In the wake of the outbreak of Zika virus in French Polynesia in 2013, and most recently in Brazil in 2015, major steps in vector control have been proposed by the World Health Organisation (WHO) to eradicate mosquito populations that spread the disease. One such tried and tested method for reducing cases of Dengue fever spread by mosquitoes is the use of genetically modified (GM) male mosquitoes [1], that when mating with females produce unviable offspring that die before reaching adulthood, hence reducing the mosquito population. The reason the Zika virus has become a major concern is because there is now strong evidence to suggest that the disease causes microcephaly in the babies of pregnant women, causing decreased brain function that results in learning difficulties and often visual and hearing impairment [2].


Stakeholders that disapprove of the use of GM mosquitoes include followers of some religions, who refrain from killing or genetically modifying living beings. As well as religious opposition to the use of GM there are also animal rights groups and environmental groups that oppose the use of genetic modification.

From a deontological viewpoint it is clear that the use of GM mosquitoes is unethical and immoral. Deontology holds that decisions should be made considering the factors of one’s duties and other’s rights. It should be clear that we as humans and the dominant race have a duty to conserve the earth and its natural beings and by using GM mosquitoes to kill off an entire species goes completely against this. We also have to consider the rights of the animal. Mosquitoes are classed as pests, however they still serve a purpose in the ecosystems they are part of and as such they should be valued and their rights should be considered as stated by deontology.

From a consequential point of view there is some concern that the reduction of mosquitoes will affect the ecosystem by altering the food chain. Animals affected include insects, spiders, salamanders, frogs, lizards and even migrating birds. Mosquito larvae are also the primary food source of many species of fish, and larvae feed on decaying matter in water that hinders plant growth.


Stakeholders that approve the use of GM mosquitoes include the WHO, who proposed their use due to the spread of the Zika virus and Dengue fever and also Oxitec; the commercial company that are developing the GM mosquitoes. It is also clearly in the best interest of sufferers and potential sufferers of the Zika virus that the mosquito population is reduced. Starting in Brazil in 2015 the disease is now widespread, and affects people in South America, Central America, Mexico and the Caribbean.

When using a utilitarian approach to investigate the effects of using GM mosquitoes it hard not to prioritise the large populations of humans living in Zika virus affected countries. Whilst there are at least 15 groups working on Zika vaccines, WHO estimates that it will be at least 18 months before vaccines could be tested in large-scale trials. Vector control using GM mosquitoes would satisfy the people affected, however to also satisfy the stakeholders against the use of genetic engineering there are a number of other methods that can be used. The simplest method of preventing contraction of the disease is by using chemical repellent and covering up exposed skin, especially in the daytime when the Aedes mosquito is most active. Due to the scale of the problem, WHO suggests that using such methods and the use of fogging (spraying pesticides) is not effective enough and so vector control is necessary to a significant scale.

When exploring biological methods of vector control there are a number of methods that avoid GM mosquitoes. In El Salvador, with the strong support of fishing communities, larvae-eating fish are kept in water storage tanks and mosquitos infected with Wolbachia bacteria can be used to produce none viable eggs. This bacterium infects 60% of common animals and does not infect humans or other mammals. Male mosquitos can also be sterilised using low doses of radiation, however whilst this method worked well with eradicating screw-worms in North America, irradiated male mosquitoes are very sickly, and female mosquitoes prefer not to mate with them. Due to this problem and the difficulty of using Wolbachia bacteria, the only effective method of eradicating large populations of mosquitoes is by the use of genetic modification [3]. This is supported by environmental concerns, where above-average rainfall caused by El Niño is expected in parts of South America until May 2016, and could cause floods and increases in diseases spread by mosquitoes. With all these factors considered and the huge population affected, by using a utilitarianism approach it seems favourable to use GM mosquitoes, thereby significantly reducing the spread of disease in South America.

It is not known what the extent of damage would be done on ecosystems if mosquito populations are reduced, however it is believed that the insect would be replaced as another species thrives in its absence. Whilst there is speculation about the damaging effects of vector control, the effects of using pesticides in the environment is thought to be much worse. Research shows that birds in regions of pesticides lay less eggs than those in unaffected regions, and the effect of pesticides that wash into rivers and streams on aquatic life is often devastating.

Another major concern is the cost of research; however the Zika response proposal by the WHO estimates that the cost of vector control, research and coordination is $18.9M (£13.2M). This is considerably less than the cost of surveillance, community engagement, risk communication and care for those affected which is $36.7M (£25.7M) [14]. Welfarism states that the best action is the one that most increases economic well-being, and based on the data above it is clear that the option which most increases economic well-being would be to use the GM mosquitoes as their overall cost is half that which would be required for the other approaches.






28: Fernando Camacho, Guy Pearson, Matt Kirkland, Will Moss



  1. This is a very complex topic as so little is known about the consequences of action or inaction; the utilitarian approach is very compelling due to the benefits to those who would other wise be infected in the future, however the damage to the ecosystems is unknown, as stated in the article. To rule out GM mosquitos based upon for deontological reasoning is not straight forward as one could also argue that it is more dutiful to make the world a better place and eliminate Zika.

    I believe that because of the level on uncertainty is not possible to identify the most morally correct form of action at the moment, but if more research was undertaken into the effect on the ecosystem as well as the possibility of other alternatives in GM a more informed decision could be made. Genetically modifying mosquitos to limit their population is undoubtedly undesirable, but it has to be wrong to not to take action to eliminate Zika based on the fear of unknown repercussions.


  2. Tough topic to tackle, good job! I didn’t even know GM could be used this way.

    I think the deontological argument is flawed as I don’t believe total eradication of the mosquito is the aim of GM vector control. It can be done partially and in stages in order to assess it’s effects before continuing. It’s true that biodiversity should be conserved and food chains preserved, but we have controlled the populations of animals before and managed these concerns. If anything, non-lethal methods of vector control like GM are ethically preferable to lethal ones. The real ethical concern is the method of genetically modifying the animals, which you did not directly address.

    The ethical factors backing the use of GM mosquitoes are well presented. Often, I find myself defending GM by stating that the ethical negatives aren’t that negative. But this case really shows the ethical positives behind using this method of vector control.


  3. Your pro and con arguments are well thought out but leave me wondering about the part that natural selection has to play in it? Who are we to choose to affect the processes of the environment by genetically modifying those organisms within it? If the natural order is that this virus must spread then should we change that to suit our needs?


  4. An extremely clear presentation but I wonder whether the possibility of a vaccine in less than two years should weigh more heavily in the cons list. I am not against interfering in the natural order under any circumstances but wonder whether we should for such relatively short term gains.


  5. I believe it would be unethical not to use the knowledge we have to try to eradicate this disease which is bringing heartache to so many families in South America


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