March 23,2005
You Say Tomato, I say Mosquito
(By Jim Burnell)
Gathering tomatoes or other fruits of the garden might not sound like a dangerous occupation, but with terrorism running rampant these days, even a walk thru the garden can require pre-emptive measures. In fact if you left the screen door open for a minute or so and heard a whiny frequency accompanied by a slight tickle it may already be too late, if that slight tickle was the allergic reaction of your skin cells to the Culex, Aedes or Anopheles mosquito, one of the several species that prefer humans, and are capable of transmitting microbial organisms to living cells.
Every year two million people die of malaria, which is transmitted by the Anopheles mosquito, but most of those deaths occur in Africa. In the U.S. malaria is considered rare, but the West Nile Virus is on the move and has reached all the states except Alaska and Hawaii.
The West Nile Virus is two millionths of an inch wide, smaller than most viruses. Viruses occupy a special taxonomy position in that they are not plant, animal or prokaryotic bacteria, and should not even be considered organisms because they are not free-living. (They cannot reproduce with out a host cell.)
The West Nile Virus has been studied for decades but did not arrive in the US until 1999. It is most similarly assocciated with other viruses that cause encephalitis, (inflammation of the brain), and it is highly fatal to avian species, corvids, mostly non-migratory birds distinguished by same sex characteristics. The West Nile Virus is also fatal to horses although there is a two-dose vaccine available for horses. It is not known when a vaccine will be discovered for humans or birds, so the best method of dealing with the virus is through avoidance. The West Nile Virus is past on to its animal host through the saliva of the female mosquito at the time of injection. The female mosquito needs a blood meal to complete reproduction, and pass on proteins to her offspring. The male mosquito does not eat blood but lives only on nectar and fruit juices.
Avoiding mosquitoes can be a big problem if you’re an outdoors person unless your companion is more susceptible to mosquito bites than you are. Some people attract more mosquitoes than others. (They must have a better bloodline.) Mosquitoes can lay their eggs in as little as one tablespoon of water which hatch and become adults in as little as seven to ten days. Finding all the water sources in which they can breed is next to impossible, but eliminating the obvious places will help. (Rain gutters, bird baths, flower pots etc.) In order to avoid mosquitoes it helps to know how they find you. They use sensors on their antenna to pick up body heat, odor and carbon-dioxide from exhaled breath to find their meal. That’s why black-light traps do not really work well, (mosquitoes use thermal imaging, not ultra violet). The female mosquito will work her way upwind zigzagging back and forth to the sources of these bodily cues. As she gets closer she uses colors and moisture in the air to close in on her target. British researchers found that mosquitoes would respond to animal bodies up to forty-five feet away. Mosquitoes become inactive when temperatures drop below forty-five degrees F or above eighty-two degrees F or when wind speeds are higher than six meters per second.
Some repellents are very effective at binding the mosquito sensory antenna. Repellants composed of heavy irregular shaped molecules work best. They block the pores of the sensory hairs of the mosquito antenna forcefully changing the mosquitoes point of view, causing her to fly past a living target. Area repellants like candles and incense with citronella have been proven effective at averting mosquitoes and even a plain wax candle can work as a decoy to trick mosquitoes. One of the best and most familiar repellents is a chemical product called Deet, which was developed by the USDA and patented by the US Army in 1946 and then registered in 57 for use by the general public. It is a broad spectrum repellent targeting many different insect pests, however one thing that might not be so well known is that Deet should not be used in conjunction with any other insecticide containing Permethrin as it can cause severe cellular damage according to Duke Universities Journal of Toxicology and Environmental Health.
One of the most interesting, and recent repellants I have discovered while researching this article is the use of a common perennial herb or weed called catnip. Researchers at Iowa State University and the US Forest Service released information in 2001 on the effectiveness of nepetalactone, an essential oil found in catnip that works 10 times more efficiently than Deet although they say nothing about its duration comparison. Iowa State had submitted a patent application for the use of catnip compounds for insect repellents and commercial products are already available to the general public, (although I do not know if that means that thorough testing on humans or animals were completed). Caveat Emptor. Obviously cats will be meowing all over the neighborhood once these products become popular. (Skeeter-free, Natures Herbal, Natural Herbal Shield are a few). Some companies may be cheating the law by not calling there products a “Repellant”, so as to bypass FDA regulations.
You may want to try mixing your own concoction of catnip repellant. It’s available at nurseries and in the wild if you know what it looks like. Catnip was introduced to the US from Europe in the late 18th Century, and has been used for seasoning and teas for years. It is thought to have many healing properties among them help for (inducing sleep, migraine headaches, fevers, sedative, fatigue, restlessness, pain killers, improving circulation and symptoms associated with the flu.) It is also high in vitamin C. Catnip was also called the “Hang-mans Root” and was used by early American colonial executioners to put them in the mood before an execution. In England it was used to flavor beer because it cost less than hops. Over the years their have been many other plant-derived repellants to combat insects such as lavender extract, cedar wood, neem oil, Rosemary, peppermint geranium, lemongrass and others.
As far as electronic devises sold to repel insects, be sure the experts who tested these devices were not on the companies payroll, or be careful of which expert you listen to. Some of these products do more damage than good. In May 2001 the FTC sent warning letters to 60 companies selling these devises, warning them not to make claims without scientific evidence. In August 2002, Lentek International was charged by the FTC, for making false claims that their electronic mosquito repelling devices, repel mosquitoes. (
WWW.ftc.gov/opa/2002/08/lentek.htm)
One proven method that partially worked for my dad when I was growing up, was the nightly mosquito hunt. Each night before bedtime the five of us kids were assigned a rolled up newspaper and a room, and we could not go to bed until every mosquito in the house was extinguished. It worked 90% of the time and gave the walls and ceilings that natured texture look. The funny thing bout it was the other 10% of the time the mosquitoes only got dad.
Mosquitoes play an important role in the food chain, mostly in their larvae and pupae stages, transforming algae, bacteria and organic matter into meals for fish and other aquatic creatures and wading birds etc. and it would not be beneficial to eliminate all of them.
So far this year in Ca there have been no human cases of the West Nile Virus reported. Last year out of 830 reported human infections, 27 were fatal. In November 2003 a bio Technology Company called Acambis started the first human clinical trial of a West Nile Virus vaccine. So far it has performed well in hamster, mice, monkeys and horses. Most cases of the disease occurs in the elderly and others with impaired immune systems, there have been cases of transmission through blood transfusions, and organ transplants. In most cases those who have West Nile Virus do not even know they have it. A few will develop flu like symptoms 4 to 10 days after the infection, and a rare few will develop encephalitis.
Sources:
University of Ca. Publication 7451
Author: Bruce Eldridge, Dept. of Entomology, UC Davis
Catnip as a Mosquito Repellent
Author: Jeffrey s. Hoard
National Association for Holistic Aromatherapy
Dept of Health and Human Services
Center for Disease Control and Prevention
Grow your own mosquito repellant
Author: Ann Lovejoy
Integrated Pest Management of Alaska
Iowa State University Extension Fact Sheet
Mosquito
Iowa State University
Joel Coats, Entomology
Brian Meyer, Agriculture Communications
Encyclopedia Britannica 2005
