RESUMEN
The Northern Territory (NT) of Australia is currently free of the dengue mosquito Aedes (Stegomyia) aegypti (L). However, on 17 February 2004, two Ae. aegypti adults were captured in two routine CO2 -baited encephalitis virus surveillance traps in Tennant Creek, located 990 km south of Darwin in the NT. The detection triggered an immediate survey and control response undertaken by the NT Department of Health and Community Services, followed by a Commonwealth of Australia-funded Ae. aegypti elimination program. This report details the methods and results of the detection and subsequent elimination activities that were carried out between 2004 and 2006, returning the NT to its dengue vector-free status. There have been very few successful Ae. aegypti elimination programs in the world. This purposeful mosquito elimination for Australia was officially declared on 5 April 2006.
Asunto(s)
Aedes , Control de Mosquitos/métodos , Animales , Australia , Humanos , Insectos Vectores , Enfermedades Transmitidas por Vectores/prevención & control , Enfermedades Transmitidas por Vectores/transmisiónRESUMEN
The aims of this review were to compare planning for both mosquito control and land use in east-central Florida, USA, and in New South Wales, Queensland, and the Northern Territory, Australia. Saltwater mosquito production in mangroves and salt marsh is the predominant mosquito control concern in all the areas. Urban encroachment towards saltwater mosquito habitats is a problem in both Florida and Australia. In east-central Florida and the Northern Territory, mosquito control is supported by comprehensive source reduction programs, whereas in Queensland and New South Wales, larviciding is the main method of control. The long-term control by source reduction programs reduces vulnerability to mosquito issues as population encroaches towards wetlands, whereas larviciding programs have to respond repeatedly as problems arise. Problems from urban encroachment are exacerbated if mosquito control and land-use planning are not integrated. Further, urban planning that is not informed by mosquito management can lead to increased mosquito problems by inadvertent design or allowing residential development close to mosquito habitats. This increases the need for mosquito control and related resourcing. At the regional level of governance, Florida and the Northern Territory generally have greater integration between planning for development and mosquito control than at the local government level in New South Wales and Queensland, where there is a lack of integration between mosquito agencies and planners. It is concluded that coordination of planning and mosquito control is more effective at higher government levels than at local levels, which have less connectivity between management areas and/or insufficient resources. The lesson is that collaboration can assist in avoiding or resolving conflicts.
Asunto(s)
Ecosistema , Control de Mosquitos/métodos , Australia , Florida , Control de Mosquitos/instrumentación , Control de Mosquitos/estadística & datos numéricosRESUMEN
In northern Australia the northern salt marsh mosquito Aedes vigilax is a vector of Ross River virus and is an appreciable pest. A coastal wetland adjacent to Darwin's residential suburbs offers a favorable habitat for Ae. vigilax, and despite vigilant mosquito control efforts, peaks of Ae. vigilax occur in excess of 500/trap/night some months. To improve mosquito control for disease and nuisance biting to nearby residential areas, we sought to investigate meteorological drivers associated with these Ae. vigilax peaks. We fitted a cross-sectional logistic regression model to weekly counts of female Ae. vigilax mosquitoes collected between July, 1998 and June, 2009 against variables, tide, rainfall, month, year, and larval control. Aedes vigilax peaks were associated with rainfall during the months September to November compared with January, when adjusted for larval control and tide. To maximize mosquito control efficiency, larval control should continue to be implemented after high tides and with increased emphasis on extensive larval hatches triggered by rainfall between September and November each year. This study reiterates the importance of monitoring and evaluating service delivery programs. Using statistical modelling, service providers can obtain solutions to operational problems using routinely collected data. These methods may be applicable in mosquito surveillance or control programs in other areas.
Asunto(s)
Aedes/fisiología , Animales , Australia , Estudios Transversales , Ecosistema , Femenino , Larva , Modelos Logísticos , Control de Mosquitos/métodos , Dinámica Poblacional , Lluvia , Clima Tropical , Tiempo (Meteorología) , HumedalesRESUMEN
Effective arbovirus surveillance is essential to ensure the implementation of control strategies, such as mosquito suppression, vaccination, or dissemination of public warnings. Traditional strategies employed for arbovirus surveillance, such as detection of virus or virus-specific antibodies in sentinel animals, or detection of virus in hematophagous arthropods, have limitations as an early-warning system. A system was recently developed that involves collecting mosquitoes in CO2-baited traps, where the insects expectorate virus on sugar-baited nucleic acid preservation cards. The cards are then submitted for virus detection using molecular assays. We report the application of this system for detecting flaviviruses and alphaviruses in wild mosquito populations in northern Australia. This study was the first to employ nonpowered passive box traps (PBTs) that were designed to house cards baited with honey as the sugar source. Overall, 20/144 (13.9%) of PBTs from different weeks contained at least one virus-positive card. West Nile virus Kunjin subtype (WNVKUN), Ross River virus (RRV), and Barmah Forest virus (BFV) were detected, being identified in 13/20, 5/20, and 2/20 of positive PBTs, respectively. Importantly, sentinel chickens deployed to detect flavivirus activity did not seroconvert at two Northern Territory sites where four PBTs yielded WNVKUN. Sufficient WNVKUN and RRV RNA was expectorated onto some of the honey-soaked cards to provide a template for gene sequencing, enhancing the utility of the sugar-bait surveillance system for investigating the ecology, emergence, and movement of arboviruses.
Asunto(s)
Infecciones por Arbovirus/epidemiología , Arbovirus/aislamiento & purificación , Culicidae/virología , Insectos Vectores/virología , Control de Mosquitos/instrumentación , Alphavirus/genética , Alphavirus/aislamiento & purificación , Infecciones por Alphavirus/epidemiología , Infecciones por Alphavirus/transmisión , Infecciones por Alphavirus/virología , Animales , Infecciones por Arbovirus/transmisión , Infecciones por Arbovirus/virología , Arbovirus/genética , Australia/epidemiología , Secuencia de Bases , Dióxido de Carbono , Bovinos , Enfermedades de los Bovinos/epidemiología , Enfermedades de los Bovinos/virología , Pollos , Culicidae/fisiología , Femenino , Flavivirus/genética , Flavivirus/aislamiento & purificación , Infecciones por Flavivirus/epidemiología , Infecciones por Flavivirus/transmisión , Infecciones por Flavivirus/virología , Miel , Insectos Vectores/fisiología , Datos de Secuencia Molecular , Filogenia , Enfermedades de las Aves de Corral/epidemiología , Enfermedades de las Aves de Corral/virología , ARN Viral/química , ARN Viral/genética , Vigilancia de Guardia , Análisis de Secuencia de ARNRESUMEN
The National Notifiable Diseases Surveillance System received 7,609 notified cases of disease transmitted by mosquitoes for the season 1 July 2009 to 30 June 2010. The alphaviruses Barmah Forest virus and Ross River virus, accounted for 6,546 (79%) of these notifications during the 2009-10 season. There were 37 notifications of dengue virus infection locally-acquired from North Queensland and 581 notified cases in Australia that resulted from overseas travel. This number of overseas acquired cases continues to rise each year due to increasing disease activity in the Asia-Pacific region and increased air travel. Detection of flavivirus seroconversions in sentinel chicken flocks across Australia provides an early warning of increased levels of Murray Valley encephalitis virus and Kunjin virus activity. Flavivirus activity was detected in western and northern Australia in 2009-10, which prompted public health action. No human cases of Murray Valley encephalitis virus infection were notified, while there were 2 cases of Kunjin virus infection notified. There were no notifications of locally-acquired malaria in Australia and 429 notifications of overseas-acquired malaria during the 2009-10 season. This annual report presents information of diseases transmitted by mosquitoes in Australia and notified to the National Notifiable Diseases Surveillance System.
Asunto(s)
Infecciones por Arbovirus/epidemiología , Malaria/epidemiología , Animales , Informes Anuales como Asunto , Infecciones por Arbovirus/historia , Infecciones por Arbovirus/transmisión , Australia/epidemiología , Pollos/virología , Historia del Siglo XXI , Humanos , Malaria/historia , Malaria/transmisión , Vigilancia de la Población , Vigilancia de GuardiaRESUMEN
Mosquitoes are problematic as vectors and pests in many tropical cities, including Darwin, the principal city in the Northern Territory of Australia. To monitor peaks in mosquito populations, the Medical Entomology unit of the Health Department sets overnight CO(2) -baited traps weekly. Trap setting and retrieving, followed by mosquito counting and identification, are labor intensive. Aiming to reduce this workload, we tested the hypothesis that fortnightly trapping is as effective as weekly trapping across seasons and ecologically distinct systems in Darwin. We applied cross-sectional negative binomial mixed effects models, which adjusted for rain and calendar month, to existing historical data. Culex annulirostris peaks were effectively identified using fortnightly trapping across all three ecological systems, during wet/dry and build-up seasonal patterns. For Aedes vigilax, fortnightly trapping was adequate in identifying peaks during wet and dry season months, but inadequate during build-up months across all three ecological systems. Therefore, weekly trapping should continue during build-up months, but trapping could be reduced to fortnightly for wet and dry season months for all ecological systems. Trapping for Cx. annulirostris monitoring could be reduced to fortnightly in all areas and seasons. Evaluation of programs can maximize staff efficiency and improve service delivery by reducing the need for unnecessary tasks.
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Culicidae , Ecosistema , Control de Mosquitos/métodos , Estaciones del Año , Aedes , Animales , AustraliaRESUMEN
Adult mosquito traps are commonly used in biosecurity surveillance for the detection of exotic mosquito incursions or for the demonstration of elimination. However, traps are typically deployed without knowledge of how many are required for detecting differing numbers of the target species. The aim of this study was to determine the sensitivity (i.e., detection probability) provided by carbon dioxide-baited EVS traps for adult female Australian southern saltmarsh mosquitoes, Aedes camptorhynchus, a recent biosecurity problem for New Zealand. A mark-release-recapture study of three concurrently released cohorts (sized 56, 296, and 960), recaptured over four days with a matrix of 20 traps, was conducted in Australia. The detection probability for different numbers of traps and cohorts of different sizes was determined by random sampling of recapture data. Detection probability ranged from approximately 0.3 for a single trap detecting a cohort of 56 mosquitoes to 1.0 (certainty of detection) when seven or more traps were used. For detection of adult Ae. camptorhynchus around a known source, a matrix of traps provides a strong probability of detection. Conversely, the use of single traps deployed over very large areas to detect mosquitoes of unknown entry pathway is unlikely to be successful. These findings have implications for the design of mosquito surveillance for biosecurity.
Asunto(s)
Aedes/fisiología , Control de Mosquitos , Animales , Australia , Culicidae/fisiologíaRESUMEN
BACKGROUND: Microbial and insect-growth-regulator larvicides dominate current vector control programmes because they reduce larval abundance and are relatively environmentally benign. However, their short persistence makes them expensive, and environmental manipulation of larval habitat might be an alternative control measure. Aedes vigilax is a major vector species in northern Australia. A field experiment was implemented in Darwin, Australia, to test the hypotheses that (1) aerial microbial larvicide application effectively decreases Ae. vigilax larval presence, and therefore adult emergence, and (2) environmental manipulation is an effective alternative control measure. Generalised linear and mixed-effects modelling and information-theoretic comparisons were used to test these hypotheses. RESULTS: It is shown that the current aerial larvicide application campaign is effective at suppressing the emergence of Ae. vigilax, whereas vegetation removal is not as effective in this context. In addition, the results indicate that current larval sampling procedures are inadequate for quantifying larval abundance or adult emergence. CONCLUSIONS: This field-based comparison has shown that the existing larviciding campaign is more effective than a simple environmental management strategy for mosquito control. It has also identified an important knowledge gap in the use of larval sampling to evaluate the effectiveness of vector control strategies.
Asunto(s)
Aedes/efectos de los fármacos , Ecosistema , Insectos Vectores/efectos de los fármacos , Insecticidas/toxicidad , Control de Mosquitos/métodos , Aedes/crecimiento & desarrollo , Animales , Australia , Femenino , Insectos Vectores/crecimiento & desarrollo , Larva/efectos de los fármacos , Larva/crecimiento & desarrollo , MasculinoRESUMEN
West Nile virus Kunjin subtype (WNV/KUNV) is enzootic across the tropical north of Australia, with epizootic spread into other jurisdictions. The clinical spectrum of illness in humans is poorly described. We report a clinical case of WNV/KUNV encephalitis and performed a retrospective chart audit of all cases of WNV/KUNV notified in the Northern Territory from 1992 to 2010. Thirteen cases of WNV/KUNV disease were identified; case notes were available for 10 of these presentations. Six of these patients had confirmed infection and presented with neuroinvasive illness, whereas the other four suspect cases comprised three cases with arthralgia, myalgia, and/or rash and one case with fever alone. On the available evidence, WNV/KUNV is of lower virulence compared with the New York 1999 strain. Difficulties in serological diagnosis, especially when paired acute and convalescent sera are not available, may adversely impact the accuracy of the epidemiological and clinical understanding of this virus.
Asunto(s)
Fiebre del Nilo Occidental/epidemiología , Virus del Nilo Occidental/clasificación , Anciano de 80 o más Años , Humanos , Masculino , Northern Territory/epidemiologíaRESUMEN
Ross River virus (RRV) causes the most common human arbovirus disease in Australia. Although the disease is nonfatal, the associated arthritis and postinfection fatigue can be debilitating for many months, impacting on workforce participation. We sought to create an early-warning system to notify of approaching RRV disease outbreak conditions for major townships in the Northern Territory. By applying a logistic regression model to meteorologic factors, including rainfall, a postestimation analysis of sensitivity and specificity can create rainfall cut-points. These rainfall cut-points indicate the rainfall level above which previous epidemic conditions have occurred. Furthermore, rainfall cut-points indirectly adjust for vertebrate host data from the agile wallaby (Macropus agilis) as the life cycle of the agile wallaby is intricately meshed with the wet season. Once generated, cut-points can thus be used prospectively to allow timely implementation of larval survey and control measures and public health warnings to preemptively reduce RRV disease incidence. Cut-points are location specific and have the capacity to replace previously used models, which require data management and input, and rarely provide timely notification for vector control requirements and public health warnings. These methods can be adapted for use elsewhere.
Asunto(s)
Infecciones por Alphavirus/prevención & control , Infecciones por Alphavirus/transmisión , Modelos Biológicos , Control de Mosquitos/métodos , Virus del Río Ross , Animales , Culicidae/fisiología , Culicidae/virología , Brotes de Enfermedades , Ecosistema , Humanos , Northern Territory/epidemiología , LluviaRESUMEN
The National Notifiable Diseases Surveillance System received 8,677 notifications of diseases transmitted by mosquitoes in Australia from 1 July 2008 to 30 June 2009. The alphaviruses, Barmah Forest and Ross River, accounted for 6,574 (78%) of these notifications during 2008-09. There were 1,009 notifications of dengue virus infection locally-acquired in North Queensland and 484 notified cases resulted from overseas travel. Notification rates of dengue virus infection for 2008-09, regardless of where infection was acquired, exceeded the five-year mean rate and may be attributed to increased disease activity in the Asia-Pacific region. North Queensland was the site of several outbreaks of locally-acquired dengue virus infection involving all 4 serotypes. These dengue outbreaks affected several locations with over 1,000 notifications. Detection of flavivirus seroconversions in sentinel chicken flocks across Australia provides an early warning of increased levels of Murray Valley encephalitis virus and Kunjin virus activity. Increased levels of flavivirus activity were detected in western and northern Australia, which prompted public health action. This action preceded 4 notifications of Murray Valley encephalitis infections, 2 (fatal) cases acquired in the Northern Territory and two in Western Australia. There were no notifications of locally-acquired malaria in Australia and 567 notifications of overseas-acquired malaria during 2008-09. This annual report presents information of diseases transmitted by mosquitoes in Australia and notified to the National Notifiable Diseases Surveillance System.
Asunto(s)
Infecciones por Arbovirus/epidemiología , Malaria/epidemiología , Australia/epidemiología , Notificación de Enfermedades , Humanos , Incidencia , Vigilancia de GuardiaRESUMEN
The efficacy of alpha-cypermethrin (Cyperthor) and lambda-cyhalothrin (Demand) to prevent mosquito larval colonization of water-containing receptacles was investigated using 2 differing applications in disused car tires in Darwin, Australia. Insecticide treatments were applied uniformly to the inside surfaces of 2 categories of tires: 1) dry tires that were partially filled with water 24 h after spraying and 2) wet tires partially filled with water prior to spraying. All mosquito larvae, pupae, and dead adults were collected from the treatment and control tires weekly over the 24-wk study period and were later identified to species in the laboratory. Control tires were colonized by Aedes notoscriptus in wk 2 and by Culex quinquefasciatus in wk 4. Aedes notoscriptus failed to colonize any alpha-cypermethrin-treated tires until wk 22 and did not colonize any lambda-cyhalothrin-treated tires during the 24-wk trial. Culex quinquefasciatus colonized alpha-cypermethrin and lambda-cyhalothrin-treated tires from wk 11 and wk 15, respectively. These results indicate both insecticides using either application method can prevent colonization of Ae. notoscriptus for at least 20 wk and demonstrate great potential for the prevention of breeding in receptacles for other receptacle-breeding Aedes species, such as the dengue vectors, Ae. aegypti and Ae. albopictus.
Asunto(s)
Aedes/efectos de los fármacos , Insecticidas/farmacología , Control de Mosquitos/métodos , Nitrilos/farmacología , Piretrinas/farmacología , Animales , Conducta Animal , ReproducciónRESUMEN
BACKGROUND: Annual biological rhythms are often depicted as predictably cyclic, but quantitative evaluations are few and rarely both cyclic and constant among years. In the monsoon tropics, the intense seasonality of rainfall frequently drives fluctuations in the populations of short-lived aquatic organisms. However, it is unclear how predictably assemblage composition will fluctuate because the intensity, onset and cessation of the wet season varies greatly among years. METHODOLOGY/PRINCIPAL FINDINGS: Adult mosquitoes were sampled using EVS suction traps baited with carbon dioxide around swamplands adjacent to the city of Darwin in northern Australia. Eleven sites were sampled weekly for five years, and one site weekly for 24 years, the sample of c. 1.4 million mosquitoes yielding 63 species. Mosquito abundance, species richness and diversity fluctuated seasonally, species richness being highly predictable. Ordination of assemblage composition demonstrated striking annual cycles that varied little from year to year. The mosquito assemblage was temporally structured by a succession of species peaks in abundance. CONCLUSION/SIGNIFICANCE: Ordination provided strong visual representation of annual rhythms in assemblage composition and the means to evaluate variability among years. Because most mosquitoes breed in shallow freshwater which fluctuates with rainfall, we did not anticipate such repeatability; we conclude that mosquito assemblage composition appears adapted to predictable elements of the rainfall.
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Culicidae/fisiología , Periodicidad , Clima Tropical , Animales , Australia , Dinámica Poblacional , Lluvia , Estaciones del AñoRESUMEN
The National Notifiable Diseases Surveillance System (NNDSS) received 8,671 notifications of diseases transmitted by mosquitoes in Australia for the season 1 July 2007 to 30 June 2008. This represented a 39% increase from the annual average of 6,259 notifications for the previous 5 years. The alphaviruses, Barmah Forest and Ross River, accounted for 7,760 (89%) of these notifications during the 2007/08 season and represents an increase when compared with the mean of the past 5 seasons. Detection of flavivirus seroconversions in sentinel chicken flocks across Australia provides an early warning of increased levels of Murray Valley encephalitis virus (MVEV) and Kunjin virus activity. Unusual MVEV activity in mosquitoes and sentinel chicken flocks was reported in southeast Australia during the 2007/08 season. Two cases of MVEV were reported, one each from New South Wales and Western Australia. There were 365 notifications of dengue virus infection that were acquired overseas compared with an average of 164 overseas-acquired dengue cases per annum reported to NNDSS over the 5 seasons from 2002/03 to 2006/07. There were no reports of locally-acquired malaria notified in Australia and 505 notified cases of overseas-acquired malaria during the season 2007/08. The exotic dengue vector Aedes aegypti was first detected on Groote Eylandt, Northern Territory in October 2006 and led to a 2-year Ae. aegypti eradication project. The successful eradication of Ae. aegypti from Groote Eylandt was officially announced in May 2008. The success of the program was due to the selection of appropriate chemicals that were successful in treating mosquito adults, larvae and egg infested receptacles. This annual report presents information on diseases transmitted by mosquitoes in Australia and notified to NNDSS.
Asunto(s)
Infecciones por Arbovirus/epidemiología , Malaria/epidemiología , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Animales , Australia/epidemiología , Pollos , Niño , Preescolar , Culicidae , Notificación de Enfermedades/estadística & datos numéricos , Vectores de Enfermedades , Humanos , Lactante , Recién Nacido , Masculino , Persona de Mediana Edad , Programas Nacionales de Salud , Vigilancia de la Población , Enfermedades de las Aves de Corral/epidemiología , Enfermedades de las Aves de Corral/virología , Vigilancia de GuardiaRESUMEN
Understanding the contributions of environmental variation and density feedbacks to changes in vector populations is essential for designing effective vector control. We analyzed monitoring datasets describing larval densities over 7 yr of the two dominant mosquito species, Aedes vigilax (Skuse) and Culex annulirostris (Skuse), of the greater Darwin area (Northern Territory, Australia). Using generalized linear and linear mixed-effects models, we tested hypotheses regarding the environmental determinants of spatio-temporal patterns in relative larval abundance in both species. The most important spatial drivers of Ae. vigilax and Cx. annulirostris larval densities were elevation and water presence. Ae. vigilax density correlates negatively with elevation, whereas there was a positive relationship between Cx. annulirostris density and elevation. These results show how larval habitats used by the saltwater-influenced breeder Ae. vigilax and the obligate freshwater breeder Cx. annulirostris are separated in a tidally influenced swamp. The models examining temporal drivers of larval density also identified this discrimination between freshwater and saltwater habitats. Ae. vigilax larval densities were positively related to maximum tide height and high tide frequency, whereas Cx. annulirostris larval densities were positively related to elevation and rainfall. Adult abundance in the previous month was the most important temporal driver of larval densities in both species, providing a clear dynamical link between the two main life phases in mosquito development. This study shows the importance of considering both spatial and temporal drivers, and intrinsic population dynamics, when planning vector control strategies to reduce larval density, adult population density, and disease transmission effectively.
Asunto(s)
Aedes , Culex , Ambiente , Animales , Larva , Northern Territory , Densidad de Población , Factores de Tiempo , Clima TropicalRESUMEN
We compare the community composition, abundance, and seasonality of mosquito species detected by the encephalitis virus surveillance (EVS) CO2 traps and Centers for Disease Control and Prevention (CDC) light traps. Traps were run concurrently for a year during routine weekly monitoring in the vicinity of the city of Darwin in northern Australia. The EVS CO2 traps detected far more individuals than CDC light traps notwithstanding a weaker suction fan, but species richness was similar. Regardless of variation in community composition among sites, differences between trap types were remarkably consistent. Seasonal trends in the abundance of 5 key species from each trap type were similar, but markedly more so in strongly seasonal species. Although EVS CO2 traps outperformed CDC light traps for routine monitoring, the historical transition from the latter to the former is unlikely to have major consequences for the identification of community composition or detection of seasonal trends in key species.
Asunto(s)
Culicidae/fisiología , Control de Mosquitos/instrumentación , Animales , Australia , Biodiversidad , Culicidae/clasificación , Femenino , Geografía , Estaciones del Año , Especificidad de la EspecieRESUMEN
The efficacy of maximum label rates of bifenthrin applications to dry tires to prevent Aedes mosquito breeding was investigated by field colonization and bioassay trials in shaded and unshaded locations. Aedes notoscriptus and Culex quinquefasciatus larvae were the most abundant species present in the field colonization trial. Colonization and survival of Ae. notoscriptus larvae to the late instar occurred significantly earlier in treated tires in shaded compared with unshaded locations (P = 0.002). Bifenthrin applications in shaded tires only prevented early instar survival for approximately 2.6 wk. Aedes notoscriptus late instars did not appear in the treated unshaded tires. Culex quinquefasciatus colonized treated tires from the 2nd wk in both shaded and unshaded treatments. In the bioassay, water from bifenthrin-treated tires, through extrapolation, was found to kill approximately 100% of late instar Ae. notoscriptus for only approximately 2.0-2.2 wk in shaded and unshaded tires. Under conditions optimal for Aedes breeding, such as shaded locations, high ambient temperatures, high relative humidity, and high amounts of leaf/organic matter accumulations, bifenthrin may not be effective as a larval control measure in tires for greater than 2.0-2.6 wk.
Asunto(s)
Aedes , Cruzamiento , Control de Mosquitos/métodos , Piretrinas , Animales , Humedad , Larva , Lluvia , TemperaturaRESUMEN
Dengue transmission in Australia is currently restricted to Queensland, where the vector mosquito Aedes aegypti is established. Locally acquired infections have been reported only from urban areas in the north-east of the state, where the vector is most abundant. Considerable attention has been drawn to the potential impact of climate change on dengue distribution within Australia, with projections for substantial rises in incidence and distribution associated with increasing temperatures. However, historical data show that much of Australia has previously sustained both the vector mosquito and dengue viruses. Although current vector distribution is restricted to Queensland, the area inhabited by A. aegypti is larger than the disease-transmission areas, and is not restricted by temperature (or vector-control programs); thus, it is unlikely that rising temperatures alone will bring increased vector or virus distribution. Factors likely to be important to dengue and vector distribution in the future include increased dengue activity in Asian and Pacific nations that would raise rates of virus importation by travellers, importation of vectors via international ports to regions without A. aegypti, higher rates of domestic collection and storage of water that would provide habitat in urban areas, and growing human populations in northern Australia. Past and recent successful control initiatives in Australia lend support to the idea that well resourced and functioning surveillance programs, and effective public health intervention capabilities, are essential to counter threats from dengue and other mosquito-borne diseases. Models projecting future activity of dengue (or other vector-borne disease) with climate change should carefully consider the local historical and contemporary data on the ecology and distribution of the vector and local virus transmission.
Asunto(s)
Clima , Dengue/epidemiología , Aedes , Animales , Australia/epidemiología , Dengue/transmisión , Reservorios de Enfermedades/estadística & datos numéricos , Humanos , Insectos Vectores , Control de Mosquitos , Vigilancia de la PoblaciónRESUMEN
In 2005, a widespread infestation of Aedes albopictus was discovered in the Torres Strait, the region between northern Australia and New Guinea. To contain this species, an eradication program was implemented in 2006. However, the progress of this program is impeded by the difficulty of morphologically separating Ae. albopictus larvae from the endemic species Aedes scutellaris. In this study, three real-time TaqMan polymerase chain reaction assays that target the ribosomal internal transcribed spacer 1 region were developed to rapidly identify Aedes aegypti, Ae. albopictus, and Ae. scutellaris from northern Australia. Individual eggs, larvae, pupae, and adults, as well as the species composition of mixed pools were accurately identified. The assay method was validated using 703 field-collected specimens from the Torres Strait.
Asunto(s)
Aedes/clasificación , Aedes/genética , Estadios del Ciclo de Vida/genética , Reacción en Cadena de la Polimerasa/métodos , Animales , ADN Intergénico/genética , Larva/clasificación , Larva/genética , Óvulo/clasificación , Pupa/clasificación , Pupa/genética , Sensibilidad y Especificidad , Especificidad de la EspecieRESUMEN
OBJECTIVES: To describe the epidemiology of Ross River virus (RRV) infection in the endemic Darwin region of tropical northern Australia and to develop a predictive model for RRV infections. METHODS: Analysis of laboratory confirmed cases of RRV infection between 01 January 1991 and 30 June 2006, together with climate, tidal and mosquito data collected weekly over the study period from 11 trap sites around Darwin. The epidemiology was described, correlations with various lag times were performed, followed by Poisson modelling to determine the best main effects model to predict RRV infection. RESULTS: Ross River virus infection was reported equally in males and females in 1256 people over the 15.5 years. Average annual incidence was 113/100 000 people. Infections peaked in the 30-34 age-group for both sexes. Correlations revealed strong associations between monthly RRV infections and climatic variables and also each of the four implicated mosquito species populations. Three models were created to identify the best predictors of RRV infections for the Darwin area. The climate-only model included total rainfall, average daily minimum temperature and maximum tide. This model explained 44.3% deviance. Using vector-only variables, the best fit was obtained with average monthly trap numbers of Culex annulirostris, Aedes phaecasiatus, Aedes notoscriptus and Aedes vigilax. This model explained 59.5% deviance. The best global model included rainfall, minimum temperature and three mosquito species. This model explained 63.5% deviance, and predicted disease accurately. CONCLUSIONS: We have produced a model that accurately predicts RRV infections throughout the year, in the Darwin region. Our model also indicates that predicted anthropogenic global climatic changes may result in an increase in RRV infections. Further research needs to target other high-risk areas elsewhere in tropical Australia to ascertain the best local climatic and vector predictive RRV infection models for each region. This methodology can also be tested for assessing utility of predictive models for other mosquito-borne diseases endemic to locations outside Australia.