Read All About It: Disease Burden of West Nile Virus Does Not Warrant Spraying

1. The disease burden for West Nile virus in Davidson County for 2002 and 2003 was not significant and did not warrant the unintended risks involved in spraying.

2. The disease burden in cities that do not spray but place a heavy emphasis on less toxic approaches was not significantly higher than cities that spray. In addition, a fourteen city/county comparison of cities that spray compared to those that do not show there is no significant difference in West Nile virus cases.

3. Spraying creates resistant mosquitoes, kills beneficial insects (some which act as natural controls for mosquitoes), and may have unintended consequences on other ecosystems.

4. Spraying presents potential health risks to people with respiratory illnesses, chemical sensitivities and asthma.

5. Safer and more effective methods are available for mosquito management which can reduce mosquito populations to the point where adult insecticides are not necessary.

6. Spraying is the least effective form of mosquito control. It should be use only as an element of the last resort, for short-term relief in an emergency. It is not a good use of economic resources in non-emergencies.

THE STATE ENTOMOLOGIST TALKS ABOUT MOSQUITO CONTROL

Statements by Ms. Kristy Gottfried, Medical Entomologist, State of Tennessee Department of Health (Ms. Gottfried left her position for another job in 2004. She made these statements at a public forum held at the Health Department in December of 2003.)

If you ask any student of entomology the most effective method of killing mosquitoes they will say permanent control (eliminating standing water) and larviciding (killing mosquitoes in the larval stage in standing water that can not be removed). It probably would be safe to say everyone in the entomological field would agree with that statement.

There are a few reasons why adulticiding (spraying insecticides) is not the preferred method of choice and actually only should be used either in an emergency situation (for example: 15 people have West Nile virus in a 2 block radius) or when all preferred methods have failed miserably where the risk to public health is classified as significant.

a. It is much easier to kill mosquitoes in the larval form because they are in a relatively concentrated area-like a puddle instead of dispersed over 3 blocks. Adulticides have essentially no residual effects-meaning that after application, the insecticide must hit the flying mosquito, not the ones protected by any barrier (trash can, leaves) to actually kill the mosquito. Insecticides that land and dry on a leaf will not kill a mosquito hours later.

b. Larviciding is considered species specific meaning it will not kill other wildlife in the habitat while adulticides may have negative effects on non-target organisms (other insects primarily) that are beneficial to the environment. . . .

c. There are lots of other implied tasks that are necessary to do prior to and after adulticiding that take entomological knowledge (either formal or self taught training)-which means that you have to have people on staff that have a background in entomology or willing to learn new skills." (Summarized by us: trapping to ensure the mosquitoes succeed the acceptable threshold, trapping prior to and after the spray event for effectiveness, testing for resistance.)*See comments about the Health Department's testing below.

Every talk I give, I emphasize that fact that there are lots of implied task that must be accomplished if they want to adulticide and actually ensure they are killing mosquitoes. Larvaciding is much easier because larvae (immature mosquitoes) are easily identified to genus, easily counted and takes much less training/knowledge for an operator than collecting and identifying adults.

d. Adulticiding is a "short-term solution" and essentially treating the problem and not the cause. It will knock mosquito populations down but only for a few days, because the breeding sites are still producing a next generation of adult mosquitoes. The cause of mosquito control problems must be identified and dealt with effectively and that is through identification of mosquito breeding sites and elimination of those sites or continued surveillance/treatment. . .

One above ground pool with 1 foot of water that is not maintained properly will produce thousands and thousands of mosquitoes and effect the entire neighborhood.

*Dr. Laurence Zwiebel, mosquito expert and researcher from Vanderbilt University responded to Dr. Hager's report that, according to their tests, spraying was effective last year. "Now, I am not arguing with the numbers Dr. Hager just mentioned but I do find them extraordinary from the point of view from what I have seen both from the literature in the United States and my own experience in many parts of the world. Mosquito spraying programs are a very dicey business. They have to be used appropriately and I believe their efficiency has to be continually monitored with a specific cadre of individuals who are collecting mosquitoes and assessing the situation, and not just sporadically but rigorously throughout the time period."

WAS THE RISK OF WEST NILE VIRUS SIGNIFICANT IN DAVIDSON COUNTY?

The 2000 Census shows the population of Tennessee as 5,689,283. In all of Tennessee, there was one death from West Nile virus in 2003 (from Shelby County) compared to eight deaths in 2002 (one death in Davidson County).

In 2002, Memphis had 71% of Tennessee's confirmed cases of West Nile virus. Many of these cases were in a small area in downtown Memphis. This is a good example of when the short-term use of insecticide in a localized area would have been appropriate. 87% of the cases were in Western Tennessee. Davidson County had one case and one death. At the time, the Health Department was spraying nuisance mosquitoes for individual property owners on demand and used 8 drums of pesticide.

In 2003, Davidson County had no deaths and one confirmed case of West Nile virus. This is an incident rate of .17 per 100, 000 in both 2002 and 2003. Also in 2003, the Health Department stopped spraying "Nuisance Mosquitoes" on demand and began a new policy of mass spraying only for "West Nile Mosquitoes." This resulted in no difference in the incidence of West Nile virus from 2002. 6.5 drums of Anvil 2+2 were used at a cost of $33,000 for the product and about $23,000-37,000 in employee time. (These numbers were given to us by Dr. Brent Hager of the Metro Public Health Department.

Last year, Rutherford County, Washington D.C. and Fort Worth, Texas did not spray. They spent their money on safer and more effective methods of mosquito control. Their rates of West Nile virus in 2003 ranged from .52-.56 per 100,000 and no deaths. The statistics show the incidence rate is not significantly higher. In addition, these methods are less costly and present fewer risks.

CONCLUSION: The statistics show that West Nile virus does not and has not posed a significant risk to Davidson County residents.

POSITIVE MOSQUITO POOLS ARE NOT A REASON TO SPRAY

In 2003 and 2004, the Health Department made its decision to spray based on positive mosquito pool testing. 50 mosquitoes were crushed and sent to a lab. A positive test can mean one mosquito to 50 mosquitoes or no mosquitoes have West Nile virus.

The State Entomologist Ms. Kristy Gottfried and Dr. Zwiebel have said positive mosquito pools do not provide enough information to begin spraying. Ms. Gottfried said, "If I get a positive mosquito pool test, I say, Õso what?Õ That tells me I should be testing more to find out what is going on."

Dr. Zwiebel states, the testing is imprecise and false positives can and do occur.

Both of these experts have offered advice and recommendations to the Health Department. These experts are up-to-date and in the top of their field. Their advice has been ignored.

CONCLUSION: Positive mosquito pools do not constitute an emergency.

FOURTEEN CITY/COUNTY STATISTICAL COMPARISION

We are looking at the human cases of West Nile virus in areas that spray versus those that do not spray to see if there is any significant difference to help determine if the risks and expenses of spraying are worthwhile.

CONSIDERING THE EFFECTS OF SPRAYING ON PEOPLE WITH ASTHMA

The Allergy and Asthma Foundation of America ranked Nashville as the ninth-worst city in the nation for asthmatics in 2003. Washington, D.C. (ranked 50) and Fort Worth, Texas (ranked 72) have not used airborne pesticides partly because of the high incidence of asthma in their cities. Clearly, we should consider the risk to asthmatics.

The City of Murfreesboro's decision not to begin a spraying program was based on the advice of University of Tennessee Agricultural Extension Service experts who say such programs are ineffective and more cost prohibitive than other, more effective, options like public education and providing larvicides for public areas where standing water is a problem. "Spraying programs can adversely affect the health of small children and those with breathing problems," the service said at the time. (Murfreesboro info: www.murfreesborotn.gov/news/mosquito.htm)

SUMMARY OF WORLD-RENOWNED MOSQUITO EXPERT AND RESEARCHER FROM VANDERBILT UNIVERSITY OPINIONS ON SPRAYING IN DAVIDSON COUNTY

Dr. Laurence Zwiebel, who helps developing countries around the world with mosquito control for mosquito-borne illnesses, spoke about the risks of spraying at a public forum in December 2003. Below are some of his main points.

Adult insecticides are a critical component in mosquito control strategies but, as is stated very clearly in the CDC's information packet, it is an element of the last resort.

A number of opportunities are available to reduce mosquito populations to the point where adult insecticides are not necessary.

In addition to the risks to humans, the non-judicious use of insecticides contributes to mosquito problems by creating resistant mosquitoes.

Collateral damage to beneficial insects and other elements of the ecosystem is a very large concern and often is counter-productive both from an economic point of view and an element of species diversity.

"I don't feel that the disease burden warrants these types of risk," said Dr. Zwiebel.

THE UNINTENDED CONSEQUENCES OF SPRAYING IN 2003 (that we know about)

BURNT/No Spray Nashville has collected complaint forms from Nashville Citizens who experienced some of the unintended consequences of spraying. Below is a summary of some of those reports.

1. Even though they left their homes when spraying occurred, two people who have been diagnosed with Multiple Chemical Sensitivities reported problems with breathing and burning skin after they returned home. The problems were so severe that both feel they may have to move if spraying continues.

A woman who is asthmatic was outside when spraying occurred. She said she could taste the spray. Her breathing was labored so she went inside and used her inhaler with Albuterol to help her breathe easier. She also watched as children followed the truck by foot and bike "like an ice cream truck. " The children were sprayed.

There were reports of fish dying in peopleÕs ponds right after their neighborhoods had been sprayed. In one incident 200 fish died. A Koi Club member was told by Brian Todd of the Health Department that the spray does not pose any risks to fish. The fact sheet for the pesticide says, "highly toxic to bees, fish and other aquatic life".

Healthy people reported a variety of symptoms from sore throat to feeling nauseated. These are common side effects from the insecticide used by the Health Department in 2003.

People reported truck drivers not sounding their horns, spraying people on the street, spraying properties which had been opted out and spraying some areas twice.

CHEMISTRY DEPARTMENT CHAIR AT FISK UNIVERSITY CAUTIONS

Dr. Robert Wingfield, who has a background in Toxicology and Environmental Education, made these points at a public forum held in December of 2003:

1. It is very important people know when pesticides are being used and they take the appropriate precautions. (Our note: We feel the notification policies are inadequate and and precautions incomplete.)

2. The public should know something about the possible effects of the pesticide. (Our note: The Health Department has not supplied ANY information regarding possible effects or what to do.)

3. There are groups who are most susceptible to the effects like: immune-compromised, pregnant women, children. These people must be taken into consideration. (Our note: Opting out is not very helpful since the spray drifts. It is particularly troubling for people with Multiple Chemical Sensitivities.)

4. After spraying: DonÕt go outside right away. DonÕt let your dog run in the grass or your kids play in the grass. Allow time for the pesticide to degrade.

5. The EPA and CDC recommends a 30 minute wait period, however waiting 24 hours would better allow for significant degradation of thepesticide. Sun light and water play a role in degrading pesticides.

A FEW POINTS ON INTEGRATED PESTICIDE MANAGEMENT by STATE ENTOMOLOGIST

Ms. Kristy Gottfried, Medical Entomologist, State of Tennessee Department of Health shared these points at the forum in December 2003:

Integrated Pest Management a combination of strategies

Preventative Measures: Public Education-clean up back yard and taking personal responsibility; Monitoring mosquito populations by testing;Breeding site reduction with help of the public

Biological control and larval control

Last resort: When everything else has failed, spraying insecticides is short-term relief. We cannot say that pesticides are 100% safe.

The best way to control mosquitoes is by larval control and all the other preventative methods. You can't get rid of every mosquito. There has to be some level of acceptance for mosquitoes.

There are about 152 species of mosquitoes. Probably, only three of them actually transmit West Nile virus. So, youÕre only talking about a small proportion. (Our note: females are the only mosquitoes that bite.)

WHEN SHOULD INSECTICIDES BE USED?

Dr. Laurence Zwiebel made this reference to the emergency use of insecticides. He said, if there is disagreement in what an emergency is, then it is probably not an emergency.

RECOMMENDATIONS FOR MOSQUITO MANAGEMENT IN DAVIDSON COUNTY

1.) Cease spraying for non-emergencies.

2.) Dr. Zwiebel has volunteered his time and expertise to help with mosquito control decisions on the West Nile Task Force. He has helped developing countries around the world and, probably, was paid well for it. The Metro Public Health Department should graciously accept his offer and work with him to help establish better testing, larviciding and emergency response standards.

3.) The State Entomologist, Ms. Gottfried, recommended hitting larvicide hard and getting summer helpers (paid or volunteers). The 2004-2005 budget for spraying should beredirected to help cover the costs of these recommendations.

4.) We suggest the Health Department increase public education by working with knowledgeable citizens like Dr. Zwiebel, members of some of the groups listed below and government experts like Ms. Gottfried to help design well-balanced and engaging PSAs, flyers, programs and methods of education. The staff of three needs the support of our community. We are willing to assist.