Snake Oil

West Nile: Fact and Fiction

Mosquito BiteWith the return of the mosquitoes comes the return of the West Nile virus hysteria. Fear is driving people to slather their bodies with DEET (a questionably safe and widely available, unpronounceably-long-named chemical compound) and driving local governments to spray organophosphates and synthetic pyrethroids throughout our neighboorhoods. Of course, the party line says that DEET is safe, but read this about the toxicity.

From Beyond Pesticides:


  • There are 175 different species of mosquitoes in the U.S. and only a handful of those are vectors for disease. Only adult female mosquitoes bite and require blood meals; males feed on flower nectar.
  • West Nile virus (WNv) and St. Louis encephalitis are primarily associated with the Culex mosquitoes.
  • Adult Culex females live between 2-4 weeks, depending on climate, species, predation, and a host of other factors.


  • Less than one percent of those infected with WNv will develop severe illness, according to the Centers for Disease Control. The vast majority of people (about 80%) who become infected with WNv will show no symptoms and never become sick. Some 20% may experience mild flu-like symptoms within 3 – 15 days.
  • Brian Rogers, D.O., MPH, City of Fort Worth Health Authority states, “The risk of becoming seriously ill and dying from West Nile is extremely minimal. Fewer than 1 percent of mosquitoes in areas where the virus has been found actually carry the virus.”
  • The U.S. Fish and Wildlife Services states, “Contrary to media descriptions of ‘the deadly West Nile virus,’ [it] is rarely fatal in humans. Less than one percent of people who acquire the disease will experience severe illness. Within this small proportion, the fatality rate is about 3-15%.”
  • A person who has been infected with WNv may have life-long immunity even if they show no symptoms.


  • According to the Centers of Disease Control and Prevention (CDC), spraying adulticides, pesticides intended to kill adult mosquitoes, is usually the least efficient mosquito control technique.
  • Adulticiding programs spray pesticides indiscriminately and do not get at the mosquitoes until they have matured. They also do not restrict, control, or prevent mosquitoes from carrying WNv or continuing to breed.
  • Close to 99.9 % of sprayed chemicals go off into the environment where they can have detrimental effects on public health and ecosystems, leaving 0.10% to actually hit the target pest.


  • The U.S. EPA warns, “no pesticide is 100 percent safe.”
  • National Research Council found that pregnant women and children have a greater risk of getting sick from pesticides.
  • Brian Rogers, Ft. Worth Health Authority states that, “Spraying for mosquitoes would harm more people than it would help.”
  • New York State Department of Health states that adverse outcomes during or after an aerial or ground spraying of adulticides might include acute asthma attacks, other respiratory problems, and/or dermatological problems.
  • Synthetic pyrethroids are neurotoxic and have been linked to cancer. People (particularly children) with respiratory problems, such as asthma, are especially vulnerable to these pesticides and will suffer disproportionately from exposure.
  • Washington, DC cites both lack of efficacy and asthma concerns among reasons for its no-spray policy.
  • In 1998, EPA rejected “child safety” claims for DEET products and required all such claims to be removed from existing products.
  • On June 3, 2001 the Associated Press reported that in New York more than 50% of dead crows collected in response to West Nile virus died from exposure to pesticides and lead, rather than from West Nile virus.
  • A 1999 Mount Sinai School of Medicine study examined four pyrethroid pesticides, including sumithrin, and concluded, “[E]ach pyrethroid compound is unique in its ability to influence several cellular pathways. These findings suggest that pyrethroids should be considered to be hormone disruptors, and their potential to affect endocrine function in humans and wildlife should be investigated.”
  • Commercial fishermen in Maine filed a $125 million lawsuit claiming that the dramatic decrease in the lobster harvest was due to the spraying of an adulticide containing malathion.
  • Reports of inappropriate and/or illegal spraying practices are common. Children are known to follow spray trucks for entertainment. Other practices include fogging during daylight hours, during wind speeds higher than 10 mph, and in no-spray zones. Proper integrated pest management is often ignored.

Organophosphates, which include malathion (Fyfanon), naled (Dibrom) and chlorpyrifos (Mosquitomist), are a highly toxic class of pesticides that affect the central nervous, cardiovascular and respiratory systems. Symptoms of exposure include: numbness, tingling sensations, headache, dizziness, tremors, nausea, abdominal cramps, sweating, incoordination, blurred vision,35 difficulty breathing, slow heartbeat, unconsciousness, incontinence, convulsions and fatality.36 Some organophosphates have been linked to birth defects and cancer. Breakdown times range from a few days to several months, depending on conditions.

Synthetic pyrethroids, which include resmethrin (Scourge) and sumithrin (Anvil), are adulticides patterned after pyrethrum, yet have been chemically engineered to have greater toxicity and longer breakdown times.17 Almost all synthetic pyrethroid mosquito products use synergists like piperonyl butoxide (PBO), a petroleum distillate, which increases potency and compromises the body’s ability to detoxify the pesticide. Petroleum distillates are carcinogenic and linked to birth defects and other illnesses. Animal studies have shown children to be more sensitive than adults and that exposure may inhibit neonatal brain development.18 Pyrethroids are highly toxic to fish and honey bees, even in low doses.
Symptoms of exposure include: dermatitis and asthma-like reactions, eye and skin irritation and flu-like symptoms.19 Synthetic pyrethroids are endocrine disruptors and have been linked to breast and prostate cancer.20 People with asthma and pollen allergies should be especially cautious. Exposure has resulted in deaths from respiratory failure. Breakdown times range from a few hours to several months.


  • Lyndhurst, Ohio, passed a landmark ordinance in 2003 prohibiting the spraying of pesticides for WNv. During a Task Force sponsored forum, a panel of experts discussed the hazards and low efficacy of adulticides. The Council stated, “[T]here is substantial belief that the more effective way of controlling the mosquito populations is by larvacide treatment and thorough education…” Concluding that, “[T]he dangers of WNV are minimal and affect a very small segment of the population and that the long-term health and environmental risks of spraying with synthetic pesticides poses a much greater risk.”
  • Washington, DC health officials continue their no-spray policy stating that pesticide spraying is inappropriate in a heavily populated area with asthmatics. Instead,
    officials focus on larval control and pubic education, with education materials distributed in four languages. The Department of Health is also implementing a Tire Round-Up program for residents to discard old tires, a major breeding site for mosquitoes.
  • In York County, Virginia, officials distribute the mosquito eating fish, Gambusia holbrooki, to residents in order to decrease pesticide use for mosquito control. Several thousand of the fish have been bred by the county’s fishery as part of its mosquito prevention program.
  • In Dallas, Texas, the City Council’s Health, Environment and Human Services Committee adopted a mosquito control plan in 2003 that calls for more public education and allows the use of pesticide sprays only as a last resort and upon approval of the pertinent council member.
  • Ft. Worth, Texas has not sprayed for mosquitoes since 1991. In 2003, Ft. Worth had 3 WNV cases and no deaths. Brian Boerner, Director of Environmental Management, states, “the spraying of chemicals also has the potential of contaminating our waterways, killing the beneficial fish and organisms that feed on mosquito larva, adding harmful volatile organic chemicals to the atmosphere-a precursor chemical to ozone formation-and providing a potential inhalation or ingestion hazard to residents.”
  • Nassau County, New York joins others in using predacious fish in hard to reach salt-water marshes.
  • Marblehead, MA has a WNV Response Plan that requires a town hall meeting before any adulticides are used (and only if there’s been a locally-acquired human death).
  • In 2003, Boulder, Colorado focused on larviciding, getting SpyCentre surveillance installers and public education without the use of adulticides and offered free WNv information workshops for neighborhood groups and distributes free samples of Mosquito Dunks, a least-toxic larvacide product, for use in stagnant water.
  • In preparation for WNv, Lane county, OR have an easy to read public educational flyer that is put in local newspapers and distributed with utility bills early in the season.
  • In 2003, Seattle, Washington adopted an Integrated Pest Management Plan for Mosquito Control, which identifies public education, personal protection, and breeding source reduction on public property as, “…the most effective and appropriate techniques for the City to use.

West Nile virus sure does sell a lot of bug spray.

Zemanta Pixie

Derek Markham

Things I dig include: simple living, natural fatherhood, attachment parenting, natural building, unassisted childbirth (homebirth), bicycles, permaculture, organic and biodynamic gardening, vegan peanut butter cookies with chocolate chips, bouldering, and the blues. Find me elsewhere at @NaturalPapa, @DerekMarkham, Google+, or RebelMouse.

2 thoughts on “West Nile: Fact and Fiction

  • All I have to say is hooray for bats! Eating half of their body weight in flying insects per day. West nile is pretty prevalent here in Southern Ontario Canada with only a few contracting it anually.
    Good writeup!

  • Thanks for reading!
    Can you imagine eating half your weight of anything?


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