Mosquitoes are small, long-legged flies with slender bodies that require pools of standing water to complete their development (Figure 1). As adults, male and female mosquitoes feed on plant nectar (Figure 2), but most species of female mosquitoes must feed on animal blood in order to produce eggs (Figure 3). During this process, female mosquitoes can transmit pathogens to humans such as viruses that cause West Nile fever and St. Louis encephalitis, and parasites that cause malaria and canine heartworm. Adults can vary in length from 0.15 to 0.5 inch. Mosquito eggs are usually around 0.025 inches long and are laid on or near water. Eggs hatch into larvae, called wrigglers, that molt three times before developing into pupae, called tumblers. Larvae and pupae live in water (Figure 1) while adults are free flying.
Mosquitoes and Disease Transmission
Mosquitoes are reviled because they can transmit potentially deadly pathogens to humans and animals, including livestock and pets. However, only six of the 65 species present in the state of Ohio pose the threat of disease transmission to humans and domestic animals (Table 1).
|Common Name||Scientific Name||Medical Importance|
|Asian tiger mosquito||Aedes albopictus||Eastern equine encephalitis, La Crosse encephalitis, St. Louis encephalitis, canine heartworm, West Nile virus, Zika|
|Banded spring mosquito||Aedes canadensis||La Crosse encephalitis|
|Eastern treehole mosquito||Aedes triseriatus||La Crosse encephalitis, St. Louis encephalitis|
|Common malaria mosquito||Anopheles quadrimaculatus||Avian malaria|
|Cattil mosquito||Coquillettidia perturbans||Eastern equine encephalitis|
|Northern house mosquito||Culex pipiens||St. Louis encephalitis, West Nile virus
In addition to disease transmission, when female mosquitoes bite humans and other animals, they can cause an allergic reaction, resulting in a red, itchy welt near the bite site. When mosquitoes bite, they stick their proboscis into the skin and acquire blood from a capillary. While females are sucking blood, they also release anti-coagulants that prevent blood from clotting. The immune system of the unfortunate human or animal recognizes these foreign proteins from the mosquito, resulting in swelling and itching. During blood-feeding, mosquitoes also can transmit parasites and viruses that cause illness and diseases. The most common diseases that are transmitted in Ohio include West Nile virus, La Crosse virus, St. Louis encephalitis virus, and Eastern equine encephalitis virus. The Ohio Department of Health and the Center for Disease Control (CDC) have detailed information on all these viruses. Several species of mosquitoes also transmit canine heartworm to dogs and cats.
Preventing Mosquito-borne Diseases
Currently, there are vaccines that protect humans from yellow fever (transmitted in the tropics) and horses from contracting West Nile virus. Heartworm preventives can kill juvenile filarial worms acquired from the bite of an infected mosquito. However, the best way to prevent the spread of mosquito-vectored disease is to control the mosquito! Despite popular belief, mosquitoes do not travel very far from where they develop. Some travel less than 45 yards, but in general most mosquitoes do not travel more than half a mile. Controlling mosquito-borne diseases is accomplished by preventing mosquito bites and using known, effective methods to prevent mosquito larvae and pupae from completing their development as well as killing adult mosquitoes.
Controlling Mosquitoes In and Around the Home
First and foremost, make sure that mosquitoes cannot enter your home. This includes filling any gaps around windows or doors of the house and ensuring there are adequate screens with mesh that is 16 by 16, or 14 by 18 squares per inch on open doors and windows. Mosquito nets can be used on outside patios to make them mosquito-proof (Figures 6 and 7).
Drain, Dress, and Defend
The American Mosquito Control Association suggests remembering the three Ds for preventing mosquito bites: drain, dress, and defend (American Mosquito Control Association 2021).
- Drain breeding areas to stop mosquitoes before they are able to bite. The items on this checklist ensure your yard does not contain mosquito breeding habitats:
- Dump and clean bird baths every week.
- Install drains where standing water occurs after rains (Figure 8).
- Properly dispose of tires. According to the EPA, tires provide the perfect environment for mosquitoes to breed; one tire can provide the habitat for thousands of larval and pupal mosquitoes!
- Pick up or store toys, buckets (Figure 9), and any other items in the yard that can collect water.
- Ensure that gutters drain properly by regularly removing organic waste.
- Remove yard waste and plug tree holes.
- Dress in appropriate clothing to prevent mosquitoes from biting you.
- Avoid wearing dark clothing. Studies have shown dark colors make you more attractive to mosquitoes (Browne and Bennett 1981).
- Whenever possible, wear long sleeves and long pants.
- Make sure clothing is not sheer and clothing is free of holes.
- Wear hats to prevent mosquito bites on the head.
- Defend yourself from being a mosquito magnet to prevent mosquito bites. You can do this by using Center for Disease Control (CDC)-recommended and EPA-approved pesticides around your home and yard, as well as by following directions on repellents.
Repellents smell and taste bad to mosquitoes, mask body odors that are attractive to female mosquitoes, or both. Repellents last anywhere from one to five hours depending on the person, type of repellent, and type of application.
Natural repellents approved by the CDC have lemon eucalyptus oil as a main ingredient, and recent studies by Consumer Reports indicate these can be highly effective (Consumer Reports April 16, 2021; Consumer Reports May 3, 2021).
Chemical repellents are available at convenience stores, camping stores, and most general stores.
- DEET is the most effective, and the most commonly used.
- Higher percentages (approximately 15–20%) tend to last longer than lower percentages, but children should avoid using high percentage DEET and reapply more often.
- DEET can also irritate skin or cause reactions in some individuals
- Picaridin (e.g., Cutter Advanced; Sawyer Premium Insect Repellent) is also an effective repellent and can be used if DEET causes irritation or reactions (Consumer Reports April 16, 2021; Consumer Reports May 3, 2021). This man-made chemical was synthesized to resemble the natural compound piperine found in black pepper plants. However, this compound has some adverse environmental effects, particularly to aquatic amphibians that are natural predators of mosquitoes (Almeida et al. 2018). Therefore, environmentally-conscious people might elect to use an alternative method to repel mosquitoes.
- Clip-on fans that contain metofluthrin have been shown to be nearly as effective at repelling mosquitoes as DEET, but they may not be as effective for taller people. Other fans without metofluthrin need to be further investigated for their effectiveness.
- Another option is to soak clothing in permethrin. This also is effective against ticks.
- Permethrin is the only pesticide approved by the EPA for the use of soaking clothing.
- Do NOT apply permethrin directly to the skin.
- Make sure to buy permethrin approved for treating clothing.
- Apply permethrin to clothing that is NOT currently being worn and ensure that all clothing is completely dry before putting it on your body.
- Permethrin should always be applied in a well-ventilated area that is away from the wind.
- Permethrin-treated clothing should be washed separately from other clothing.
- Permethrin applied to clothing and outdoor gear/material (e.g., tents, backpacks, etc.) bonds to fibers within fabrics for up to six weeks (42 days) or six washes. After that time, it should be reapplied.
- AVON Skin So Soft™ contains an active ingredient that is an established repellant comparable in efficacy to picaridin. However, the concentration of the active ingredient is quite low and needs to be re-applied after approximately 20 minutes to continue to repel mosquitoes (Shrek and McGovern 1989).
- Personal diffusers, such as OFF!® Clip-On™ Mosquito Repellent and the Terminix® ALLCLEAR® Sidekick Mosquito Repeller can provide protection against mosquitoes (Revay et al. 2013).
Pesticides are used to kill pests. Note that applying most pesticides requires specialized training that should be done by licensed professionals. However, there are a few commercially-available pesticides that have been approved to be used by homeowners to control mosquitoes. For example, “mosquito dunks” that contain a bacterially-derived toxin that kills mosquito larvae and other aquatic invertebrates can be placed in stagnant water (USEPA July 22, 2020). These are particularly useful in standing water that cannot be drained.
To control adult mosquitoes, residual insecticides can be applied to the foliage of bushes and shrubs, tall grass, and lower branches of shade trees. These include pesticides that contain only pyrethroids:
Pesticides in conjunction with an insect growth regulator are effective insecticides:
Sugar-baited traps that have garlic oil can also be used to control mosquitoes:
- Final Feed
- Terminex AllClear
(USEPA July 15, 2021)
These pesticides can be used by homeowners to control mosquitoes in small areas such as backyards. Note that pyrethroids are also toxic to other insects, including beneficial pollinators, and most labels prohibit spraying pyrethroids on flowers being visited by bees. All pesticides should be applied only according to the instructions listed clearly on the label, and homeowners should wear protective clothing (long sleeves, long pants, and gloves) and ensure that it is not too windy or going to rain during or shortly after pesticide application.
Because of the risks associated with pesticide application, we strongly recommend that homeowners leave mosquito control to trained professionals, especially as most municipalities in Ohio regularly monitor and spray for mosquitoes during the summer months. Homeowners should check with their local health departments for more information about times and dates for mosquito spraying in their area. Also, if mosquitoes are abundant in your backyard, report this to your local health department. In most cases, the health department should send out a mosquito control specialist to determine why the mosquitoes are so abundant and set up stations to routinely monitor and/or spray for mosquitoes around your home.
Other Tactics to Prevent Being Bitten by Mosquitoes
Other simple and easy ways to prevent mosquito bites are avoiding the areas where they breed, including fens, marshes, bogs, and other bodies of stagnant water. Also, timing your outside-activities to occur at times of day when mosquitoes are less active can be effective. Most mosquito species are active at dawn and dusk.
Factors That Make People More Attractive to Mosquitoes
Some people are more attractive to mosquitoes based on the way they smell.
- Scientific studies have shown that mosquitoes are attracted to high temperatures (Clements 1999), carbon dioxide (Takken and Klein 1989), and lactic acid (Acree et al. 1968), which is a component of human sweat. Therefore, increased physical activity likely makes someone more attractive to mosquitoes.
- Blood type might also play a factor in attractiveness. According to a research study people with the O blood type were the most attractive to mosquitoes (Shirai et al. 2004).
- Other studies indicate that alcohol consumption, and especially drinking beer, makes people more attractive to mosquitoes (Lefèvre et al. 2010).
In addition to these, many additional factors likely play a role in how attractive people are to mosquitoes. If you notice that you get bitten more frequently than others, it is particularly important for you to protect yourself from mosquito bites by dressing appropriately and using effective insect repellants.
What Does NOT Work
Control methods that do not work even after vigorous testing include:
- Devices that produce ultrasonic frequencies (Foster et al. 1985; Coro and Suarez 1998; Lell and Kremsner 2000), which includes smart phone apps that produce a high frequency sound (Coro and Suarez 1998). In fact, one study found that high frequencies actually increase biting rates (Andrade and Cabrini 2010), and high frequency sounds can actually be irritating to pets and other animals.
- Black lights and UV lights are not effective controls either (Frick and Tallamy 1996).
- Wristbands with repellents inside of them do not protect other parts of the body from mosquito bites; the wrist band only protects a small area around the wrist (Revay et al. 2013; Webb et al. 2011).
- Birds and bats are generalist predators, so they do not prey solely on mosquitoes (Kale 1968; Gonsalves et al. 2013). Thus, installing bat boxes or bird feeders around your property does not help to reduce mosquito populations.
- Citronella candles and lemon-scented plants, although marketed to repel mosquitoes, are also ineffective in preventing mosquito bites (Pearson 2017).
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