Alternatives to Adulticide Spraying


    A number of locales around the country have decided not to spray adulticides, with Fort Worth, Texas, and our nation's capital Washington, DC, being prime examples.  Officials in both of these cities cited scientific research that demonstrates that adulticiding is not effective, as well as concerns over health risks to people.  Those officials emphasize intensified larval programs, careful water management, and education outreach.  Moreover, officials in some other countries that battle much more serious diseases such as malaria have determined that the only really effective management and prevention of transmission of mosquito-borne disease is to utilize mosquito bed nets.  See, for example, "An integrated malaria control program with community participation on the Pacific Coast of Colombia." 

No-Spray Policies in Other Countries:  It has often been stated by health officials that once transmission to people of the West Nile virus has initiated the only remedy or protection for the public is to utilize insecticidal spray, supposedly to "break the transmission cycle." This may seem superficially reasonable, but it is in fact contradicted by scientific evidence.  See a more thorough discussion of this point, featuring a comprehensive policy in Colombia that focuses on public health education, community development and availability of primary health care. The goal of these measures is to produce a long-term adjustment in cultural practices around water management, health-care seeking behavior and the utilization of mosquito bed nets.

    If using mosquito bed nets sounds like a primitive method for use only in jungles in third-world countries, it turns out that they would work just fine in this country if preventing West Nile disease is a very important matter and we want to use the most effective measures to halt transmission of the virus to humans.

    Although most transmission of the WNv occurs in sylvan settings away from the home, the groups most at risk for serious disease are commonly house-bound and will be at risk only to transmission in the home.  In the circumstance of infected mosquitoes becoming trapped inside the home, these vectors will be attracted to the motionless source of carbon dioxide and water vapor when a person is sleeping. In this circumstance the mosquitoes' primary tendency to bite birds will not prevail, and they are much more likely to bite humans.  Their crepuscular nature (appearing or acting in twilight) will persist and the 40% biting activity that occurs in the 2 hours before dawn will focus on the sleeping residents of the home.  Mosquito bed nets would be very effective in this situation.

    Moreover, a fundamental assumption in the main report cited by vector control and public health officials to justify aerial spraying in this region (see a critique of "Efficacy of Aerial Spraying of Mosquito Adulticide in Reducing Incidence of West Nile Virus, California, 2005"), is that the infections all took place at the place of residence.  The authors are so convinced of domiciliary transmission that they did no landscape epidemiology whatsoever to refine the information about place of transmission.  If this is indeed where infections happen in our area, we would expect that the recommended course of action by knowledgeable researchers would focus on water management and mosquito bed nets instead of on a method of highly questionable efficacy, aerial adulticiding.

No-Spray Policies in This Country:  As to locales around the U.S. that have decided not to spray adulticides a 2002 report prepared by Tom Hemmick was written to give more information about the hazardous aspects of the pesticides being sprayed, as well as about the non-toxic alternatives.  Appendix C to the report contains an annotated list, updated in 2007, of locales that did not spray and the reasons they are not spraying. We quote from the web page, West Nile Virus and Mosquito Control Practices, which presents the report and the appendix:

"The TV and other media within their West Nile reporting have often failed to give the public the facts in two areas: 1) the hazardous aspects of pesticides being sprayed, and 2) the non-toxic alternatives. This report gives additional information on both aspects."

    Among the non-toxic alternatives are: removal of standing water, larvaciding, mosquito dunks, disposal of old tires, fish to eat mosquito larvae in ponds, encouraging natural predators such as birds, bats and dragonflies, yard clean-ups, public education programs, and others. Prevention activities, which stop mosquitoes in the larval stages, (before they become flying, biting adults) are the keys to successful non-toxic control.

    It is also possible to do some very effective and safe biological controls, which have not been used widely to date.  An example is Romanomermis culicivorax, a mosquito-parasitic nematode that has achieved much higher kill rates than mosquito fish.  This organism is an obligate parasite of larval Culicidae, mosquitoes, and infects nothing else.  That is, it presents no risk to either human health or the environment.  Please see our discussion of the currently limited use of bio-controls by SYMVCD for a discussion of this method and others.

    A number of jurisdictions have recently adopted non-toxic programs, recognizing the hazards of pesticides being sprayed. The report lists these jurisdictions, and the non-toxic alternatives being used. Examples include universities, communities and towns in Md., NY State, Texas and many others, in addition to those shown in the Sept., 2000 report.

    The adulticides sprayed by authorities are more toxic than the original annoyance. A number of scientists, doctors and professors who have criticized the pesticide spraying are referenced herein. For example, a NY State Health Dept. study indicated that more people were sickened from the spraying than from the West Nile virus.

    Of course, we are sympathetic to all of the victims of West Nile Virus and wish that their suffering had not occurred. But it is critical to do mosquito control in the right way to be sure it is effective and to avoid the undesirable, toxic side-effects. Ironically, the sprays intended to help protect sensitive people (children, elderly, asthma patients, etc.) are instead weakening immune systems, making individuals more susceptible to disease."

    A report from Nashville, Tennessee, concerned a careful analysis of 14 cities that did not spray, and the conclusion was that cities that elected not to spray pesticides (but used safer methods of mosquito control) have controlled West Nile Virus as well as those that have sprayed.

    The locales from the Hemmick report are as follows:

In Other Countries:

Revised 3-11-07.