Questions about West Nile, EEE answered

Published 8:20 am Monday, August 11, 2003

By By Bill Crist Special to the Advance
Ricky Elliott, environmentalist with the Escambia County Health Department sat down and answered several questions about West Nile Virus (WNV) recently. Two birds from Escambia County tested positive for the virus earlier this week and there have been numerous confirmed cases of humans contracting the virus in Alabama and surrounding states.
Elliott stressed that the most important step area residents could take to protect themselves from the mosquito-borne virus, was to take immediate action to clean up their environment by removing mosquito breeding grounds and protecting themselves through clothing and repellent any time they go outdoors.
Q. If I'm bitten by an infected mosquito, will the bite mark be any different than if it was not infected?
A. No. The bite mark will be the same. There is no way to tell which mosquito is infected and which is not.
Q. How far can mosquitoes fly? How far do they typically fly from where they hatch?
A. It varies among the different species of mosquitoes. Ochlerotatus mosquitoes, also known as salt marsh mosquitoes, are strong fliers and are known to fly many miles from their breeding site. Culex mosquitoes, which are the principal carriers of WNV in our area, are usually weak fliers and do not move far from where they were hatched, although they have been known to fly up to two miles.
Q. How many times does a female mosquito lay eggs?
A. A female mosquito can lay a raft of eggs (200-400) every third night.
Q. How long does a mosquito live?
A. It varies on the environment and can last from four days to over a month. The mosquito goes through four separate and distinct stages during its life cycle: egg, larva, pupa and adult. Eggs are laid one at a time or attached together to form rafts. They float on the surface of the water. These rafts can contain 200-400 eggs. Some mosquitoes lay their eggs on damp soil where they remain until flood or rainwater covers them. Most eggs hatch into larvae within 48 hours although some might withstand subzero temperatures before hatching. The larva lives in the water and comes to the surface to breath. Larvae shed their skins four times, growing larger each time. They have siphon tubes for breathing and hang upside down from the water surface. At the end of the fourth skinning (molt) the larvae turn into pupa. This is a resting, non-feeding stage. During this stage the pupa tumbles around in the water. This is when the mosquito changes into an adult. In the south, this part of a mosquitoes life cycle takes about two days. At the end of the pupa stage, the pupal skin splits and the adult mosquito emerges. The new adult will sit on top of the water for a short time until its wings dry. Blood feeding and mating will begin to occur in two days. In the south with our warm climate, it usually takes about 10 days for a mosquito to go through the four stages.
Q. Why do mosquitoes bite us?
A. Only females require a blood meal and bite animals – both warm blooded and cold blooded and birds. Human blood meals are seldom the first choice of a female mosquito. They prefer horses, cattle, smaller mammals and birds.
Q. Is there anything I should do if I notice my child has been bitten by a mosquito?
A. Just keep a watch on your child to see if he/she shows any symptoms. Mild symptoms include fever, headache and body aches, with a skin rash on the trunk of the body and swollen lymph nodes. Severe symptoms include headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness and paralysis. It is estimated that 1 in 150 persons infected with the WNV will develop a more severe form of the disease. Less than 10 percent of clinically ill patients will die.
Q. How can I protect my outdoor pets?
A. Drain all containers that are holding water. Keep vegetation mowed down. If there are lights around the dog yard replace them with yellow lights. Be sure and fill any holes that your pets may dig that hold water. There is an EEE vaccine available for horses. There is also an unproven WNV vaccine for horses.
Q. If I clean up my yard, but my neighbors don't, what's the point?
A. If you clean your yard then you are eliminating the mosquito's breeding ground. Any work that is done is better than no work at all It is very important that everyone in the county cleans up their yard, empties containers and keeps grass cut to eliminate potential mosquito breeding areas. Four or five people cannot do it all. We must approach mosquito control as a entire county. It is very important that we have 100 percent participation. The county and municipalities are providing adulticide spraying. Larvacide briquets are available at the health department. However, the most important part of a mosquito control program is the participation of the public.
Q. With all the swamps and woods, will what I do at my house make a difference?
A. There is no way that we can eliminate all swamps, marshy area and wet areas in the county. We must do what we can, where we can. The first area to target is your own home. Then help your neighbors and community.
Q. What's the best "device" for keeping mosquitoes away when we're in the yard? I've seen candles, bug zappers, smokers…all types of things.
A. Repellents are the best. For over 40 years DEET has been the standard in mosquito repellents. Be sure and read the label and follow directions. A product containing 23.8 percent DEET provides five hours of protection. A product containing 20 percent DEET provides four hours of protection. A product containing 6.65 percent DEET provides almost two hours of protection. A product containing 4.75 percent DEET will provide roughly one hour of protection. Oil of citronella is used for space repelling. Oil of citronella is the active ingredient in some candles, torches or coils that may be burned to produce a smoke that repels mosquitoes. These are only useful outdoors under windless conditions. Their effectiveness is less that repellent spray. Bug zappers and mosquito trapping devices are relatively new inventions. They should be thoroughly researched before you purchase them. Their overall effectiveness is not high.

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