Quiz of the Day
World Mosquito Day
Thursday, 20 August 2026
August 20 marks Sir Ronald Ross's 1897 discovery linking mosquitoes to malaria — the deadliest animal in human history and the science fighting it
1. World Mosquito Day commemorates whose discovery in 1897?
- Ronald Ross's discovery that mosquitoes transmit malaria
- Walter Reed's proof that mosquitoes transmit yellow fever
- Louis Pasteur's discovery of germ theory
- Alexander Fleming's discovery of penicillin
On August 20, 1897, British doctor Ronald Ross working in Secunderabad, India, discovered malaria parasites in the stomach tissue of a mosquito that had fed on a malaria patient. This proved the mosquito-malaria transmission cycle and earned him the Nobel Prize in Medicine in 1902. He called August 20 'Mosquito Day' himself to mark the discovery's anniversary.
2. Why is the mosquito considered the deadliest animal in the world?
- Mosquito bites cause fatal allergic reactions in millions
- Mosquito-transmitted diseases have killed more people than all wars combined
- Its direct venom kills more people than any other creature
- It transmits diseases that kill approximately 700,000–1 million people per year
Mosquitoes transmit malaria, dengue fever, yellow fever, Zika virus, West Nile virus, chikungunya, lymphatic filariasis, and encephalitis — collectively killing an estimated 700,000–1 million people annually. By comparison, all other animals combined kill far fewer. Historically, the death toll is staggering: malaria alone may have killed half of all humans who ever lived, fundamentally shaping human evolution, history, and civilization.
3. Only female mosquitoes bite humans. Why?
- Males don't have the mouth parts to bite
- Males prefer animal blood exclusively
- Female mosquitoes use biting as a defense mechanism
- Females need blood protein to develop eggs
Female mosquitoes need blood meals for the protein (specifically albumin and globulin) needed to develop their eggs. Both male and female mosquitoes feed primarily on plant nectar and fruit juices for energy. Female mosquitoes can lay 100–200 eggs after a single blood meal. The scientific name for the biting mouth parts — 'proboscis' — can detect blood vessels at the microscopic level.
4. What is the parasite responsible for the most deadly form of malaria?
- Plasmodium ovale
- Plasmodium vivax
- Plasmodium malariae
- Plasmodium falciparum
Plasmodium falciparum causes the most severe and deadly form of malaria — accounting for the majority of malaria deaths, primarily in sub-Saharan Africa. It's particularly dangerous because infected red blood cells stick to blood vessel walls, blocking blood flow to organs. The parasite completes its life cycle in both mosquitoes (Anopheles species) and human hosts — making it exquisitely evolved to use two different animals.
5. How do mosquitoes find their human targets?
- Through detecting carbon dioxide, body heat, and chemical odors
- By sensing electrical fields around the body
- Primarily by sight
- Mainly by body heat alone
Mosquitoes can detect carbon dioxide (from breathing) from up to 50 meters away. As they get closer, they use thermal sensors to detect body heat and chemoreceptors to detect skin chemicals like lactic acid, octanol, and specific fatty acids. Research shows that people with Type O blood attract roughly twice as many mosquitoes as Type A blood — mosquitoes genuinely have preferences.
6. Which organization developed the first malaria vaccine, and when was it approved?
- WHO approved the RTS,S/AS01 vaccine in 2021
- GlaxoSmithKline's vaccine was approved by the EU in 2015
- The Serum Institute developed an approved vaccine in 2018
- Pfizer approved a malaria mRNA vaccine in 2020
The RTS,S/AS01 vaccine (brand name Mosquirix) became the first malaria vaccine recommended by the WHO in 2021, after over 30 years of development by GlaxoSmithKline. It provides about 30% protection against severe malaria in children — far lower than most vaccines but still significant given malaria's massive death toll. A newer vaccine, R21/Matrix-M, showed 75%+ efficacy in trials and was approved by several African countries in 2023.
7. What is dengue fever, and how many people are infected annually?
- A bacterial infection — 1 million cases
- A waterborne disease — 100 million cases
- A malaria variant — 50 million cases
- A mosquito-borne viral disease — 400 million cases annually
Dengue fever infects approximately 400 million people annually — with about 100 million developing symptomatic illness and 40,000 deaths. Unlike malaria (which is spread by Anopheles mosquitoes), dengue is spread by Aedes aegypti mosquitoes, which breed in small water containers near human habitation and bite primarily during the day. Dengue cases have increased 30-fold in 50 years, driven by urbanization and climate change.
8. What is the 'Sterile Insect Technique' used to control mosquito populations?
- Spraying sterile chemical attractants to lure mosquitoes
- Releasing massive numbers of sterilized male mosquitoes to overwhelm the breeding population
- Using radiation to sterilize larvae in water sources
- Introducing a sterilizing fungus into mosquito habitats
The Sterile Insect Technique (SIT) irradiates male mosquitoes to sterilize them, then releases millions into the wild. When they mate with wild females, no viable eggs are produced, crashing the population. It's been used effectively against agricultural pests since the 1950s. A modern variant uses male mosquitoes carrying a lethal gene (developed by Oxitec) — trials in Florida, Brazil, and Cayman Islands have reduced Aedes aegypti populations by over 90%.
9. What is a 'Wolbachia' mosquito, and how does it combat disease?
- A mosquito with a genetic modification that prevents biting
- A sterile hybrid mosquito species
- A mosquito infected with bacteria that prevents dengue and malaria viruses from replicating
- A smaller, slower mosquito bred for laboratory study
Wolbachia is a naturally occurring bacteria that infects many insects but not Aedes aegypti. Scientists discovered that introducing Wolbachia into Aedes mosquitoes dramatically reduces their ability to transmit dengue and other viruses. Field trials in Australia, Indonesia, and Brazil releasing Wolbachia-infected mosquitoes showed dengue infections fell by up to 77%. The bacteria spreads through mosquito populations naturally — an elegant biological solution.
10. Which bed net treatment has saved millions of lives in malaria-endemic regions?
- Citronella-treated nets
- Carbon dioxide-absorbing net material
- Insecticide-treated bed nets (ITNs) using pyrethroids
- UV-light-emitting nets
Insecticide-treated bed nets (ITNs) are considered one of the most cost-effective public health interventions ever developed — a single net costs $2–5 and protects 2 people for 3–5 years. The global scale-up of ITN distribution from 2000 to 2015 is estimated to have prevented approximately 450 million malaria cases and saved over 1 million lives. The charity Against Malaria Foundation has been ranked as one of the most effective in the world for distributing them.
11. What evolutionary pressure have mosquitoes and malaria placed on human genetics?
- Driving the spread of sickle cell trait in African populations
- Increasing human skin thickness
- Selecting for larger spleens in tropical populations
- Causing humans to develop stronger immune responses generally
Sickle cell trait (carrying one copy of the sickle cell gene) provides about 50% protection against severe malaria — a massive survival advantage in malaria-endemic regions. This explains why the gene is common in populations from sub-Saharan Africa, the Mediterranean, Middle East, and India. Unfortunately, inheriting two copies causes sickle cell disease, a painful and life-limiting condition. Malaria may be the strongest selective pressure on human evolution in the last 10,000 years.
12. How long does the average mosquito live?
- 3–6 months
- 24–48 hours
- 1–2 weeks
- 2–8 weeks depending on species and sex
Male mosquitoes live only 1–2 weeks and die shortly after mating. Female mosquitoes typically live 2–8 weeks, depending on species, temperature, and humidity — with warmer temperatures accelerating their metabolism and shortening their lives. Some species can overwinter in a dormant state for months. Despite their short lives, female mosquitoes can lay multiple batches of 100–200 eggs.
13. How many mosquito species exist in the world?
- About 400
- About 1,200
- Over 10,000
- Over 3,500
There are over 3,500 mosquito species, but only about 200 bite humans and only a few dozen transmit significant diseases. The Anopheles, Aedes, and Culex genera contain the most medically important species. Most mosquito species are harmless — many feed only on animals or plant nectar. Eliminating all mosquitoes is theoretically possible but ecologically complex, as they serve as food sources for birds, bats, and fish.
14. What role did mosquitoes play in the building of the Panama Canal?
- They forced workers to build the canal faster to escape endemic zones
- They had no significant impact
- They inspired the use of water locks in the canal design
- They killed so many workers with malaria and yellow fever that France abandoned the first attempt
France's attempt to build the Panama Canal from 1881 to 1889 failed catastrophically — not for engineering reasons, but because malaria and yellow fever killed approximately 22,000 workers. When the US took over in 1904, Colonel William Gorgas led a massive mosquito eradication campaign — draining standing water, screening buildings, and applying oil to water surfaces — reducing disease deaths by 90% and making the canal completion possible.
15. Climate change is expected to do what to the mosquito's geographic range?
- Reduce it as extreme heat kills mosquitoes
- Expand it significantly into previously cooler temperate regions
- Keep it roughly the same
- Eliminate mosquitoes from equatorial zones
As temperatures rise, mosquito-borne diseases are advancing into previously inhospitable regions. Aedes aegypti mosquitoes have been found as far north as Washington DC and southern Europe. Malaria has reappeared in areas of Greece and the United States where it was previously eradicated. The CDC projects that by 2080, 8–10 billion additional people could be at risk of dengue fever — nearly everyone alive — due to climate-driven mosquito range expansion.