Potential Adverse Effects of Pesticides Used to Combat West Nile Virus

From: Robina Suwol
Date: 02 Jun 2003
Time: 05:56:03
Remote Name:


Maryland Pesticide Network
544 Epping Forest Road, Annapolis, Maryland, 21401,

Duke University Medical Center Professor Warns Maryland About the Potential Adverse Effects of Pesticides Used to Combat West Nile Virus.

Public exposure to two pesticides commonly used to manage nuisance mosquitoes and combat West Nile virus may be creating a dramatic public health problem larger than the insects themselves. In a letter to Maryland state officials, Duke University Medical Center professor of pharmocology, cancer biology and neurobiology, Mohamed B. Abou-Donia, Ph.D. warns of the dangers of prolonged use of high dose N,N-Diethyl m-Toluamide (DEET), used in over the counter mosquito repellents, and a magnification effect when used in combination with the insecticide permethrin (used to kill adult mosquitoes). In research conducted by Dr. Abou-Donia, profuse brain cell death and behavioral changes were found in rats exposed to DEET. A magnification effect occurred when DEET was applied to rats also exposed to the pesticide permethrin, used for mosquito control in Maryland. Rats dermally exposed to a combination of DEET and permethrin had tremendous reductions in muscle control, strength, memory and coordination.
"Since the recent outbreak of West Nile Virus (WNV), Maryland state officials have been recommending the use of DEET products/mosquito repellents. Maryland state officials are also planning to apply the insecticide permethrin for protection against the WNV. The liberal and unrestricted use of these chemicals and consequent exposure to the public, concerns me, considering the results of our research on the neurotoxic effects of these chemicals", wrote Abou-Donia in a recent letter to Maryland County health officers forwarded to the health officers by the Maryland Pesticide Network.
Abou-Donia warns Maryland state officials and the public to be cautious in recommending and using DEET products, and suggests DEET never be used on infants or combined with other insecticides, sunscreens, or even over the counter drugs such as antihistamines. In the U.S. many insect repellents contain up to 100 percent DEET, but doctors have recommended using products that contain no more than thirty percent DEET, and recently all products containing a higher dose were outlawed in Canada.
In general, WNV is a mild disease. It only becomes serious encephalitis if the virus can cross the blood-brain barrier. Among the agents that have been shown to impair the blood-brain barrier are in the pyrethroid chemical family, of which permethrin is a member. Therefore exposure to permethrin may have the potential to worsen the process of WNV infection.
Permethrin is also considered a possible carcinogen and possible endocrine disruptor by the US EPA. Short- term adverse effects include exacerbation of respiratory illnesses such as asthma, and effects on the nervous system such as itching, numbing, burning or tingling.

Last changed: March 14, 2006