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 December 21, 2017
Understanding those deadly mosquitoes

 Crocodiles and sharks are not the deadliest living creatures. Public enemy No. 1 is that tiny speck of a living thing that irritates many Filipinos on a daily basis. It's called the mosquito.

Every year, crocodiles kill 1,000 people, while sharks manage to take 10 lives. In contrast, mosquitoes snatch the lives of 725,000 people each year, according to the Geneva-based World Health Organization (WHO).

Mosquitoes have been around for at least 350 years, the age of the oldest mosquito fossil. Beating their wings 300 to 500 times a second produces that distinctive whine that novelist D.H. Lawrence penned as a "small, high, hateful bugle" in his ear.

Science says there are over 2,500 different species of mosquitoes throughout the world, all of which live in specific habitats, exhibit unique behaviors and bite different types of animals. Though the average mosquito lifespan is only about three weeks, some varieties have been known to live as long as two months in laboratory conditions.

Mosquitoes track people down by sensing their body odors and temperature, and the carbon dioxide human beings exhale. "Only female mosquitoes have the mouth parts necessary for sucking blood," notes the National Geographic. "When biting with their proboscis, they stab two tubes into the skin: one to inject an enzyme that inhibits blood clotting; the other to suck blood into their bodies. They use the blood not for their own nourishment but as a source of protein for their eggs."

After a female-sucking mosquito has bitten, some saliva remains in the wound. The proteins from the saliva (called anticoagulants) evoke an immune response from man's body. The area swells (the bump around the bite area is called a wheal), and people itch, a response provoked by the saliva. Eventually, the swelling goes away, but the itch remains until man's immune cells break down the saliva proteins.

One of the diseases that mosquitoes carry is the dengue virus. Also known as "break bone" fever, dengue is the Swahili term for "a sudden overtaking by a spirit." Caused by four distinct virus serotypes (varieties recognized as distinct by the immune system), it is a distant cousin of yellow fever.

The dengue virus is transmitted to humans through the bite of infected Aedes aegypti and Aedes albopictus mosquitoes. Most Aedes mosquitoes are found indoors rather than outdoors. The Aedes aegypti prefers to rest in shaded places while Aedes albopictus prefer to rest in shrubs and trees. Both mosquitoes bite only during daytime but their peak biting time is after sunrise and at dusk---especially one hour before sunset.

Not all Aedes mosquitoes, however, are carriers of the dengue virus; only those that have bitten people infected with the virus."Mosquitoes generally acquire the virus while feeding on the blood of an infected person," the WHO explains.

The UN health agency says that, when a person is bitten by an infected mosquito, the dengue virus is deposited in the person's bloodstream. The time between the bite of a dengue-carrying mosquito and the start of dengue fever symptoms averages four to six days, with a range of three to 14 days.

According to the WHO, an infected person can be a source of dengue virus for mosquitoes for about six days. But, unlike rabies, an infected person cannot transmit the dengue virus directly into another person.

Climate change has been cited as one of the reasons mosquitoes have proliferated in recent years. "Climate change greatly influences the El Niño cycle that is known to be associated with increased risks of some diseases transmitted by mosquitoes, such as dengue," the UN Chronicle reports. "In dry climates, heavy rainfall can provide good breeding conditions for the mosquitoes. Increased humidity, and droughts may turn rivers into strings of pools, the preferred breeding sites of mosquitoes."

The best protection against dengue is not to be bitten by the mosquito carrying the virus. According to Dr. Willie T. Ong, there are several things you can about that. "There's no need to panic (when it comes to dengue), because we have 10 ways to beat dengue," says the 2007 recipient of the Outstanding Filipino Physician award from the Department of Health.

1 Clean up your backyard.

Mosquitoes love to stay in the dark and damp areas. If your garage is littered with boxes and assorted garbage, clean them up or throw them away. Don't let them become mosquito havens. Schedule a weekend clean-up day.

2 Empty containers with stagnant water.

The dengue-carrying mosquitoes breed in stagnant water. This means that flower pots, garbage cans, aquariums, unused swimming pools, tires and other piles are potential breeding grounds for mosquitoes. So, after the rains fill them with water, throw the water away. Next time, keep these containers closed and upside down. Flower vases should also be replaced weekly.

3 Check your surroundings for stagnant water.

Some ornamental plant leaves have this "whorl" or cup-like shape that can hold water. Turn them over and throw the water away. Upturned coconut shells are also notorious for holding water. Nonmoving rivers, especially in squatter areas, are full of mosquito eggs.

4 Close your doors and windows.

Some people open their doors in the morning for a whiff of fresh air. They also believe that mosquitoes would leave the house and go into the sunlight. "But my advice is to keep your doors shut at all times," he advices. If it's too stuffy, then place a screen door that keeps the flies and mosquitoes outside.

5 Spray insecticide regularly.

To rid your house of mosquitoes, flies and cockroaches, spray insecticides every few days. Make sure you spray those dark corners, crevices, and cabinets. You'll be amazed at the number of pests you'll find dead in the morning. Just make sure that household members are not exposed to the insecticide, as they are not the target. Just spray selected rooms when people are not around.

6 Wear pants, pajamas, long sleeves and socks.

Mosquitoes are attracted to your breath as you exhale, so they know how to reach you even in the dark. "I guess they love bare, plump skin, especially the kids who don't drive them away and let them suck as much blood as they want," Dr. Ong believes.

7 Apply insect-repellants or use mosquito nets.

If your kids are going hiking, camping or off to school, you can apply insect repellants like Off-Lotion. Kids like to play outdoors and are prime targets of these mosquitoes. You can wipe it on selected areas of the clothing like collars, sleeves and pants. Avoid applying lotion on the eyes, mouth or hands.

8 Kill those mosquitoes.

When it comes to dengue, it's either kill or be killed. Instruct everyone to kill as many mosquitoes and flies as they can. Once you've got them trapped in your bathroom, show no mercy. Mosquitoes belong into the forest, not in your home.

9 Involve the whole community.

The best way to defeat dengue is if the whole community is aware of the threat. Ask your community leaders to schedule a clean-up day. The danger is in those empty houses and lots, which are excellent breeding places for mosquitoes. Become a volunteer to monitor and clean up your surroundings.

10 Spread the word: Dengue fever is here.

You'll never know where dengue will strike next so better be prepared. Inform your neighborhood.

There are several other ways of beating the dengue-carrying mosquitoes. But, in the meantime, follow those above reminders.