Limelight:
Beware the killer female
By
Lubna Abdel Aziz
Listlessness abounds. The silence is profound. She bides her time, hiding in a secluded corner, her exquisite long legs restless, aching to take off. She has her eyes focussed on you, and the man has not been born who can resist her. Your special perfume seduces her. Your very movements entice her. The heat of your body guides her. She marks the spot, and suddenly without warning she aims at your gentle skin. She stabs you with her sharp probes or stylets, which form the centre of the proboscis, covered and protected by her lower lip. As they enter your skin her lower lip bends and slides upward out of the way. Her saliva flows into the wound through channels formed by the stylets helping her to sip her cocktail with ease, because the saliva keeps the blood from clotting. Like millions of others around the world, that very minute, you too have been bitten by a female mosquito. She holds very still until she has sucked three times her weight of your precious blood, and slowly pulls the stylets out of the wound. She struggles to fly again. Like most of us you are allergic to her saliva. You can reach out and catch but she escapes leaving you with an irritating itch, maybe a rash, "and if you are really unlucky, she will kill you".
The female bloodsucker will then lay from 100-300 eggs at a time in or near water, swamps, marshes or pools, for they must have moisture to hatch. There are 2,500 species of mosquitoes but only a few are killers. They are divided onto groups of about 100 called "Genus". The house mosquito for example belongs to the Genus Culex. Some other members of this genus carry encephalitis. Some mosquitoes in the Genus Anopheles carry malaria. Others in the Genus Aedes transmit yellow fever. Those are the killer species.
Many kinds of mosquitoes do not spread disease. Only the female mosquito of certain species transmits various diseases to more than 700 million people annually around the world. This angel of death will kill one out of every 17 people currently alive. About 300 million new cases of malaria occur annually killing 3 million, one million children in Africa alone. The female of some species must suck blood before they can lay eggs that will hatch. Each species prefers the blood of certain kinds of animals. Some like frogs, other snakes or birds, others cows, horses and humans. Some male mosquitoes live 10-20 days, but females live 30 or more. "She can deposit 30 or 40 malarial parasites in the human blood stream with a single bite. Within 2 weeks they will multiply to trillions. She is one of the great killers of all time," wrote The Daily Telegraph
The story of mosquitoes is as old as the universe. They are found everywhere on the planet except in Antarctica, and they thrive wherever they are found. With all our modern technology, we cannot eliminate a tiny mosquito. Quite the contrary, our mobile progressive lifestyle has aided the little insect to spread, and travel, and prosper, breeding havoc and destruction wherever she is found. Ships, trains and planes make the world smaller and interconnected. Dangerous mosquitoes get a free ride to new places, bringing infections of epidemic proportions.
In prehistoric times humans stayed closely within their tribal communities, allowing them to deal with their own germs or develop resistance to them. Invaders and foreign traders brought outside germs that the community was unable to resist. Death and destruction followed. The invaders too were ill equipped to deal with the existing strains of germs in the new communities and they too fell victims to them.
Before 1820 deductions about the mosquito were scientific conjecture at best because until then the technology of the microscope did not exist. But with the microscope suspicions were eventually confirmed of the many sins committed against humankind by the mosquito. French scientist Charles Laveran was the first to see malaria parasite in the human blood. In 1880 he drew blood from a soldier of the French Foreign Legion in Algeria and under the microscope saw little moving animals, a discovery that earned him a Nobel Prize in 1907. The discovery did not hinder the mosquito from roaming the earth to kill and destroy at will. It was not until 30 years later in 1910, that a drug was developed "chloroquine" both for prevention and treatment. But in less than a century, the resilient mosquito developed resistance to the drug and was wild and free again unhampered by any earthly force.
The war between killer insects and man continues. The biggest culprits among the killer mosquitoes are the Anopheles, vectors of malaria, Aedes Aegypti that breed dengue and yellow fever, and Culex Pipens that breeds the West- Nile virus. Billions of people are at risk, in almost every country in sub-Saharan Africa, half of South America and much of Asia. The spread of diseases increases rather than decreases with time. Every year 10 per cent of the world's population suffers from malaria. Every 12 seconds a malaria-infected child dies.
Environmentalists claim that "global warming and the decline in the quality of the world eco-system exact a considerable toll of infectious diseases and deaths worldwide." Don Melnick, professor of anthropology and biological sciences at Columbia University dismisses the global warming theory as baseless. While a warm climate is a necessary condition for mosquitoes to flourish, it is not a sufficient cause for malaria to become endemic. He cites Singapore, which is located two degrees from the equator, reporting no deaths from malaria in 1994, while Malaysia just next door suffering from endemic malaria and dengue fever. The difference according to Melnick is not the climate but the economic conditions of the two nations. Poverty is behind the killer.
If we are ready to blame it on economics, how can we explain what happened in New York City in 1999. The greatest city of the New World was gripped by mosquito fear when a mysterious outbreak of encephalitis devastated both man and beast. The dead were everywhere -- birds, horses, and humans -- the killer: Culex Pipens. Investigations lasted for months. Finally the CDC (Center for Disease Control) revealed that the mystery behind the New York siege was the West Nile virus, a brand new potentially fatal mosquito-borne disease, which found its way to America from Africa. It seems to have taken permanent residence and defies extradition. A new West Nile virus outbreak raced through the North-western US again this month afflicting 16 cities in its flight.
How can you help but admire that tiny organism that continues to thrive through the ages repeating the same theme century after century mindless of all the science aimed at her.
While there is still much that we do not know, we do know enough to take precautions against the brutal killer. We should use screens on our windows and doors. Despite the heat and discomfort we should wear long sleeves and long pants while outdoors, limiting the skin available for the predator. Insect repellent is effective but better still cut on outdoor activities as much as you can. "Darwin would have been amazed at the speed with which those mosquitoes that exploit the human environment adapt and versify today," wrote tropical disease specialist Andrew Spielman of Harvard University in his book Mosquito.
Where there are humans there are mosquitoes. They depend on us for their survival. Were we to disappear, many mosquito species would likely become extinct. Yet we must accept the fact that they were here before us and will likely survive us. It is science's moral responsibility to find a permanent cure to eliminate the diseases mosquitoes spread in order for us to survive with them on this planet before they ultimately destroy us.
