Which Mosquito Repellents are safe for use.

A Community Health

How to Control Mosquito

Part 5: Mosquito (insect) Repellent

How to seek safe and effective ways of preventing mosquito bites

The best way to reduce mosquito-borne diseases is through mosquito control and personal protection. We can do a few things to reduce the number of mosquito bites that we get while enjoying the outdoors. Firstly, wear clothing that covers most of your body, secondly, use a mosquito repellent, beside mosquito repellents and clothing, we can try to control the mosquito population, mosquitoes need water to breed and will use any source of standing water.

An insect repellent or a mosquito repellent is a substance applied to skin, clothing, or other surfaces which discourages insects (and arthropods in general) from landing or climbing on that surface. It has been estimated that 300 to 400 compounds are released from the body as by-products of metabolism and that more than 100 volatile compounds can be detected in human breath. Carbon dioxide and lactic acid are the two best-studied mosquito attractants, carbon dioxide, released mainly from breath but also from skin, serves as a long-range airborne attractant and can be detected by mosquitoes at distances of up to 36 meters. Lactic acid, in combination with carbon dioxide, is also an attractant. Mosquitoes have chemo-receptors on their antennae that are stimulated by lactic acid. Usually insect repellents work by masking human scent, or by using a scent which insects naturally avoid. Permethrin is different in that it is actually a contact insecticide.

Insect repellents help prevent and control the outbreak of insect-borne diseases such as malaria, Lyme disease, Dengue fever, bubonic plague, and West Nile fever. Pest animals commonly serving as vectors for disease include the insects flea, fly, and mosquito; and the arachnid tick.

Female mosquitoes bite people and animals because they need the protein found in blood to help develop their eggs. Mosquitoes are attracted to people by skin odors and carbon dioxide from breath. The active ingredients in repellents make the person unattractive for feeding. Repellents do not kill mosquitoes. Repellents are effective only at short distances from the treated surface, so we may still see mosquitoes flying nearby.

To be effective, a repellent must show an optimal degree of volatility, making it possible for an effective repellent vapor concentration to be maintained at the skin surface without evaporating so quickly that it loses its effectiveness. Many factors play a role in how effective any repellent is, including the frequency and uniformity of application, the number and species of the organisms attempting to bite, the user's inherent attractiveness to blood-sucking arthropods, and the overall activity level of the potential host. Abrasion from clothing, evaporation and absorption from the skin surface, wash-off from sweat or rain, higher temperatures, or a windy environment all decrease repellent effectiveness. Each 10°C increase in temperature can lead to as much as a 50% reduction in protection time. The repellents currently available must be applied to all exposed areas of skin; unprotected skin a few centimeters away from a treated area can be attacked by hungry mosquitoes

Synthetic repellents tend to be more effective and longer lasting than 'natural' repellents, However, some plant-based repellents are comparable to, or somewhat better than synthetics - depending on the formula, Essential oil repellents can be short-lived in their effectiveness, since essential oils can evaporate completely.

A test of various insect repellents by an independent consumer organization found that repellents containing DEET or picaridin are more effective than repellents with 'natural' active ingredients. All the synthetics gave almost 100% repellency for the first 2 hours, where the natural repellent products were most effective for the first 30-60 minutes, and required reapplication to be effective over several hours. However, some products in the market like essential oil candle and natural herb mosquito coil can give protection to an entire room up to 8 hours.

For protection against mosquitos, the U.S. Centers for Disease Control issued a statement in May 2008 recommending equally DEET at a concentration of 7.5 percent to 100 percent, Picaridin, oil of lemon eucalyptus and IR3535 for skin. Lower DEET concentrations are sufficient for most outdoor protection, and a 15-percent concentration is recommended for children. Permethrin is recommended for clothing, gear, or bed nets. When DEET-based repellents are applied in combination with permethrin-treated clothing, protection against bites of nearly 100% can be achieved.

Common insect repellents :

[1] Chemical compounds:

1. DEET (N,N-diethyl-m-toluamide), inhibit the mosquito’s chemo-receptor.

DEET / N,N-diethyl-m-toluamide

N,N-diethyl-m-toluamide, or N,N-diethyl-3-methylbenzamide (DEET) is the most effective, remains the gold standard of currently available insect repellents. This substance was discovered and developed by scientists at the U.S. Department of Agriculture and was patented by the U.S. Army in 1946. It was subsequently registered for use by the general public in 1957. It is a broad-spectrum repellent that is effective against mosquitoes, biting flies, chiggers, fleas, and ticks. Twenty years of empirical testing of more than 20 000 other compounds has not resulted in another marketed chemical product with the duration of protection and broad-spectrum effectiveness of DEET. This substance has a remarkable safety profile after 40 years used by millions of people worldwide, but toxic reactions can occur, someone cannot use DEET as a mosquito repellent due to skin irritation or to its potential to damage things like plastic, more than 30 studies were conducted to assess acute, chronic, and subchronic toxicity; mutagenicity; oncogenicity; and developmental, reproductive, and neurologic toxicity The results of these studies did not require any change to the product to comply with EPA safety standards, nor did they indicate any new toxicities with normal use. Studies of high doses of DEET orally administered to mice and rats did not reveal any potential in humans for teratogenicity or oncogenicity.

DEET is an effective active ingredient found in many repellent products and in a variety of formulations, including solutions, lotions, creams, gels, aerosol and pump sprays, and impregnated towelettes, in 5% to 100% concentrations.

• A product containing 23.8% DEET provided an average of 5 hours of protection from mosquito bites.
• A product containing 20% DEET provided almost 4 hours of protection
• A product with 6.65% DEET provided almost 2 hours of protection
• Products with 4.75% DEET were both able to provide roughly 1 and a half hour of protection.

Autan of SC Johnson contains 12,50% DEET

Soffell contains 13,00% DEET

2. Permethrin : an effective pesticide, is for use on clothing only, never apply it to our skin, it is a neurotoxin !
3. Picaridin, also known as Icaridin/ Bayrepel / KBR 3023, derives from pepper. Picaridin is derived from pepper and has been approved for use in the US since 2005. It is available in some versions of Avon® Skin So Soft lotions, and sold as Cutter Advanced Insect Repellent too. Though this mosquito repellent is not quite as effective as DEET, it can be used on infants two months or older, and it has a smell that many people find pleasant or at least less off-putting than DEET. Some claim picaridin is just as effective as DEET, but these claims are difficult to prove because both chemicals can be used at different concentration levels.
4. Vitamin B-1 (Thiamin) : Some studies suggest that taking thiamine (vitamin B1) 25 mg to 50 mg three times per day is effective in reducing mosquito bites. This safe vitamin apparently produces a skin odor that is not detectable by humans, but is disagreeable to pregnant mosquitoes, It seems to be especially effective for those people with large allergic reactions. Thiamine takes about 2 weeks before the odor fully saturates the skin. Vitamin B1. Consistant anecdotal evidence suggests that mozzies hate the smell of this vitamin.

[2] Essential Oils:

1. Essential oil of the lemon eucalyptus and its active ingredient p-menthane-3,8-diol (PMD), Plant-based repellents are generally less effective than DEET-based products, but CDC found oil of lemon eucalyptus to be more effective than other plant-based treatments, product containing 40% oil of lemon eucalyptus was just as effective as products containing high concentrations of DEET.
2. Citronella oil : effectiveness in repelling Aedes aegypti, but requires reapplication after 30-60 minutes.
3. Catnip Oil / Nepetalactone, the essential oil in catnip that gives the plant its characteristic odor, is about ten times more effective at repelling mosquitoes than DEET
4. Neem oil : is mosquito repellent for up to 12 hours.

Electronic Repellent :

Electronic repellents utilize one to two sound frequencies (ultrasound / inaudibly high frequency sounds) to simulate dragonflies and other male mosquitoes, creating a competitive environment for the blood-sucking female, these devices come in a compact unit that we can take anywhere for protection. Some units even have a built-in red flashlight for nighttime use.

Electric Mosquito Repellent :

A most effective way to keep a room free of mosquitoes and other small pests all night long by heat, releases natural Pyrethrins smokeless into the air, killing mosquitoes in the room, repelling those outside. Using a chip in an electrical mosquito vaporizer, contains upto 0,5% volatile natural pyrethrins to kill and repel mosquitoes.

Mosquito Coils :

To kill & repel Mosquito

Burning mosquito coils indoors generates smoke that can control mosquitoes effectively, the smoke due to emission of fine particles (particulate) may contain pollutants of health concern that exceed health-based air quality standards, they contain many volatile organic compounds (VOC), like formaldehyde, including carcinogens and suspected carcinogens, in the smoke of mosquito coils, the particles pollutants are fine and ultrafine.

Ingredient of Mosquito Coils :

1. Pyrethroid / Synthetic Pyrethrins : Contain : 0,1% - 0.3% Alletrin, D-Alletrin, D-trans Allethrin, bio-Allethrin and esbio-Allethrin,

and fragrances of perfumes: popular flower fragrances such as Lavender, Sandalwood.

2. Pyrethrum flower : Environment-friendly (Eco-friendly) Mosquito Coils :Contain : 0,2% - 0,5% Natural dried pulverized Pyrethrum flowers.
3. Combination of natural Pyrethris and synthetic PyrethroidsContain : 0,2% natural Pyrethrins + 0,1% synthetic pyrethroid D-Allethrin.

How safe are mosquito coils?

The growing menace of mosquitoes has forced people to turn to mosquito repellents in the form of body lotions, creams, coils and mats. For many families burning Mosquito Coils are a daily ritual. Mosquito Coils which use synthetic pyrethroids like Allethrin are effective in controlling the mosquitoes’ bites, the fumes emitted by the Coils are toxic for mosquitoes but safe for human beings.

The proper use of Mosquito Coils, burning at temperature of about 80° C, the smoke from the Coils prevent the mosquitoes from entering the room, while those mosquitoes already inside the room are expelled or knocked down and killed, the chemicals used in these Mosquito repellents are nerve poison. they affect the nervous systems of mosquitoes.

Prolonged use of Mosquito Coils are harmful for several organs in the human body, they can lead to corneal damage, shortness of breath, asthma and even damage the liver in the long run, affect male as well as female fertility. Allethrin affects human beings adversely, but very slowly , and the effect depends upon the weight of the person. There is no danger for heavy persons but light weight children may be affected.

Don’t use Moquito Coils eveyday, use only in a limited of time,

best use 2 hours before sleeping !

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Part 4: Pyrethroids Insecticides

Chrysanthemum flowers

The flower of Pyrethrums from the plants Chrysanthemum cinerariaefolium and C. coccineum, familia Asteraceae, produce natural chemical pyrethrins,
pyrethrins are contained in the seed cases, which is grown commercially to supply the insecticide, pyrethrins are a pair of natural organic compounds that have potent insecticidal activity. pyrethrin I and pyrethrin II, the chemical structure of pyrethrins is the basis for a variety of synthetic insecticides called pyrethroids.

Pyrethrin I

Pyrethrin II

Pyrethrins are neurotoxins that attack the nervous systems of all insects. when present in amounts not fatal to insects, they still appear to have an insect repellent effect, pyrethrins are harmful to fish, birds, and mammals, including human beings. In human beings, pyrethrin irritates the eyes, skin, and respiratory systems, and it may cause other harmful effects.
pyrethrins are gradually replacing organophosphates and organochlorides as the pesticide of first choice.

Pyrethroids : Synthetic Pyrethrins

Pyrethroids are synthetic chemical compounds similar to the natural chemical pyrethrins, pyrethroid chrysanthemic acid is produced industrially in a cyclopropanation reaction of a diene as a mixture of cis- and trans isomers followed by hydrolysis of the ester, they are common in commercial products such as household insecticides and insect repellents, in the concentrations used in such products, they are generally harmless to human beings but can harm sensitive individuals. They are usually broken apart by sunlight and the atmosphere in one or two days, and do not significantly affect groundwater quality except for being toxic to fish.

Pyrethroids are axonic poisons (see Note*) that work by keeping the sodium channels open in the neuronal membranes of insects, the sodium channel is a small hole through which sodium ions are permitted to enter the axon and cause excitation. as the nerves cannot de-excite, the insect is paralyzed.
pyrethroids are usually combined with piperonyl butoxide, a known inhibitor of key microsomal oxidase enzymes, this prevents these enzymes from clearing the pyrethroid from the body of the insect, and assures the pyrethroid will be lethal and not merely a paralyzing agent. Insects with certain mutations in their sodium channel gene may be resistant to pyrethroid insecticides.

(Note*) Insecticides are neurotoxin, attack the nervous system of insects. There are two main parts of the nervous system: the nerve fibers, called axons, which carry small electrical impulses, and the synapse, the microscopic gap between nerve fibers (axons), because each nerve fiber ends at a synapse, the nerve impulse must be carried across the synapse chemically. The pesticides that attack the synapse are called synaptic poisons, and that attack the nerve fiber (axon) itself are called axonic poisons.

Allethrin

Cyfluthrin

Transflutrin

Commercial Pyrethroid Insecticides / Repellants

[1] Allethrins, [2] Bifenthrin, [3] Cyfluthrin, [4] Cypermethrin, [5] Deltamethrin, [6] Permethrin, [7] Prallethrin, [8] Rasmethrin, [9] Phenothrin or Sumithrin, [10] Tetramethrin, [11] Tralomethrin, [12] Transflutrin, [13] Imiprothrin.

[1] Allethrins are a pair of related synthetic compounds used in insecticides, they are first synthetic pyrethroids, synthetic forms of a chemical found naturally in the chrysanthemum flower.

[2] Bifenthrin a 4th generation pyrethroid, is insoluble in water, has high persistence in soil (half life = 7 days - 8 months), it is the longest residual termiticide currently registered on the market.

[4] Cypermethrin is fast-acting neurotoxin in insects, easily degraded on soil and plants but can be effective for weeks when applied to indoor inert surfaces, exposure to sunlight, water and oxygen will accelerate its decomposition.

[5] Deltamethrin is one of the safest classes of pesticides: synthetic pyrethroids, the most popular and widely used insecticides in the world and have become very popular with pest control operators and individuals in the United States in the past five years, mammalian exposure to deltamethrin is classified as safe, this pesticide is highly toxic to aquatic life, particularly fish, and therefore must be used with extreme caution around water. Deltamethrin is also one of the primary ingredients in ant chalk.

[6] Permethrin does not repel insects but works as a contact insecticide, causing nervous system toxicity that leads to the death or "knockdown" (out of the air) of the insect. effective against mosquitoes, flies, ticks, and chiggers, permethrin has low toxicity in mammals, is poorly absorbed by the skin, and is rapidly inactivated by ester hydrolysis. Permethrin should be applied directly to clothing, shoes, bed nets and camping gear or other fabrics not to skin, permethrin-treated clothing repels and kills ticks, mites, mosquitoes, and other arthropods and retains this effect after repeated laundering, the spray form is nonstaining, nearly odorless, and resistant to degradation by heat or sun (long-lasting repellent) and maintains its potency for at least 2 weeks. Combination of permethrin-treated clothing and skin application of a DEET-based repellent creates a formidable barrier against mosquito bites.

[8] Resmethrin is a pyrethroid insecticide with many uses, including control of the adult mosquito population.

[9] Phenothrin, also called sumithrin, is a synthetic pyrethroid that kills adult fleas and ticks, it has also been used to kill head lice in humans. phenothrin is often used with methoprene, an insect growth regulator that interrupts the insect's biological life cycle by killing the eggs.

[11] Tralomethrin has potent insecticidal properties; it kills by modifying the gating kinetics of the sodium channels in neurons, increasing the length of time the channel remains open after a stimulus, thereby depolarizing the neuron for a longer period of time, this leads to uncontrolled spasming, paralysis, and eventual death.

[12] Transfluthrin can be used in the indoor environment against flies, mosquitoes and cockroaches, it is a relatively volatile substance and acts as a contact and inhalation agent.

Examples :
((1)). Baygon indoor Insecticide, to kill: mosquitos Aedes aegypti, Culex quinquefasciatus, flies Musca domestica, and cockroaches: Blatella germanica, contains: [13] Imipothrin 0,05%, [4] Cypermethrin 0,10%, [12] Transfluthrin 0,06%.
((2)). Baygon indoor Insecticide, to kill: mosquitos Aedes aegypti, Culex quinquefasciatus, and flies Musca domestica, contains: [6] Permethrin 0,10%, [7] Prallethrin 0,04%, [12] Transfluthrin 0,04%.
((3)). Raid Max indoor Insecticide, to kill: mosquitoes, flies, and roaches, contains: [3] Cyfluthrin 0,06%, [12] Transfluthrin 0,06%.
Raid is the brand name of a line of insecticides produced by SC Johnson, first launched in 1956, the initial active ingredient was the first synthetic pyrethroid, Alethrin.

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Part 3: Larvacides, Pesticides, Insecticides

[A] Control the Mosquitoes in their early life cycle in the water

with Larvicides

All mosquitoes need water to breed,

So destroy completely the Larvae and mosquito-population-control efforts usually involve

draining, removing, closing and treating of the standing water sources.

USING :

Larvacides

Larvacide are insecticides that are specifically targeted against the larvae /

larval life stage of insects. Their most common use is against mosquitoes. Larvacides may be contact poisons, stomach poisons, growth regulators, or biological control agents. There are two kind of Larvacides:

1. Biological agents / Bacterial larvacides :
• Bt (Bacillus thuringiensis), Bti. (Bacillus thuringiensis israelensis), and Bacillus sphaericus. both are naturally occur soil bacteria registered as larvicides, distributed on the surface of stagnant water locations. When the mosquito larvae ingest the bacteria, crystallized toxins are produced which destroy the digestion tract, resulting in death. These larvacides will last only a few weeks in water and cause no danger to humans, non-targeted animal species, or the environment when used according to directions.
• Methoprene (Altosid): is another biological agent that interrupts the growth cycle of insect larvae, preventing them from development beyond the pupa stage, usually applied to larger bodies of water in the form of time-release briquettes which can last from one to five months.

Metoprene

isopropyl (E,E)-(RS)-11-methoxy-3,7,11-trimethyldodeca-2,4-dienoate.

Methoprene interferes with the normal life cycle of an insect by mimicking an insect growth hormone, it prevents the development of adult mosquitoes from larvae. It is effective against several types of mosquitoes, including the Culex species, the common household mosquito, which is most commonly associated with West Nile Virus. Methoprene is applied early in the mosquito breeding season to wet areas where mosquitoes live and lay eggs, such as storm water and drainage systems, granulated or briquette or pellet forms of methoprene are placed in these areas, where they slowly release larvicide for 30 days. A methoprene briquette could also be used which slowly releases larvicide for 90 days. Use of this larvicide does not cause an unreasonable health risks to human beings or other wildlife and it will not leach into the ground water supply. There is a small acute and chronic risk to some fish and freshwater invertebrate species.

2. Chemical agents / Organophosphate larvacides :
• Abate or Temephos is an organophosphate which prevents mosquito larvae from developing resistance to bacterial larvicides. Due to the small amount needed and the fast rate that temephos breaks down in water, this type of larvicide does not cause an unreasonable health risk to human beings, but at large doses it can cause nausea or dizziness, there is not a large risk to terrestrial species, but there is a toxic concern for non-targeted aquatic species. Therefore, temephos should be limited only to sites where less hazardous larvicides are ineffective and with intervals between applications.

Abate / Temephos

[B] Control the Mosquitoes in their adult life cycle on the Land and in the Air

with Pesticides & Insecticides

Pesticides are substances or mixture of substances used to kill pests (harmful organisms), they may be chemical substances, or biological agents.

Pesticides include algaecides, avicides, bactericides, fungicides, herbicides, insecticides, miticides, molluscides, nematicides, rodenticides, virucides.

Insecticides are pesticides used against insects in all developmental forms, they include ovicides used against the eggs and larvicides used against the larvae of insects. Insecticides are used in agriculture, medicine, industry and the household, all insecticides have the potential to significantly alter ecosystems; many are toxic to human beings, and others are concentrated in the food chain.

Classification of Insecticides:

1. Organochlorine compounds: DDT / Dichloro-Diphenyl-Trichloroethane is one of the best known synthetic pesticides.
2. Organophosphates: Dichlorphos, Chlorpyrifos is a toxic crystalline organophosphate insecticide, Malathion, a relatively low-human toxicity insecticide.

Dichlorphos, Chlorpyrifos usually used as aerosol spray insecticides, Malathion usually used for fogging an area to kill all mosquitoes.

3. Carbamates: or urethanes, are a group of organic compounds sharing a common functional group with the general structure -NH(CO)O-. carbamates are esters of carbamic acid (NH₂COOH). Propoxur is a carbamate derivative which is used as an mosquito insecticide.
4. Pyrethroids: synthetic pyrethrins: Allethrin, permethrin, Transfluthrin etc. (See Part 4).
5. Neonicotinoids: are synthetic analogues of the natural insecticide nicotine with a much lower acute mammalian toxicity and greater field persistence, systemic insecticides with a rapid action, often as substitutes for organophosphates and carbamates.
6. Biological insecticides: Bacillus thuringiensis, a bacterial disease of Lepidopterans and some other insects. it is used as a larvicide against a wide variety of caterpillars, it has little effect on other organisms, it is considered more environmentally friendly than synthetic pesticides.

Mosquito Fogging

What is a Fog ?

A fog is a suspension of small liquid droplets in gas / air characterized by its doplet size distribution,However, people tend to describe

There are many terms of fogs as dry fog (10-15 micron volume mean diameter), wet fog (20-30 micron), mist (30-60 micron), fine spray (above 60 micron), etc.

This insecticide fog is a heavy oil based formula designed for use in thermal foggers that can deliver spray particle sizes within the aerosol size range. This fogging insecticide is a synthetic pyrethroid formula and is ideal for outdoor applications as well as indoors.

Active Ingredients : synthetic pyrethroid such as Rasmethrin, organophosphate insecticide such as Malathion, Piperonyl butoxide.

Base Ingredients : Petroleum Destillates, light Paraffin, light Naphthenic, Gasoline.

Harmful if swallowed, inhaled, or absorbed through skin. Avoid breathing vapors or spray mist. Avoid contact with skin and eyes. Avoid direct exposure to fog.

Wash contaminated clothing prior to reuse. Do not contaminate food or feed. In food processing

This formula is combustible. Keep container sealed. Do not use, pour, spill or store near heat or open flame. IF SWALLOWED: Call a physician or Poison Control Center immediately. Gastric lavage is indicated if material is taken internally. Do not induce vomiting as this may cause aspiration pneumonia. IF INHALED: Apply artificial respiration if required. FOR SKIN: Remove contaminated clothing and wash affected areas with soap and water. FOR EYES: Flush eyes with plenty of water. Get medical attention if irritation persists.

Active Ingredients : Resmethrin: 0.20% Inert Ingredients : (Contains Petroleum Distillates ) 99.80% USDA: F1 Color: Colorless

Malathion

Malathion is an organophosphate parasympathomimetic which binds irreversibly to cholinesterase. Malathion is an insecticide of relatively low human toxicity.

Malathion is a pesticide that is widely used in agriculture, residential landscaping, public recreation areas, and in public health pest control programs such as mosquito eradication, used in conjunction with diesel fuel to fog an area where there is an infestation of mosquitoes. In the US, it is the most commonly used organophosphate insecticide.

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Part 2: Mosquito’s battery sensors

Mosquitoes have 3 (three) kind of battery of sensors designed to track their hosts (animals, birds, human-beings), they are :
1. Chemical sensors - mosquitoes can detect or recognize carbon dioxide and lactic acid up to 36 meters away, mammals and birds gives off these gases as part of their normal breathing, certain chemicals in sweat also seem to attract mosquitoes, people who sweat less don't get many mosquitoes bites, one of the many ways to stop mosquitoes from biting is to confuse or inhibit their chemical receptors with chemical compound like DEET (N,N-diethyl-3-methyl-benzamide).
2. Visual sensors - if you are wearing clothing that contrasts with the background, and you move while wearing that clothing, mosquitoes can see you and pointed on you, for mosquitoes anything that moving means "alive", and therefore full of blood.
3. Heat sensors - Mosquitoes can detect heat, so they can find warm-blooded mammals and birds very easily once they get close enough. That is why mosquitoes can always detect our present no matter we are in dark rooms or in bright places, our body temperature 37º C are higher than the ambient temperature surround us.
¬
¬With many kinds of their sensors mosquitoes are so good at finding and biting human beings, eventhough, as a matter of fact, human beings are not the first choice for most mosquitoes looking for meals, they usually prefer horses, cattles, and birds.

Same with all insects, adult mosquitoes have three basic body parts:
1. Head - where all the sensors are, along with the biting apparatus. The head has two compound eyes, antennae to sense chemicals and the mouth parts called the palpus and the proboscis, only females h¬ave the proboscis, for biting.
2. Thorax - where the two wings and six legs attach, it contains the flight muscles, compound heart, some nerve cell ganglia and ¬trachioles.
3. Abdomen - contains the digestive and excretory organs.

It has been estimated that 300 to 400 compounds are released from our body as by-products of metabolism and among them more than hundred kinds of the metabolism by-products are organic volatile compounds (VOC) that can be detected in human breath. Unfortunately, among those odors, only a small fraction have been isolated and fully characterized. Carbon dioxide and lactic acid are the two best mosquito attractants.
• Carbon dioxide, released mainly from breath but also from skin, serves as a long-range airborne attractant and can be detected by mosquitoes at distances of up to 36 meters.
• Lactic acid, in combination with carbon dioxide, is also an attractant, mosquitoes have chemoreceptors on their antennae that are stimulated by lactic acid.

Skin temperature and moisture serve as mosquito attractants. Different species of mosquitoes may show strong biting preferences for different parts of the human body, such as the head or feet, which may be related to local skin temperature and eccrine sweat gland (skin sweat gland) output. Anhydrotic persons (persons who have less sweat) show markedly decreased attractiveness to mosquitoes. Other volatile compounds, derived from sebum (oily secretion of sebaceous gland in the hair follicels to lubricate the skin and the hair), eccrine and apocrine sweat (skin sweat glands), or the cutaneous microflora bacterial action on those secretions, may also act as chemo-attractants, the whole-host odors are more attractive than carbon dioxide and lactic acid alone. Be careful that floral fragrances from perfumes, soaps, lotions, and hair-care products may also attract mosquitoes, so do the same with eating banana fruits which will more attract the mosquito to bite.
The attractiveness of different persons to the same or different species of mosquitoes varies substantially. In general, adults are more likely to be bitten than children, although adults may become less attractive to mosquitoes as they age, men are bitten more readily than women, ovulating women (pregnant) more attractive than those menstruating, larger persons tend to attract more mosquitoes, perhaps because of their greater relative heat or carbon dioxide output.

Mosquitoes use exhaled carbon dioxide, body odors and temperature, and movement as the target point of their victims. Only female mosquitoes have the mouth parts necessary for sucking blood. When biting with their proboscis (sucking organ), they pierce two tubes into the skin, one to inject an enzyme that inhibits blood clotting (an anti-coagulant), the other to suck blood into their bodies. They use the blood not for their own food but as a source of protein for their eggs, the females of most mosquito species require a blood meal to support their developing eggs. they usually feed every 3 to 4 days; in a single feeding, a female mosquito typically consumes more than its own weight in blood, some mosquito species are zoophilic, preferring to feed on animals and others are anthropophilic, showing a preference for human blood. Certain species of mosquitoes prefer to feed at twilight or nighttime, others bite mostly during the day. For food, both males and females eat nectar and other plant sugars.

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A Community Health

How to control Mosquitoes

Part 1: Mosquito life cycle.

There are more than 3 thousand species of mosquitoes, among them three are responsible for the spread of human diseases. Anopheles mosquitoes carry malaria, filariasis (elephantiasis) and encephalitis. Culex mosquitoes carry encephalitis, filariasis, and the West Nile virus, Aedes mosquitoes carry yellow fever, dengue, and encephalitis. Humans being are actually not the first choice for most mosquitoes looking for meal. They prefer horses, cattle, and birds. The females of most mosquito species require a blood meal to support their developing eggs while the male mosquitoes feed on plant nectar.

Types of Mosquitoes:

1. Anopheles mosquito : These tend to breed in bodies of permanent fresh water. Anopheles mosquitoes also have abdomens with pointed tips. They include several species, such as the common malaria mosquito (Anopheles quadrimaculatus), that can spread malaria to humans.
2. Culex mosquito : These tend to breed in quiet, standing water. Culex mosquitoes have abdomens without a sharp edge tips. They include several species such as the northern house mosquito (Culex pipiens, Culex quinquefasciatus). They are weak fliers and tend to live for only a few weeks during the summer months. They persistently bite (preferring birds over humans) and attack at dawn or after dusk. Their bite is painful.
3. Aedes mosquito : These are sometimes called "floodwater" mosquitoes because flooding is important for their eggs to emerge. Aedes mosquitoes have abdomens with pointed tips. They include such species as the yellow-fever mosquito (Aedes aegypti) and the Asian tiger mosquito (Aedes albopictus). They are strong fliers, capable of travelling great distances (up to 75 miles / 121 km) from their breeding sites. They persistently bite mammals (especially humans), mainly at dawn and in the early evening. Their bites are painful.

Life Cycle and Breeding :

Like all insects, mosquitoes life cycle begin from eggs and go through several stages in their life cycle before becoming adults. all mosquitoes need water to breed, the females lay their eggs in water, the larva and pupa stages live entirely in water. When the pupa change into adults, they leave the water and become free-flying land insects. The life cycle of a mosquito can vary from one to several weeks depending upon the species, the adult, mated females of some mosquito species can survive the winter in cool, damp places until spring, when they will lay their eggs and die.

1. Egg : All mosquitoes lay eggs in water, which can include large bodies of water, standing water, like swimming pools, or areas of collected standing water, like tree holes, gutters, empty containers, bath-cubes, female mosquitoes lay their eggs on the surface of the water, except for Aedes mosquitoes, which lay their eggs above water in protected areas that eventually flood. The eggs can be laid singly or as a group that forms a floating raft of mosquito eggs.
2. Larva : The mosquito eggs emerge into larvae, which live at the surface of the water and breathe through an air tube or siphon. The larvae filter organic material through their mouth parts and grow to about 1 to 2 cm long; as they grow, they remove their skin several times. Mosquito larvae can swim and dive down from the surface when disturbed, the larvae live anywhere from days to several weeks depending on the water temperature and mosquito species. We can distinguish the larvae of various mosquito species. Anopheles larvae lie parallel to the surface of the water, while Aedes larvae and Culex larvae extend down into the water, the air tubes of Culex are longer than the air tubes of Aedes.

3. Pupa :After the fourth change of the skin, mosquito larvae change into pupae, which live in the water anywhere from one to four days depending on the water temperature and species. The pupae float at the surface and breathe through two small tubes. Although they do not eat, pupae are quite active, At the end of the pupal stage, the pupae cover themselves with pupal cases and transform into adult mosquitoes.
4. Adult : Inside the pupal case, the pupa transforms into an adult. The adult uses air pressure to break the pupal case open, crawls to a protected area and rests while its external skeleton hardens, spreading its wings out to dry. Once this is complete, it can fly away and live on the land. One of the first things that adult mosquitoes do is seek a mate, mate and then feed. Male mosquitoes have short mouth parts and feed on plant nectar. In contrast, female mosquitoes have a long proboscis that they use to bite animals and humans and feed on their blood, the blood provides proteins that the females need to lay eggs. After they feed, females lay their eggs, they need a blood meal each time they lay eggs. Females continue this cycle and live anywhere from many days to weeks, males usually live only a few days after mating. The life cycles of mosquitoes vary with the species and environmental conditions.

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