Could we kill off all mosquitoes?
Mosquitoes are some of the most annoying — and deadliest — animals on the planet. Could we simply get rid of them?
I am a pacifist by nature. I’m the kind of guy who will carry an innocent spider out of a room rather than crushing it under a paper towel. As honourable as this sounds, however, I too have my limits; limits that are currently manifested in the field of itchy mosquito bites trailing down my left leg. Of far greater importance than this minor annoyance, however, is the fact that mosquitoes are actually considered the deadliest animal on this planet. As a vector for diseases like malaria, yellow fever, dengue fever, Chikungunya, West Nile virus, and Zika virus they are responsible for over 700,000 human deaths annually. This is far greater than the number of deaths attributed to more commonly feared predators like snakes and sharks. I hope I speak for most of my readers, therefore, in wondering what function mosquitoes serve on our planet and whether we perhaps wouldn’t be better off without them?
There are over 3,500 different species of mosquitoes, around 200 of which feed on human blood. While only a few dozen species pose a risk to humans, our first target for elimination would have to be the ruthless Anopheles gambiae, an important malaria vector and one of the deadliest mosquitoes around.
A mosquito’s life spans between 10 days to 2 months. As is popularly known, the female mosquitoes do the biting, using the protein and iron found in blood to help develop their growing eggs. While piercing under your skin, the mosquito will inject a small amount of saliva that causes a mild (and harmless) immune system reaction resulting in the characteristic itchy bump. If you ever felt that mosquitoes were unfairly attracted to you, this could actually be the case. They are drawn to chemicals like lactic acid in your skin and the CO2 you produce by breathing, both of which can vary significantly between based on your body type and genetics. A particularly high concentration of attractive skin bacteria is concentrated around your feet and ankles, explaining why mosquitoes particularly enjoying biting these areas. Finally, there is also evidence that blood type O attracts more mosquitoes than other types. (Source: TIME)
The Circle of Life
The Lion King and subsequent school biology lessons have taught us that every species plays a vital role within our magical ecosystem; removing one of these species may cause unexpected, cascading and devastating effects. To formulate an open and constructive opinion of our terrorising little friends, we can, therefore, ask ourselves the simple question: what do mosquitoes eat and what eats mosquitoes?
Mosquito larvae mature in pools of water and feed on a mixed diet of algae and other small debris. In doing this they play a minor role in keeping lakes and ponds clean. Not convinced? Nor am I, particularly as there are other less-annoying species that perform a similar duty.
A more impressive fact is that “during the peak breeding seasons, [mosquitoes] outnumber every other animal on Earth, except termites and ants”. As a result, mosquito larvae are an important- and abundant source of food for other aquatic species including dragonfly and damselfly nymphs, tadpoles, turtles and various fish. This is particularly true in the Arctic tundra, where they provide a significant food resource for local birds.
The aptly named mosquitofish is a highly celebrated protagonist that has historically been used by governments to curb mosquito populations. It was introduced to with varying success in Australia in the 1920s and 30s, where it competed heavily with local fish and frog populations due to its notably aggressive character. In the Russian city of Sochi, mosquitofish contributed so heavily to the eradication of malaria in the region that the species was honoured with a bronze statue in a central town park. (Source: Forbes)
Adult mosquitoes are a food source for an even wider variety of species from “fish and frogs to salamanders and lizards to venus fly traps and birds and bats, and even other insects”. They also pollinate a number of plants, including a variety of orchids. However, despite all of these examples, mosquitoes are not a keystone species; that is, they do not play a unique or critical role to the functioning of our ecosystem. None of the animals mentioned above exclusively feed on mosquitoes and none of the plants is exclusively pollinated by the little tyrants either. In their natural habitat, even mosquitofish prefer a more balanced diet with generous portions of algae and plankton, and minor servings of mosquito.
22,000 deaths and US$ 7 billion in losses
With our ecosystemic conscious cleared, we are now left with the question of how to eradicate mosquitoes? It will be of no surprise that humanity has already put a lot of thought to this very question. Given the short reproductive cycles of mosquitoes and the immense size of their population, however, it is not an easy one to answer.
While global elimination may not be feasible, we have been successful at reducing or eradicating more localised populations. In 1881, the French embarked on the original attempt to build the Panama Canal but stopped shortly after due to engineering difficulties and skyrocketing worker mortality rates largely caused by malaria and yellow fever. It is estimated that mosquitoes were responsible for over 22,000 deaths and US$ 7 billion in losses on the project.
By the time the US took control of the Panama Canal in 1904, public health efforts surrounding the control of mosquitoes had matured. Over the course of two years, an impressive 7-step sanitation program helped to eradicate yellow fever and drastically reduce malaria-related deaths in the Canal Zone and the cities of Panama and Colon, allowing construction to resume.
Science to the Rescue?
Insect sterilisation was first explored in the 1950s to help eliminate screwworm (an agricultural pest) by exposing males to low-level gamma radiation. Females that would mate with the exposed males would produce infertile offspring. When the same technique was experimented on with mosquitoes, it was observed that radiation sterilisation led to a reduction in male libido.
Sterilising male mosquitos with low-level gamma radiation reduces their libido.
A current program lead by British biotech company Oxitec in southern Brazil involves mutating male mosquitoes in a way that causes their offspring to die before reproducing. Initial studies are showing success, reducing wild populations by over 90%. Scientists are also experimenting with contemporary genetic- and bio-engineering techniques that create infertile male or female mosquitoes. There’s so much buzz around this challenge (excuse the pun) that even Alphabet, Google’s parent company, is getting involved in the game.
Continuing down this path does pose some important questions about bioethics, however. Though many might agree with eradicating mosquito populations, we may quickly face a slippery slope that begins to justify the elimination of other unpopular species, like cockroaches or rats, that play a more vital role in our ecosystem.
I have to admit that I agree with these concerns and, despite posing the opening question to this article, I am weary of human attempts to play God by meddling too much with nature. One of my favourite authors, Yuval Noah Harari, reflects on this concern more deeply in his book Homo Deus. Nevertheless, I applaud the continued experimentation by the scientific community to curb the spread of deadly diseases through mutation of mosquitoes and associated pathogens. Though, I would perhaps add an additional request to explore further mutations that reduce the annoying itchiness and mute that menacing buzzing sound.
