You ought to be excited to see scientists launch 750 million genetically engineered mosquitoes this 12 months


Mosquitoes are probably most people’s least favorite insect.

Mosquito-borne diseases include malaria, yellow fever, and the Zika virus, all of which can lead to extreme illness, birth defects, or death. According to the World Health Organization, malaria kills over 400,000 people each year, while dengue kills around 20,000 people.

Vaccines have been developed for dengue, malaria and Zika, but production can be very slow and result in poor effectiveness. Drugs can help but can be expensive. Insecticides are successful in the short term, but mosquitoes can become resistant, and mass-release insecticides can have health effects on plants and wildlife.

Instead, others have turned their attention to the treatment of the mosquitoes, not the symptoms: they have genetically modified the mosquitoes themselves to produce only sterile offspring, effectively wiping out an entire population of insects. Modern genetic modification techniques are fast and work on the scale of genes – but they mimick plant breeding, which has focused on the human phenotype since the beginning of history (such as the selective breeding of plants that humans have practiced since agriculture was invented ).

GM mosquitoes are successful in reducing mosquito populations and spreading disease

There are two general approaches to creating genetically modified mosquitoes: 1) altering the reproductive ability of male mosquitoes so that they cannot produce offspring, and 2) altering both male and female mosquitoes so that they are disease resistant or not spread to others can transmit species. Oxitec, the biotechnology company behind a genetically modified (GM) mosquito, Aedes aegypti, has tested the first approach to GM mosquito release in field trials in parts of Brazil, the Cayman Islands and Malaysia. These male mosquitoes mate with a woman and exchange a gene mutation that causes the larvae to die if they are not given antibiotics. These studies have shown that mosquito populations are reduced by 80-95% and cases of dengue fever are reduced by 91%.

GM mosquitoes are successful in reducing mosquito populations and spreading disease. However, there are still many scientific questions that have not been fully answered, including public health concerns, mosquito resistance risks, and the environmental impacts associated with genetic modification of a wildlife. Many people believe that genetic changes are against the natural order of the world, or that we do not know all of the possible results for the release of modified organisms into the environment.

And the skeptics are right: GM crops, originally thought to reduce our need for pesticide applications, have increased herbicide applications in the face of the development of resistant weeds and insect pests. In the case of genetically modified maize, which targets the European European corn borer pest known as Bt maize, resistance has increased pesticide use by around 7% over a period of 15 years.

A map of dengue fever in the US as of August 2020, including outbreaks in Puerto Rico, Texas, Florida, and Wisconsin

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Studies testing the safety of genetically modified plants are widespread, but the public often sees these announcements from large companies like General Mills aiming to sell a genetically modified product. In a 2014 Pew Research Center poll, only 37% of adults believed genetically modified foods were safe to eat, and only 26% believed genetically modified foods were safe to eat when they state having less scientific knowledge than their peers. Still, several science and health organizations have classified genetically modified crops as safe for human consumption.

But what does all this uncertainty about genetically modified crops mean for genetically modified mosquitoes? Oxitec is currently the first and only company approved to release genetically modified mosquitoes. As of 2009 (but not announced until 2010), 3 million genetically modified mosquitoes were released in the Cayman Islands to respond to high pesticide resistance in the US mosquito population. In response to the increase in the Zika virus in the country, the Brazilian National Biosafety Committee approved the release of genetically modified mosquitoes in Juazeiro, northeastern Brazil, in 2015. The trials were successful and Oxitec concluded that the modified mosquitoes reduced dengue mosquito populations by 95%.

It’s important to note that Oxitec wasn’t the first to change insect genetics for population control. The genetic approach to making insects sterile or disease resistant is based on the Sterile Insect Technique (SIT). SIT was developed in the 1930s to help reduce insect populations. The technique makes male insects sterile by exposing them to extremely high levels of radiation before they are released to mate with females. The technique is a great success: it eliminates several types of pests such as the screwworm in the 1950s, and from 1967 onwards it reduced the populations of the pink bollworm moth in California.

A workflow that describes the proposed phases for the development, testing and release of genetically modified mosquitoes

A workflow that describes the proposed phases for the development, testing and release of genetically modified mosquitoes

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After the success of the first trials, Oxitec had another release of genetically modified mosquitoes in 2015 in Jacobina, Bahia, Brazil. Approximately 450,000 mosquitoes were released weekly for 27 months, developed using a strain from Cuba that was crossed with a strain from Mexico. The Brazilian studies had little or no setback in the region. Many residents believed that the genetically modified mosquito caused a decrease in dengue fever cases and limited the success of the Zika virus spreading.

In 2012, Oxitec filed with the EPA in the US to release the modified insect – which contains a gene in genetically engineered male mosquitos that would spread to offspring at the larval stage and kill them – following dengue fever outbreaks in the Florida Keys over the years 2009 and 2010. When the public found out about the possible experiment, a petition on garnered over 100,000 signatures against the project (over 235,000 today). Many skeptics point to Oxitec’s rush to use genetically modified mosquitoes in their first attempts on Cayman Island – without properly consulting the public.

Due to public pressure, Oxitec scrapped their original release mechanism that would allow female mosquitoes to escape from the release capsule. Instead, they developed a rebranded version of mosquito technology called “friendly mosquito technology”. The new genetically modified mosquito is programmed in such a way that only men are released from an Oxitec capsule in water and not the biting women. The “safe” name refers to the fact that male mosquitoes don’t bite, so the company’s release wouldn’t increase female mosquito numbers.

A map showing the range of Aedes aegypti in the US and the indigenous reservations, covering most of the south and southwest of the US

A map showing the reach of Aedes aegypti in the United States and the indigenous reservations

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But environmental groups are still unhappy. Many believe that the manipulated mosquitoes are still endangering the Floridians, and fear that the spread of modified genes from male mosquitoes into the wild mosquito population could cause cascading effects on the food chain. Birds, insects and mammals feed on mosquitoes. Environmentalists are concerned about the possible effects genes can have on these organisms. Many scientists have speculated that eliminating the mosquito would affect other creatures, but others are hesitant to encourage the targeted extinction of a species.

There are other ways to reduce mosquito-borne diseases as well. A nonprofit organization in Brazil known as Eliminate Dengue is working to breed mosquitoes that are less likely to spread disease. The group is focused on breeding mosquitoes to continue a widespread and naturally occurring parasite in mosquitoes, wolbachia, which has been shown to inhibit the mosquito’s ability to spread viruses such as dengue or chikungunya. Eliminate Dengue, funded by the Gates Foundation, has released these mosquitoes in 40 areas around the world. The parasite persists in the population and reduces the need to release modified mosquitoes year after year.

The majority of scientists believe that genetically modified mosquitoes pose no risk to human health. However, the possibility of hybridization between genetically engineered mosquitoes and wild mosquitoes, where the genetically modified genetics are passed on to wild populations and into the ecosystem, is of concern to many.

The potential good can outweigh the potential bad. But with EPA approval and test releases of genetically modified mosquitoes slated for the Florida Keys and Texas, the future is already here. Only time – and the dates – will tell.

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