Brazilian city expands use of genetically engineered mosquitoes to combat Zika, dengue

A program to release genetically engineered mosquitoes as a way to control mosquito borne diseases has been expanded by the Brazilian city of Piracicaba and the British company Oxitec. Following approval by Brazil’s National Biosafety Committee Piracicaba is the first city to trial using the mosquitoes, which cause insect populations to crash by passing on a gene that causes offspring to die when they mate with wild insects. The company produces engineered Aedes aegypti mosquitoes which are thought to be the main carrier of the Zika virus which is sweeping through South and Central America, and are the main carrier of diseases like dengue fever and chikungunya. 

 

Dr. David O’Brochta, Professor of Entomology, University of Maryland (webpage):

Expertise: genetic technologies for use in insects and the application of those technologies to explore the physiology and genetics that make some mosquitoes excellent vectors of human pathogens

“Oxitec’s Aedes control technology involves the release of sterile male mosquitoes that are incapable of biting and taking blood from people and are not directly involved in transmitting pathogens. The biological basis of this biological control strategy is well understood and similar strategies have been used for decades for insects mainly of agricultural significance. That Oxitec’s approach involves the use of genetically altered mosquitoes makes it unique but not particularly risky since the insects released are sterile. The company has been using their technology on relatively small scales and has met with some success specifically in Brazil.

“While I am not specifically familiar with the status of Aedes aegypti and dengue and Zika viruses in Piracicaba, and cannot comment on whether Oxitec’s approach is the best among all available options and whether it is integrated into a larger vector control effort within the city, I do not think that Oxitec’s expansion of their area of operation is surprising and in my opinion is generally an encouraging sign that this and related genetics-based technologies for the control or local elimination of mosquitoes is moving towards the mainstream. For those vector and molecular biologist who have been developing and working with genetic technologies over the last couple of decades, it is nice to see the horizon change and genetics-based control strategies involving genetically manipulated insects become real tools to combat challenging problems.

“Area wide control using sterile insect and related approaches require the sustained production and release of insects to effect change in the size of the target population. These operations are quite specialized, requiring factories capable of producing large numbers of insects and systems for distributing and releasing them. These approaches could certainly be of value in controlling mosquitoes in some locations within the United States and the cost-benefit ratio is changing as patterns of distribution of mosquitoes like Aedes aegypti and the viruses they transmit change. The success of Oxitec’s efforts in Brazil could go a long way in helping to counter certain misconceptions about mosquito genetic control technologies involving genetically altered insect by showing that it can be effective and not necessarily risky or dangerous.”

 

Dr. Peter W. Atkinson, Divisional Dean of Life Sciences, Professor of Genetics, College of Natural and Agricultural Sciences, University of California, Riverside (webpage):

Expertise: genetics of medically and agriculturally important insects; molecular-based strategies to genetically control pest insects.

“The focused development of genetic-engineering approaches in insect pest control is almost two decades old since the demonstration that pest insects could be repeatedly genetically transformed. The past five or so years has seen the start of the translation of these genetic technologies into the field, with the example of the Oxitec technology being perhaps the best example of these decades of development coming to fruition.  I believe genetic engineering-based approaches to insect control will simply increase over the next decade as a) we acquire deeper genomic information about these pest insects, b) precise gene-editing tools such as CRISPR-Cas9 augment and extend the genetic tools that can be deployed, c)  the desire for approaches which are specific for the pest species and environmentally friendly increases, and d) as the need for sustainable and rapid solutions to insect pest control in medicine and agriculture increases as crop production and human health issues caused by pest insects increase in a shrinking and changing world.”

 

Dr. Heidi E. Brown, Assistant Professor, Department of Epidemiology and Biostatistics, Mel & Enid Zuckerman College of Public Health, University of Arizona (webpage):

Expertise: epidemiology and control of vector-borne and zoonotic diseases, Dr. Brown studies diseases transmitted by Aedes aegypti and Aedes albopictus mosquitoes.

“The idea of releasing sterile or other modified insects to compete with wild type has shown some success in the past. It is an intense operation where these modified, competing mosquitoes will need to continue to be released in order to keep the wild type population down. 

“Let’s see what history tells us: the screwworm sterile insect eradication program is from the 1950s and has been successful at protecting livestock in the U.S. Oxitec has been working on their technique for Aedes aeygpti for years and have gone through multiple iterations. So, given that the idea has been around for a very long time but examples of successful implementation are sparse, I don’t think it is a silver bullet and needs to be considered with other interventions like source reduction and individual protection. Moreover, the sustainability of the methods needs to be considered: once the disease rates go down we tend to shift our attention and the vector populations build back up. We did a fairly decent job of Aedes aegypti control in the 1950s, but with the problem ‘solved’ efforts were shifted and the vector returned.

“There are two primary vectors of dengue, chikungunya and Zika: Aedes aegypti and Aedes albopictusAedes aegypti is still considered a more efficient dengue vector, but Aedes albopictus is considered to be a more efficient chikungunya vector. Where they co-exist, they are competitors for similar breeding habitat, so, elimination of Aedes aegypti begs the question of what will happen to Aedes albopictus. Oxitec has some great modelers on their team, so I am sure they are looking at it.”

 

Dr. Thomas W. Scott, Distinguished Professor of Entomology and Epidemiology, University of California, Davis (webpage):

Expertise: The ecology, epidemiology, and prevention of vector-borne disease.

“Oxitec is making significant progress in the development and application of their transgenic strain OX513A of Aedes aegypti for disease prevention. This mosquito is the principal vector of multiple, increasingly important diseases; i.e., dengue, chikungunya, Zika and urban yellow fever. Their strategy is based on the release of genetically modified males that mate with wild females causing death in progeny before they become adults. This kills mosquitoes before they can reproduce or transmit a virus and reduces the overall mosquito population.

“Oxitec has directed considerable effort at successfully addressing concerns about risk and carried out increasingly larger and more complicated field trials. Trial results to date are encouraging, reporting impressive reductions in mosquito populations that are consistent with reduction in risk of human infection and disease.

“It will be helpful if future trials can demonstrate disease reduction, determine that the strategy can be scaled-up to modern mega-cities with millions of people, establish sustainability of disease reduction, verify cost effectiveness, and lead to discussion about how this approach can be integrated with other control methods that already exist or are currently in development. Today’s announcement that Oxitec will expand their productive collaboration in Brazil is an encouraging step forward in the global fight against Aedes-transmitted disease.”

 

 

Reference:

Oxitec announcement: http://www.oxitec.com/oxitec-vector-control-solution-in-brazil-attacking-source-of-zika-virus/

 

Declared interests (see GENeS register of interests policy):

Dr. David O’Brochta: “I have no financial or professional relationships with Intrexon/Oxitec other than knowing some of the staff through mutual attendance at scientific conferences over the years.”  

Dr. Peter W. Atkinson: “I have no conflicts of interest other then undertaking research on the genetic engineering of insects but in an academic environment.  I do not have, nor have had, any links with Oxitec or the company that bought it. 

Dr. Thomas W. Scott: “I collaborated with Oxitec in a research project that studied a different genetically modified strain of Aedes aeypti than OX513C. Our collaboration ended during 2013. I serve on the Vector Control Advisory Group (VCAG) for the World Health Organization (WHO), which serves as an advisory body to WHO on new forms of vector control for malaria and other vector-borne diseases. Oxitec submitted an application to VCAG during the time that I was on the committee.”

No further interests declared.

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