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Pagendam D, Elfekih S, Nassar MS, Nelson S, Almalik AM, Tawfik EA, Al-Fageeh MB, Hoffmann AA. Spatio-Temporal Modelling Informing Wolbachia Replacement Releases in a Low Rainfall Climate. INSECTS 2022; 13:949. [PMID: 36292897 PMCID: PMC9604250 DOI: 10.3390/insects13100949] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/19/2022] [Revised: 10/13/2022] [Accepted: 10/13/2022] [Indexed: 06/16/2023]
Abstract
Releases of Aedes aegypti carrying Wolbachia bacteria are known to suppress arbovirus transmission and reduce the incidence of vector-borne diseases. In planning for Wolbachia releases in the arid environment of Jeddah, Saudi Arabia, we collected entomological data with ovitraps across a 7-month period in four locations. Herein, we show that mosquito presence in basements does not differ from that of non-basement areas of buildings. In modelling mosquito presence across the study sites, we found the spatial structure to be statistically significant in one of the four sites, while a significant spatial structure was found for egg production data across three of the four sites. The length scales of the spatial covariance functions fitted to the egg production data ranged from 143 m to 574 m, indicating that high productivity regions can be extensive in size. Rank-correlation analyses indicated that mosquito presence tended to persist from the dry to wet season, but that egg production ranks at locations could reverse. The data suggest that, in Jeddah, the quality of the local environment for breeding can vary over time. The data support the feasibility of dry season releases but with release numbers needing to be flexible depending on local rates of invasion.
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Affiliation(s)
- Dan Pagendam
- CSIRO Data61, Dutton Park, Brisbane, QLD 4101, Australia
| | - Samia Elfekih
- CSIRO H&B, Australian Centre for Disease Preparedness (ACDP), Geelong, VIC 3052, Australia
- Pest and Environmental Adaptation Research Group, Bio21 Institute and the School of Biosciences, University of Melbourne, Parkville, VIC 3052, Australia
| | - Majed S. Nassar
- King Abdulaziz City for Science and Technology (KACST), Riyadh 11442, Saudi Arabia
| | - Samuel Nelson
- CSIRO Data61, Black Mountain, Canberra, ACT 2601, Australia
| | - Abdulaziz M. Almalik
- King Abdulaziz City for Science and Technology (KACST), Riyadh 11442, Saudi Arabia
| | - Essam A. Tawfik
- King Abdulaziz City for Science and Technology (KACST), Riyadh 11442, Saudi Arabia
| | - Mohamed B. Al-Fageeh
- King Abdulaziz City for Science and Technology (KACST), Riyadh 11442, Saudi Arabia
| | - Ary A. Hoffmann
- Pest and Environmental Adaptation Research Group, Bio21 Institute and the School of Biosciences, University of Melbourne, Parkville, VIC 3052, Australia
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Metzger ME, Wekesa JW, Kluh S, Fujioka KK, Saviskas R, Arugay A, McConnell N, Nguyen K, Krueger L, Hacker GM, Hu R, Kramer VL. Detection and Establishment of Aedes notoscriptus (Diptera: Culicidae) Mosquitoes in Southern California, United States. JOURNAL OF MEDICAL ENTOMOLOGY 2022; 59:67-77. [PMID: 34617571 PMCID: PMC8755992 DOI: 10.1093/jme/tjab165] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2021] [Indexed: 06/13/2023]
Abstract
Aedes notoscriptus (Skuse), the Australian backyard mosquito, is a pestiferous daytime-biting species native to Australia and the surrounding southwestern Pacific region. It is suspected to play a role in the transmission of several arboviruses and is considered a competent vector of dog heartworm, Dirofilaria immitis (Leidy). This highly adaptable mosquito thrives in natural and artificial water-holding containers in both forested and urbanized areas, from tropical to temperate climates, and has benefitted from a close association with humans, increasing in abundance within its native range. It invaded and successfully established in New Zealand as well as in previously unoccupied temperate and arid regions of Australia. Ae. notoscriptus was discovered in Los Angeles County, CA, in 2014, marking the first time this species had been found outside the southwestern Pacific region. By the end of 2019, immature and adult mosquitoes had been collected from 364 unique locations within 44 cities spanning three southern California counties. The discovery, establishment, and rapid spread of this species in urban areas may signal the global movement and advent of a new invasive container-inhabiting species. The biting nuisance, public health, and veterinary health implications associated with the invasion of southern California by this mosquito are discussed.
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Affiliation(s)
- Marco E Metzger
- Vector-Borne Disease Section, Division of Communicable Disease Control, Center for Infectious Diseases, California Department of Public Health, 1616 Capitol Avenue, MS-7307, Sacramento, CA 95814, USA
| | - J Wakoli Wekesa
- San Gabriel Valley Mosquito and Vector Control District, 1145 North Azusa Canyon Road, West Covina, CA 91790, USA
- Current Address: East Side Mosquito Abatement District, 2000 Santa Fe Avenue, Modesto, CA 95357, USA
| | - Susanne Kluh
- Greater Los Angeles County Vector Control District, 12545 Florence Avenue, Santa Fe Springs, CA 90670, USA
| | - Kenn K Fujioka
- San Gabriel Valley Mosquito and Vector Control District, 1145 North Azusa Canyon Road, West Covina, CA 91790, USA
| | - Robert Saviskas
- Los Angeles County West Vector & Vector-Borne Disease Control District, 6750 Centinela Avenue, Culver City, CA 90230, USA
| | - Aaron Arugay
- Los Angeles County West Vector & Vector-Borne Disease Control District, 6750 Centinela Avenue, Culver City, CA 90230, USA
| | - Nathan McConnell
- County of San Diego, Department of Environmental Health, Vector Control Program, 5570 Overland Avenue Suite 102, San Diego, CA 92123, USA
| | - Kiet Nguyen
- Orange County Mosquito and Vector Control District, 13001 Garden Grove Boulevard, Garden Grove, CA 92843, USA
| | - Laura Krueger
- Orange County Mosquito and Vector Control District, 13001 Garden Grove Boulevard, Garden Grove, CA 92843, USA
| | - Gregory M Hacker
- Vector-Borne Disease Section, Division of Communicable Disease Control, Center for Infectious Diseases, California Department of Public Health, 1616 Capitol Avenue, MS-7307, Sacramento, CA 95814, USA
| | - Renjie Hu
- Vector-Borne Disease Section, Division of Communicable Disease Control, Center for Infectious Diseases, California Department of Public Health, 1616 Capitol Avenue, MS-7307, Sacramento, CA 95814, USA
| | - Vicki L Kramer
- Vector-Borne Disease Section, Division of Communicable Disease Control, Center for Infectious Diseases, California Department of Public Health, 1616 Capitol Avenue, MS-7307, Sacramento, CA 95814, USA
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Hustedt J, Doum D, Keo V, Ly S, Sam B, Chan V, Boyer S, Liverani M, Alexander N, Bradley J, Prasetyo DB, Rachmat A, Lopes S, Leang R, Hii J. Ability of the Premise Condition Index to Identify Premises with Adult and Immature Aedes Mosquitoes in Kampong Cham, Cambodia. Am J Trop Med Hyg 2020; 102:1432-1439. [PMID: 32274992 PMCID: PMC7253129 DOI: 10.4269/ajtmh.19-0453] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Aedes-transmitted diseases, especially dengue, are increasing throughout the world and the main preventive methods include vector control and the avoidance of mosquito bites. A simple Premise Condition Index (PCI) categorizing shade, house, and yard conditions was previously developed to help prioritize households or geographical areas where resources are limited. However, evidence about the accuracy of the PCI is mixed. The current study aimed to contribute to a better understanding of the relevance by collecting data from 2,400 premises at four time points over 1 year in Kampong Cham, Cambodia. Regression models were then used to identify associations between PCI and Aedes adult female mosquitoes and pupae. In addition, receiver operating characteristic curves were used to measure the ability of PCI to identify premises in the top quartile of mosquito abundance. The density of adult Aedes females was positively associated with PCI at the household (ratio of means = 1.16 per point on the PCI scale) and cluster level (ratio of means = 1.54). However, the number of Aedes pupae was negatively associated with PCI at the household level (rate ratio = 0.74) and did not have a statistically significant association at the cluster level. Receiver operating characteristic curves suggest the PCI score had “rather low accuracy” (area under the ROC curve = 0.52 and 0.54) at identifying top-quartile premises in terms of adult female Aedes and pupae, respectively. These results suggest that caution is warranted in the programmatic use of PCI in areas of similar geography and mosquito abundance.
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Affiliation(s)
- John Hustedt
- London School of Hygiene and Tropical Medicine, London, United Kingdom.,Malaria Consortium, Phnom Penh Center, Phnom Penh, Cambodia
| | - Dyna Doum
- Malaria Consortium, Phnom Penh Center, Phnom Penh, Cambodia
| | - Vanney Keo
- Malaria Consortium, Phnom Penh Center, Phnom Penh, Cambodia
| | - Sokha Ly
- Cambodian National Dengue Control Program, Phnom Penh, Cambodia
| | - BunLeng Sam
- Cambodian National Dengue Control Program, Phnom Penh, Cambodia
| | - Vibol Chan
- World Health Organization, Phnom Penh, Cambodia
| | | | - Marco Liverani
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Neal Alexander
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - John Bradley
- London School of Hygiene and Tropical Medicine, London, United Kingdom
| | | | - Agus Rachmat
- US Naval Medical Research Unit-2, Phnom Penh, Cambodia
| | - Sergio Lopes
- Malaria Consortium, Phnom Penh Center, Phnom Penh, Cambodia
| | - Rithea Leang
- Cambodian National Dengue Control Program, Phnom Penh, Cambodia
| | - Jeffrey Hii
- Malaria Consortium, Phnom Penh Center, Phnom Penh, Cambodia
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Jain J, Kushwah RBS, Singh SS, Sharma A, Adak T, Singh OP, Bhatnagar RK, Subbarao SK, Sunil S. Evidence for natural vertical transmission of chikungunya viruses in field populations of Aedes aegypti in Delhi and Haryana states in India-a preliminary report. Acta Trop 2016; 162:46-55. [PMID: 27282096 DOI: 10.1016/j.actatropica.2016.06.004] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2016] [Accepted: 06/05/2016] [Indexed: 02/02/2023]
Abstract
Aedes aegypti and Aedes albopictus are principal vectors for the transmission of chikungunya virus (CHIKV). India is a hub for both dengue and chikungunya infections and there are several reports of co-infection of dengue and chikungunya virus in the clinical scenario. The present pilot entomological survey was conducted to evaluate vertical transmission of CHIKV in Aedes field populations. Aedes immature (larvae and pupae) collection was done in 2012, over a period of six months from selected sites in Delhi and Haryana, India. The immatures collected were reared for adult emergence and species identification was done. A. aegypti male and female mosquitoes were separated and pooled collection spot-wise, RNA extracted and RT PCR performed to test for the presence of CHIKV in the pools. Container index (CI) and minimum infection rate (MIR) were estimated. From study areas that tested positive for CHIKV, adult collections were made and females upon feeding on uninfected blood in laboratory were allowed to lay eggs. The progeny that emerged from these field-collected mothers were tested for CHIKV presence. Our pilot survey showed the existence of A. aegypti population even during peak summer season in a few foci which eventually helped the mosquitoes to tide over adverse environmental conditions and with the start of rainfall, the population exploded within a short period of time. Immatures collected from field and progeny of adults collected from the field were CHIKV positive demonstrating the presence of vertical transmission of chikungunya virus in field population of A. aegypti. The present study further demonstrates the importance of identifying permanent breeding sites for proper Aedes species control.
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Affiliation(s)
- Jaspreet Jain
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, 110067, New Delhi, India.
| | - Raja Babu S Kushwah
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, 110067, New Delhi, India; Vector Biology Divisions, National Institute of Malaria Research, Sector 8, Dwarka, 110077, New Delhi, India.
| | - Shashi S Singh
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, 110067, New Delhi, India.
| | - Anil Sharma
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, 110067, New Delhi, India.
| | - Tridibes Adak
- Vector Biology Divisions, National Institute of Malaria Research, Sector 8, Dwarka, 110077, New Delhi, India.
| | - Om P Singh
- Vector Biology Divisions, National Institute of Malaria Research, Sector 8, Dwarka, 110077, New Delhi, India.
| | - Raj Kamal Bhatnagar
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, 110067, New Delhi, India.
| | - Sarala K Subbarao
- Epidemiology and Communicable Diseases Division, Indian Council of Medical Research, New Delhi, India.
| | - Sujatha Sunil
- Insect Resistance Group, International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, 110067, New Delhi, India.
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Williams CR, Mincham G, Ritchie SA, Viennet E, Harley D. Bionomic response of Aedes aegypti to two future climate change scenarios in far north Queensland, Australia: implications for dengue outbreaks. Parasit Vectors 2014; 7:447. [PMID: 25240382 PMCID: PMC4261586 DOI: 10.1186/1756-3305-7-447] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2014] [Accepted: 09/16/2014] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Dengue viruses are transmitted by anthropophilic mosquitoes and infect approximately 50 million humans annually. To investigate impacts of future climate change on dengue virus transmission, we investigated bionomics of the mosquito vector, Aedes aegypti. METHODS Using a dynamic life table simulation model (the Container inhabiting mosquito simulation CIMSiM) and statistically downscaled daily values for future climate, we assessed climate change induced changes to mosquito bionomics. Simulations of Ae. aegypti populations for current (1991-2011) and future climate (2046-2065) were conducted for the city of Cairns, Queensland, the population centre with most dengue virus transmission in Australia. Female mosquito abundance, wet weight, and the extrinsic incubation period for dengue virus in these mosquitoes were estimated for current and future climate (MPI ECHAM 5 model, B1 and A2 emission scenarios). RESULTS Overall mosquito abundance is predicted to change, but results were equivocal for different climate change scenarios. Aedes aegypti abundance is predicted to increase under the B1, but decrease under the A2 scenario. Mosquitoes are predicted to have a smaller body mass in a future climate. Shorter extrinsic incubation periods are projected. CONCLUSIONS It is therefore unclear whether dengue risk would increase or decrease in tropical Australia with climate change. Our findings challenge the prevailing view that a future, warmer climate will lead to larger mosquito populations and a definite increase in dengue transmission. Whilst general predictions can be made about future mosquito borne disease incidence, cautious interpretation is necessary due to interaction between local environment, human behaviour and built environment, dengue virus, and vectors.
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Affiliation(s)
- Craig R Williams
- Sansom Institute for Health Research, University of South Australia, GPO Box 2471, Adelaide 5001, Australia.
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Arana-Guardia R, Baak-Baak CM, Loroño-Pino MA, Machain-Williams C, Beaty BJ, Eisen L, García-Rejón JE. Stormwater drains and catch basins as sources for production of Aedes aegypti and Culex quinquefasciatus. Acta Trop 2014; 134:33-42. [PMID: 24582840 DOI: 10.1016/j.actatropica.2014.01.011] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2013] [Revised: 01/15/2014] [Accepted: 01/25/2014] [Indexed: 12/01/2022]
Abstract
We present data showing that structures serving as drains and catch basins for stormwater are important sources for production of the mosquito arbovirus vectors Aedes aegypti and Culex quinquefasciatus in Mérida City, México. We examined 1761 stormwater drains - located in 45 different neighborhoods spread across the city - over dry and wet seasons from March 2012 to March 2013. Of the examined stormwater drains, 262 (14.9%) held water at the time they were examined and 123 yielded mosquito immatures. In total, we collected 64,560 immatures representing nine species. The most commonly encountered species were Cx. quinquefasciatus (n=39,269) and Ae. aegypti (n=23,313). Ae. aegypti and Cx. quinquefasciatus were collected during all 11 months when we found water-filled stormwater drains, and both were found in stormwater drains located throughout Mérida City. We also present data for associations between structural characteristics of stormwater drains or water-related characteristics and the abundance of mosquito immatures. In conclusion, stormwater drains produce massive numbers of Ae. aegypti and Cx. quinquefasciatus across Mérida City, both in the wet and dry seasons, and represent non-residential development sites that should be strongly considered for inclusion in the local mosquito surveillance and control program.
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Affiliation(s)
- Roger Arana-Guardia
- Laboratorio de Arbovirología, Centro de Investigaciones Regionales Dr. Hideyo Noguchi, Universidad Autónoma de Yucatán, Calle 96 s/n x Av. Jacinto Canek y Calle 47, Paseo de las Fuentes, Mérida, Yucatán CP 97225, Mexico
| | - Carlos M Baak-Baak
- Laboratorio de Arbovirología, Centro de Investigaciones Regionales Dr. Hideyo Noguchi, Universidad Autónoma de Yucatán, Calle 96 s/n x Av. Jacinto Canek y Calle 47, Paseo de las Fuentes, Mérida, Yucatán CP 97225, Mexico
| | - María Alba Loroño-Pino
- Laboratorio de Arbovirología, Centro de Investigaciones Regionales Dr. Hideyo Noguchi, Universidad Autónoma de Yucatán, Calle 96 s/n x Av. Jacinto Canek y Calle 47, Paseo de las Fuentes, Mérida, Yucatán CP 97225, Mexico
| | - Carlos Machain-Williams
- Laboratorio de Arbovirología, Centro de Investigaciones Regionales Dr. Hideyo Noguchi, Universidad Autónoma de Yucatán, Calle 96 s/n x Av. Jacinto Canek y Calle 47, Paseo de las Fuentes, Mérida, Yucatán CP 97225, Mexico
| | - Barry J Beaty
- Department of Microbiology, Immunology and Pathology, Colorado State University, 3185 Rampart Road, Fort Collins, CO 80523, United States
| | - Lars Eisen
- Department of Microbiology, Immunology and Pathology, Colorado State University, 3185 Rampart Road, Fort Collins, CO 80523, United States
| | - Julián E García-Rejón
- Laboratorio de Arbovirología, Centro de Investigaciones Regionales Dr. Hideyo Noguchi, Universidad Autónoma de Yucatán, Calle 96 s/n x Av. Jacinto Canek y Calle 47, Paseo de las Fuentes, Mérida, Yucatán CP 97225, Mexico.
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Cheong YL, Burkart K, Leitão PJ, Lakes T. Assessing weather effects on dengue disease in Malaysia. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2013; 10:6319-34. [PMID: 24287855 PMCID: PMC3881116 DOI: 10.3390/ijerph10126319] [Citation(s) in RCA: 100] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/23/2013] [Revised: 11/04/2013] [Accepted: 11/08/2013] [Indexed: 11/23/2022]
Abstract
The number of dengue cases has been increasing on a global level in recent years, and particularly so in Malaysia, yet little is known about the effects of weather for identifying the short-term risk of dengue for the population. The aim of this paper is to estimate the weather effects on dengue disease accounting for non-linear temporal effects in Selangor, Kuala Lumpur and Putrajaya, Malaysia, from 2008 to 2010. We selected the weather parameters with a Poisson generalized additive model, and then assessed the effects of minimum temperature, bi-weekly accumulated rainfall and wind speed on dengue cases using a distributed non-linear lag model while adjusting for trend, day-of-week and week of the year. We found that the relative risk of dengue cases is positively associated with increased minimum temperature at a cumulative percentage change of 11.92% (95% CI: 4.41-32.19), from 25.4 °C to 26.5 °C, with the highest effect delayed by 51 days. Increasing bi-weekly accumulated rainfall had a positively strong effect on dengue cases at a cumulative percentage change of 21.45% (95% CI: 8.96, 51.37), from 215 mm to 302 mm, with the highest effect delayed by 26-28 days. The wind speed is negatively associated with dengue cases. The estimated lagged effects can be adapted in the dengue early warning system to assist in vector control and prevention plan.
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Affiliation(s)
- Yoon Ling Cheong
- Geoinformation Science Lab, Department of Geography, Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin 10099, Germany; E-Mail:
- Medical Research Resource Centre, Institute for Medical Research, Jalan Pahang, Kuala Lumpur 50588, Malaysia
| | - Katrin Burkart
- Climatological Section, Department of Geography, Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin 10099, Germany; E-Mail:
| | - Pedro J. Leitão
- Geomatics Lab, Department of Geography, Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin 10099, Germany; E-Mail:
| | - Tobia Lakes
- Geoinformation Science Lab, Department of Geography, Humboldt-Universität zu Berlin, Unter den Linden 6, Berlin 10099, Germany; E-Mail:
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Tran HP, Huynh TTT, Nguyen YT, Kutcher S, O'Rourke P, Marquart L, Ryan PA, Kay BH. Low entomological impact of new water supply infrastructure in southern Vietnam, with reference to dengue vectors. Am J Trop Med Hyg 2012; 87:631-9. [PMID: 22869632 DOI: 10.4269/ajtmh.2012.12-0335] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
We did a prospective study in southern Vietnam where new water infrastructure was added. New 1,200-L tanks may present potential breeding grounds for Aedes aegypti, particularly when sealed lids were not always supplied. Some householders in these communes received a piped water supply, however there was no reduction in water storage practices. The prevalence of Aedes aegypti immatures in tank and tap households reached 73%, but were non-significantly different from each other and from control households that received no infrastructure. In all three communes, standard jars comprised from 48% to 71% of containers but were associated with > 90% of III-IV instars and pupae on occasions. In contrast, project tanks contributed from 0-21% of the total population. Non-functional or no lids were apparent 4 months after installation in 45-76% of new tanks, but there was no difference between communes with lids and without lids.
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Affiliation(s)
- Hau P Tran
- Institute Pasteur, Ho Chi Minh City, Vietnam.
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The extinction of dengue through natural vulnerability of its vectors. PLoS Negl Trop Dis 2010; 4:e922. [PMID: 21200424 PMCID: PMC3006136 DOI: 10.1371/journal.pntd.0000922] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2010] [Accepted: 11/18/2010] [Indexed: 11/21/2022] Open
Abstract
Background Dengue is the world's most important mosquito-borne viral illness. Successful future management of this disease requires an understanding of the population dynamics of the vector, especially in the context of changing climates. Our capacity to predict future dynamics is reflected in our ability to explain the significant historical changes in the distribution and abundance of the disease and its vector. Methodology/Principal Findings Here we combine daily weather records with simulation modelling techniques to explain vector (Aedes aegypti (L.)) persistence within its current and historic ranges in Australia. We show that, in regions where dengue presently occurs in Australia (the Wet Tropics region of Far North Queensland), conditions are persistently suitable for year-round adult Ae. aegypti activity and oviposition. In the historic range, however, the vector is vulnerable to periodic extinction due to the combined influence of adult activity constraints and stochastic loss of suitable oviposition sites. Conclusions/Significance These results, together with changes in water-storage behaviour by humans, can explain the observed historical range contraction of the disease vector. For these reasons, future eradication of dengue in wet tropical regions will be extremely difficult through classical mosquito control methods alone. However, control of Ae. aegypti in sub-tropical and temperate regions will be greatly facilitated by government policy regulating domestic water-storage. Exploitation of the natural vulnerabilities of dengue vectors (e.g., habitat specificity, climatic limitations) should be integrated with the emerging novel transgenic and symbiotic bacterial control techniques to develop future control and elimination strategies. Dengue transmission has not always been confined to tropical areas. In some cases, this has been due to a reduced geographic range of the mosquitoes that are able to carry dengue viruses. In Australia, Aedes aegypti mosquitoes once occurred throughout temperate, drier parts of the country but are now restricted to the wet tropics. We used a computer modelling approach to determine whether these mosquitoes could inhabit their former range. This was done by simulating dengue mosquito populations in virtual environments that experienced 10 years of actual daily weather conditions (1998–2007) obtained for 13 locations inside and outside the current tropical range. We discovered that in areas outside the Australian wet tropics, Ae. aegypti often becomes extinct, particularly when conditions are too cool for year-round egg-laying activity, and/or too dry for eggs to hatch. Thus, despite being a global pest and disease vector, Ae. aegypti mosquitoes are naturally vulnerable to extinction in certain conditions. Such vulnerability should be exploited in vector control programs.
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Tipayamongkholgul M, Fang CT, Klinchan S, Liu CM, King CC. Effects of the El Niño-southern oscillation on dengue epidemics in Thailand, 1996-2005. BMC Public Health 2009; 9:422. [PMID: 19930557 PMCID: PMC2785791 DOI: 10.1186/1471-2458-9-422] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2009] [Accepted: 11/20/2009] [Indexed: 12/03/2022] Open
Abstract
Background Despite intensive vector control efforts, dengue epidemics continue to occur throughout Southeast Asia in multi-annual cycles. Weather is considered an important factor in these cycles, but the extent to which the El Niño-Southern Oscillation (ENSO) is a driving force behind dengue epidemics remains unclear. Methods We examined the temporal relationship between El Niño and the occurrence of dengue epidemics, and constructed Poisson autoregressive models for incidences of dengue cases. Global ENSO records, dengue surveillance data, and local meteorological data in two geographically diverse regions in Thailand (the tropical southern coastal region and the northern inland mountainous region) were analyzed. Results The strength of El Niño was consistently a predictor for the occurrence of dengue epidemics throughout time lags from 1 to 11 months in the two selected regions of Thailand. Up to 22% (in 8 northern inland mountainous provinces) and 15% (in 5 southern tropical coastal provinces) of the variation in the monthly incidence of dengue cases were attributable to global ENSO cycles. Province-level predictive models were fitted using 1996-2004 data and validated with out-of-fit data from 2005. The multivariate ENSO index was an independent predictor in 10 of the 13 studied provinces. Conclusion El Niño is one of the important driving forces for dengue epidemics across the geographically diverse regions of Thailand; however, spatial heterogeneity in the effect exists. The effects of El Niño should be taken into account in future epidemic forecasting for public health preparedness.
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Affiliation(s)
- Mathuros Tipayamongkholgul
- Graduate Institute of Epidemiology, College of Public Health, National Taiwan University, Taipei, Taiwan.
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Williams CR, Ritchie SA, Long SA, Dennison N, Russell RC. Impact of a bifenthrin-treated lethal ovitrap on Aedes aegypti oviposition and mortality in north Queensland, Australia. JOURNAL OF MEDICAL ENTOMOLOGY 2007; 44:256-62. [PMID: 17427694 DOI: 10.1603/0022-2585(2007)44[256:ioablo]2.0.co;2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/14/2023]
Abstract
Lethal ovitraps (LOs) containing an insecticide-treated ovistrip are used as a lure-and-kill device for the container-breeding dengue vector, Aedes aegypti (L.). We aimed to affirm that the pyrethroid bifenthrin could be used effectively in LOs against Ae. aegypti in north Queensland, Australia, by quantifying oviposition in and mortality caused by LOs. Small cage experiments in which individual gravid Ae. aegypti were given a choice of LOs and untreated ovitraps revealed that although LOs were less acceptable for oviposition, they provided an average 64.6% adjusted mortality. Although 92% of mosquitoes ovipositing in LOs died, 61.8% of mosquitoes that visited but did not oviposit in an LO also died, demonstrating that lethal contact occurred without egg laying. The bifenthrin content of strips (approximately 0.1 mg/cm2; 7 mg/strip) did not decrease significantly after 4 wk of field exposure nor did the toxic effect of the LOs. Large cage trials with groups of 10 Ae. aegypti confirmed that bifenthrin-treated LOs provided consistent control (average adjusted mortality 79.7%). Four-week field trials in north Queensland showed that although LOs were acceptable to ovipositing Ae. aegypti (mean time to first egg 10.9 d; mean eggs 47.3), insecticide-free ovitraps were oviposited in more readily (6.8 d, 199 eggs). The number of eggs laid per mosquito in laboratory LOs allowed calculation of the number of Ae. aegypti killed in field-deployed LOs; rapid estimates can be made by simply dividing the number of eggs on the strip by 2.84. Overall, the studies demonstrated that bifenthrin-treated LOs have potential for use as a lure-and-kill device against Ae. aegypti and that they should be effective in the field for at least 4 wk. Given that untreated ovitraps were more acceptable for Ae. aegypti oviposition, the removal of alternative oviposition sites before deployment of LOs in the field should maximize their effectiveness.
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Affiliation(s)
- Craig R Williams
- School of Public Health and Tropical Medicine, James Cook University, P.O. Box 6811, Cairns, Queensland 4870, Australia.
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Chadee DD. Key premises, a guide to Aedes aegypti (Diptera: Culicidae) surveillance and control. BULLETIN OF ENTOMOLOGICAL RESEARCH 2004; 94:201-207. [PMID: 15191621 DOI: 10.1079/ber2004297] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The population densities of Aedes aegypti Linneaus in four towns in Trinidad were studied using standard house-to-house inspections of all water-holding containers to determine whether persistently positive containers and premises existed over a three-month period in the wet season, from May to July 2002. From a total of 1503 houses inspected, 223 were positive with 41 persistently positive over the three month period and classified as 'key premises'. The definition of the term key premises is described and the rationale for its utilization discussed. A total of 24,439 containers was inspected from Santa Margarita (6407), Mt Lambert (5709), St Augustine (5384) and Curepe (6939) of which 1.3% or 334 containers were positive for A. aegypti larvae and pupae. A total of 16,507 immatures of A. aegypti were retrieved from these containers which comprised 17 container types but when these were ranked according to productivity levels, only water drums (average 53.5%), buckets (22.2%), tubs and basins (8.0%), water tanks (5.4%), brick holes (4.2%) and tyres (2.0%) were significant (P < 0.001) producers. The role that key premises play in the introduction and re-infestation of A. aegypti-free communities is described and illustrated. These results suggest that A. aegypti control programmes could be more cost effective and sustainable by concentrating efforts on key premises and key containers to control mosquito densities and Dengue transmission while reducing manpower needs and insecticide use.
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Affiliation(s)
- D D Chadee
- Insect Vector Control Division, Ministry of Health, St Joseph, Trinidad, West Indies.
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