Why do mosquitoes appear to be repelled by magnets?

Why do mosquitoes appear to be repelled by magnets?

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A few days ago, I was playing with magnets and thought of placing one near a live mosquito (I had it held between my two fingers so it had no chance of escaping). When near the magnet, it twitched and flew away! I tried the same with semi-alive mosquitoes, but nothing really happened.

I googled about this and learnt that mosquitoes have got to do something with magnets, but I'm still confused. Could anyone tell me why mosquitoes get repelled by magnetic fields?

PS. I'm no biology student, so please go easy on me, thank you ahead of time!

Source (PDF)

EDIT: Strickman et. al. (2000) says:

we found that some specimens had a significant magnetic remanence Could this possibly be the reason why mosquitoes may get repelled by magnetic fields?

That paper also states:

the mosquitoes were able to detect the magnetic fields but sensed a magnetic pattern that was impossible in nature.


Strickman, D., Timberlake, B., Estrada-Franco, J., Weissman, M., Fenimore, P. W., & Novak, R. J. (2000). Effects of magnetic fields on mosquitoes. Journal of the American Mosquito Control Association-Mosquito News, 16(2), 131-137.

According to the research cited by the OP (Strickman et al. 2000), mosquitoes alter their behavior in the presence of a magnetic field, and the measured changes in behavior are statistically significant. The authors of the study found that the external surfaces of mosquitoes attract ferromagnetic particles from the air. They speculate that changing their orientation to the earth's magnetic field helps mosquitoes navigate while approaching a potential host.

Reference Cited Strickman, D., Timberlake, B., Estrada-Franco, J, Weissman, M, Fenimore, PW, and R.J. Novak. 2000. Effects of magnetic fields on mosquitoes. Journal of the American Mosquito Control Association 16(2):131-137.

New study reveals how day- and night-biting mosquitoes respond differently to colors of light and time of day

Credit: Pixabay/CC0 Public Domain

In a new study, researchers found that night- versus day-biting species of mosquitoes are behaviorally attracted and repelled by different colors of light at different times of day. Mosquitoes are among major disease vectors impacting humans and animals around the world and the findings have important implications for using light to control them.

The University of California, Irvine School of Medicine-led team studied mosquito species that bite in the daytime (Aedes aegypti, aka the Yellow Fever mosquito) and those that bite at night (Anopheles coluzzi, a member of the Anopheles gambiae family, the major vector for malaria). They found distinct responses to ultraviolet light and other colors of light between the two species. Researchers also found light preference is dependent on the mosquito's sex and species, the time of day and the color of the light.

"Conventional wisdom has been that insects are non-specifically attracted to ultraviolet light, hence the widespread use of ultraviolet light "bug zappers" for insect control. We find that day-biting mosquitoes are attracted to a wide range of light spectra during the daytime, whereas night-biting mosquitoes are strongly photophobic to short-wavelength light during the daytime," said principal investigator Todd C. Holmes, Ph.D., a professor in the Department of Physiology and Biophysics at the UCI School of Medicine. "Our results show that timing and light spectra are critical for species-specific light control of harmful mosquitoes."

The new study titled, "Circadian Regulation of Light-Evoked Attraction and Avoidance Behaviors in Daytime- versus Nighttime-Biting Mosquitoes," is published in Current Biology. Lisa S. Baik, a UCI School of Medicine graduate student researcher who recently completed her Ph.D. work, is first author.

Mosquitoes pose widespread threats to humans and other animals as disease vectors. It is estimated historically that diseases spread by mosquitoes have contributed to the deaths of half of all humans ever to have lived. The new work shows that day-biting mosquitoes, particularly females that require blood meals for their fertilized eggs, are attracted to light during the day regardless of spectra. In contrast, night-biting mosquitoes specifically avoid ultraviolet (UV) and blue light during the day. Previous work in the Holmes lab using fruit flies (which are related to mosquitoes) has determined the light sensors and circadian molecular mechanisms for light mediated attraction/avoidance behaviors. Accordingly, molecular disruption of the circadian clock severely interferes with light-evoked attraction and avoidance behaviors in mosquitoes. At present, light-based insect controls do not take into consideration the day versus night behavioral profiles that change with daily light and dark cycles.

"Light is the primary regulator of circadian rhythms and evokes a wide range of time-of-day specific behaviors," said Holmes. "By gaining an understanding of how insects respond to short wavelength light in a species-specific manner, we can develop new, environmentally friendly alternatives to controlling harmful insects more effectively and reduce the need for environmentally damaging toxic pesticides."

Who Mosquitoes Like Best

Although researchers have yet to pinpoint what mosquitoes consider an ideal hunk of human flesh, the hunt is on. "There's a tremendous amount of research being conducted on what compounds and odors people exude that might be attractive to mosquitoes," says Joe Conlon, PhD, technical advisor to the American Mosquito Control Association. With 400 different compounds to examine, it's an extremely laborious process. "Researchers are just beginning to scratch the surface," he says.

Scientists do know that genetics account for a whopping 85% of our susceptibility to mosquito bites. They've also identified certain elements of our body chemistry that, when found in excess on the skin's surface, make mosquitoes swarm closer.

"People with high concentrations of steroids or cholesterol on their skin surface attract mosquitoes," Butler tells WebMD. That doesn't necessarily mean that mosquitoes prey on people with higher overall levels of cholesterol, Butler explains. These people simply may be more efficient at processing cholesterol, the byproducts of which remain on the skin's surface.

Mosquitoes also target people who produce excess amounts of certain acids, such as uric acid, explains entomologist John Edman, PhD, spokesman for the Entomological Society of America. These substances can trigger mosquitoes' sense of smell, luring them to land on unsuspecting victims.

But the process of attraction begins long before the landing. Mosquitoes can smell their dinner from an impressive distance of up to 50 meters, explains Edman. This doesn't bode well for people who emit large quantities of carbon dioxide.

"Any type of carbon dioxide is attractive, even over a long distance," Conlon says. Larger people tend to give off more carbon dioxide, which is why mosquitoes typically prefer munching on adults to small children. Pregnant women are also at increased risk, as they produce a greater-than-normal amount of exhaled carbon dioxide. Movement and heat also attract mosquitoes.

So if you want to avoid an onslaught of mosquito bites at your next outdoor gathering, stake out a chaise lounge rather than a spot on the volleyball team. Here's why. As you run around the volleyball court, the mosquitoes sense your movement and head toward you. When you pant from exertion, the smell of carbon dioxide from your heavy breathing draws them closer. So does the lactic acid from your sweat glands. And then -- gotcha.

With a long track record -- mosquitoes have been around for 170 million years -- and more than 175 known species in the U.S., these shrewd summertime pests clearly aren't going to disappear any time soon. But you can minimize their impact.

Mosquito magnet? Blame your DNA, study says

Are you a mosquito magnet? If so, your genes may be to blame.

New research shows that if mosquitoes are attracted to the scent of a particular person, they are likely to be attracted to her twin’s scent as well. On the flip side, if they are repelled by someone’s odor, they’re likely to find her twin repellent, too.

Scientists tested 37 sets of twins who were willing to place their hands in a Y-shaped glass tube. Groups of 20 mosquitoes were released into the tube and given 30 seconds to assess the scents inside. Then a gate was opened, allowing them to fly toward the hands they preferred and away from the hands they disliked. (Although the mosquitoes could smell the volunteers’ hands, they couldn’t actually reach them.)

After running versions of the experiment 40 times with each set of twins, they found that the overlap in mosquito preference was about twice as high for identical twins (who share virtually all their DNA) as it was for fraternal twins (who share only half). That allowed them to calculate that 62% to 83% of a person’s degree of mosquito attractiveness is determined by DNA, according to a study published Wednesday in the journal PLOS One.

To put that into perspective, other studies have found that genes are about 80% responsible for a person’s height and 50% to 80% for a person’s IQ.

Scientists have suspected for some time that those who find themselves playing the role of pincushion at barbecues and other outdoor gatherings have an unfortunate genetic inheritance.

They knew that biology played a role in either attracting or repelling mosquitoes. For instance, women who are pregnant are a much bigger draw than women who aren’t. They also know that people who are infected with the malaria parasite are more attractive to mosquitoes during the window when the infection can be spread.

Previous studies have shown that mosquitoes are drawn to people (or not) on the basis of their odor. Bacteria that live on skin play a role in producing body odor, but skin cells probably play a role too. If so, that might be controlled by genes.

So the researchers recruited 18 pairs of identical twins and 19 pairs of fraternal twins. All of them were women (so that the gender of the volunteers wouldn’t skew the trial results) and all of them were post-menopausal (so that changes in their menstrual cycle wouldn’t be a factor).

They also collected dozens of female Aedes aegypti mosquitoes, the species that spreads dengue fever. The mosquitoes were 5 to 7 days old, and in their short lives all they had been able to eat was a glucose solution.

In some tests, the researchers compared the odor of one twin’s hand against clean air. In other tests, they tested twin-versus-twin. And in others, both ends of the Y-shaped tube were pumped with clean air.

The experimental results leave no doubt that some people are genetically programmed to be attractive to mosquitoes, and other lucky individuals have DNA that functions as a natural mosquito repellent. The researchers hope to use this knowledge to trick mosquitoes into thinking that everyone is in that second category.

“We could possibly develop a drug, a pill that you might take when you go on holiday that would cause your body to produce natural repellents and would minimize the need to actually put repellents on your skin,” said James Logan, a medical entomologist at the London School of Hygiene and Tropical Medicine and the study’s senior author.

The next step for Logan and his team is to figure out which genes are responsible for mosquito magnetism, he said in a video released by his university. Genes involved in the major histocompatibility complex are believed to be involved in body odor, so that’s one place to look, according to the study.

Once the genes are found, public health experts might be able to use that information to control mosquito-borne diseases, such as dengue and malaria, Logan said.

Research rocks! For more stories like this, follow me on Twitter @LATkarenkaplan and “like” Los Angeles Times Science & Health on Facebook.

What is a Mosquito Magnet®? (with pictures)

There are literally hundreds of products on the market today which claim to repel, trap, electrocute or otherwise dispatch disease-carrying mosquitoes. Many of these devices or chemical repellents only offer marginal protection, or no substantial protection at all. One promising type of mosquito trap, however, is called a Mosquito Magnetreg, and it works primarily by imitating one of the best mosquito magnets of them all human beings.

Scientists believe mosquitoes are attracted to carbon dioxide, which explains why they will seek out humans who expel a lot of it through normal respiration. The Mosquito Magnet® uses a tank of compressed propane and a catalytic converter to generate carbon dioxide gas. A patented nozzle design disperses this gas in roughly the same concentration as human respiration. A chemical attractant is also mixed into the carbon dioxide emission. To a mosquito, the Mosquito Magnet® smells just like a large warm-blooded animal.

Once the mosquito reaches the source of the carbon dioxide emission, a powerful vacuum draws it into a waiting mosquito net, where it will eventually dehydrate and expire within 24 hours. The commercial Mosquito Magnet® can be placed at the edge of a mosquito-plagued area, hopefully presenting a more appealing target than the humans using the space for recreation and cooking.

Theoretically, a homemade mosquito magnet could be constructed from materials found around the garage, although some of the parts used on the commercial version may not be easy to replicate. Small canisters of compressed propane gas are not difficult to obtain, but finding a suitable catalytic converter capable of turning propane into carbon dioxide could prove problematic. The nozzle would also need to be adjusted to duplicate natural respiration. Mosquitos are not attracted to higher concentrations of carbon dioxide, which would be lethal to most living things.

Setting up a shop vac to collect the mosquitoes would also be possible, but the canister would have to contain a suitable mosquito net or other mechanism to prevent the mosquitoes from escaping once the vacuum was turned off. All things considered, an enterprising do-it-yourselfer could probably create a workable alternative, but the commercial Mosquito Magnet® has already solved many of the technical difficulties he or she would face.

There are some experts who question the effectiveness of a mosquito magnet system. Such a device may trap a few thousand adult mosquitoes during an average night, but there are usually hundreds of thousands of other mosquitoes and flying insects to take their place. Mosquito traps which use attractants can actually bring more insects into an area than they can eliminate. If such a device as a Mosquito Magnet® were implemented, proper placement would be critical for maximum effectiveness.

An estimated 10% of the human population could also be considered mosquito magnets. They naturally attract far more mosquitoes and other flying insects as other people. Scientists now believe that genetics does play a role in whether or not a particular person would be a true mosquito magnet. Other factors such as skin care products, deodorants and fragrances only appear to play a small role in the phenomenon.

Human mosquito magnets often excrete a higher level of certain chemicals, such as cholesterol and uric acid. Female mosquitoes are attracted to these fragrances, since they signal a healthy and abundant blood supply. Larger adults also release more carbon dioxide when they breath out, which also makes them more attractive to mosquitoes seeking the most promising targets. Pregnant women are also more likely to become mosquito magnets, although scientists are not exactly sure why. Elevated hormone levels may be more of an attractant to mosquitoes and other flying insects.

If someone claims that he or she is a mosquito magnet, there is probably more than a grain of truth to it. Such people may benefit from sweating as little as possible during outside events and wearing chemical insect repellents which contain DEET.

A regular contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

A regular contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

When and Where Are Mosquitoes Most Active?

Different parts of the country will see increased mosquito activity during different times of the year. It mostly depends on when temperatures climb above 50°F on a regular basis. For some parts of the country, that means mosquitoes emerge as early as February or March. Other areas may not see intense activity until June or later. In the most temperate parts of the nation, mosquitoes can be present year-round. With that in mind, it&rsquos difficult to map out specific mosquito seasons.

For example, Texas has 85 different species of mosquito, more than any other state. Since Texas has a very warm climate, mosquito season in the southern part of the state can start as early as February.

South Florida, too, has an especially early start to the mosquito season. In most years, Florida sees activity in early February. In fact, since southern Florida has a warm, moist climate, mosquitoes tend to thrive all year. In the northern part of Texas and the southern part of California, as well as in Mississippi, Georgia, Alabama, New Mexico and parts of Arizona, the mosquito season tends to start in early March.

In northern California, Utah, Nevada, Colorado, Kansas, Kentucky, and nearby states, the mosquito season usually starts in early April. In parts of Oregon, Idaho, Wyoming, Illinois, and the eastern seaboard states, mosquitoes may not arrive until late April.

For the most northern parts of the United States, mosquitoes may not start appearing until May or even later. The mosquito season is shortest in Alaska, where it sometimes lasts for only part of June and into July.

If you&rsquod like more information about when mosquito season is most likely to affect your area, Mosquito Magnet® has a handy map showing mosquito seasons.

Are Mosquitoes Attracted To Light Skin

Wearing dark clothes against light skin is one example of why you might be more attractive to mosquitoes than someone wearing camouflage. Find out the truth behind the 10 biggest myths surrounding the potentially deadly insect.

8 Things That Attract Mosquitoes And How To Avoid Them

Despite your best efforts to repel mosquitoes you may still find them buzzing around your yard this season.

Are mosquitoes attracted to light skin. Most of their day-to-day targets will be found in the shade or within foliage so they are naturally attracted to dark colors. So to all you Type Os make sure you lather up with repellent and wear light-coloured long-sleeved clothing unless you want to go speed dating with multiple mosquitoes. Mosquitoes are attracted to light but not all types of light and not at all times.

Its important to note that mosquitoes are not attracted to any type of light so dont attempt to use UV-light or an excessively bright flashlight. If youre a mosquito magnet youre probably tired of having itchy bumpy skin. Dont wear scent when outdoors during mosquito season.

They also appear to like black blue and red the most. Wear light-colored loose-fitting clothing and ensure that minimal skin is exposed. Those devices should be fitted with substances emitting light carbon dioxides heat moisture and odors that mosquitoes find attractive.

Many outdoor superstores carry lightweight outerwear so that wearing long layers is still cool and comfortable even in. Mosquitos are not necessarily attracted to a light source much less to one so intense as the sun. However when used in addition to an attractant such as dry ice this can have a major impact on mosquito populations.

Males just hang around us because they suspect females will be there too. Mosquitoes are attracted to dark colours such as black and navy blue as they use vision along with scent to locate their targets. Mosquitoes are pesky annoyances but their dangers go beyond an itchy bump on your skin.

Youre just their type. This drives the female to take a shot at our skin. Mosquitoes are attracted to warm bodies so staying cool is an effective way to avoid bites.

Avoid peak mosquito times. Cues like body temperature carbon dioxide in the breath and certain skin chemicals like lactic acid all help mosquitoes orient and find their next meal writes University of Wisconsin-Madison. The New Jersey light trap needs to be permanently mounted onto a platform up to 6 feet above the ground.

It is best to dress in light colours such as white or pastels to. People are usually prone to mosquito bites due to a combination of scent light heat and humidity. We find that day-biting mosquitoes are attracted to a wide range of light spectra during the daytime whereas night-biting mosquitoes are strongly photophobic to short-wavelength light during the.

Mosquitoes are attracted to sweat and the natural bacteria that congregate on your skin. Mosquitoes are attracted to black and darker colors. Mosquitoes are attracted to sweat but the act of sweating can mask more effective attractors of mosquitoes such as perfumes.

Mosquitoes do exhibit blood -sucking preferences say the experts. An electrical outlet should be nearby to constantly supply light. Remove areas of standing water such as dog bowls bird baths and garbage cans as mosquitoes can use these areas to breed.

It is common sense that mosquitoes are very attracted to carbon dioxide. Wear long sleeves pants and closed shoes. Then all you need is a lure and thats what the remainder of this article is all about.

People with fair skin usually have a stronger reaction to mosquito bites however the bites are simply more prominent. The short answer is yes. Keep your lawn and gutters clean.

Wearing dark clothes will attract mosquitoes. A combination of sweat and bacteria creates a scent on our skin that mosquitoes simply adore but your significant other probably doesnt. This can limit the area available for mosquitoes to bite.

One in 10 people are highly attractive to mosquitoes reports Jerry Butler PhD professor emeritus at. In addition to finding you by smell mosquitoes can detect you more easily by sight if youre wearing clothes that contrast with the color of your skin or your background. People have a reaction when mosquitoes bite that causes small red and itchy bumps.

This is from the mosquito saliva that prevents blood from clotting while they are drinking. Female mosquitoes which can transmit deadly diseases like malaria dengue fever West Nile virus and filariasis are attracted to us by smelling the carbon dioxide we exhale being capable of. Are Mosquitoes more attracted to people with fair skin.

Keeping yourself covered in long sleeves pants and shoes will reduce mosquito attraction and also make it harder for them to bite you. They like to fly around in relatively dark spaces but a single small lightbulb wont scare them away. They are attracted by carbon dioxide and a warm body that would suggest the presence of blood.

Mosquitoes can see and use their vision to locate targets from a distance. Mosquitoes are attracted to light.

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Mosquito netting is mainly used for the protection against the malaria transmitting vector, Anopheles gambiae. The first record of malaria-like symptoms occurred as early as 2700 BCE from China. The vector for this disease was not identified until 1880 when Sir Ronald Ross identified mosquitoes as a vector for malaria. [4]

Mosquito netting has a long history. Though use of the term dates from the mid-18th century, [1] Indian literature from the late medieval period has references to the usage of mosquito nets in ritual Hindu worship. Poetry composed by Annamayya, the earliest known Telugu musician and poet, references domatera, which means "mosquito net" in Telugu. [5] Use of mosquito nets has been dated to prehistoric times. It is said that Cleopatra, the last active pharaoh of Ancient Egypt, also slept under a mosquito net. [6] Mosquito nets were used during the malaria-plagued construction of the Suez Canal. [6]

Mosquito netting can be made from cotton, polyethylene, polyester, polypropylene, or nylon. [7] A mesh size of 1.2 millimetres (0.047 in) stops mosquitoes, and smaller, such as 0.6 millimetres (0.024 in), stops other biting insects such as biting midges/no-see-ums. [8]

A mosquito bar is an alternate form of a mosquito net. It is constructed of a fine see-through mesh fabric mounted on and draped over a box-shaped frame. It is designed to fit over an area or item such as a sleeping bag to provide protection from insects. A mosquito bar could be used to protect oneself from mosquitoes and other insects while sleeping in jungle areas. [9] The mesh is woven tightly enough to stop insects from entering but loosely enough to not interfere with ventilation. The frame is usually self-supporting or freestanding although it can be designed to be attached from the top to an alternative support such as tree limbs. [9]

Mosquito nets are often used where malaria or other insect-borne diseases are common, especially as a tent-like covering over a bed. For effectiveness, it is important that the netting not have holes or gaps large enough to allow insects to enter. It is also important to 'seal' the net properly because mosquitoes are able to 'squeeze' through improperly secured nets. Because an insect can bite a person through the net, the net must not rest directly on the skin. [10]

Mosquito netting can be hung over beds from the ceiling or a frame, built into tents, or installed in windows and doors. When hung over beds, rectangular nets provide more room for sleeping without the danger of netting contacting skin, at which point mosquitoes may bite through untreated netting. Some newer mosquito nets are designed to be both easy to deploy and foldable after use. [11] [12]

Where mosquito nets are freely or cheaply distributed, local residents sometimes opportunistically use them inappropriately, for example as fishing nets. When used for fishing, mosquito nets have harmful ecological consequences because the fine mesh of a mosquito net retains almost all fish, including bycatch such as immature or small fish and fish species that are not suitable for consumption. [13] [14] [15] [16] In addition, insecticides with which the mesh has been treated, such as permethrin, may be harmful to the fish and other aquatic fauna. [14]

Mosquito nets treated with insecticides—known as insecticide-treated nets (ITNs) or bednets—were developed and tested in the 1980s for malaria prevention by Dr. P. Carnevale and his team in Bobo-Dioulasso, Burkina Faso. ITNs are estimated to be twice as effective as untreated nets, [17] and offer greater than 70% protection compared with no net. [18] These nets are dip-treated using a synthetic pyrethroid insecticide such as deltamethrin or permethrin which will double the protection over a non-treated net by killing and repelling mosquitoes. For maximum effectiveness, ITNs should be re-impregnated with insecticide every six months. This process poses a significant logistical problem in rural areas. Newer, long-lasting insecticidal nets (LLINs) have now replaced ITNs in most countries. [19]

The distribution of mosquito nets or bednets impregnated with insecticides such as permethrin or deltamethrin has been shown to be an extremely effective method of malaria prevention. [3] According to a 2015 Nature study, mosquito nets averted 68% of an estimated 663 million averted cases of malaria infection since 2000. [3] It is also one of the most cost-effective methods of prevention. These nets can often be obtained for around $2.50–$3.50 (2–3 euros) from the United Nations, the World Health Organization (WHO), and others. ITNs have been shown to be the most cost-effective prevention method against malaria and are part of WHO's Millennium Development Goals (MDGs). [20] Generally LLINs are purchased by donor groups and delivered through in-country distribution networks.

ITNs protect people sleeping under them and simultaneously kill mosquitoes that contact the nets. Some protection is provided to others by this method, including people sleeping in the same room but not under the net. However, mathematical modeling has suggested that disease transmission may be exacerbated after bed nets have lost their insecticidal properties under certain circumstances. [21] Although ITN users are still protected by the physical barrier of the netting, non-users could experience an increased bite rate as mosquitoes are deflected away from the non-lethal bed net users. [21] The modeling suggests that this could increase transmission when the human population density is high or at lower human densities when mosquitoes are more adept at locating their blood meals. [21]

In December 2019 it was reported that West African populations of Anopheles gambiae include mutants with higher levels of sensory appendage protein 2 (a type of chemosensory protein in the legs), which binds to pyrethroids, sequestering them and so preventing them from functioning, thus making the mosquitoes with this mutation more likely to survive contact with bednets. [22]

Distribution Edit

While some experts argue that international organizations should distribute ITNs and LLINs to people for free to maximize coverage (since such a policy would reduce price barriers), others insist that cost-sharing between the international organization and recipients would lead to greater use of the net (arguing that people will value a good more if they pay for it). Additionally, proponents of cost-sharing argue that such a policy ensures that nets are efficiently allocated to the people who most need them (or are most vulnerable to infection). Through a "selection effect", they argue, the people who most need the bed nets will choose to purchase them, while those less in need will opt out.

However, a randomized controlled trial study of ITNs uptake among pregnant women in Kenya, conducted by economists Pascaline Dupas and Jessica Cohen, found that cost-sharing does not necessarily increase the usage intensity of ITNs nor does it induce uptake by those most vulnerable to infection, as compared to a policy of free distribution. [23] [24] In some cases, cost-sharing can decrease demand for mosquito nets by erecting a price barrier. Dupas and Cohen's findings support the argument that free distribution of ITNs can be more effective than cost-sharing in increasing coverage and saving lives. In a cost-effectiveness analysis, Dupas and Cohen note that "cost-sharing is at best marginally more cost-effective than free distribution, but free distribution leads to many more lives saved." [23]

The researchers base their conclusions about the cost-effectiveness of free distribution on the proven spillover benefits of increased ITN usage. [25] ITNs protect the individuals or households that use them, and they protect people in the surrounding community in one of two ways. [26]

  • First, ITNs kill adult mosquitoes infected with the malaria parasite directly which increases their mortality rate and can therefore decrease the frequency in which a person in the community is bit by an infected mosquito. [27]
  • Second, certain malaria parasites require days to develop in the salivary glands of the vector mosquito. This process can be accelerated or decelerated via weather more specifically heat. [28]Plasmodium falciparum, for example, the parasite that is responsible for the majority of deaths in Sub-Saharan Africa, takes 8 days to mature. Therefore, malaria transmission to humans does not take place until approximately the 10th day, although it requires blood meals at intervals of 2 to 5 days. [29] By killing mosquitoes before maturation of the malaria parasite, ITNs can reduce the number of encounters of infected mosquitoes with humans. [27]

When a large number of nets are distributed in one residential area, their chemical additives help reduce the number of mosquitoes in the environment. With fewer mosquitoes, the chances of malaria infection for recipients and non-recipients are significantly reduced. (In other words, the importance of the physical barrier effect of ITNs decreases relative to the positive externality effect [ clarification needed ] of the nets in creating a mosquito-free environment when ITNs are highly concentrated in one residential cluster or community.)

Unfortunately, standard ITNs must be replaced or re-treated with insecticide after six washes and, therefore, are not seen as a convenient, effective long-term solution to the malaria problem. [30] [31] [32]

As a result, the mosquito netting and pesticide industries developed so-called long-lasting insecticidal mosquito nets, which also use pyrethroid insecticides. There are three types of LLINs — polyester netting which has insecticide bound to the external surface of the netting fibre using a resin polyethylene which has insecticide incorporated into the fibre and polypropylene which has insecticide incorporated into the fibre. All types can be washed at least 20 times, but physical durability will vary. A survey carried out in Tanzania concluded that effective life of polyester nets was 2 to 3 years [33] with polyethylene LLINs there are data to support over 5 years of life with trials in showing nets which were still effective after 7 years. [34] When calculating the cost of LLINs for large-scale malaria prevention campaigns, the cost should be divided by the number of years of expected life: A more expensive net may be cheaper over time. In addition the logistical costs of replacing nets should be added to the calculation.

Scientific trials Edit

A review of 22 randomized controlled trials of ITNs [35] found (for Plasmodium falciparum malaria) that ITNs can reduce deaths in children by one fifth and episodes of malaria by half.

More specifically, in areas of stable malaria "ITNs reduced the incidence of uncomplicated malarial episodes by 50% compared to no nets, and 39% compared to untreated nets" and in areas of unstable malaria "by 62% compared to no nets and 43% compared to untreated nets". As such the review calculated that for every 1000 children protected by ITNs, 5.5 lives would be saved each year.

Through the years 1999 and 2010 the abundance of female anopheles gambiae densities in houses throughout western Kenya were recorded. This data set was paired with the spatial data of bed net usage in order to determine correlation. Results showed that from 2008 to 2010 the relative population density of the female anopheles gambiae decreased from 90.6% to 60.7%. [36] The conclusion of this study showed than as the number of houses which used insecticide treated bed nets increased the population density of female anopheles gambiae decreased. This result did however vary from region to region based on the local environment.

A 2019 study in PLoS ONE found that a campaign to distribute mosquito bednets in the Democratic Republic of Congo led to a 41% decline mortality for children under five who lived in areas with a high malaria risk. [37]

Malaria and other arboviruses are known to contribute to economic disparity within that country and vice versa. This opens the stage for corruption associated to the distribution of self-protection aides. [38] The least wealthy members of society are both more likely to be in closer proximity to the vectors' prime habitat and less likely to be protected from the vectors. [39] This increase in probability of being infected increases the demand for self-protection which therefore allows for higher pricing and uneven distribution of self-protection means. A decrease in per capita income exaggerates a high demand for resources such as water and food resulting in civil unrest among communities. Protecting resources as well as attempting to obtain resources are both a cause for conflict.

Mosquito nets have been observed to be used in fisheries across the world, where their strength, light weight and free or cheap accessibility make them an attractive tool for fishing. People who use them for fishing catch vast numbers of juvenile fish. [40]

Mosquito nets do reduce air flow to an extent and sleeping under a net is hotter than sleeping without one, which can be uncomfortable in tropical areas without air-conditioning.

How Do Humans Influence Larval Development?

Larvae of most nuisance and vector species develop in habitats directly or indirectly associated with human activities, including polluting water, discarding containers, improperly maintaining gutters, ineffectively managing flood and irrigation water, and building catch basins that alternate between being wet and dry. In many cases, exposure to nuisance or vector mosquitoes can be significantly reduced or prevented without the use of pesticides by eliminating or preventing these conditions. The main exception is the naturally existing areas along streams in which floodwaters collect. When flooded, these areas become suitable sites for the hatching of eggs of Aedes, Ochlerotatus, and Psorophora mosquitoes and can produce huge numbers of nuisance biting adults.

Carrying diseases such as malaria, West Nile virus and yellow fever, a few species of mosquitoes are responsible for more than one million deaths each year. Certain species of mosquitoes actually prefer feeding on humans, and even show preferences between people. A common wives’ tale suggests to kids that mosquitoes prefer sweeter blood (“eat more veggies!”). However, there is no scientific evidence supporting changing your diet (e.g. eating garlic, increasing vitamin B intake, avoiding bananas) as a method for avoiding mosquito bites. Instead, mosquitoes appear to be selectively targeting people based on their skin microbiota. Microbiota refer to the bacteria that naturally reside in or on the human body. Our skin alone is home to over 1000 different species of bacteria. After puberty, the composition of our individual microbiomes tend to stay constant, even with continuous exposure to new bacteria in the surrounding environment.

According to recent studies, our skin microbiota produce a combination of volatile compounds that determines a mosquito’s blood host preference. Researchers identified individual bacteria species on people’s skin using species-specific RNA sequences, like using fingerprints to identify individual humans. Once the bacteria in a person’s skin microbiome had been accounted for, researchers found that the presence and abundance of certain species of bacteria were correlated with a person’s attractiveness to mosquitoes. Interestingly, the combination of volatiles that are considered ‘attractive’ may differ based on the species of mosquito.

These findings are only correlational and there may be other factors that determine a person’s attractiveness to mosquitos. For example, genetics determining body odor likely play a role. The exact mechanisms that determine the composition of the skin microbiome and the volatile compounds produced are not yet known, but one could imagine targeting specific species of bacteria in the skin microbiota as a potential long-term mosquito repellent.