Littérature scientifique sur le sujet « Aedes camptorhynchus »

SUMMARYIn Australia, Ross River virus (RRV) is predominantly identified and managed through passive health surveillance. Here, the proactive use of environmental datasets to improve community-scale public health interventions in southeastern Tasmania is explored. Known environmental drivers (temperature, rainfall, tide) of the RRV vector Aedes camptorhynchus are analysed against cumulative case records for five adjacent local government areas (LGAs) from 1993 to 2009. Allowing for a 0- to 3-month lag period, temperature was the most significant driver of RRV cases at 1-month lag, contributing to a 23·2% increase in cases above the long-term case average. The potential for RRV to become an emerging public health issue in Tasmania due to projected climate changes is discussed. Moreover, practical outputs from this research are proposed including the development of an early warning system for local councils to implement preventative measures, such as public outreach and mosquito spray programmes.

The mechanisms driving dynamics of many epidemiologically important mosquito-borne pathogens are complex, involving combinations of vector and host factors (e.g., species composition and life-history traits), and factors associated with transmission and reporting. Understanding which intrinsic mechanisms contribute most to observed disease dynamics is important, yet often poorly understood. Ross River virus (RRV) is Australia’s most important mosquito-borne disease, with variable transmission dynamics across geographic regions. We used deterministic ordinary differential equation models to test mechanisms driving RRV dynamics across major epidemic centers in Brisbane, Darwin, Mandurah, Mildura, Gippsland, Renmark, Murray Bridge, and Coorong. We considered models with up to two vector species (Aedes vigilax, Culex annulirostris, Aedes camptorhynchus, Culex globocoxitus), two reservoir hosts (macropods, possums), seasonal transmission effects, and transmission parameters. We fit models against long-term RRV surveillance data (1991–2017) and used Akaike Information Criterion to select important mechanisms. The combination of two vector species, two reservoir hosts, and seasonal transmission effects explained RRV dynamics best across sites. Estimated vector-human transmission rate (average β = 8.04x10-4per vector per day) was similar despite different dynamics. Models estimate 43% underreporting of RRV infections. Findings enhance understanding of RRV transmission mechanisms, provide disease parameter estimates which can be used to guide future research into public health improvements and offer a basis to evaluate mitigation practices.

SUMMARYRoss River virus (RRV) is a mosquito-borne virus endemic to Australia. The disease, marked by arthritis, myalgia and rash, has a complex epidemiology involving several mosquito species and wildlife reservoirs. Outbreak years coincide with climatic conditions conducive to mosquito population growth. We developed regression models for human RRV notifications in the Mildura Local Government Area, Victoria, Australia with the objective of increasing understanding of the relationships in this complex system, providing trigger points for intervention and developing a forecast model. Surveillance, climatic, environmental and entomological data for the period July 2000–June 2011 were used for model training then forecasts were validated for July 2011–June 2015. Rainfall and vapour pressure were the key factors for forecasting RRV notifications. Validation of models showed they predicted RRV counts with an accuracy of 81%. Two major RRV mosquito vectors (Culex annulirostris and Aedes camptorhynchus) were important in the final estimation model at proximal lags. The findings of this analysis advance understanding of the drivers of RRV in temperate climatic zones and the models will inform public health agencies of periods of increased risk.

A major contributor to the transmission of vector-borne disease in many countries are mosquitoes that emerge from saltmarshes. This is particularly the case for Australia, where saltmarsh mosquitoes are arguably the most important for vector-borne infections. The saltmarsh habitat influences the distribution, abundance and success of adult mosquitoes. This occurs through the intrinsic nature of environmental and ecological factors in saltmarshes and can also be impacted by anthropogenic factors. In this thesis, my research is focused on Aedes camptorhynchus, the temperate mosquito vector of Ross River virus (RRv); the most prominent and ecologically important vector-borne disease in Australia. Understanding the diversity of saltmarsh habitats and the ecology of saltmarsh mosquitoes within these habitats has potential to improve mosquito vector management and human disease. I conducted a high-level scoping review of research literature undertaken on saltmarsh mosquito vectors in Australia (Chapter 2). I found that saltmarsh ecology, in particular the ecology of saltmarsh mosquito vectors, is poorly understood partly due to the expanse and diversity of saltmarsh habitats across the country, and the number of vectors involved in the transmission of disease. I emphasise the utility of ecological health and ecosystem function with respect to human health, vector management and the need for greater knowledge surrounding local saltmarsh ecology and mosquito vector dynamics. In Chapter 3, I conducted a comparative study between three superficially similar temperate saltmarshes to identify how environmental conditions and aquatic invertebrate assemblage influence mosquito vector abundance. I identified distinct differences in mosquito assemblage between saltmarsh systems and seasons. Environmental variables were dominant in predicting mosquito numbers and vegetation (samphire) cover was ubiquitous among saltmarshes in predicting first instar mosquito abundance. Aquatic conditions differed in ability to predict the numbers of Ae. camptorhynchus first instars or pupae. The abundance and diversity of aquatic invertebrates contrasted between saltmarsh habitats. Saltmarshes with the least anthropogenic disturbance had greater aquatic invertebrate diversity and fewer vector mosquitoes. This work demonstrates the value in understanding natural saltmarsh aquatic ecology in the context of vector ecology and saltmarsh ecosystem health. Having identified ecological differences among saltmarsh systems and their influence on vector abundance, I (Chapter 4) conducted a fine-scale field evaluation of the saltmarsh with the highest density of mosquito vectors to determine specific environmental drivers and locations of mosquito egg distribution. I determined that vegetation, particularly samphire (Sarcornia quinquiflora), was preferred by Ae. camptorhynchus for oviposition relative to shrubby glasswort (Tecticornia arbuscula), runnels and bare soil. No correlation between aquatic invertebrates, tidal connectivity, soil moisture and elevation on oviposition habitat selection was found. I discovered that this saltmarsh was less influenced by regular tidal inundations relative to rainfall, resulting in dryer habitat conditions. By understanding oviposition habitat selection and factors determining hatching success we can improve vector surveillance, and management efforts can be more targeted and efficient. Lastly (Chapter 5), I investigated if a prominent ostracod micro-crustacean affected local populations of Ae. camptorhynchus. My aim was to identify if Ae. camptorhynchus competed with this abundant microcrustacean leading to changes in development and survival or if the main limitation was resources. I found that the most limiting factor for Ae. camptorhynchus survival and development was resources, rather than competition. When resources were limited it resulted in delayed mosquito development, decreased larval survival and smaller emergent adult mosquitoes. Of these three parameters only adult mosquito size changed when food resources were abundant and ostracod density increased, resulting in decreased adult mosquito size. I conclude that underlying effects of non-culicid aquatic interactions on mosquito development and survival are context dependent and could have the potential to impact vector-borne disease transmission. In summary, the work presented in this thesis has contributed to a greater understanding of the ecology of mosquitoes in saltmarshes. This research demonstrates the complexity of superficially similar saltmarsh systems and how detailed knowledge of these systems can inform vector surveillance and management; and how aquatic invertebrate interactions within saltmarsh systems may influence vector mosquito abundance, distribution, and potentially disease transmission. The contributions I have made to temperate saltmarsh habitats and mosquito vector research provide insights into the ecology of a prominent RRv vector and the ecological significance of saltmarsh habitats. Moreover, this thesis contributes to the growing knowledge around ecosystem health, with emphasis on the requirement to understand the ecology of vectors in saltmarsh habitats and the potential impact manipulation of these habitats can have to human health through influence on vectorial abundance and life history.

In 1998, the Southern Saltmarsh Mosquito Aedes camptorhynchus (‘Campto’) was accidentally transported from Australia to Hawke’s Bay in New Zealand, from where it dispersed to another 10 localities mainly on the North Island. After an investment of NZ$70 million over 10 years, this saltmarsh carrier of Ross River virus was eradicated in a world-first program which surprised many. How did it get there? How did it spread? How did the team cope when it arrived at Kaipara Harbour, said to be the largest harbour in New Zealand? This book draws together the entire unprecedented campaign, uncovering the twists and turns and nasty surprises the team had to deal with along the way. Written in an approachable way, it also contains new unpublished technical information which will be sought after by professionals.