Frequently Asked Questions

Please click on the links below to view the FAQ answers.

Mosquito Biology

Are those tons of mosquitoes clinging to my house?

Male mosquitoes swarm during mating and some will rest on the sides of houses. Both male and female mosquitoes will seek shade during hot weather and, if a house is shady and cool, then mosquitoes may cling to the walls. Generally, large swarms of insects clinging to a house or side of buildings are non-biting midges (see our "Insects Commonly Mistaken for Mosquitoes" section). These look very much like mosquitoes, but do not bite. They are often called "blind" mosquitoes. If midges are clinging to your house it is a good idea to wash them down with a hose to prevent them from staining your wall.

What attracts mosquitoes to me?

Why some people seem to be more attractive than others to mosquitoes can involve many factors. Carbon dioxide is the most universally recognized mosquito attractant and draws mosquitoes from up to 35 meters. When female mosquitoes sense carbon dioxide they usually adopt a zigzagging flight path within the plume to locate its source. Once in the general vicinity of a potential host, other cues predominate, including body odors (sweat, lactic acid, etc.) and heat. Odors produced by skin microflora also play a part in inducing the mosquito to land. Over 350 compounds have been isolated from odors produced by human skin. Either singly or in combination, many of these compounds may be attractants - and many may be repellents. Visual stimuli, such as movement, also factor into host-seeking. The ingestion of garlic, vitamin B12 and other systemics has been proven in controlled laboratory studies to have no impact on mosquito biting. Conversely, eating bananas did not attract mosquitoes as the myth suggests, though perfumes do. People drinking beer have been shown to be more attractive to mosquitoes. Limburger cheese has also been found to be attractive. Scientists have theorized that this may explain the attractancy some mosquitoes find for human feet.

Why do mosquitoes leave welts on the skin when they bite?

When the female mosquito pierces the skin for her “blood meal”, she injects a small amount of saliva into a capillary. The saliva makes penetration of her proboscis or mouthparts easier and prevents the blood from clotting. Welts or red itchy bumps that may appear after the bite of the mosquito are actually an allergic reaction to the saliva. Some people are more allergic to mosquito saliva than others and tend to react stronger. Some people may be more allergic to specific species of mosquitoes than others, which is why you may react stronger to mosquitoes in one area than another. The swelling and itching may last from a few hours to a few days. Occasionally individuals may be highly sensitive to mosquito saliva and swell significantly, even to the point where they need medical attention. In any case, people should avoid scratching these welts as bacteria from the fingernails may be introduced into the wound and cause infection.

Are mosquitoes beneficial to the environment?

Mosquitoes can serve as a link in the food chain. Although no species depend completely on mosquitoes as a food source, indiscriminate predators will eat mosquito larvae and or adults if other food sources are not available. During their aquatic stage, mosquito larvae provide food for other aquatic insects such as dragonfly nymphs, beetles, and fish. Mosquito control treats larvae that are in areas not generally controlled by natural predators. Many salt marsh mosquitoes hatch in the high marsh where fish cannot get to them. By treating the areas that are not being controlled by natural predators, mosquitoes remain part of the overall food chain. As adults, both male and female mosquitoes need plant nectar for food. Mosquitoes may serve as an incidental pollinator as they collect nectar for nourishment.

If mosquitoes were eradicated, how would this affect the ecosystem?

All organisms have their place in nature, and mosquitoes are no exception. If mosquitoes went extinct, other species will fill the niches left by mosquitoes after an initial shuffling period of variable length. However, mosquitoes' ability to adapt to changing environments would make them all but impossible to eradicate.

Are mosquitoes beneficial to the environment?

Mosquitoes can serve as a link in the food chain. Although no species depend completely on mosquitoes as a food source, indiscriminate predators will eat mosquito larvae and or adults if other food sources are not available. During their aquatic stage, mosquito larvae provide food for other aquatic insects such as dragonfly nymphs, beetles, and fish. Mosquito control treats larvae that are in areas not generally controlled by natural predators. Many salt marsh mosquitoes hatch in the high marsh where fish cannot get to them. By treating the areas that are not being controlled by natural predators, mosquitoes remain part of the overall food chain. As adults, both male and female mosquitoes need plant nectar for food. Mosquitoes may serve as an incidental pollinator as they collect nectar for nourishment.

How long do mosquitoes live?

Most adult female mosquitoes live 2-3 weeks, though this can vary by species. Some over-winter in garages, culverts and attics can live as long as 6 months.

Why do mosquitoes feed on blood?

Female mosquitoes imbibe blood to mature their eggs. It serves no nourishment function, and males do not take blood meals at all. Both male and female mosquitoes feed upon plant nectars for food and energy.

How much blood does a mosquito take in a meal?

When feeding to repletion, mosquitoes imbibe anywhere from 0.001 to 0.01 milliliter.

How high do mosquitoes fly?

Mosquitoes have been found breeding up to 8,000 feet in the Himalayas and 2,000 feet underground in Indian mines. In general, mosquitoes that bite humans prefer to fly at heights of less than 25 feet. Asian Tiger Mosquitoes have been found breeding in treeholes over 40 feet above ground.

How much do they weigh?

Smaller species found around houses commonly weigh about 2.5 milligrams. The largest species weigh in at a whopping 10 milligrams.

How far can mosquitoes fly?

Some species, like the Asian Tiger Mosquito, prefer to breed around houses, have limited flight ranges of about 300 feet. Most have ranges of 1-3 miles, however, the undisputed champions are saltmarsh breeders - having been known to migrate up to 100 miles in exceptional circumstances, although 20 to 40 miles are more common when looking for a host. Mosquitoes can also be carried large distances when caught in an updraft.

How fast can mosquitoes fly?

Depending upon the species, mosquitoes can fly at about 1 to 1.5 miles per hour.

Disease / Parasite Transmission

What is dog heartworm and do only dogs get it?

Dog heartworm is a very common disease of canines and to a lesser extent cats caused by a parasitic worm (Dirofilaria immitis) that can be debilitating, even fatal. It is transmitted to dogs by the bite of an infected mosquito. Adults live in the dog's heart and release microscopic young worms into the dog's blood. Human infections are sometimes discovered, usually during lung X-rays. Pet owners should talk to their veterinarians about protective medication to avoid dog heartworm. For more information: www.heartwormsociety.org

Can mosquitoes transmit AIDS?

Many studies have been conducted on this issue in the United States and abroad. The experts have concluded that the insects are not capable of such transmission. Many biological reasons would lead one to this same conclusion, but the extensive experimental studies are the most powerful evidence for the conclusion.

  1. HIV DOES NOT replicate in mosquitoes. Thus, mosquitoes cannot be a biological vector as they are for malaria, yellow fever, or dengue. In fact, mosquitoes digest the virus that causes AIDS.
  2. There is no possibility of mechanical transmission (i.e., flying contaminated syringes); though HIV can be transmitted by dirty needles. However, the amount of "blood" on a mosquitoes' mouth parts is tiny compared to what is found on a "dirty" needle. Thus, the risk is proportionally smaller. Calculations based on the mechanical transmission of anthrax and Rift Valley fever virus, both of which produce very high titers in blood, unlike HIV, showed that it would take about 10,000,000 mosquitoes that first fed on a person with AIDS and then continued feeding on a susceptible person to get 1 transmission.
  3. Mosquitoes are not flying hypodermic needles. Mosquitoes regurgitate saliva into the bite wound (the normal route for disease transmission) through a separate tube from that through which it imbibes blood.

Which mosquitoes transmit West Nile Virus (WNV)?

At least 43 species of mosquitoes have been found infected with the West Nile virus in the United States. Not all of these, however, are capable of maintaining the virus in such a manner as to permit them to transmit it among organisms. Many of these infected mosquitoes feed only upon birds, thus contributing to a cycling of the virus among avian populations. Other species feed upon these infective birds and then will feed upon mammals, including humans. These are called "bridge vectors" because they serve as a conduit for the virus to travel from its reservoir in birds to its final host in humans or other mammals. In urban settings, Culex pipiens is usually the primary vector. In rural areas, particularly in the western part of the United States, Culex tarsalis is the primary transmitter. As control measures for each of these mosquitoes are considerably different, it's important to know which is known to be in your area. Contact your local mosquito abatement district or the Technical Advisor of the American Mosquito Control Association (904-215-3008) for information regarding the mosquitoes found in your area.

Should I be worried about West Nile Virus?

West Nile Virus (WNV) is transmitted by mosquitoes, and by the end of 2004 it had spread over much of the country. Most people who are infected will not experience any symptoms, or may experience flu-like symptoms (West Nile fever) and then recover. In rare cases, the virus may cause West Nile encephalitis with severe symptoms requiring hospitalization. While WNV can affect anyone, risk increases with age. People over 50 are at higher risk to develop serious symptoms.

WNV is here to stay, and our office is prepared to do surveillance for the virus and to respond in the event of an outbreak. There is still much to learn about WNV, and we are working in cooperation with agencies and research facilities across North America to find out the best way to deal with it. There is a vaccine available for horses, and we recommend that horse owners consult with their veterinarian. People can reduce their risk of infection simply by reducing their exposure to mosquito bites.

Controlling and/or Repelling Mosquitoes

How long will my repellent last?

According to the Center for Disease Control,
 

  • A product containing 23.8% DEET provides an average of 5 hours of protection from mosquito bites.
  • A product containing 20% DEET provides almost 4 hours of protection from mosquito bites.
  • A product with 6.65% DEET provides almost 2 hours of protection from mosquito bites.
  • A product with 4.75% DEET provides roughly 1 and a half hour of protection from mosquito bites.

These examples represent results from only one study and are only included to provide a general idea of how such products may work. Actual protection will vary widely based on conditions such as temperature, perspiration, and water exposure.

Choose a repellent that provides protection for the amount of time that you will be outdoors. A product with a higher percentage of active ingredient is a good choice if you will be outdoors for several hours while a product with a lower concentration can be used if time outdoors will be limited. Simply re-apply repellent, following label instructions, if you are outdoors for a longer time than expected or start to be bitten by mosquitoes. Content source from http://www.cdc.gov/ncidod/dvbid/westnile/qa/insect_repellent.htm .

What about using (bats, birds, citronella plants, bug zappers, etc) to control mosquitoes?

Many people also believe that erecting purple martin and bat houses will reduce mosquito populations. However, in-depth studies have shown that mosquitoes comprise no more than 0 to 3% of the diet of purple martins. Likewise, bats are opportunistic feeders and will eat a variety of insects. They most likely feed on whatever is most numerous and easiest to catch, and if necessary will travel far from their roosting sites in search of prey. Martins and bats will consume mosquitoes, but are not likely to significantly reduce the population. They should be protected and encouraged because they are interesting residents of the natural environment, not because of their ability to control pests. Citronella plants have also not been proven to effectively repel mosquitoes.

Do Ultrasonic devices work?

At least 10 studies in the past 15 years have unanimously denounced ultrasonic devices as having no repellency value whatsoever. Mate location through wing beat frequency caused a great deal of research to be conducted for ultrasound to be used as a chemical-free form of control. Yet, all attempts to affect mosquito behavior by ultrasound have fizzled, despite large amounts of money spent on research and development. Clever, high-tech, and imperceptible (by humans) use of ultrasound proved to be an effective marketing tool for repeller manufacturers. By appealing to the public’s chemophobia, homeowners were urged to buy ultrasonic repellers and the like to rid their houses of pests without the need to inhale "even one breath of poisonous spray". Unfortunately, no such miracle cure exists. A pioneering study testing five different ultrasonic devices against four mosquito species convincingly demonstrated that ultrasound in the 20-70 kHz range used by these devices had no effect on reorienting flight by female mosquitoes either toward or away from human subjects. Additional tests have shown that sound generators capable of a wide range of frequencies were also ineffective in repelling mosquitoes. The fact is that these devices just do not work - marketing claims to the contrary.

Do mosquito traps work?

Consumer interest has been generated by the marketing of devices designed to attract, then either trap or kill, mosquitoes. Many products even claim to significantly decrease, or virtually eliminate local populations by decreasing the number of egg-laying females. All of these traps utilize some form of attractant that lures the host-seeking female mosquitoes to a capture or killing device. In some cases, mosquitoes are captured via an impellor fan that suctions them into a net, where they desiccate. Other systems use a sticky surface to which the mosquitoes adhere when they land, or electric grids to electrocute mosquitoes drawn into contact. Each requires some level of maintenance, i.e. propane tanks need replacement, capture nets need emptying, adhesive boards require replacement and grids require cleaning to ensure their continued effectiveness.

The process of a mosquito questing for a blood meal involves a complex, interconnected cascade of behaviors, each probably having its own cues, be they sight, smell, or body temperature. The complexity of these behaviors may account for the bewildering variations in trapping efficiency noted for certain species of mosquitoes at different times, seasons and places. With 174 species of mosquitoes currently recognized in the United States, this is no small issue and will require many years before research can provide a clarification. There is some anecdotal evidence that these baited traps, indeed, capture more females of some species than others, depending, to some extent, on the concentration of carbon dioxide emitted and the mosquito species. There may also be seasonal and circadian variables that affect mosquito responses to certain attractants. Nonetheless, these devices will trap and kill measurable numbers of mosquitoes. Whether this will produce a noticeable reduction in the mosquito population in each case will depend upon a number of factors, e.g. individual tolerance level, absolute mosquito population size, proximity, size and type of breeding habitat producing re-infestation, wind velocity and direction, and species of mosquito present, and others. Thus, the homeowner must still use repellents and practice source reduction methods as adjuncts to realize any measure of relief. Please be cautioned against putting too much faith in traps as your sole means of control. These traps represent an evolving technology that is a most welcome addition to our mosquito control armamentarium. Their potential is great, but shouldn't be overestimated. It's highly unlikely that these devices, whatever their improvements, will ever fully supplant organized community-wide mosquito control programs, for there is no single silver bullet that will prove to be the ultimate answer to mosquito problems.

Are backyard misting systems effective?

Scheduled sprays used by these misters can needlessly broadcast pesticides into the environment, which affects mosquitoes and non-target insects alike. Modern mosquito control strategies emphasize an integrated approach, based upon a profound knowledge of the target, so that its various vulnerabilities can be exploited by the many tools we've developed for that purpose. Effective mosquito control requires continual survey of adult mosquito populations to determine if certain triggers for control are met. This reduces the use of adulticides to only those times when they are required.

Do Bug-Zappers Work?

Bug zappers do indeed kill some mosquitoes. However, the only two controlled studies conducted to date by independent investigators at the University of Notre Dame showed that mosquitoes comprised merely 4.1% and 6.4% respectively of the daily catch over an entire season. Even more important was the finding in both studies that there was no significant difference in the number of mosquitoes found in yards with or without bug zappers. What is particularly disturbing, however, is the number of non-pest insects that comprise the vast majority of trap catch. Many of these insects are beneficial predators on other insect pests. They in turn constitute a major part of the diet of many songbirds. Indeed, reduced numbers of moth and beetle prey species have contributed significantly to the decline of songbird populations in many affluent suburbs. Insect electrocution devices undoubtedly bear some responsibility for this phenomenon. Mosquitoes continue to be more attracted to humans than to the devices. One study conducted in homeowners' backyards showed that of the insects killed by these devices, only 0.13% were female mosquitoes. An estimated 71 billion to 350 billion beneficial insects may be killed annually in the United States by these electrocuting devices.

What can homeowners do to reduce mosquito bites?

The number one thing a homeowner can do to prevent mosquitoes is to not give them a place to lay their eggs and develop. Mosquitoes will generally take at least 7 days to complete the life cycle of egg to adult and water is needed for this to happen. If standing water is changed or discarded at least once a week, mosquitoes will not have a chance to develop. If possible, schedule your activities to avoid the times when mosquitoes are most active - usually dawn and dusk. You should also dress in light, loose-fitting clothing. Mosquitoes are relatively weak fliers, so placing a large fan on your deck can provide a low-tech solution. Citronella candles have a mild repellent effect, but do not offer significantly more protection than other candles producing smoke.

Mosquito Control Operations

SuperUser Account

Shining A Light On LAMP Testing

  • Authored by Colby Colona
    June 15, 2021

Earlier blog entries have mentioned “LAMP” testing, but what exactly is that? So let’s shine a light on the subject! (You see what I did there?)

A major component of our operations is collecting mosquitoes (to read more about surveillance, click HERE). I have previously covered what happens to most collected mosquitoes (for a review, click HERE). Still, at TMAD, we like to go big or go home, which is why in 2018, our board of directors voted to invest in implementing our own in-house West Nile Virus testing.

We were the first mosquito control district in the state to incorporate this specific technology into our routine operations, and we are especially proud of this!

That’s nice and all, but what is it?

LAMP stands for “loop-mediated isothermal amplification.” It’s a mouthful, but the basic idea is simple: isolate and amplify genetic material to show the presence of the West Nile virus. By having this equipment and technology in our own lab, we eliminate turnaround time and can even test mosquito samples on the same day as collection. This is a big deal for public health! During peak West Nile virus season, we can essentially set out a trap, collect extra mosquitoes from that trap, and test them as soon as they are brought back to the lab. Then, instead of waiting a week or two weeks for results from the state lab, we can know the same day if we need to send out our trucks or our plane to a specific area. This allows us to be more “proactive” rather than “reactive.” 

 

 

 

 

 

 

 

The Process

LAMP testing is all about the genetic material within the cells or ribonucleic acids (RNA). Ribonucleic acids are present in living cells, and the general purpose is to carry instructions about making proteins to your cell’s DNA (deoxyribonucleic acid). Once mosquitoes are collected from a trap, this RNA must be extracted. This means that the rest of the cell needs to be essentially dissolved so that the RNA is easily isolated.

This is done by pulverizing the mosquitoes (making a mosquito milkshake!), separating the solids from the liquids by centrifuging, taking out some of the “slush” (i.e., homogenate), and then washing away the “unnecessary” parts of the cell to get the RNA by itself. 

This is the most labor-intensive part of the test and usually takes about 45 minutes to an hour, depending on how many samples are being extracted. Cells are stubborn little things!

After the extraction has taken place and the RNA is isolated, we must then amplify it to make it easily visible to the processing equipment. Finally, dyes and primers are added to enable the RNA to show up in the last step-the all-powerful Genie!

The Genie is the little machine that does all the final analysis and clearly reports positive and negative results. It usually takes about thirty minutes for this processing to complete.

 

How do you know the test was done correctly?

In every test run in our lab, we also run a positive and negative control. What does that mean? For every group of samples tested, we also run one sample that we know will be positive by adding specific reagents and one test with only water added instead of mosquito RNA to know it will be negative. If either shows anything other than the expected positive or negative result, we know that the test was possibly contaminated and will retest. This ensures that we are only working with the most accurate results better to serve the public health needs of our citizens. 

You should see four “peaks.” These represent a positive result for the presence of the West Nile virus. The dotted yellow line is a positive control, and though hard to see, a light green line flat on the X-axis represents negative control. This demonstrates that the test is not contaminated and the results are accurate.

 

How many samples can you run at once?

We can run up to 16 samples at once, including the positive and negative controls. We can do this twice a day if we need even more samples tested, for a total of 32 samples a day. We are exploring our options for increasing this number in the future.

Final thoughts

We strive to use science-based evidence to make our treatment decisions. LAMP testing is just one facet of the ongoing Integrated Mosquito Management strategy we use in our operations. Knowing where the West Nile virus is located quickly, we can better target our treatments and keep our citizens safer!

Have more questions or want to chat? Call our office, and we will be happy to help!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 


 

Previous Article Who oversees pesticide applications?
Print
1451 Rate this article:
No rating
Please login or register to post comments.