps can reduce vector Aedes (Stegomyia) spp. adult mosquito densities and dengue virus transmission as measured by sequential sero-conversion rates in children 6–16 years of age in a dengue endemic location: Lipa City, Philippines. To achieve this, we will carry out a parallel, two-armed cluster randomised trial evaluating AD efficacy for reducing the incidence of dengue over a 2-year period with 4 consecutive months of vector control during peak dengue transmission each year. Discussion For decades, it has been commonly accepted that an integrated approach to mosquito control is required. The World Health Organization (WHO) Global Strategic Framework for Integrated Vector Management recommends a range of interventions, in combination, to increase control impact to reduce transmission. This efficacy trial of the first commercial product using the AD approach will be informative in assessing the general utility of AD in reducing not only adult vector densities but, more importantly, reducing the incidence of dengue. The AD technique may complement source reduction and larviciding campaigns by more efficiently targeting the most productive containers and those beyond human reach. If successful, this mosquito control strategy could prove an invaluable tool in the fight against urban mosquito vectors and a reduction in the burden of associated disease. Trial registration ISRCTN44272773. Registered on 31 January 2019. Electronic supplementary material The online version of this article (10.1186/s13063-019-3376-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Ferdinand Salazar
- Department of Medical Entomology, Research Institute for Tropical Medicine, Filinvest City Alabang, Muntinlupa City, Philippines
| | - Jason Angeles
- Department of Medical Entomology, Research Institute for Tropical Medicine, Filinvest City Alabang, Muntinlupa City, Philippines
| | - Ava Kristy Sy
- Department of Virology, Research Institute for Tropical Medicine, Filinvest City Alabang, Muntinlupa City, Philippines
| | - Marianette T Inobaya
- Department of Epidemiology and Biostatistics, Research Institute for Tropical Medicine, Filinvest City Alabang, Muntinlupa City, Philippines
| | - Ariza Aguila
- Department of Medical Entomology, Research Institute for Tropical Medicine, Filinvest City Alabang, Muntinlupa City, Philippines
| | - Tom Toner
- Liverpool School of Tropical Medicine, Liverpool, UK
| | - Michael J Bangs
- PT Freeport Indonesia/International SOS, Kuala Kencana, Indonesia. .,Kasetsart University, Bangkok, Thailand.
| | | | - Richard E Paul
- Functional Genetics of Infectious Diseases Unit, Institut Pasteur, Paris, France. .,Génomique évolutive, modélisation et santé UMR 2000, Centre National de la Recherche Scientifique (CNRS), Paris, France.
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Seixas G, Paul REL, Pires B, Alves G, de Jesus A, Silva AC, Devine GJ, Sousa CA. An evaluation of efficacy of the auto-dissemination technique as a tool for Aedes aegypti control in Madeira, Portugal. Parasit Vectors 2019; 12:202. [PMID: 31053095 PMCID: PMC6499953 DOI: 10.1186/s13071-019-3454-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [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: 12/07/2018] [Accepted: 04/22/2019] [Indexed: 01/10/2023] Open
Abstract
Background The frequency and intensity of arboviral epidemics is steadily increasing and posing an intractable public health burden. Current vector control methods are proving ineffectual and despite progress in the development of high technology approaches, there is an urgent need for the development of tools for immediate implementation. Several studies suggest that the auto-dissemination of pyriproxyfen (PPF) is a promising new approach to larviciding although there is little detail on the conditions under which it is optimally effective. Here, we evaluate the efficacy of the approach in urban and rural sites in Madeira, Portugal. Results Auto-dissemination of PPF through adapted Biogents Sentinel traps (BGSTs) resulted in a modest but consistent impact on both juvenile and adult mosquito populations, but with considerable spatial heterogeneity. This heterogeneity was related to the distance from the BGST dissemination station as well as the local density of adult mosquitoes. There was evidence that the impact of PPF was cumulative over time both locally and with gradual spatial expansion. Conclusions The density of adult mosquitoes and the spatial distribution of dissemination devices are key factors in mediating efficacy. In addition, urban topography may affect the efficiency of auto-dissemination by impeding adult mosquito dispersal. Further studies in a range of urban landscapes are necessary to guide optimal strategies for the implementation of this potentially efficacious and cost-effective approach to larviciding.
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Affiliation(s)
- Gonçalo Seixas
- UEI Parasitologia Médica, Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Rua da Junqueira 100, 1349-008, Lisbon, Portugal
| | - Richard E L Paul
- Functional Genetics of Infectious Diseases Unit, Department of Genomes and Genetics, Institut Pasteur, 75015, Paris, France.,Centre National de la Recherche Scientifique (CNRS), Génomique évolutive, modélisation et santé UMR 2000, 75724, Paris Cedex 15, France
| | - Bianca Pires
- UEI Parasitologia Médica, Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Rua da Junqueira 100, 1349-008, Lisbon, Portugal
| | - Gonçalo Alves
- UEI Parasitologia Médica, Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Rua da Junqueira 100, 1349-008, Lisbon, Portugal
| | - Ana de Jesus
- UEI Parasitologia Médica, Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Rua da Junqueira 100, 1349-008, Lisbon, Portugal
| | - Ana-Clara Silva
- Unidade de Engenharia Sanitária, Departamento de Promoção e Proteção da Saúde, Instituto de Administração da Saúde e Assuntos Sociais, IP-RAM, Funchal, Madeira, Portugal
| | - Gregor J Devine
- Mosquito Control Laboratory, QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia.
| | - Carla A Sousa
- UEI Parasitologia Médica, Global Health and Tropical Medicine, GHTM, Instituto de Higiene e Medicina Tropical, IHMT, Universidade Nova de Lisboa, UNL, Rua da Junqueira 100, 1349-008, Lisbon, Portugal.
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