August 20 is World Mosquito Day. On this day, more than 100 years ago, British scientist Sir Ronald Ross discovered that malaria is transmitted to humans by the female anopheles mosquito. It was a major breakthrough in the war against an insect that has plagued humans.
Mosquitoes are viewed as the deadliest animal in the world because they are responsible for millions of infections from the diseases they carry. Malaria kills an estimated 600,000 people a year and about half the world’s population is now at risk from the mosquito-borne virus, dengue. This is why it’s important to take precautions to avoid mosquito bites, especially when travelling to areas where mosquito-carrying diseases are endemic.
Understanding mosquito behavior
- Only female mosquitoes bite and they use the blood to mature their eggs. Mosquitoes find blood by following odour plumes that contain a mixture of carbon dioxide released when we exhale, volatiles released from the skin, heat and moisture. And, yes, mosquitoes are selective. In a group of people there is generally one unlucky person who has the best body chemistry to attract the most mosquitoes, and one person who attracts the least.
- Mosquitoes have feeding preferences, some feeding almost exclusively on humans, some on animals (such as cattle), and others on birds or reptiles. The more often a mosquito feeds on a human, the more likely it is to pick-up a pathogen and transmit a disease.
- More than 90% of global malaria deaths occur in sub-Saharan Africa, where the main malaria vectors have a strong preference for feeding on humans and a long lifespan that provides enough time for the parasite to develop inside the mosquito, once the mosquito takes an infected blood meal from a person with malaria.
- The itches and red bumps from mosquito bites are caused by mosquito saliva that’s injected into the skin before the mosquito sucks your blood. Most people have minor allergic reactions to the saliva, causing the area around the bite to swell and itch.
Protection from mosquitoes
- Wear long-sleeved shirts and pants which exposes less skin to attract mosquitos, and select light colored clothing as mosquitoes are more attracted to dark colors.
- Use topical mosquito repellent on exposed areas of skin and reapply regularly as indicated.
- Consider placing mosquito coils or repellent candles if available, around areas where you are sitting outside, but use these with other measures for maximum impact.
What Doesn’t Work
- Don’t trust your fate on old wives’ tales. For example:
- Eating garlic does not repel mosquitoes though it may repel humans if you eat enough of it or squeeze it on your skin!
- Vitamin B does not affect mosquito attraction to humans.
- Eating bananas does not make you more attractive to mosquitoes, so don’t shy away from this nutrient-laden fruit.
On the other hand, drinking beer has actually been shown to increase the number of mosquito bites. Of course, depending on how much you drink you may be less aware of how much you are being bitten! If you are drinking alcohol, using some of the other measures listed (such as wearing repellent) is a good idea.
Helen Pates Jamet, Ph.D., is Head of Entomology at Vestergaard, a leading manufacturer of long-lasting insecticidal bed nets under the PermaNet® brand. Dr. Jamet has spent more than 20 year studying the behavior of mosquitos and developing ways to protect people from the diseases they transmit.
