General

	Q. What are the symptoms of dengue and how is it treated? A. Dengue fever is a severe flu-like illness. Infants and young children exhibit a non-specific fever with a rash. Older children and adults may have a mild fever or rapid onset of the classical disease with high fever, severe headache, muscle and joint pains and rash. Dengue haemorrhagic fever (DHF) is a potentially fatal complication of dengue fever that is characterised by high fever and internal haemorrhaging which may lead to circulatory failure and death if untreated. Currently, there are no specific treatments or vaccines for dengue fever. Patients with DHF require hospitalisation for careful monitoring and may need fluid replacement therapy to maintain circulatory fluid volume. Dengue is a notifiable disease in Australia. This means that confirmed cases of dengue are reported to the Notifiable Disease Database System in each state and from there to the Communicable Disease Network Australia and the national database. This reporting process plays a significant role in tracking and controlling dengue fever in your community. If there is an outbreak in your area or you suspect that you have contracted dengue fever please see your doctor. For more information on dengue fever see http://www.health.qld.gov.au/dengue/ Follow this link to see a video that explains the symptoms and transmission cycle of dengue fever. http://www.who.int/tdr/diseases/dengue/lifecycle.htm
	Q. Where does dengue occur? A. Dengue fever is endemic (maintained within a particular population without the need for external inputs) in over 100 countries across Southeast Asia, the Western Pacific, Central and South America, Africa and the Eastern Mediterranean. It is estimated that 40% of the world’s population is at risk of dengue infection. Each year, up to 100 million people are infected with dengue worldwide with as many as 25,000 deaths from the disease annually. The most serious dengue epidemics occur in Southeast Asia and the Western Pacific, however, epidemic dengue activity is increasing in the Americas and the Caribbean. Although dengue often occurs in economically impoverished regions, it is by no means restricted to so-called third-world settings, as recent outbreaks in Singapore and Cairns demonstrate.
	Q. Is Dengue a serious health risk in Australia? A. Although dengue fever is not endemic on the Australian mainland, over the last 20 years outbreaks have occurred with increasing frequency in far north Queensland and the islands of the Torres Strait. Dengue fever is brought into Australia by people who have visited or reside in regions where the disease is present. Since the 1980s all four dengue serotypes (or ‘strains’) have been introduced to north eastern Australia. In 2004, there were two fatalities from dengue haemorrhagic fever (DHF) in the region, the first in almost a century. Dengue is a debilitating disease and a serious health risk and there is some concern that it may become endemic in Australia. The most recent outbreak of dengue fever was in Cairns in January-March 2008 with 22 confirmed cases (as of May 2008).
	Q. How do mosquitoes transmit dengue to humans? A. The transmission cycle for dengue fever is human to Aedes mosquito to human. A female mosquito may acquire the dengue virus after ingesting blood from a person infected with dengue. Over the next 10 days, the virus replicates inside the mosquito’s body, until it reaches its salivary glands. At this stage, the mosquito is able to pass the dengue virus to humans. The dengue virus is injected into the person with the mosquito’s saliva when the mosquito bites (takes a blood meal). After being bitten by a dengue-carrying mosquito, it can take between 4 and 13 days for the person to get dengue fever (DF).
	Q. Do all mosquitoes spread dengue viruses? A. Dengue viruses are transmitted to humans through the saliva of female Aedes mosquitoes, primarily Aedes aegypti and Aedes albopictus, when they bite (take a blood meal). The mosquito generally acquires the virus while feeding on the blood of an infected person. Because the virus must incubate in the mosquito’s body before the insect can transmit it to another person, only mosquitoes aged about 12 days or older can transmit dengue fever to humans.
	Q. Are the mosquitoes that transmit dengue fever native to Australia? A. Aedes aegypti and Aedes albopictus are the two main mosquito vectors (transmitters) of dengue fever. Aedes aegypti is found throughout central and northern Queensland and in the Torres Strait. Aedes albopictus has been found in recent years in the Torres Strait. Although these mosquitoes are not native to Australia, the Aedes aegypti or dengue mosquito has been living in Australia for over 100 years.
	Q. What is Wolbachia? A. Wolbachia pipientis is a naturally occurring bacterium which can be found in over 20 percent of all insects, but does not infect humans or any other vertebrates. Wolbachia is commonly found in Australian arthropods such as butterflies, flies, ladybirds, beetles, wasps, spiders, etc, that commonly live in association with humans in their backyards and houses and play a beneficial ecological role. There are a number of different types (strains) of Wolbachia each with a unique biology. A great deal of research has been undertaken over the years, exploring the effects of the bacterium on the invertebrates that carry it. In this project we are working with the popcorn strain of Wolbachia pipientis
	Q. Why is it worthwhile conducting research aimed at introducing Wolbachia pipientis into mosquito populations? A. There is currently no vaccine for dengue fever and dengue outbreaks are increasing worldwide and in Australia at disturbing rates. The mobility of human populations is helping to bring strains of the virus into regions where it was not previously present. Prevention strategies commonly involve large scale applications of insecticide that are not only expensive to maintain but often carry considerable environmental risks and concerns. A second arm of these strategies is the role of the public in the management and removal of potential breeding sites (pot plant bases, tyres, buckets etc) from their yards, homes and businesses. Although these strategies have been in place for some time, dengue fever outbreaks are occurring with increasing frequency in northern Queensland. We hope that by using Wolbachia pipientis to reduce the lifespan of the mosquitoes that transmit dengue, we could potentially eliminate the old mosquitoes in the population, those which are able to transmit the dengue virus.
	Q. How is this research being funded? A. This research is being funded by the Bill and Melinda Gates Grand Challenges in Global Health Initiative. (http://www.gatesfoundation.org/GlobalHealth/BreakthroughScience/GrandChallenges/default.htm). This initiative is aimed at solving diseases that affect the developing world. In June 2005, 43 projects were chosen to receive a total of US$440 million over five years. Our international research team comprises laboratories from Australia, Japan, USA, Vietnam and Thailand that work in different disciplines that range from mosquito/Wolbachia biology to social and epidemiological aspects of disease prevention.
	Q. What is the role of Wolbachia pipientis in combating the spread of dengue fever? A. Wolbachia pipientis is a naturally occurring bacterium which can be found in more than 20 percent of all insects. Wolbachia pipientis does not occur in or infect any vertebrates, including humans. One strain of Wolbachia (Wolbachia pipientis ‘popcorn’) was recently found to reduce the lifespan of the fruit fly, Drosophila, by up to 50 percent. Our project aims to transfer this life-shortening Wolbachia from fruit flies to Aedes aegypti, and Aedes albopictus, the mosquitoes that transmit dengue. By selectively removing the older mosquitoes in the population, those that can transmit dengue virus, this novel approach can have a significant impact on dengue transmission. Laboratory studies are currently well underway. We have been able to introduce life-shortening Wolbachia pipientis into Aedes aegypti mosquitoes by microinjecting the bacteria into mosquito embryos at the University of Queensland. The mosquitoes infected with Wolbachia pipientis ‘popcorn’ live approximately half as long as normal uninfected mosquitoes in laboratory conditions and they can successfully transmit Wolbachia to their progeny. This is crucial for the spread of the bacterium.
	Q. How will the research show that introducing Wolbachia into Aedes mosquito populations has reduced dengue fever outbreaks? A. During this project we will generate mosquitoes containing life-shortening Wolbachia pipientis, collate ecological data to determine optimal release strategies, consult with the broader community surrounding potential release options and demonstrate the application of this method in securely enclosed field cages. An important part of our research will also involve analysis of the interaction between the dengue virus and Wolbachia pipientis, to determine if the presence of Wolbachia has any effect at all in the transmission or virulence of the virus. This is the stage at which current funding for the project ends. However, if our research is successful and project funding is continued, we would move towards an implementation phase and in time the release of Wolbachia pipientis-carrying mosquitoes.
	Q. Is it safe to be bitten by mosquitoes carrying Wolbachia pipientis? A. Yes, it is safe to be bitten by mosquitoes that are infected with Wolbachia pipientis. Numerous species of Aedes and Culex mosquitoes are naturally infected with Wolbachia and people across the world and in Australia are bitten by these mosquitoes every day without any harmful effects. Other insects that commonly bite humans such as wasps can also have these bacteria. Wolbachia cannot be transmitted to any vertebrates, including humans.
	Q. What if the Aedes mosquito carrying Wolbachia-pipientis was eaten by another organism, could it be transferred? A. Wolbachia and Wolbachia pipientis have been the focus of a great deal of scientific research over the years. There are no reports of transfer of Wolbachia between infected insects and the predators that feed on them. The association between Wolbachia and insects is very old and intimate, and the transfer of the bacteria by predation is highly unlikely. The mosquito Aedes albopictus is naturally infected with a strain of Wolbachia. Despite breeding in similar containers as Aedes aegypti plus at times being eaten by Aedes aegypti, the Wolbachia infection has never transferred into this species naturally. Researchers are currently testing if the presence of Wolbachia pipientis in Aedes mosquitoes has any effect on jumping spiders and other insects that eat these mosquitoes.
	Q. Does Wolbachia pipientis live beyond the life of the mosquito? Can Wolbachia pipientis get into or survive in soil or water independently? A. Wolbachia pipientis is an obligate intracellular bacterium. That means that it can only live inside the cells of the host insect’s body, but not outside the insect body. Importantly it is for this reason that Wolbachia, unlike many other common microorganisms, cannot be cultured (grown) in the laboratory in free culture, and is routinely maintained in infected insects or in insect cell cultures, but cannot survive long in soil or water.
	Q. Are there different strains of Wolbachia? Do they have different effects? A. Yes, there are many different Wolbachia strains. These strains infect a whole range of insect species causing different effects. Some common Wolbachia strains cause crossing incompatibilities. In other words, the natural presence of Wolbachia in some male insects eliminates offspring produced by these males and non-wolbachia-carrying females. The life-shortening strain of Wolbachia that we want to use to control dengue also causes incompatibility between infected and uninfected mosquitoes and this mechanism is crucial to allow this bio-control agent to spread in dengue endemic areas.
	Q. How will the life-shortening Wolbachia spread through the mosquito population? A. Wolbachia can only be transmitted from the parent Aedes mosquito to its offspring via the female’s egg. Female mosquitoes carrying Wolbachia have an advantage compared to uninfected females, because they can reproduce either with uninfected or infected males. However, if the female mosquitoes are uninfected and mate with a male that carries the Wolbachia infection, the female eggs will not develop into adult mosquitoes. This reproductive distortion makes infected females more successful, increases their presence in the population, and in consequence allows the natural spread of Wolbachia-which is only transmitted through the eggs from generation to generation. This accelerates the spread of the Wolbachia, until the entire Aedes mosquito population carries the Wolbachia.
	Q. How long will this approach take to reduce dengue in affected communities? A. Currently, we don’t know how effective this control strategy will be. By the end of the project we should have sufficient data to predict the time taken for this strategy to have a noticeable effect on mosquito age and on dengue transmission. We are currently constructing secure cages on the James Cook University Campus where we can safely release mosquitoes in a controlled, enclosed environment similar to the natural environment in which Aedes mosquitoes actually live. These cages will be used to do controlled experiments to determine the feasibility of this disease control strategy in “natural” conditions.
	Q. What should people living in dengue-prone areas do to prevent the spread of dengue virus? A. Aedes aegypti and Aedes albopictus mosquitoes are the main vectors (transmitters) of dengue fever in Australia and are extremely adaptable to urban settings. Aedes aegypti are found in reasonable numbers from the islands of the Torres Strait to Mackay and west to Emerald. It is suspected that they are also located further south. Aedes albopictus were recently found in the Torres Strait. In urban areas storage of water in rainwater tanks and other urban water sources such as old tyres, palm fronds, blocked gutters, tarpaulins and litter provide excellent habitats for Aedes mosquito larvae. Because of this, individual householders and business owners have a vital role to play in preventing the spread of dengue in their region, by removing containers that might collect water and be a suitable habitat for Aedes mosquito larvae. There is currently no vaccine for dengue fever.
	Q. Are all populations of Aedes mosquitoes the same genetically? A. Mosquito populations can be quite different genetically, even in areas geographically close. We can use genetic markers to identify how closely related are the mosquitoes from different areas. There is genetic variation in mosquito populations that may affect the spread of Wolbachia. As such, we are currently undertaking a series of experiments to address this question. We are introducing Wolbachia to local mosquitoes that are adapted to the north Queensland environment and surveying its effects in laboratory and cage experiments. Furthermore, population surveys in north Queensland suggest that the situation is ideal for an application of Wolbachia.
	Q. Will climate change, temperature change or humidity effect the successful transference of Wolbachia pipientis through the mosquito population? A. Climate change, temperature and humidity changes are likely to affect the outcome of the Wolbachia pipientis strategy. We are currently undertaking a series of experiments exploring the effects of high temperatures on the lifespan of Aedes mosquitoes – including those carrying Wolbachia pipientis.
	Q. Could this approach be used for other mosquito-transmitted diseases? A. Yes, this strain of Wolbachia could potentially reduce the lifespan of other disease carrying mosquitoes. Collaborating researchers are currently attempting to transfer the life-shortening strain of Wolbachia into mosquitoes that transmit malaria, lymphatic filariasis and Ross River fever. Given the serious nature of these diseases internationally, this would be a considerable break through.
	Q. Why is this approach better than insecticides? A. Some people may ask, why not eliminate the mosquitoes that transmit dengue all together as was done in the past with insecticides? The life-shortening Wolbachia pipientis control strategy is a form of biological control and should be self-sustaining due to the unique ability of Wolbachia to spread into mosquito populations. In addition to reducing the current use of insecticides, (which harm a large range of insects, including those that are beneficial to agriculture for example) the successful application of this life-shortening approach is much more targeted, focusing only on the mosquitoes that transmit dengue. The mosquitoes will still be able to feed, mate, breed and play their role in the environment, but wont live to an old age and this should lead to large reductions in the occurrence of dengue fever.
	Q. Does reducing the lifespan of the Aedes mosquitoes affect the environment? A. Aedes mosquitoes mate mostly 2-3 days after they emerge and can blood feed by day 2-4. After 6-8 days they can lay eggs, so the younger Aedes mosquitoes produce the majority of the reproductive output of a mosquito population. Therefore, removal of the oldest individuals from the population, by modifying mosquito lifespan, should not significantly reduce the overall size of the mosquito population. As such mosquitoes will continue to be present in the environment and will still contribute to specific roles in natural ecosystems.
	Q. What roles do the Aedes mosquitoes play in the environment? A. The main role that mosquitoes play in the environment is as food for other insects and invertebrates (for example, spiders and dragonflies) which in turn are food sources for reptiles, amphibians, birds, small mammals and so on.
	Q. How can we be assured that, once introduced artificially (via micro injection) into Aedes aegypti mosquitoes, Wolbachia pipientis won’t be transmitted from there to other species, with unforeseeable consequences? A. The transmission of Wolbachia between insect species is thought to occur very rarely in nature due to the bacteria’s intracellular lifestyle. Wolbachia lives inside the cells and tissues of their hosts, and cannot survive outside them. This close association makes it almost impossible for the bacteria to be transmitted to other insect species.
	Q. Will the Wolbachia pipientis introduced to Aedes mosquitoes mutate or change over time? Will the mosquitoes become resistant to Wolbachia over time? Will it make them more fit, creating some kind of super mosquito? A. Several international research groups involved in this project are currently investigating the effects of the Wolbachia pipientis infection on mosquitoes, by looking at their longevity, reproduction, fitness, ability to transmit dengue, biting behavior, etc. All these parameters will be crucial to our understanding of the biology of Wolbachia pipientis and whether its presence will make the mosquitoes more or less robust than those without Wolbachia. We are sequencing the complete genome of the life-shortening Wolbachia ‘popcorn’ strain, so we will be able to have genetic markers to determine any genetic change occurring in the bacteria.
	Q. When will the mosquitoes containing life-shortening Wolbachia be released into the environment? A. Upon completion of this project we aim to have achieved the following key milestones. 1. produced the necessary lines of mosquitoes containing life-shortening Wolbachia, 2. collated the necessary ecological data to determine optimal release strategies, 3. consulted with the broader community surrounding potential release options and 4. demonstrated the application of this method in securely enclosed field cages. The project is currently funded up until (but not beyond) this point. Once this information is collected we hope to be in a position to determine if this biological control strategy should move to an implementation phase.

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