Ecology of Arboviruses and Their Vectors in Australia. In: Lal R, Stewart BA, editors. Soil Restoration. New York: Springer; 1992. pp. 1-36. [DOI: 10.1007/978-1-4612-4688-6_1]

Land Use Influences Mosquito Communities and Disease Risk on Remote Tropical Islands: A Case Study Using a Novel Sampling Technique

Land use changes, such as deforestation and urbanization, can influence interactions between vectors, hosts, and pathogens. The consequences may result in the appearance and rise of mosquito-borne diseases, especially in remote tropical regions. Tropical regions can be the hotspots for the emergence of diseases due to high biological diversity and complex species interactions. Furthermore, frontier areas are often haphazardly surveyed as a result of inadequate or expensive sampling techniques, which limit early detection and medical intervention. We trialed a novel sampling technique of nonpowered traps and a carbon dioxide attractant derived from yeast and sugar to explore how land use influences mosquito communities on four remote, tropical islands in the Australian Torres Strait. Using this technique, we collected > 11,000 mosquitoes from urban and sylvan habitats. We found that human land use significantly affected mosquito communities. Mosquito abundances and diversity were higher in sylvan habitats compared with urban areas, resulting in significantly different community compositions between the two habitats. An important outcome of our study was determining that there were greater numbers of disease-vectoring species associated with human habitations. On the basis of these findings, we believe that our novel sampling technique is a realistic tool for assessing mosquito communities in remote regions.

Isolation of arboviruses from mosquitoes (Diptera: Culicidae) collected from the Gulf Plains region of northwest Queensland, Australia

As part of investigations into Japanese encephalitis (JE) virus and related flaviviruses in northern Australia, 153,529 mosquitoes were collected and processed for virus isolation from the Gulf Plains region of northwest Queensland. Collections from within 30 km of each of the townships of Croydon, Normanton and Karumba yielded 3,087 (2.0%), 66,009 (43.0%), and 84,433 (55.0%) mosquitoes, respectively, from which 16 viruses were isolated. Four isolates of Murray Valley encephalitis (MVE), two of Kunjin (KUN), three of Ross River (RR), and one of Sindbis (SIN) viruses were obtained from Culex sitiens subgroup mosquitoes. Molecular identification of the mosquito species composition of these virus positive pools revealed that most isolates were from pools containing mainly Culex annulirostris Skuse and low numbers of Culex palpalis (Taylor). Only three pools, one each of MVE, KUN, and RR, were from mosquitoes identified exclusively as Cx. annulirostris. Other viruses isolated include one Edge Hill virus from Ochlerotatus normanensis (Taylor), an isolate of SIN from Anopheles meraukensis Venhuis, two isolates of RR from Anopheles amictus Edwards, and single isolates of RR from Anopheles bancroftii Giles andAedes lineatopennis (Ludlow). The isolate of RR from Ae. lineatopennis was the first reported from this species. The public health implications of these isolations in the Gulf Plains region are discussed briefly.

Ross River virus: ecology and distribution

Ross River virus is the most common mosquito-borne pathogen in Australia, and approximately 5000 human cases are reported annually. The infection is not fatal, but there is considerable morbidity associated with a debilitating polyarthritis that is the major symptom. The virus is annually active in most regions of Australia, but exists as strains that vary in virulence. Native macropods are thought to be the natural vertebrate hosts, although horses and humans may be involved during epidemic activity, and vertical transmission of the virus occurs in mosquitoes. Different mosquito species are involved as vectors in various regions and in different seasonal and environmental conditions. In coastal areas the saltmarsh mosquitoes Aedes camptorhynchus and Ae. vigilax are the most important vectors in southern and northern regions, respectively, whereas in inland areas Culex annulirostris is the most important vector, although various Aedes species can be involved depending on region and conditions, and the epidemiology of the disease and vector control imperatives vary with circumstance concomitantly.

Arboviruses associated with human disease in Australia

Mosquito-borne arboviruses are an important public health issue in Australia. The alphaviruses Ross River and Barmah Forest virus are widespread and active annually, and cause debilitating polyarthritis. The flaviviruses Murray Valley encephalitis, Kunjin and Japanese encephalitis virus are restricted in distribution and activity but may cause life-threatening illness, and dengue viruses are active in some areas.

Mosquito-borne arboviruses in Australia: the current scene and implications of climate change for human health

Of the mosquito-borne arboviruses, the encephalitic Murray Valley encephalitis and Kunjin viruses are a major public health concern, but the arthritides Ross River and Barmah Forest viruses are more important in a public health sense, being responsible for a far greater number of infections. Reported cases of Ross River totalled approximately 30,000 during 1991-1996; there have been several widely separated outbreaks of Barmah Forest in recent years and case reports are increasing annually. Surveillance programmes have increased our understanding of the geographic regions, climatic conditions and vector factors associated with viruses. Virus activity is widespread but is often localised, is driven primarily by mosquito abundance and various species are involved; host factors are involved also, but are not well understood. Typically, mosquito populations are governed by availability of habitat and environmental conditions. Models of climate change predict increases in rainfall, tides and temperature for parts of Australia, and such changes have the potential to increase the risk of arbovirus transmission by increasing the distribution and abundance of vectors, and duration of mosquito and arbovirus seasons. However, the amplitude of climate change is uncertain and the ecology of arbovirus transmission is complex. It is likely that some areas will have increases in arbovirus activity and human infection with predicted climate change, but risk of increased transmission will vary with locality, vector, host and human factors.