![Window with insect screen](https://upload.wikimedia.org/wikipedia/commons/d/dd/Window_with_insect_screen.JPG)
A mosquito net is a type of
mesh
A mesh is a barrier made of connected strands of metal, fiber, or other flexible or ductile materials. A mesh is similar to a web or a net in that it has many attached or woven strands.
Types
* A plastic mesh may be extruded, oriented, exp ...
ed curtain that is circumferentially draped over a bed or a sleeping area, to offer the sleeper
barrier protection against
bites and stings from
mosquito
Mosquitoes (or mosquitos) are members of a group of almost 3,600 species of small flies within the family Culicidae (from the Latin ''culex'' meaning " gnat"). The word "mosquito" (formed by ''mosca'' and diminutive ''-ito'') is Spanish for "li ...
s,
flies
Flies are insects of the order Diptera, the name being derived from the Greek δι- ''di-'' "two", and πτερόν ''pteron'' "wing". Insects of this order use only a single pair of wings to fly, the hindwings having evolved into advanced m ...
, and other
pest insect
Economic entomology is a field of entomology, which involves the study of insects that benefit or harm humans, domestic animals, and crops. Insects that cause losses are termed as pests. Some species can cause indirect damage by spreading diseases ...
s, and thus against the diseases they may carry. Examples of such preventable insect-borne diseases include
malaria
Malaria is a mosquito-borne infectious disease that affects humans and other animals. Malaria causes symptoms that typically include fever, tiredness, vomiting, and headaches. In severe cases, it can cause jaundice, seizures, coma, or death. S ...
,
dengue fever,
yellow fever
Yellow fever is a viral disease of typically short duration. In most cases, symptoms include fever, chills, loss of appetite, nausea, muscle pains – particularly in the back – and headaches. Symptoms typically improve within five days. ...
,
zika virus
''Zika virus'' (ZIKV; pronounced or ) is a member of the virus family ''Flaviviridae''. It is spread by daytime-active '' Aedes'' mosquitoes, such as '' A. aegypti'' and '' A. albopictus''. Its name comes from the Ziika Forest of Uganda, w ...
,
Chagas disease and various forms of
encephalitis, including the
West Nile virus
West Nile virus (WNV) is a single-stranded RNA virus that causes West Nile fever. It is a member of the family '' Flaviviridae'', from the genus '' Flavivirus'', which also contains the Zika virus, dengue virus, and yellow fever virus. The v ...
.
To be effective the mesh of a mosquito net must be fine enough to exclude such insects without obscuring visibility or ventilation to unacceptable levels. It is possible to increase the effectiveness of a mosquito net greatly by pretreating it with an appropriate
insecticide or
insect repellent
An insect repellent (also commonly called "bug spray") is a substance applied to skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellents help prevent and cont ...
. Research has shown mosquito nets to be an extremely effective method of malaria prevention, averting approximately 663 million cases of malaria over the period 2000–2015.
History
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
Sir Ronald Ross (13 May 1857 – 16 September 1932) was a British medical doctor who received the Nobel Prize for Physiology or Medicine in 1902 for his work on the transmission of malaria, becoming the first British Nobel laureate, and the f ...
identified mosquitoes as a vector for malaria.
Mosquito netting has a long history. Though use of the term dates from the mid-18th century,
Indian literature from the late medieval period has references to the usage of mosquito nets in ritual Hindu worship. Poetry composed by
Annamayya
Tallapaka Annamacharya (Telugu : తాళ్ళపాక అన్నమాచార్య) (IAST: taḷḷapāka annamācārya; 22 May 1408 – 4 April 1503), also popularly known as Annamayya, was a 15th-century Hindu saint and the ear ...
, the earliest known
Telugu
Telugu may refer to:
* Telugu language, a major Dravidian language of India
*Telugu people, an ethno-linguistic group of India
* Telugu script, used to write the Telugu language
** Telugu (Unicode block), a block of Telugu characters in Unicode
S ...
musician and poet, references ''domatera'', which means "mosquito net" in
Telugu
Telugu may refer to:
* Telugu language, a major Dravidian language of India
*Telugu people, an ethno-linguistic group of India
* Telugu script, used to write the Telugu language
** Telugu (Unicode block), a block of Telugu characters in Unicode
S ...
.
Use of mosquito nets has been dated to prehistoric times. It is said that
Cleopatra, the last active
pharaoh
Pharaoh (, ; Egyptian: '' pr ꜥꜣ''; cop, , Pǝrro; Biblical Hebrew: ''Parʿō'') is the vernacular term often used by modern authors for the kings of ancient Egypt who ruled as monarchs from the First Dynasty (c. 3150 BC) until the ...
of
Ancient Egypt, also slept under a mosquito net.
Mosquito nets were used during the malaria-plagued construction of the
Suez Canal.
Construction
Mosquito netting can be made from
cotton
Cotton is a soft, fluffy staple fiber that grows in a boll, or protective case, around the seeds of the cotton plants of the genus '' Gossypium'' in the mallow family Malvaceae. The fiber is almost pure cellulose, and can contain minor pe ...
,
polyethylene
Polyethylene or polythene (abbreviated PE; IUPAC name polyethene or poly(methylene)) is the most commonly produced plastic. It is a polymer, primarily used for packaging ( plastic bags, plastic films, geomembranes and containers including b ...
,
polyester,
polypropylene
Polypropylene (PP), also known as polypropene, is a thermoplastic polymer used in a wide variety of applications. It is produced via chain-growth polymerization from the monomer propylene.
Polypropylene
belongs to the group of polyolefins a ...
, or
nylon
Nylon is a generic designation for a family of synthetic polymers composed of polyamides ( repeating units linked by amide links).The polyamides may be aliphatic or semi-aromatic.
Nylon is a silk-like thermoplastic, generally made from pe ...
. A mesh size of stops mosquitoes, and smaller, such as , stops other biting insects such as
biting midges/no-see-ums.
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
A sleeping bag is an insulated covering for a person, essentially a lightweight quilt that can be closed with a zipper or similar means to form a tube, which functions as lightweight, portable bedding in situations where a person is sleeping ...
to provide protection from insects. A mosquito bar could be used to protect oneself from mosquitoes and other insects while sleeping in jungle areas.
The mesh is
woven
Woven fabric is any textile formed by weaving. Woven fabrics are often created on a loom, and made of many threads woven on a warp and a weft. Technically, a woven fabric is any fabric made by interlacing two or more threads at right angles to on ...
tightly enough to stop
insect
Insects (from Latin ') are pancrustacean hexapod invertebrates of the class Insecta. They are the largest group within the arthropod phylum. Insects have a chitinous exoskeleton, a three-part body ( head, thorax and abdomen), three ...
s 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.
Usage
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.
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.
Where mosquito nets are freely or cheaply distributed, local residents sometimes
opportunistically use them inappropriately, for example as
fishing net
A fishing net is a Net (device), net used for fishing. Nets are devices made from fibers woven in a grid-like structure. Some fishing nets are also called fish traps, for example #Fyke nets, fyke nets. Fishing nets are usually meshes formed by ...
s. 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.
In addition, insecticides with which the mesh has been treated, such as
permethrin
Permethrin is a medication and an insecticide. As a medication, it is used to treat scabies and lice. It is applied to the skin as a cream or lotion. As an insecticide, it can be sprayed onto clothing or mosquito nets to kill the insects th ...
, may be harmful to the
fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of ...
and other
aquatic fauna.
Insecticide-treated nets
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
Burkina Faso (, ; , ff, 𞤄𞤵𞤪𞤳𞤭𞤲𞤢 𞤊𞤢𞤧𞤮, italic=no) is a landlocked country in West Africa with an area of , bordered by Mali to the northwest, Niger to the northeast, Benin to the southeast, Togo and Ghana to ...
. ITNs are estimated to be twice as effective as untreated nets,
and offer greater than 70% protection compared with no net. 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.
Effectiveness
The distribution of mosquito nets or bednets impregnated with insecticides such as
permethrin
Permethrin is a medication and an insecticide. As a medication, it is used to treat scabies and lice. It is applied to the skin as a cream or lotion. As an insecticide, it can be sprayed onto clothing or mosquito nets to kill the insects th ...
or
deltamethrin
Deltamethrin is a pyrethroid ester insecticide. Deltamethrin plays a key role in controlling malaria vectors, and is used in the manufacture of long-lasting insecticidal mosquito nets; however, resistance of mosquitos and bed bugs to deltamethri ...
has been shown to be an extremely effective method of malaria prevention.
According to a 2015 ''Nature'' study, mosquito nets averted 68% of an estimated 663 million averted cases of malaria infection since 2000.
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 United Nations (UN) is an intergovernmental organization whose stated purposes are to maintain international peace and security, develop friendly relations among nations, achieve international cooperation, and be a centre for harmoniz ...
, the
World Health Organization
The World Health Organization (WHO) is a specialized agency of the United Nations responsible for international public health. The WHO Constitution states its main objective as "the attainment by all peoples of the highest possible level of ...
(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
The Millennium Development Goals (MDGs) were eight international development goals for the year 2015 that had been established following the Millennium Summit of the United Nations in 2000, following the adoption of the United Nations Millenn ...
(MDGs). 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.
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.
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.
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.
Distribution
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
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...
, conducted by economists
Pascaline Dupas
Pascaline Dupas is a French economist whose research focuses on development economics and applied microeconomics, with a particular interest in health, education, and savings. She is a professor in economics at Stanford University, holds senior ...
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.
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."
[
The researchers base their conclusions about the cost-effectiveness of free distribution on the proven spillover benefits of increased ITN usage. ITNs protect the individuals or households that use them, and they protect people in the surrounding community in one of two ways.
* 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 bitten by an infected mosquito.][Killeen GF, Smith TA (2007) Exploring the contributions of bednets, cattle, insecticides and excito-repellency to malaria control: A deterministic model of mosquito host-seeking behaviour and mortality. ''American Journal of Tropical Medicine and Hygiene''.]
* 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. ''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. By killing mosquitoes before maturation of the malaria parasite, ITNs can reduce the number of encounters of infected mosquitoes with humans.
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 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.
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
Tanzania (; ), officially the United Republic of Tanzania ( sw, Jamhuri ya Muungano wa Tanzania), is a country in East Africa within the African Great Lakes region. It borders Uganda to the north; Kenya to the northeast; Comoro Islands ...
concluded that effective life of polyester nets was 2 to 3 years; 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. 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
A review of 22 randomized controlled trial
A randomized controlled trial (or randomized control trial; RCT) is a form of scientific experiment used to control factors not under direct experimental control. Examples of RCTs are clinical trials that compare the effects of drugs, surgical te ...
s of ITNs 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%. The conclusion of this study showed that 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.
Associated problems
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. 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. 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.
Alternatives
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.
Some alternatives are:
*The use of a fan to increase air flow.
*The application of an insect repellent
An insect repellent (also commonly called "bug spray") is a substance applied to skin, clothing, or other surfaces to discourage insects (and arthropods in general) from landing or climbing on that surface. Insect repellents help prevent and cont ...
to the skin; this also may be less effective (reducing rather than eliminating bites), more expensive, and may pose health risks with long-term use.
*The use of indoor residual spraying of insecticides. This was a common practice in the late-20th Century. However, due to an increased awareness of the environmental hazards associated with the insecticide DDT used for some of these programs, this practice became less common. For example - American funding for African programs were cut and the number of malaria-infected subjects skyrocketed. In order to see results from the use of indoor residual spraying programs 80% of homes in the affected area need to be sprayed and the application of insecticide needs to be constant in order to suppress certain species which are immune to the insecticide. Large-scale application results in a dependence on continual spraying. If the aggressive style of application is not maintained then the risk of an increase of genetically-resistant mosquitos increases. This would ultimately result in an unrealistic mediation process.[Chareonviriyaphap , Theeraphap . "Review of insecticide resistance and behavioral avoidance of vectors of human diseases in Thailand." BioMed Central 6 (2013): Web. 21 Feb. 2014.]
See also
*Nothing But Nets
Nothing But Nets is a global, grassroots campaign of the United Nations Foundation to raise awareness and funding to fight malaria, a leading cause of death among children in Africa.
The campaign aims to prevent malaria deaths by purchasing, d ...
*Against Malaria Foundation
The Against Malaria Foundation (AMF) is a United-Kingdom based charity that provides long-lasting insecticidal nets (LLINs) to populations at high risk of malaria, primarily in Africa. As of December 2021, the foundation has raised $425 million ...
* Spread the Net
*Four-poster bed
__NOTOC__
A four-poster bed is a bed with four vertical columns, one in each corner, that support a tester, or upper (usually rectangular) panel. This tester or panel will often have rails to allow curtains to be pulled around the bed. There ar ...
*Canopy bed
A canopy bed is a bed with a canopy, which is usually hung with bed curtains. Functionally, the canopy and curtains keep the bed warmer, and screen it from light and sight. On more expensive beds, they may also be elaborately ornamental.
History ...
* Screened porch
References
External links
World Health Organization factsheet
Organization Malaria NIMBY Not In My Back Yard
"Malaria and Poverty" article from Wiley
{{DEFAULTSORT:Mosquito net
Protective gear
Insect control
Nets (devices)
Culicidae
Flies and humans