Wolbachia is common in our environment - May 2010
Wolbachia occurs naturally in the environment living inside the cells of many insect species and being passed from one generation to the next inside the insect egg. If you would like to see some examples of common Australian insects that naturally contain Wolbachia click here
New study independently confirms virus interference - April 2010
A new study just published in PLoS-Pathogens provides independent confirmation of our results that were recently published in Cell. Zhiyong Xi and colleagues at Michigan State University show that Aedes aegypti mosquitoes infected with a different strain of Wolbachia than the one our studies are focused on also blocks dengue infection in the mosquito [PDF]
Risk Analysis on the Australian release of Aedes aegypti containing Wolbachia
– March 2010
A comprehensive risk analysis of releasing Wolbachia infected Aedes aegypti into the Australian environment has now been completed by the CSIRO. The report concludes that there is negligible risk that Aedes aegypti containing Wolbachia would “cause more harm” than the current Australian situation. A plain English summary can be found here [Summary] or you can download the complete report [Full Report]
A Wolbachia Symbiont in Aedes aegypti Limits Infection with Dengue, Chikungunya, and Plasmodium – December, 2009
In a recent scientific breakthrough published in the journal Cell, our team has shown that Wolbachia infection directly inhibits the ability of a range of human pathogens to infect Aedes aegypti. This Wolbachia-mediated pathogen interference effect will work synergistically with the life- shortening strategy proposed previously to provide a powerful approach for the control of insect transmitted diseases - a very exciting discovery. [Article] [PDF] [supplemental data] [Video Summary]
Other science results supporting our approach - October 2009
An interesting paper was published in 'Science' in October 2009 that has bearing on our program. Dr Steve Sinkins from Oxford University used Wolbachia infected Aedes aegypti to show that they were resistant to the nematode that causes lymphatic filariasis. The idea that Wolbachia infected mosquitoes are resistant to a range of human pathogens will be useful to control a range of diseases in addition to dengue. [Article] [PDF]
Cairns Risk Assessment Workshop on Release of wMelpop Aedes aegypti - 17-18 September, 2009 A risk assessment of the proposed release of Ae. aegypti carrying wMelpop Wolbachia is being undertaken by the CSIRO. They held an expert opinion workshop in Cairns in September with the aim of combining scientific and community opinion on the likelihood of different hazards occuring in the project. This data is being modelled to evaluate the risk of a pilot release and the risk that wMelpop Ae. aegypti will increase the likelihood of harm beyond that currently being experienced.
Wolbachia Infection Reduces Feeding ability in the Dengue Fever Mosquito - August 2009
We have shown that the blood feeding behaviour of Ae. aegypti is altered by the presence of Wolbachia infection. As the Wolbachia infected mosquitoes age, it becomes more and more difficult for them to obtain blood from a human host. When these mosquitoes are examined closely it appears that their proboscis (mouthpart structure) does not function correctly. Instead of successfully inserting their stylet into the skin, the entire proboscis bends in half when the infected female mosquito presses it against human skin. This change in feeding may further reduce the time window of a female mosquito's life when she could transmit dengue virus. (See Project Publications page publication link.) [Video]
Cytoplasmic incompatibility(CI) in populations with overlapping generations - The mathematics of the project, August 2009
CI-causing infections produce a frequency-dependent reproductive advantage for infected females. However, many such infections impose fitness costs, such as life-shortening, that lead to unstable equilibrium frequencies below which the infections tend to be eliminated. An idealized model of overlapping generations with age-independent parameters produces a simple expression showing how the unstable point depends on the population growth rate, the intensity of CI, and the infection's effects on development time, longevity and fecundity. (See Project Publications page publication link.)
Community Engagement - ESC Grant, July 2009
Recently our community engagement activities have expanded in Vietnam through the award of an additional grant from the University of Toronto that is focused on our Ethical, Social and Commercial activities in this country. The first introduction workshop was held in Hanoi on Tuesday 28 July to educate senior Ministry of Health officials on the concepts and future planning of the Wolbachia project.
Regulatory Approval - June, 2009
We have begun the process of obtaining Australian government regulatory approval for an open field test of the Wolbachia method. This has involved the commissioning of an independent and comprehensive risk assessment report by CSIRO in Australia. This risk assessment will form the basis of our submission to State and Federal government agencies for regulatory approval to begin field testing of the method.
Characterization of the Aedes aegypti population on an island field site in Vietnam - Friday, February 06, 2009
We have now assessed the long-term seasonal abundance and spatial distribution of Ae. aegypti as a precursor to the development of a vector control strategy based on the release of Wolbachia transinfected mosquitoes. For the small island field site of approximately 600 households, we estimated an upper Ae. aegypti population size of 26,000 adult female mosquitoes. Therefore, for a Wolbachia-based intervention, we envisage that multiple, broad scale releases from numerous locations in the village (as opposed to a few, focal releases) will most likely be required – this will counteract any spatial heterogeneity, dampen the effect of transient key premises and enhance movement rates of Wolbachia.
Life-shortening Wolbachia transferred to Aedes aegypti - Friday, January 02, 2009
Research describing the stable introduction of a life-shortening Wolbachia infection into the primary dengue vector Aedes aegypti was published in this week’s edition of Science (2 January 2009). This milestone piece of work conducted by researchers at The University of Queensland used embryonic microinjection to successfully generate two lines of Aedes aegypti each carrying heritable life-shortening Wolbachia bacteria. The Wolbachia infection halves mosquito lifespan under laboratory conditions, and induces strong cytoplasmic incompatibility needed for the bacteria to spread into natural populations. These two infected mosquito lines are currently being mated in the laboratory to a genetically diverse Aedes aegypti populations from Australia and Vietnam in preparation for their use in contained field cage trials to further evaluate the efficacy of our proposed strategy.
Application of popcorn Wolbachia for the control of other diseases - Wednesday, November 12, 2008
Studies are underway to determine if life-shortening Wolbachia strains can be introduced into Anopheles farauti, a mosquito vector of malaria. This work will allow us to evaluate this strategy for use against malaria, a major source of mortality and morbidity throughout the tropics. Initial experiments are being carried out to determine if life-shortening Wolbachia can co-exist with other strains of Wolbachia in Drosophila flies. These studies will help determine the likely outcome of introducing life-shortening Wolbachia into mosquito species that are naturally infected with other strains of Wolbachia.
How does Wolbachia cause life-shortening in insects - Monday, November 03, 2008
In order to identify which gene or genes are responsible for the life-shortening induced by popcorn Wolbachia in mosquitoes, we have now sequenced the complete genome of the popcorn Wolbachia using next generation sequencing technologies. This sequence is now being compared to other Wolbachia genomes currently available, in particular those of related strains which are not able to reduce insect lifespan. This comparative analysis will allow the identification of the genetic basis of life-shortening.
Wolbachia shown to directly interfere with RNA virus replication in insects - Wednesday, October 22, 2008
In a new discovery published in Science in Oct, 2008 22(5902):702 it is shown that the presence of Wolbachia in fruitflies leads to a reduction in viral replication when flies are challenged with pathogenic RNA viruses. This exciting result might have implications for our project. If Wolbachia infections in mosquitoes result in reduced replication rates of dengue viruses, this should act to increase the extrinsic incubation period, and act synergistically with the proposed life-shortening strategy. Experiments with mosquitoes are currently underway to see if the results generalize to Aedes aegypti.
Improvement of age-grading methodologies - Friday, October 10, 2008
Being able to determine the age of wild-caught mosquitoes is crucial in order to assess the efficacy of our life-shortening approach and the success of mosquito control strategies. In follow-up work from our recent studies (Cook et al.2006 PNAS) we have used microarray analysis to identify additional novel gene candidates that show a strong transcriptional relationship with age. This work represents an improvement to the age-grading model developed previously in the lab and will soon be evaluated in the field.
Development of new mosquito age-grading technique - Thursday, November 16, 2006
A new method for age-grading mosquitoes using transcriptional profiles was published this month in the Proceedings of the National Academy of Science. This work was the result of collaboration between research groups at The University of Queensland, Queensland Institute of Medical Research and James Cook University. The development and evaluation of this method was an early milestone for this project and a valuable technique for the broader mosquito research community.