What according to you is the most dangerous animal on our planet?
If the number of people killed by the animal annually gives is a tangible measure of its threat, then you might be surprised to know that the most dangerous animal on the planet, responsible for more than half a million deaths per year is the MOSQUITO. When it comes to killing humans, no other animal even comes close.
You weren’t expecting that were you?
Take a look at this infographic-
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What makes the tiny mosquito the deadliest animal on this planet?
Despite their innocuous-sounding name, the fact that they transmit devastating diseases that create a global impact and affect between two to three million people annually makes them deadly. The list of diseases caused by mosquitoes includes major names like Zika Virus, Dengue, Malaria, Chikungunya, etc. The rapid spread of these diseases has always called for a need to address the issue of their population growth and strategize ways to deal with the associated pandemics.
Oxitec, a British biotechnology company, founded at the Oxford University specializes in creating genetically modified mosquitoes and similar genetic methods to control insect pest population. Their contention is that reduction in mosquito population to a particular controllable level will slash down the occurrence of diseases transmitted by them and help prevent massive outbreaks.
Why do we need genetically modified mosquitoes?
The recent sporadic spread of the Zika virus and the not-so-uncommon outbreak of dengue in South-East Asian countries have proven that traditional methods like spraying pesticides and fogging to control the breeding of mosquitoes were not effective, these methods have in fact proved harmful to people and environment in some cases. So what can we do to have a large scale counteraction against any mosquito outbreak?
Genetic modification of specific mosquito vectors is an active technological area wherein we use the natural instincts of mosquitoes to restrict their reproduction. Gene altering techniques are used to modify certain traits of the mosquitoes.
Oxitec is one of the pioneering companies working in this domain to solve the problem of growing population of Aedes Aegypti.
How will genetically modified mosquitoes lead the fight against wild mosquitoes?
All the Aedes Aegypti-borne diseases are spread by only female mosquitoes and NOT by the male ones!
According to the technique, the male mosquitoes are dosed with genes making them sterile.
‘Sterile’ here means that males can produce sperms and fertile the female egg but with the offspring which will die in the early stage of development.
These sterile genetically modified mosquitoes are released in the environment as a part of a radical approach where these males mates with females (which usually happens once in the lifespan of female) resulting in dramatic suppression of their population growth.
Oxitec is parenting this technique by eliminating the need for damaging irradiation thus by overcoming the drawbacks of Sterile Insect Technique (SIT) previously used.
Sterile Insect Technique
This is a pretty old technique that has been used over the ages to get rid of many farm pests. In this technique, the males of the target species are radiated, and its progeny is weakened. The offsprings produced after mating with the natural females were made to die within a period of time. In this way, the population is controlled. But irradiation does not work with mosquitoes as it weakens the male species. The females don’t choose to mate with these irradiated male counterparts, and the whole objective is compromised.
Oxitec follows the same technique, but instead of using radiation to sterilize the male mosquitoes it uses gene replacement techniques. The gene added into the mosquitoes produces a protein that stops their cells from functioning normally. Thus the modified mosquitoes die before reaching adulthood.
The gene produces a protein known as tTA (tetracycline-repressible activator variant), which is a special kind of protein that can act as a switch that controls the activity of other genes. When inserted into an insect (they work only with insect cells) the protein causes other genes of the insect to stop expressing themselves, and this causes the mosquito to die.
Then to propagate this breed into the wild, they use an antidote called tetracycline which suppresses the gene that produces tTa. These mosquitoes then reproduce with the females, and the offspring die early , since they do not have access to the antidote outside of the laboratory.
This technique is species specific affecting only the target pest by not harming other insects and ecosystem. The protein does not affect other animals if the mosquito were to bite them or they were to eat the mosquitoes. It also has no effects on vertebrates. (Source)
What is Oxitec doing differently?
Oxitec’s genetically modified mosquitoes do not have to be irradiated as mentioned above, they are fit and healthy replicas of natural wild male mosquitoes. Like all natural male mosquitoes, Genetically modified mosquitoes will seek out wild females to mate. And unfortunately, it will be tough for Aegypta and her friends to find the difference between the two!
There are two kinds of techniques that can be used to create genetically modified mosquitoes. Their classification is on the basis of the desired result.
| Population Suppression | Population Replacement |
| Oxitec is working on this technique. In this approach, the mosquito is genetically re-engineered using Sterile Insect Technique to die before reaching mating period. This makes the process “self-limiting” as Oxitec calls it. The gene does not stay in the environment and does not propagate. The objective is to control the population of mosquitoes in target areas. | In this approach, the gene treatment technique directly modifies the insect so that the disease-carrying parasites become nontransferable. Here the aim is to change the genetic make-up of the wild species permanently. |
Should we be worried about any side effects arising out of breeding genetically modified mosquitoes?
The term ‘genetically modified’ rings alarm bells for many of us trepidation. There has always existed a controversy with regards to genetically modified crops or GMO food products. So it is understandable that we would, by extension, apply the same filter when we speak about genetically modified mosquitoes. But this is different. Genetically modified crops were meant to get greater yield and better harvests. They were in a way, supposed to mimic and speed up the natural order of things. GM mosquitoes, comparatively, are designed to inhibit certain traits, and its effects are highly precise and controlled. Moreover, the use of these techniques is always monitored and regulated by local government agencies as well as international committees (Source). They do not allow the testing phase to even begin without proper studies of all possible scenarios.
The genes inserted into the mosquito do not pass onto humans. The protein produced by the GM mosquito is nontoxic and not found in their saliva. Therefore the overall technique is safe.
Has this method been tested anywhere so far?
The approach has proved successful in trials in South America. This project is one step closer to reality because the FDA’s Center for Veterinary Medicine could not find any significant impact on human health and environment post field trials conducted in Cayman Islands and Brazil against dengue mosquitoes. Oxitec’s genetically modified mosquitoes achieved a 90% reduction in dengue mosquitoes in these areas. (Source). Thus the National Technical Commission of Biosecurity approved the commercial release of Oxitec’s GM dengue mosquito.
The current increase in the number of Zika virus cases has brought the study of engineering genetically modified mosquitoes into the spotlight. With proper guidelines in place by environmental agencies and with local governments monitoring of the trials, this technique could save countless lives.
Check out these short videos to get more insight into Oxitec’s technology.
