Mosquitoes: The Problem and Solution

May 25, 2021 | Alexandra Rodrigues and Marinanicole Miller | Outbreak News

Beyond the pestilence of itchy bites, mosquitos play a critical role in the ecosystem at the bottom of the food chain, and their lesser known role as pollinators [1].  The itchy bites they leave behind are notable as it is through these bites that they transmit infectious diseases such as dengue, yellow fever, malaria, and Zika virus, among others.  As carriers of disease, or vectors, they help these viruses infect millions of people and kill approximately 725,000 people, annually [2].  

As climate change progresses, tropical mosquito species invade previously uninhabitable places.  As temperatures rise, warmth-seeking mosquitoes migrate further north, away from the equator, putting nearly half a billion more people at risk for contracting the viruses they carry in the next 30 years [4].  Places that were threatened by yellow fever-carrying mosquitos throughout four months of the year in 2019, may be threatened for seven months of the year by 2050 due to the expected increase in temperature in these places [3]. In the U.S., southern states may see this dramatic increase much sooner. Florida is experiencing a dramatic increase in West Nile virus, eastern equine encephalitis, Zika virus, chikungunya, and dengue, which was thought to be eliminated from the U.S. decades ago [4].   

Just last month, the Florida Keys received genetically modified mosquitoes as part of a pilot program intended to reduce the Aedes aegypti female population*, and therefore limit their ability to transmit deadly diseases such as dengue, yellow fever, and Zika virus [5].  This is the first time a genetically modified mosquito program has been piloted in the U.S.  Oxitec, a British-based biotechnology firm, is responsible for engineering these male Aedes aegypti that pass on a gene that kills female offspring before they mature [5].  Their male offspring then pass on the altered gene as they mate throughout life. Previously, fumigation from trucks and helicopters were used to limit these mosquito populations; however, these traditional methods have become less effective [5]. Now, about a month after placement, the mosquito eggs are hatching tens of thousands of genetically modified mosquitoes [6].

The genetically-modified organism (GMO) solution raises concerns among some environmentalists and local residents, who feel that the long-term consequences of this type of program are unknown and potentially catastrophic to the ecosystem [6].  Supporters of this program, including the Food and Drug Administration (FDA) in 2016 and later the Environmental Protection Agency (EPA) in 2020, cite similar projects that had a success rate of over 90% in Brazil, Panama, the Cayman Islands, and Malaysia [5,6]. Furthermore, the Aedes aegypti species is invasive in these areas and therefore not needed in their ecosystems.  Removing an invasive species is not known to have a negative environmental impact [5].

The long-term goal of this program is to reduce disease transmission of Zika, dengue, and yellow fever. If successful, Oxitec will present their results to the EPA and ask for authorization to use these mosquitoes in other parts of the U.S. They may also consider expanding to other species such as the Aedes albopictus, which also transmits dengue virus in Florida [5].  This pilot program is an exciting look at the future of controlling insect-borne disease transmission and understanding the widespread epidemiological consequences of climate change.

*only female Aedes aegypti bite and spread disease