Cox News Service

Mosquitoes are much in the news these days, thanks to West Nile virus, the bug-borne exotic disease that in one year spread from Massachusetts to Maryland via migrating birds.

But mosquitoes are a problem in many areas. Here's a primer on the pest, and how to protect yourself.

— Individually they're tiny; collectively they're huge.

You do the math: A female house mosquito lives for several months in warm weather. She lays up to 300 eggs at a time - usually on or near standing water - roughly every third night of her life. In summer, each egg can reach adulthood within a week and start the reproductive cycle again. And the next generation isn't likely to go far: Though some species such as salt marsh mosquitoes can migrate up to 100 miles, the species most likely to transmit disease in the South spends its life within 2 miles of its birthplace.

``If you have a mosquito problem, it's not your neighbor who's to blame in most cases,'' said Cathy Rebmann, who oversees mosquito-borne diseases for the Georgia Division of Public Health. ``It's usually in your own yard.''

— They're not just pests; they're parents.

Only female mosquitoes bite, and only because they have to: They need the extra boost of protein to lay eggs. (Male mosquitoes, who don't need the protein, don't suck blood; they drink plant nectar.) The bites itch because the mosquito pumps in an anti-coagulant through her proboscis, the needlelike ``nose'' that she uses to pierce your skin, to keep the blood flowing until she has finished her meal.

The eggs hatch within 24 hours into larvae, which spend the first one to two weeks of their lives in water, breathing through a siphon and eating microorganisms that float by. As they grow, the larvae shed their skins; after the fourth molting, they morph into pupae, tiny comma-shaped organisms that float on the water's surface. After two days, the pupal skin splits and a damp adult mosquito emerges. It spreads its wings to dry, finds a mate and, if it's female, sets off in search of a snack. Males die soon after mating.

— And you thought West Nile virus was the worst they could come up with.

West Nile, a Third World pathogen that arrived in New York last summer, is just one of the disease organisms that hitch- hike in mosquitoes on their way to infecting humans. Some others: St. Louis encephalitis, Eastern equine encephalitis and La Crosse encephalitis, which can cause potentially fatal swelling of the brain; dengue, once known as ``breakbone fever'' for the severe skeletal pain it can cause; yellow fever, which disables the liver; Rift Valley fever, which can develop into encephalitis or hemorrhagic fever; filariasis, in which millions of microscopic worms infest the lymph nodes; and malaria, a parasitic disease that kills more than 1 million people every year. Collectively, mosquitoes cause more human deaths than any other creature.

— In case that wasn't bad enough ...

There's a chance that mosquitoes can be held responsible for sickle cell anemia - and for helping to encourage the slave trade.

Residents of Central Africa, where malaria is endemic, have evolved a minor genetic mutation that protects them against the mosquito-borne disease. According to some historians, that built-in immunity made enslaved Africans particularly attractive to Southern planters, because until this century malaria was endemic in the Southern U.S. as well.

Unfortunately, the mutation that confers malaria protection also causes sickle cell trait and sickle cell anemia. In Africa, said microbiologist Barbara Hanson of Canisius College in Buffalo, N.Y., it may save more lives than it takes, because the chance of potentially fatal malaria infection is so high. In the United States, where the immunity is unnecessary, we experience only its negatives: the severe pain, anemia and stroke risk of sickle cell disease.

— It used to be much worse than it is now.

It's only in the past few decades that Southerners have had the luxury of considering mosquitoes pests. Before window screens, central air conditioning and municipal drainage programs, they were a lethal threat; New Orleans was regularly immobilized by yellow fever epidemics. The Centers for Disease Control and Prevention, originally the Communicable Disease Center, was founded in Atlanta in 1946 largely to deal with mosquito-borne diseases; it replaced a federal agency called the Office of Malaria Control in War Areas.

``Mosquito-transmitted diseases have been a part of our public health picture from the founding of the country until not that long ago,'' said Dr. Roger Nash of the CDC. ``It's only in recent years that the U.S. population has been free of the problem.''

— Unfortunately, it's going to get worse again.

Public health authorities rely on winter to reduce the risk of mosquito-borne diseases, because the low temperatures kill most of the infected mosquitoes. But the likelihood of mosquitoes surviving winter in the South and becoming a year-round disease threat is rising as the planet gets warmer. A study done at Maastricht University in the Netherlands predicts that Georgia's risk of malaria will increase 1.7 times by 2020.

— Can't we just bomb them with pesticides until every last one of them is dead?

``It is generally considered bad form to talk about eradicating another species simply to satisfy our own selfish desires,'' said Laurence J. Zweibel, an assistant professor of biology at Vanderbilt University whose laboratory studies the mosquitoes that transmit malaria. ``They do fill an important niche in the ecology of a region, but it's hard to get people to focus on the positives of mosquitoes.''

Mosquitoes are an important food source for bats, some birds - swallows, purple martins - and other, larger insects. Besides, they're hard to get rid of. A complete mosquito control program, such as the one that New York state is now conducting to rein in West Nile virus, is expensive and labor-intensive, ranging from searching out stagnant water where mosquitoes can breed, to applying chemicals to eliminate larvae, to spraying at ground level and from the air to destroy adult mosquitoes. And spraying campaigns, including the one in New York, inevitably raise public anxieties over pesticide exposure and collateral damage to fish and birds.

PREVENTION TIPS

— Mosquitoes need water to complete their life cycle. Don't let them have it. Empty any outdoor container that could hold stagnant water, from a plant saucer to a tree stump. Containers that must have water in them, such as birdbaths or dog dishes, should be scrubbed and refilled twice a week. Gutters should be checked to make sure they don't retain water. Fill low areas in the lawn or yard where water may collect, and be sure not to allow water to gather on the cover of a backyayd pool. If you have an ornamental pond, stock it with fish that will eat mosquito larvae. Get rid of old tires - they're the No. 1 breeding habitat for mosquitoes around the world.

— Try not to be outside when mosquitoes do the most biting; for many species, that's between dusk and nightfall. Wear long sleeves and long pants, if possible, but wear repellent whether you cover your skin or not. Check the label to be sure whether the repellent you're using goes on skin or clothing, and whether it should be used on children at all.

— DEET (N,N-diethyl-meta-toluamide) is widely considered the most effective repellent and is sold in many different concentrations, in such popular products as Off, Cutter and SkinTastic, but it is a potent chemical that can dissolve some plastics, and some individuals develop rashes and headaches after exposure to it. According to the U.S. Environmental Protection Agency, concentrations of 15 percent or less are safe for children, but it should not be used on hands or near the eyes or mouth. Repellents used on children also should not be used under clothing, and both skin and clothing should be washed with soap and water.

— Once bitten, you want medications to prevent inflammation and infection. To reduce swelling, pharmacists recommend ibuprofen or a topical cream or ointment containing 1 percent hydrocortisone or 2 percent diphenhydramine hydrochloride. To stop infection, use Neosporin or other anti-bacterial creams that contain neomycin, polymyxin B and bacitracin.

Copyright 2000 Cox News Service. All rights reserved.