GMO Mosquitoes: Will Zika Change the Equation?

As the Zika virus outbreak continues and mosquito season in this hemisphere approaches, there will be a ramp up in vector control activities. These activities are aimed at reducing mosquito populations and are practiced for several types of mosquitoes, most notably those that spread West Nile Fever. However, even prior to the Zika outbreak, because of the threat of dengue and chikungunya, aggressive campaigns against Aedes mosquitoes had taken place in certain areas such as Texas, Hawaii, and Florida.

Florida, which has had several instances of local transmission of both dengue and chikungunya, has been a national leader in mosquito control as exemplified by the Key West Mosquito Control District. Over the past years, faced with a continual threat of dengue, the use of Oxitec's sterile male genetically modified mosquitoes to reduce Aedes aegypti populations has been contemplated as a means to augment ordinary mosquito control operations. 

However, in today's context, "genetically modified" evokes an unjustified Frankenstein/Jurassic Park horror in many people and has stalled release of these mosquitoes in the US (they have been part of trial releases in the Cayman Islands, Panama, and Brazil).

Given this context, pre-Zika, my colleagues and I sought to understand how the public conceives of GMO mosquitoes and what their support or opposition is influenced on. To meet this aim we fielded surveys to residents of a Florida community in which the release of these mosquitoes is being contemplated. PLoS Currents Outbreaks just published the results of that work.

There were several findings that we found particularly striking:

  • Being a female was significantly associated with being opposed to the use of GMO mosquitoes
  • Having never known anyone with chikungunya or dengue was significantly associated with opposition to use of GMO mosquitoes

The 2nd finding is what I deem the most important, as it reflects the role of risk assessment on an individual level and will likely change as people's threat assessment changes. A headline-grabbing virus like Zika may be just the threat that will cause people to think differently about GMO mosquitoes -- something that is already happening.

We hope to follow this paper with a follow-up post-Zika study of the same area as well as explore the mechanics and public health communication strategies used in the Cayman Islands, Panama, and Brazil. Additionally, it will be important to put GMO mosquitoes firmly in the tradition of such endeavors as the eradication of the agricultural screwworm pest, irradiated sterile mosquitoes, and Wolbachia-infected mosquitoes.

It is the role of public health authorities and physicians to help calibrate the general public's analysis and our hope is that this paper can help move the discussion of GMO mosquitoes further forward.


Will Dengue Unravel the Mystery of Zika?

One of the puzzles about Zika virus and its newly discovered penchant to cause fetal anomalies is understanding why these facts about Zika are being noticed now given relatively large outbreaks of the virus that occurred in Micronesia and French Polynesia. In those outbreaks, complications such as Guillain-Barre Syndrome were noted but not microcephaly was noted (French Polynesia recently reported 8 microcephaly cases from their outbreak).

One tantalizing hypothesis which is gaining evidence is the role of preexisting dengue antibodies. Dengue, a flavivirus like Zika, has the ability to cause severe disease by employing preexisting antibodies to one strain to enhance infection with another. This phenomenon is known as antibody-dependent enhancement and was discovered by Dr. Scott Halstead who, early on, thought this was playing a role with Zika.  

Now, evidence is beginning to be presented that shows that this may be more than a hypothesis. A pre-publication paper published by researchers at Florida Gulf Coast University illustrates that dengue monoclonal antibodies and immune sera both have the potential to enhance Zika infection in a cell culture model. 

These preliminary findings were pathbreaking in their own right but yesterday at the Cura Zika symposium at the University of Pittsburgh's School of Public Health a leading Zika researcher at the institute presenting some extremely important data on this phenomenon that deserve a wide audience.

Dr. Ernesto Marquez, working out of Recife, presented data illustrating that in Brazil -- as opposed to Southeast Asia and other other areas in which dengue and Zika co-circulate --monotypic infection is much more common. What this means is that Recife women are more likely to have been infected with just 1 (out of 4 strains) of dengue than in Thailand where multi-typic infection is the norm. DENV-3 is the 

What Marquez noted in his data was the almost unique association of DENV-3 to enhance infection. There is much more to this presentation and much nuance to how these antibodies work (for example, their quantity) so I suggest watching it online. It is a great example of how scientific analysis proceeds. 

The obvious policy question that comes to mind is how would the dengue vaccine, approved for use in Brazil, Mexico, and the Philippines, interact with Zika? Would it foster antibody dependent enhancement? Or would it be protective? Other questions to answer would involve looking at case-control data between dengue-naive and non-naive pregnant women who are infected and assessing how their clinical courses may differ. 

Nonetheless, science is advancing quite rapidly on this fascinating virus.