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■Bio-mathematics, Statistics and Nano-Technologies: Mosquito Control Strategies

11.1

INTRODUCTION

Mosquitos are vectors for some of humanity’s most deadly illnesses, and they are pub-

lic enemy number one in the fight against global infectious disease. Mosquito-borne dis-

eases cause millions of deaths worldwide every year. There are more than 3000 species

of mosquitos, but the members of three bear primary responsibility for the spread of hu-

man diseases. Anopheles mosquitos are the only species known to carry malaria. They also

transmit filariasis and encephalitis. Culex mosquitos carry encephalitis, filariasis, and the

West Nile virus. And Aedes mosquitos, of which the voracious Asian tiger is a member,

carry yellow fever, dengue, and encephalitis [1]. Global warming has moved the mosquitos

on the way to some temperate and higher altitudes, affecting people who are vulnerable to

such diseases [2].

The most important way to prevent the transmission of mosquito diseases is to reduce

or disable the contact of the vector transmitters with a human. This can be achieved by

using different types of mosquito repellents. The most used and effective mosquito repel-

lents are DEET-based chemical repellents. However, the use of DEET and other synthetic

repellents like DMP and allethrin has raised several concerns in terms of environmental

and human health risks [3]. With an increasing concern for public safety, a renewed in-

terest in the use of natural products of plant origin is desired because natural products are

effective, environmentally friendly, biodegradable, inexpensive, and readily available [4,

5, 6]. Many studies have reported evidence of repellant activities of plant extracts or es-

sential oils against mosquito vectors around the world. Thus, plant essential oils with low

toxicities for the environment and humans are considered as an alternative to conventional

synthetic insecticides [7, 8]. Essential oil has been the active principle of most important

herbal remedies since ancient times. Ancient Greek and Roman scholars wrote about using

plants on skin and clothing, so it is no surprise that the new resurgence of essential oils in

popular culture is entering the fight against the bite.

There are many plant essential oils extracted from different families that can be ap-

plied as green repellents against mosquito vectors, such as: citronella, peppermint, clove,

eucalyptus, catnip, immortelle, basil, thyme, lavender, rosemary and others. These oils are

considered safe by the Environmental Protection Agency (EPA) at low concentrations but

provide a limited duration of protection against mosquitos (< 3 h). Most of these essential

oils are highly volatile and that is the reason for the short duration of their repellent effec-

tiveness. As a result, repellents containing only essential oils in the absence of an active

ingredient such as DEET should not be recommended as repellents for use in disease-

endemic areas, whereas those containing high levels of essential oils could cause skin

irritation, especially exposed to sunlight [9]. Even though many studies have shown that

almost all plant-based repellents offer limited protection and require frequent reapplication,

the growing demand for natural alternative repellents indicates the need for development

of natural repellents with improved efficiency, long-lasting protection and enhanced safety

[5, 8, 10].