Mosquitos might be as useless as they are annoying

The recent release of genetically modified mosquitos in Florida and Brazil with the goal of eradicating disease vectors has sparked a debate – how important are mosquitos to the ecosystem, and will their absence have a ripple effect on the rest of the environment? To answer this question, it’s essential to understand where these disease vectors came from, and how long they have been there.

In 2009, over four weeks, 19,000 of the first genetically modified Aedes aegypti mosquitos were released in the Cayman Islands. Aedes aegypti, commonly known as the yellow fever mosquito, spreads dengue, chikungunya, and Zika.

The company Oxitec developed male mosquitos carrying a gene that results in lethality during the larval or pupal life stage. In theory, this would mean that any wild female mated with a genetically modified male would produce non-viable offspring, reducing mosquito populations and thus reducing disease.

In 2013, 450,000 of the same genetically modified male Aedes aegypti were released over the span of 27 months in Jacobina, Brazil, and in 2021, 144,000 were released in the Florida Keys.

In 2022, 2.4 billion Oxitec mosquitos were approved for release in Florida and California. It is clear that genetically modified mosquito-release programs are gaining more popularity, and we will likely see not only more but new releases across the world to combat mosquito-borne disease. And not without reason, previous release programs have significantly reduced mosquito populations.

However, when most people hear that over a billion genetically modified animals will be released, there is rightful cause for concern. As a graduate student working on mosquitos, many of my daily conversations revolve around mosquitos, and in 2021, when genetically modified mosquitos were released in the USA for the first time, almost all of my conversations with friends and family revolved around that. But what was surprising to me was that their concerns were not about hypothetical mutations or increases in mosquito populations but about the potential environmental impact eliminating a mosquito species may have.

 During our early education, most of us were taught that every living thing has a place in the ecosystem and that removing one species could collapse the entire network. But what if the species wasn’t supposed to be in that network in the first place? What if humans introduced them? Many disease-carrying mosquito species in the Americas are a relatively new addition.

Aedes aegypti, the primary disease carrier in Florida, makes up only 4% of the mosquito population. The species originated in West Africa and was introduced to the Americas 400-550 years ago. After its introduction from West Africa to the Americas, Aedes aegypti spread worldwide due to trade routes.

The first documented yellow fever outbreak in the Americas occurred in Barbados and the Yucatan Peninsula in 1647, and the first dengue outbreak did not occur until 1780 in Philadelphia. The Malaria vector Anopheles gambiae was not introduced to the Americas until 1930, when it was found in Brazil and was likely also carried on trade ships from West Africa.

USA efforts to control mosquito populations began in 1904, and in 1947, the Pan American Sanitary Bureau instated a program to reduce Aedes aegypti populations. During the 27-year effort, Aedes aegypti was declared eradicated from 18 continental countries in the Americas. However, since then, mosquito populations have been on the rise again.

Aedes aegypti was thought to have diverged from its nearest ancestor around 16 million years ago, likely somewhere in the southwestern Indian islands, and moved to Africa 85,000 years ago. In the history of Aedes aegypti existence, it has only been in the Americas for .003% of that.

However, an animal’s short presence in an area doesn’t mean it cannot become embedded in the food chain. The question is, has Aedes become essential to its environment in the Americas? While many believe mosquitos are an indispensable food source for several animals, such as fish, birds, frogs, bats, and other insects, how vital mosquito species are to an area is poorly studied.

However, no current literature indicates that Aedes aegypti, or any other pathogen-spreading mosquito, is a primary food source for any predator.  This is likely because mosquitos have such low nutritional value that most animals find it worthless to expend the energy trying to catch them.

Aedes aegypti’s history is so closely tied to humans that most pathogen-spreading Aedes aegypti are typically found around manufactured structures. Aedes aegypti dwelling in human settlements prefer human blood over any other animal. The mosquito has also adapted to laying eggs in manufactured structures such as tire wells and flowerpots and will seek out artificial structures over natural ones. Much like dogs and cats, the mosquito species has been domesticated and relies on humans for food and shelter.

            Additionally, while some mosquitos are important pollinators due to Aedes aegypti’s close association with humans, most of the flowers they encounter are in someone’s garden, typically trafficked by much better pollinators such as bees. While Aedes communis, a close relative of Aedes aegypti, is an important pollinator of the blunt-leaf orchid, Aedes aegypti itself has not been documented to be vital to the life of any plant.

Aedes aegypti spread deadly pathogens that affect millions of people across the world. Current vector control methods, such as transgenic mosquitos, are working to reduce this pathogen spread. Although in reality, we will likely never be rid of the pesky mosquito, if we were to wake up tomorrow and my wish was to be granted that these mosquitos disappeared from the earth, I doubt anyone would miss them.