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As West Nile Virus Spreads, Is the Cure Worse Than the Disease?
(Beyond Pesticides, August 27, 2003)
As West Nile virus (WNv) spreads west across the country, the media and the public should keep in mind the real risks of the virus and the pesticides commonly used against them. Beyond Pesticides' executive director, Jay Feldman, was on CNN on August 24th to debate the issue along with Allen James, President of Responsible Industry for a Sound Environment, a chemical pesticide industry association.

Throughout the short segment, Mr. James stated that the Centers for Disease Control (CDC) and the U.S. Environmental Protection Agency (EPA) have "declared that we should use insecticides, and that they are effective with virtually no risk to the human population." Later he again stated "pesticide risks … are minimal and have been declared safe by CDC and EPA."

Yet there is a common misconception that if pesticides are registered by EPA, then they are safe to use. The U.S. General Accounting Office has told Congress on several occasions that, "The general public receives limited and misleading information on pesticide hazards" and is misled on pesticide safety by statements characterizing pesticides as "safe" or "harmless."[1] EPA warns on its website that "no pesticide is 100 percent safe." [2]

In it's 2001 Revised Guidelines for Surveillance, Prevention, and Control for WNv, the CDC stated that spraying adulticides, pesticides intended to kill adult mosquitoes, is usually the least efficient mosquito control technique. [3]

It should be recognized "that the pesticides that are being used to kill adult mosquitoes are hazardous chemicals. These are chemicals that have been linked to cancer, birth defects, neurological conditions, and respiratory effects," stated Mr. Feldman. "And so, in that context, you have to ask yourself, is it worth the spraying that might go on? We've come to the conclusion with experts around the country that, in this case, what Mr. James is describing is a cure that's worse than the disease itself."

According to the August 24th edition of the Dallas Morning News, a Dallas entomologist that opposes spraying, L. Gene Helmick-Richardson, told the newspaper that aerial spraying is "a tragic overreaction … I'm more frightened of the pesticides that the city might use than I am of West Nile."

Brian Rogers, D.O., MPH, with the City of Fort Worth Health Authority, has stated that because Fort Worth has a high rate of Asthma Chronic Obstructive Pulmonary Disease and other respiratory disorders, he believes that "spraying for mosquitoes would harm more people than it would help."

Mr. Rogers has also stated "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." According to the New York State Department of Health, more people were reported to have gotten sick from pesticide spraying than from exposure to the virus in 2000. [4]

According to the CDC, less than one percent of those infected with WNv will develop severe illness. A 2000 analysis of the WNv outbreak published in the New England Journal of Medicine found that risk for severe illness was most closely correlated with increasing age. In the U.S., people older than 50 years and those with weakened immune systems have the highest risk of severe encephalitis. A person who has been infected with WNv is likely to have life-long immunity to the disease whether or not they showed symptoms. [5]

It should be noted that not all mosquitoes carry the WNv. There are 150 different species of mosquitoes in the U.S. and only a small fraction of those actually transmit disease. WNv and St. Louis encephalitis are primarily associated with the Culex mosquitoes. [6] On top of that, only adult female mosquitoes bite animals and require blood meals; males feed on the nectar of flowers.

Mosquito control should focus on preventing adult mosquito populations, educating the public on what can be done around their homes as well as on the real risks of pesticides and WNv, and the reduction of mosquito breeding sites, according to Mr. Feldman.

Mr. Feldman stated that the CDC is "not doing enough to educate people on the very small public-health threat that the disease actually represents and putting this into perspective with the exposure to the chemicals as a solution. CDC is very clear that the most effective method to manage the mosquitoes is to control breeding sites at the larval stage." He went on to say, "it then becomes should you move on, and, communities across the United States are saying no to pesticide spraying because of impacts on children and the general public."

According to David Pimentel, Ph.D., an entomologist at Cornell University, close to 99.9 % of sprayed chemicals go off into the environment where they can have detrimental effects on public health and ecosystems, leaving 0.1 % to actually hit the target pest. [7] Adulticides present considerable risk to all living things, and kill beneficial insects and natural mosquitoes predators [8], potentially increasing the number of mosquitoes.

Ray Parsons, Ph.D., a medical entomologist and assistant director for the Houston, Texas Mosquito Control Division says it is difficult to determine the effectiveness of pesticide spraying because there are currently no accurate means of measuring Culex mosquito populations. [9] Therefore, scientists cannot accurately determine what percentage of the population has decreased after spraying.

Mr. Feldman in the CNN segment also "urge[d] people to stay away from DEET-related repellents because of the scientific literature associated with those chemicals and use essential oils and other safer products."

Although the CDC recommends the use of DEET products, in 1998 EPA rejected "child-safety" claims of all DEET products. According to EPA, "child-safety claims must be removed from all end-use product labels… Child-safety claims are misleading and irreconcilable with the intended use and pesticidal ingredients of DEET products." In addition to the contradiction of EPA removing all "child-safety" claims while CDC touts DEET as safe, EPA states that there is evidence that the concentration of DEET within a product does not affect its safety.[10] Also, a recent study by Duke University researchers found that combined exposure to DEET (N,N-diethyl-m-toluamide) and permethrin could lead to motor deficits and learning and memory dysfunction. [11]

Although they may have to be reapplied more often than DEET products, the use of herbal repellents that contain cedarwood, garlic, lemongrass, frankincense, cinnamon, geranium, eucalyptus, basil, rosemary, cloves, peppermint, lemon balm (citronella), onions, feverfew, thyme, neem oil, and/or marigold are just as effective and are safer to use.

"[T]he bottom line question here is whether we ought to be exposing the public to two public-health hazards, West Nile virus and pesticides," said Mr. Feldman. "And what communities across this country are saying is it's unnecessary, we can adopt a full-blown comprehensive program that prevents mosquito infestation."

Mr. James got the last word stating, "We must have people feeling comfortable using these products." Mr. Feldman feels that misleading the public in order for them to feel "comfortable" is not appropriate in light of the risks of pesticide exposure and the ineffectiveness of adulticide spraying for mosquitoes.

For more information, see a copy of the CNN transcript and go to Beyond Pesticides' West Nile and Mosquito Management webpage.

References
[1] U.S. General Accounting Office. 1997. Nonagricultural Pesticides: Risks and Regulation. GAO/RCED-86-97. Washington, DC.

[2] U.S. EPA. 2002. Questions and Answers: Pesticides and Mosquito Control. Department of Prevention, Pesticides and Toxic Substances. http://www.epa.gov/pesticides/factsheets/pesticides4mosquitos.htm.

[3] Centers for Disease Control and Prevention. 2001. Epidemic/Epizootic West Nile Virus in the United States: Revised Guidelines for Surveillance, Prevention, and Control. Atlanta, GA. http://www.cdc.gov/ncidod/dvbid/westnile/resources/wnv-guidelines-apr-2001.pdf.

[4] New York City Health Information. 2001. West Nile Virus Surveillance and Control: An Update for Health Care Providers in New York City. New York City Department of Health 20(2). http://www.nyc.gov/html/doh/pdf/chi/chi20-2.pdf.

[5] West Nile Virus Questions and Answers on Survey. New York City Department of Health. March 21, 2000. http://www.ci.nyc.ny.us/html/doh/html/wnv/wnvqa.html.

[6] Centers for Disease Control and Prevention, Division of Vector-Borne Infectious Diseases. West Nile Virus: Entomology. http://www.cdc.gov/ncidod/dvbid/westnile/insects.htm; CDC Answers Your Questions About St. Louis Encephalitis. http://www.cdc.gov/ncidod/dvbid/arbor/SLE_QA.htm.

[7] Pimentel, D. 1995. "Amounts of Pesticides Reaching Target Pests: Environmental Impacts and Ethics." Journal of Agricultural and Environmental Ethics 8(1):17-29.

[8] Howard, J. et al. 1997. "Impact of Naled (Dibrom 14) on the Mosquito Vectors of Eastern Equine Encephalitis Viris." Journal of the American Mosquiot Control Association 13(4): 315-325.

[9] Parsons, R. 2001. Assistant Director for Mosquito Control, Harris County Mosquito Control Division. Telephone interview. September. http://www.hd.co.harris.tx.us/msq/msq.htm.

[10] U.S. EPA. 1998. Reregistration Eligibility Decision Facts: DEET. Office of Prevention, Pesticides and Toxic Substances. EPA-738-F-95-010.

[11] Abou-Donia, M., et al. 2001. "Subchronic Dermal Application of N,N-Diethyl m-Toluamide (DEET) and Permethrin to Adult Rats, Alone or in Combination, Causes Diffuse Neuronal Cell Death and Cytosketletal Abnormailieis in the Cerebral cortex and the Hippocampus, and Purkinje Neuron Loss in the Cerebellum." Experimental Neurology 172:153-171.