Mosquitopia Part 2: A few Reasons for Saving Mosquitoes

This is the second installment on mosquitoes to coincide with the Rachel Carson Legacy Symposium “Mosquitopia? The Place of Pests in a Healthy World” being held this weekend (2427 October 2019). Here, the authors summarize some of the main arguments against trying to rid the world of mosquitoes. This special feature is part of our ongoing blog series “Silent Spring Continued: A World without Insects.”
*Featured image: Pictorial Monograph of Birds (1885) by Numata Kashu (1838-1901). Digitally enhanced by Rawpixel Ltd, CC BY-NC 4.0.

By Marcus Hall and Dan Tamir

Far from a complete list, below we highlight some of the main arguments for saving mosquitoes.

Strategic: We must remind ourselves that we are ultimately battling disease, not mosquitoes, and that there may be more effective, more economical, more ethical ways to do this than mosquito control. Malaria once emanated from swamps and bad air, though with more evidence it became clear that mosquitoes were the vectors of this disease. Should we be putting greater efforts into battling the plasmodia pathogens rather than the carriers of them? Should we be focusing at still smaller levels, such as on the chemicals set in motion by the pathogens? Zoologist Marston Bates once called DDT the “sledge-hammer approach to mosquito control” since DDT caused so much collateral damage to other living things, from birds and fish to desirable insects such as bees.[1] Early anti-malarial medications such as Atrabrine was itself a sledge-hammer approach in human blood streams, since people felt pretty nauseous after taking this medication. Because there are pros and cons to every remedy, we need to return to cost-benefit analyses before marching forward with any one solution.

Medical: Another issue focuses on the importance of maintaining discrete, residual levels of pathogens in a population so as to maintain an epidemiologic signal that our bodies can react to and maintain resistance against. When malaria was largely eradicated from parts of Madagascar, only to return five years later, it returned with atypically dangerous virulence. Maintaining some mosquitoes and so the disease, means that human physiologies would not become naively adapted to a malaria-free environment. A related issue is that certain kinds of less dangerous malaria can provide protection from more dangerous malaria: a person infected by Plasmodium vivax is given some protection from being infected by more dangerous Plasmodium falciparum. As a protective measure, humans could theoretically be artificially inoculated with P. vivax, yet mosquitoes will inoculate them for free.

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Mosquito administering vaccine. (Image modified, via pngimg, CC BY-NC 4.0)

Ecological: There are many ecological arguments that point to the beneficial role of mosquitoes in ecosystems. Metric tons of flying biomass certainly alter natural processes, whether as foodstuff for other organisms or modifiers of animal behavior, as in the case of caribou and Homo sapiens who move to avoid them. There are the parasites and pathogens carried by mosquitoes, which infect not only humans, but also many other mammals, as well birds and reptiles. Microbes transmitted by mosquitoes to bats help control bat numbers, and thereby also control the spread of human diseases propagated by bats. Some mosquitoes even control other species of mosquito, since adults of certain species feed on the larvae of others.[2] These mosquito-borne benefits are therefore good reasons for maintaining mosquitoes in ecosystems, or bringing them back if overly controlled.

Evolutionary: Parasites and hosts coevolve, sometimes with beneficial results for both, as each generally becomes more tolerant of the other through time. Or at least this is Joshua Lederberg’s argument for why the virulence of parasites can diminish over time.[3] Cautious, hands-off approaches to vector control therefore allow nature to take its course, with harmful results balanced increasingly by beneficial ones. In short, there are crucial long-term roles for our bodily symbionts, and human interferences in their transmission may produce more harm than good.

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Man on mountain, via pixabay (public domain).

Ethical & Social: On a more fundamental level, do humans have the right to kill, or exterminate other creatures—even the right to transform or disrupt whole ecosystems? Is it justifiable to act when we are still quite unsure about how all the pieces of an ecosystem fit together? If we are placing ourselves at the top of the pyramid of creation, what does that tell us about ourselves and our place in the future? We have, to date, never been able to rid the earth of mosquitoes, despite dogged efforts to do so. What makes us think we can do so now? Hubris has been the rule and not the exception in the history of humanity. Yet is it even thinkable that humans have the right not to seek every means possible to control and curtail disease-spreading organisms? Can it be fair to pay more attention to insects than to humans made sick by them? And is it right to rely on expert opinion, when the individuals directly affected by anti-mosquito treatments have different viewpoints?

Economic: Millions of funds and thousands of individuals are now dedicated to vector control and related research. In terms of spending efficiency, should these limited resources be dedicated to other measures, such as bed nets, tighter houses, better-equipped hospitals, and health education? Mosquito control is one of many health measures, and perhaps one of lesser priority depending on circumstances. An ongoing challenge is to focus on effective resource allocation, which may change by the year. Another economic issue focuses on the potential utility of mosquitoes to science or medicine; for example, mosquitoes can detect miniscule quantities of C02, and produce amazing anti-coagulants, with both traits suggesting entrepreneurial opportunities, unless these are curtailed by exterminators.

Aesthetic: Insects in general and mosquitoes in particular, are exquisitely engineered organisms, marvelously adapted to their various roles, and elegantly effective in carrying them out. We cannot help but admire them, even paint them, sculpt them, and marvel at their buzzes. Mosquitoes manage to pair with each other by harmonizing the frequencies of their beating wings, and artists can amplify and project these harmonic sounds.[4]

[1] Marston Bates in J. Logan, The Sardinian Project (Baltimore: Johns Hopkins U. Press, 1954), x.

[2] O. Roux and V. Robert, “Larval predation in malaria vectors and its potential implication in malaria transmission: an overlooked ecosystem service?,” Parasites & Vectors 12: 217.

[3] Joshua Lederberg [1993] quoted at Pierre-Olivier Méthot, “Why do Parasites Harm Their Host? On the Origin and Legacy of Theobald Smith’s ‘Law of Declining Virulence’,” History and Philosophy of the Life Sciences 34 (2012): 567.

[4] University College London, “Built-in sound amplifier helps male mosquitoes find females,” Science Daily (2018), 25 September 2018. Available at https://www.sciencedaily.com/releases/2018/09/180925110014.htm. See also: http://robinmeier.net/?p=38 (thanks to Peter Coates for alerting us to this source).


In the final installment tomorrow, the authors will offer up some major arguments for pursing a mosquito-free future.

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