Welcome to our first e-newsletter for the Eliminate Dengue project. As our project moves forward we are actively looking for different ways to communicate with people about our project, its progress and future plans. This newsletter is one of these methods and complements other approaches like public meetings, our traditional newsletter, media spots and our website www.eliminatedengue.com. Currently our project is on track to move to field testing in North Queensland, Australia in January 2011. This depends critically on government regulatory approval and community support. We are very interested in hearing from people about our progress and especially any concerns people may have and would encourage people to contact us at j.sutton1@uq.edu.au.

I hope you find this newsletter useful in keeping you updated and answering some of your questions.

Scott O'Neill
Head, School of Biological Sciences
The University of Queensland

Scientific updates

The Eliminate Dengue team has been working hard to discover more about the biology of the Dengue transmitting mosquito, Aedes aegypti. A summary of the work that is being undertaken in laboratories across the world can be found here.

The scientific work has resulted in the publication of 20 papers in prestigious international scientific journals such as Cell, Nature, Science and Proceedings of the National Academy of Science. Copies of all papers produced by the Eliminate Dengue team can be downloaded here.

Here are some of our published results so far.

• The lifespan of female mosquitoes is halved when it is infected with the wMelPop strain of Wolbachia, a naturally occurring bacterium found in fruitflies. This reduction in lifespan is important, because many mosquito-borne diseases are only transmitted by older mosquitoes. (view PDF)
• Mosquitoes infected with Wolbachia have a greatly reduced ability to carry viruses that cause human disease, including Dengue and Chikungunya. They also have a lower chance of being infected with malaria parasites. (view PDF)
• The age of mosquitoes is critically important in predicting their ability to carry disease, so we have developed a new method to identify the age of field caught mosquitoes using transcriptional profiling. (view PDF)
• We have documented large variation in the number of mosquitoes occupying houses in central Vietnam, from just a few to more than 40. Interventions to reduce the number of naturally occurring mosquitoes will be required before releasing Wolbachia infected mosquitoes to ensure mosquito numbers remain at acceptable levels for householders.
  (view PDF)

Over the coming months much of our scientific work is focused on:

• Undertaking mathematical modelling to better understand Wolbachia dynamics and the predicted impact on disease transmission
• Continuing to obtain data on biosafety aspects
• Characterizing different Wolbachia strains in the mosquito to determine which is likely to be most effective at preventing dengue transmission
• Completing experiments in large outdoor field cages to determine how well Wolbachia spreads into breeding populations of mosquitoes

Responding to your questions – Can Wolbachia be transferred to people?

During the process of talking to people about our project we frequently hear a common question – “Is it possible for Wolbachia to be transferred to people when a mosquito bites and if so is it safe for people?”

As scientists we have felt quite relaxed about the safety of Wolbachia for people since we know that it already occurs naturally in many types of mosquitoes that commonly bite people and there are no negative effects on people as a result of Wolbachia. We also allow mosquitoes containing Wolbachia to bite members of our research team on a routine basis. Mosquitoes need to take blood in order to mature their eggs – that is why they bite people. In the laboratory we need to allow our mosquitoes to bite us in order to get eggs from them. We have now maintained Aedes aegypti mosquitoes containing Wolbachia as part of this project for more than 4 years in the laboratory and they bite members of our research team regularly. In fact we estimate that some members of our team have been bitten hundreds of thousands of times without any ill effects for the researchers.

However we understand that this is a key concern for the general public and after listening to this question come up many times in consultation meetings we have gone back to the lab and undertaken a number of new experiments to generate additional information around this issue. First we used advanced microscopy techniques to determine where the Wolbachia was located in the mosquito and we did find evidence of it in a number of tissues including the salivary glands of the mosquito. So we looked more closely and did a very tedious experiment. We collected the spit of many mosquitoes and tested it for the presence of Wolbachia DNA to see if there was any evidence of Wolbachia in the mosquito saliva. We couldn’t find any Wolbachia DNA in mosquito spit – meaning that Wolbachia was not being transferred to people when mosquitoes bite. We realized later that the reason for this is because the Wolbachia bacterium is too big to travel down the salivary gland ducts in the mosquito. It would need to be a quarter of its present size to be able to do this. This result was recently published in a scientific paper available for download here if you would like to read it.

Recently we have done one more experiment to conclusively show that Wolbachia isn’t transferred to people when mosquitoes bite them. We took blood samples from a range of volunteers that had been allowing mosquitoes containing Wolbachia to bite them in the lab – in some cases many thousands of bites - and we looked in the blood for antibodies that would recognize Wolbachia. Humans make antibodies against foreign molecules when they are introduced into our bodies as a natural part of our immune system function. So if Wolbachia or even small parts of dead Wolbachia were being introduced into people when mosquitoes bite we would expect people to make antibodies that would recognize Wolbachia. However our experiments, which are still in the process of being finalized, are showing no evidence of any anti-Wolbachia antibodies being produced. This is very strong evidence that Wolbachia is not entering the human body.

Finally there is no evidence of Wolbachia being able to grow in warm blooded animals – so even if Wolbachia did enter the human body in a very rare situation we would not expect it to be able to grow in the person – it is really a bacterium that is exquisitely adapted to living only in insects. We have also been undertaking other experiments in response to people’s questions and concerns that have been raised with us in public meetings. In the next newsletter I will tell you about the results of some other experiments we have been doing that have been addressing the issue of how safe Wolbachia is for the environment and whether it might transfer into other animals that eat mosquitoes containing Wolbachia. The news is good – there looks to be no evidence that this will occur - more later.

Ecological risk assessments

The Eliminate Dengue Team is planning a trial release of Wolbachia infected Aedes aegypti in Cairns during the 2010-2011 wet season. Because of the novel nature of this project, an independent risk analysis has been undertaken by CSIRO to evaluate whether the risks and hazards associated with the release will ‘cause more harm’ to both people and the environment than naturally occurring Ae. aegypti.

The risk analysis process was undertaken over a 10 month period and involved a series of workshops and meetings with both expert scientists and the general community to capture all possible hazards that might be of concern, estimate the likelihood of these hazards occurring over a 30 year time period and finally the consequences if they did occur. The risk analysis is not balanced by the potential benefits that might occur from a successful release such as reduced dengue transmission, less disease, increased quality of life and reduced financial burden on the health system. Similarly the risk analysis did not consider whether the release might actually lead to reduced dengue transmission. Instead it was focused exclusively on the possibility that the release might lead to adverse consequences that would be more harmful than the current situation in Australia. A panel of national and international experts reviewed the final risk analysis to ensure that it was undertaken with appropriate methodology, was comprehensive and rigorous.

The risk analysis considered 50 different hazards that were finally grouped into 30 main hazards. These included the possibility that a release of Wolbachia containing mosquitoes might be harmful to humans, might represent harm to the environment in a number of different ways, through to the possibility that the release might harm the economy of the area and even housing values. Of the different hazards evaluated the one considered to be of most concern was the possibility that the release of Wolbachia containing Aedes aegypti might lead to a perception problem within the community that the dengue problem had been solved, which in turn might lead to reduced effort into controlling the mosquito in the environment. Hazards associated with direct effects on human health and the environment were all considered negligible. The final analysis concludes that the overall risk presented from a release into the environment of Wolbachia containing Aedes aegypti is negligible.

A copy of the full report can be downloaded here from our project website.

Australian regulatory approval process

It is fundamentally important to the Eliminate Dengue project that we receive formal regulatory approval within Australia prior to undertaking any field-testing here or later in Vietnam and Thailand.

As a first step in this process the University of Queensland Institutional Biosafety Committee has formally evaluated our proposal, the CSIRO risk analysis and obtained independent advice. It has now formally approved the conduct of field-testing from a safety perspective. Further to this, we have engaged with the Queensland Chief Scientist and Queensland Chief Biosecurity Officer who are guiding us through the government regulatory process at the present time. The National Arbovirus and Malaria Advisory Committee (NAMAC) in Australia have been briefed on this research project and have written a letter of support acknowledging the significant benefit to human and animal health of the Wolbachia method. Our aim is to inform all regulatory bodies, ensuring full transparency and an opportunity to provide feedback and eventual formal approval for a field release in North Queensland.

We are aiming for regulatory approval within the next few months so that we can begin planning for future field-testing in the Cairns region during the next wet season.

Update from Vietnam

The community engagement component of the Eliminate Dengue Project in Vietnam has been underway since mid-2009 and progress has been encouraging. The community living in the potential pilot release site have been enthusiastic about the promise of better health through the elimination of dengue. The project has been conducting targeted focus group and 1-on-1 interviews with Tri Nguyen Island and surrounding area inhabitants, as well as distributing education materials in the form of posters, leaflets and brochures. There is a high level of support for the project with the expectation that we inform and educate the majority of the households before a release is undertaken. The project also learned about the concerns of the community, most of which we have been able to answer to their satisfaction. Intense community engagement will continue for the next six months, with the expectation that the community will support field testing on their island.

Vector Competence experiments have been underway since March after delays in receiving ethical approval were resolved. Project staff will conduct the experiments at the Tropical Disease Hospital in Ho Chi Minh City, in collaboration with the Oxford University Clinical Research Unit. Blood will be taken from consenting viraemic patients and fed to Wolbachia infected mosquitoes to test for viral interference to confirm results from Australian trials. The experiments are due to be completed in May.

Experiments to test for the horizontal transfer of Wolbachia to predators of mosquito larvae such as fish and copepods were undertaken in 2009. These experiments concluded that there was no evidence of lateral transfer to the predator upon digesting Wolbachia infected larvae. This is an important result as many rural Vietnamese households store water in containers around the house that contain either copepods or fish. Householders have raised concern that they may be infected with Wolbachia through digesting copepods that have eaten Wolbachia larvae, so this experiment should allay these fears.

Further information

Please visit our website www.eliminatedengue.com, or contact Jenny Sutton for more information.