Mosquitoes and the West Nile Virus
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Mosquitoes and the West Nile Virus

It is mosquito season again and time to dress appropriately, use insecticides and avoid being bitten by mosquitoes, -carries of the dreaded West Nile Virus and other diseases...


Mosquito Season is Here: Avoid Being Bitten

It is the middle of summer. Hot humid days and warm hazy nights are here for another month or more. These are ideal conditions for mosquitoes to be out. They seek blood from any warm-blooded mammal and they also carry many diseases. Protect yourself from being bitten.

In the whole history of mankind, no single vector of disease and death has been greater than diseases spread from the bite of a mosquito. There are some 3500 different species of mosquito in the world; nearly all are potential vectors of numerous viruses and diseases that directly affect health and lives millions of people. Avoiding the bite of the mosquito is the first, most important challenge. Eradicating their breeding grounds is another effect way to control mosquito-borne diseases. It is widely held that eradicating mosquitoes would not have serious consequences for any ecosystems. (1)

The Mosquito and West Nile Virus

It was in the year 1937 that the first case of what became known as ‘West Nile Virus’ was identified. A person in Uganda contracted an illness that was traced to the bite of an infected mosquito. The disease was identified again later in other parts of Africa. Soon, the same disease strain was identified in Europe, Asia and the Middle East.

The disease is transmitted to humans from the bite of an infected mosquito that has previously taken blood from an infected bird. The infected bird was the original source of the virus and the mosquito, the 'innocent' carrier. While person-to-person transmission of West Nile Virus does not occur in casual contact, evidence shows that transmission of the disease can occur from blood transfusions or exchange.

Symptoms of West Nile Virus might not be evident in an infected person. If any symptoms do develop, they usually manifest 2-15 days after being bitten. Most people that show any reaction at all only manifest minor symptoms that include body aches, mild fever and headache which go away within a few days.

Serious symptoms that occur in less-than 1% of the of the mosquito bite cases include high fever, acute muscle weakness, neck and throat stiffness (difficulty swallowing, etc.,) confusion and disorientation. The risks of serious symptoms are highest in the elderly, and those with compromised immune systems. Physical effects of West Nile Virus in these patients may result in permanent muscle weakness. There is currently no known treatment against West Nile Virus so prevention is currently the best defense.

Controlling West Nile Virus: Stop the Mosquito Breeding Grounds

Your local, State or Provincial Health Department seeks to prevent the spread of mosquito-borne illnesses with education, prevention and proactively eradicating breeding grounds for mosquitoes. A larvaciding program likely exists in your community or city whereby the local Health Department, licensed contractor or trained technicians introduce various chemicals into water supplies that may harbor mosquito breeding.

Here in Toronto, the annual Mosquito Control Program began June 1 and continues until Oct. 31. The chemical larvacides used against mosquitoes include methoprene and VectoLex WSP into municipal catch basins, and another type of potent larvacide “Bti” (Bacillus thuringiensis var. israeliensis) is introduced into standing water in public parks, ditches and small ponds where water accumulates after a rainstorm. (2)

Such treated standing water carries posted signs prominently indicating the use of these larvacide agents and advises people to avoid these puddles and wet areas. Pedestrians and their pets should avoid contact with these shallow standing waters due to the chemical agents being used.

Ways to Prevent or Avoid Mosquito Bites

the leg of a little girl is covered in swollen mosquito bites

(image source) Mosquito Bites

Using an insect repellent is one of the best defenses you can have to prevent mosquito bites. In addition if possible, avoid being outdoors during the peak hours that mosquitoes are most active. These are generally the hour or so around dusk and dawn.

Wearing long pants, a hat and long sleeved shirts and wearing light colors also help to prevent mosquito bite incidents. Mosquitoes are attracted to darker colors and movement so wearing light-colored clothing when hiking, biking or near mosquito-prone areas (forest, parks, fields and streams, etc.) is known to avert detection.

Insect repellents that contain DEET are especially helpful. Do follow the instructions on the product; do not over-apply or saturate the skin. Adult formulas that contain DEET should contain no greater than 30%, and for children under the age of 12 years, no greater than 10% DEET. Do not use any DEET-containing insect repellent on children age 6-months or younger. And in all cases, never spray towards the face or use on or near the eyes, lips or mouth.

Women who are pregnant or breast-feeding a child should avoid areas where West Nile Virus has been reported and mosquito bites are a possibility. There is some evidence to suggest that West Nile Virus can be transmitted from the mother to the unborn child, and that West Nile Virus can be in present breast milk as well. The use of DEET along with proper clothing (long sleeved clothing, etc.) and avoiding areas of mosquito activity during peak hours (again, dawn and dusk hours are when mosquitoes are most active) are the best prevention.

Although there is no hard evidence that a pregnant woman using DEET affects her unborn child or that of her breast milk, it is advised that methods other than the use of DEET be used when possible.

If you discover that you have been bitten by a mosquito, you are most likely safe. Less than 1% of all mosquito bites transmit West Nile Virus to humans. However, if symptoms of fever, muscle weakness or severe headache occur up to two weeks after the incidence of a mosquito bite, see your doctor.

Avoid contracting West Nile Virus by not being mosquito bitten is always the first and best preventive. Maintain your health during the summer months of mosquito activity.

(thumbmail mosquito image courtesy Flickr)

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Comments (4)

I added West Nile Virus to my list "modern medicine" can't do anything about. The 21st century and we're still letting a bunch of bugs kick us around.

last year we had no mosquitoes, it was a drought here, this year loads of them.. and the bats are happy.. I havent seen any dragon flies which is odd because they too love mosquitoes, but perhaps their populations fell last year.. anyhow mosqutoes gotta live too.. its a pity they spread diseases.

Ranked #5 in Immune System

I find it curiously refreshing and yet somehow unsettling a the same time that there are whole groups of scientific minds that feel that if mosquitoes were brought to extinction it would be nothing but a benefit to all the world (well, at least the the higher mammals.) We know that mosquitoes existed during the time of the dinosaurs, and from the fossil record we see that many of the large dinosaurs had 'health issues' concerning bone and probably soft-tissue (joints, skin, blood etc.) and who knows? -This could be the effects of diseases that were spread by mosquitoes and they suffered the results, -same as we do today. I am a bit concerned over the chemicals being used for 'standing water eradication' of mosquito larvae. We don't know what happens to the chemicals after... And 'eco-friendly' efforts often backfire too, like the ill-advise introduction of water-borne carnivorous plants into non-native streams and ponds (plants such as the bladderwort.) The hope was that they'd eat the mosquito larvae, -which the meat-eating plants do, but they also were consuming other water-borne bugs like dragonfly nymphs and choking-off the oxygenation of the waterway, causing fish and other water creatures to suffer and die-off.. I still think that 'The Mosquito Magnet' is probably the greatest invention of our time...

Ranked #5 in Immune System

A couple of days ago it was announced here that there were several confirmed cases of West Nile Virus in mosquitoes here in Toronto and the Durham region (just east of Toronto...)