The World’s Most Deadly Animal

Although you might expect this Health Tip to be about large carnivores like polar bears or mountain lions, a tiny insect—the mosquito—is responsible for more deaths each year than all the ‘man-eating’ animals in the world combined.  These deaths do not occur due to a venomous bite or a sting causing an allergic reaction but from the diseases that they transmit.  Read on for other fascinating facts regarding ‘skeeters’.

1.  Mosquitoes have been around since the Jurassic period, making them over 150 million years old.  The name comes for the Spanish word for house fly, ‘mosca’, with the suffix for small, ‘-ito’ attached, literally translating to ‘small fly’.  Fossilized specimens of mosquitos from prehistoric times show that they have undergone relatively few evolutionary changes since their origin.
    
2. Only female mosquitoes bite humans.  The ‘bite’ actually represents the act of inserting their skin piercing mouth component (proboscis) into a vein of a host in order to ‘feed’ on its blood.  They are thought to do this for the protein and nutrients found in blood in order to help with egg development.  Male mosquitos don’t require blood feedings and instead feed on nectar and water.  When feeding, a female mosquito can suck two to three times her weight in blood.
    
3. Most mosquito bites do not result in disease.   The local swelling and itching associated with a mosquito bite is due to a minor allergic reaction to mosquito saliva.  This saliva contains both an anesthetic to lessen the sensation associated with the piercing proboscis and an anticoagulant to keep the blood that they are drawing from clotting. In most cases, mosquito bites stop itching and heal on their own without medical treatment. Treatment of uncomplicated bites includes the use of topical hydrocortisone cream or calamine lotion. An oral antihistamine, such as Benadryl, can help with itching.
    
4. Mosquitoes are capable of transmitting a number of disease-causing viruses.  They pass on these organisms without developing any signs of the disease in themselves. Viral diseases transmitted by mosquitos include yellow fever, dengue fever, Eastern equine encephalitis (EEV) and West Nile virus disease (WNV). Yellow fever has been eradicated from the U.S.  Dengue fever is primarily seen in travelers returning from the Caribbean, Central America, South America, and South Central Asia. In EEV and WNV, both of which are seen in the U.S., the virus is transmitted from infected birds to humans.  There are no documented cases of human immunodeficiency virus (HIV), the virus responsible for causing AIDS, due to mosquito bites.
    
5. Worldwide, the most important disease transmitted by mosquitos is malaria. Malaria is a serious and sometimes fatal disease caused by a parasite that commonly infects the Anopheles mosquito.  The parasite responsible for causing malaria is a micro-organism belonging to the genus Plasmodium.  The disease is passed on primarily from human to human via the mosquito bite.  When a mosquito bites a malaria-infected person, she ingests the parasites, which reproduce and travel to her salivary glands from where they can infect another human with the next bite. People who get malaria are typically very sick with high fevers, shaking chills, and flu-like illness.
    
6. Mosquitoes locate their targets by detecting the carbon dioxide (CO2) emitted in the breath of animals. This is the rationale behind the use of ‘mosquito traps’ that use CO2 to lure female mosquitos to a capture or kill device.  Although the theory sounds good, the American Mosquito Control Association advises against putting too much faith in this single method of mosquito control.  Additional methods, such as removal of standing water around the house and community-wide mosquito control programs are also necessary for a significant reduction in biting mosquito populations. Methods such as ‘Bug Zappers’ and ultrasonic devices have not been shown to be effective in killing significant numbers of female mosquitos.  In fact, ‘Bug Zappers’ typically kill more beneficial insects than harmful ones.
    
7. As many people have learned the hard way, mosquitos are attracted to some people more than others.  Research has shown that approximately 20% of us are ‘mosquito bait’ and indeed get bitten more often. The reasons for this are uncertain, but may have to do with the amount of CO2 produced, blood type, substances produced in sweat, and body temperature. Fortunately, even for those who attract mosquitos, insect repellents have been found to be an effective method for preventing mosquito bites. DEET (Cutter, OFF!, others) and Picaridin (Cutter Advanced, Skin So Soft Bug Guard Plus, others) are considered to be ‘conventional repellents’, derived from chemical sources.  Oil of Lemon Eucalyptus (PMD) and IR3535 (e.g. Avon Skin-So-Soft with IR3535) come from natural materials and are classified by the EPA as ‘biopesticide repellents’.  Any of these products will provide safe and effective protection against mosquito bites when used according to labeled instructions.

The ‘deadliest animal’ moniker for mosquitos is well-earned.  It is estimated that world-wide, mosquitoes kill nearly three quarters of a million people each year. Most of these deaths are as a result of contracting malaria. By comparison, on an annual basis, sharks kill fewer than a dozen people, crocodiles kill around 1000, and snakes are responsible for 50,000 deaths. Sadly, human beings themselves fall into the second deadliest category, accounting for approximately 500,000 deaths each year.