Mosquito threat

About two million people die from an infection that began with a mosquito bite every year. Up to a million of these deaths are from malaria - 90% in sub-Saharan Africa. Dengue fever, Japanese encephalitis and West Nile virus are other mosquito-borne diseases. People need to protect themselves from mosquito bites with bed nets, lotions and anti-malarial drugs. Mosquito repellents like coils, mats, liquid vaporizers, creams are often used at various places. However they are prone to be fatal and can cause harm to human beings. For instance, mosquito repellent creams and oils can cause adverse affects on the skin like allergic reactions. Coils, mats can produce toxic fumes when heated and cause breathing trouble, whereas liquid vaporizers can also produce fumes when heated. It is transmitted by female Anopheles mosquitoes infected with the malaria parasite. No vaccine against malaria is available.

Role of electronic

 For efficient results without any side effects, the most optimum solution is building a simple electronic circuit with minimal components which can produce output so as to repel the mosquitoes. Human beings can hear sound in the range of 20 Hz to 20 kHz. Sound of any frequency above 20 kHz is termed as ultrasonic sound. Several animals like cats, dogs, insects, mosquitoes have the feature of being able to hear this ultrasonic sound. In mosquitoes, this feature is attributed to the presence of sensory structures in their antennae. Usually ultrasound is transmitted by male mosquitoes and received by female mosquitoes. However after breeding, female mosquitoes generally avoid the ultrasound and this fact can be used to produce ultrasound in a range similar to that produced by male mosquitoes and repel away the mosquitoes.  The ultrasound produces a stress on the antennae of the mosquitoes and repels them away.

Role of ultrasound

The misconception that mosquitoes are deterred by ultrasound has been around for nearly 40 years - at least one scientific review of an electronic repellent was published in 1974. Ultrasound is a noise above the upper level of human hearing. Electronic mosquito repellents (EMR) are designed to repel female mosquitoes by emitting high-pitched sounds almost inaudible to the human ear. No more need for smelly lotions, chemical gases, smoke or rolled-up newspapers, all you need to do to beat mosquitoes is to stick close to the radio. The station broadcast a high-frequency 15kHz tone under its music, inaudible to most adults, the tone was supposed to repel mosquitoes, allowing listeners to relax in the open air without fear of getting bitten. Malaria is transmitted by female Anopheles mosquitoes infected with the malaria parasite. No vaccine against malaria is available. It is mentioned that male mosquitoes only produce a sound of 700Hz, far lower than an ultrasound frequency. In fact, it is thought that female mosquitoes have a very weak sensitivity to sound in general.

Electronic mosquito repellent

Methods of repelling mosquitoes have been around for a long time. Most of us are familiar with mosquito repellent creams, wristbands, clothes and plug in devices. Out of these, mosquito repellent wall plug vaporizer devices are the most effective. However, they vaporize chemicals that are not only harmful to mosquitoes, but to humans as well. Electronic mosquito repellers, on the other hand, are as effective, but require no toxic chemicals to work. They are much safer, and require less energy than vaporizers. An electronic mosquito repeller repels mosquitoes by using a small speaker or piezoelectric disk to generate ultrasound. Ultrasound - Sound that has a frequency of more than 20kHz is called Ultrasound. It usually cannot be perceived by the human ear. The frequency of these sound waves is in the order of 20kHz to 100kHz. These sound waves cannot be heard by humans, however they can be heard by some animals, usually those that are small.

Limitations:

It requires a lot of frequency setting. Ultrasound signals travel at an angle of 45 degrees from the source. In case of any obstacles in the path, the signals get reflected or diverted showing effect for lesser mosquito population.

Advantages

• Rechargeable, Long Life, Experiment able, Effective, No side effects, Cheap and Easy to make.
• An electronic mosquito repeller is quite handy, especially those living in hot and humid climates, where mosquitoes are very common. As it is compact and rechargeable. It is also very useful for picnics, camps, and outdoor areas.
• If scaled down a bit, after some experimentation, this project can cost very less.
• This is ideal for poor people living in rural areas tropics, where medical facilities may not be adequate. In such places, prevention, not cure, is essential for a long lifespan, and a cheap device like this can make things much better.

Skepticism

Electronic mosquito repellents (EMRs) are small, handheld devices that emit a high-frequency buzz almost inaudible to the human ear. Manufacturers claim that the buzz mimics the beating of male mosquito wings. EMRs are used indoors and outdoors and are purported to repel mosquitoes within a range of 2.5 meters — about 8 feet. Electronic mosquito repellents - buzzing devices marketed to prevent malaria — don’t prevent bites and therefore don’t prevent disease transmission, according to a new review of studies. Accordingly, EMRs should not be manufactured, advertised or used for mosquito bite and malaria prevention, as they do not do so. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic. The researcher analyzed 10 studies conducted in North America, Russia and Africa. All were field-based studies — occurring in a natural setting rather than a laboratory. All studies found that there was no difference in the number of mosquitoes that landed on the bare body parts of the human subjects with or without an EMR. Hence, these devices do not work in repelling mosquitoes. As EMRs do not repel mosquitoes, they would not prevent malaria. Perhaps more confirmatory studies focusing in only malaria-endemic areas may either completely support their analysis or provide some hope for malaria control by this method, if at all applicable.