Analysis shows no Increase in Occurrence of West Nile Virus in Cities That Do Not Spray Pesticides
The No Spray Nashville group analyzed data based on statistics provided by the health departments at 14 major cities including Dallas, Fort Worth, Washington, D.C., Memphis, etc., determining that “results show no significant difference in West Nile virus rates between communities that spray and those that don’t.” (Data is from the years 2002 and 2003.)
Here is their analysis:
FOURTEEN CITIES/COMMUNITY COMPARATIVE ANALYSIS
WHAT WE DID:
We looked at 14 communities with mosquito control programs in place. All of the communities use some level of surveillance, testing, larviciding and public education to help control mosquitoes and mosquito-borne illnesses. Seven communities sprayed pesticides as a regular part of their programs. The other seven communities did not. We compared the West Nile virus cases for the communities that spray to the communities that don’t for the years 2002 and 2003.
WHAT WE FOUND:
The communities that sprayed had an average of 1.37 people with West Nile virus per 100,000. The communities that didn’t spray had 1.19 people with West Nile virus per 100,000. The results show no significant difference in West Nile virus rates between communities that spray and those that don’t. Communities that did not spray put a strong emphasis on public education, selective larviciding and some employ seasonal help to help locate breeding sites of mosquitoes.
MORE DETAILS ABOUT THE COMPARATIVE ANALYSIS:
We looked at the human cases of West Nile virus in areas that spray versus those that don’t spray to see if there is any significant difference to help determine if the risks and expenses of spraying are worthwhile.
Populations based on 2000 Census. West Nile virus numbers are confirmed cases from state, city, CDC reports and phone calls for 2002 and 2003. Information was often double-checked with a second reference.
SPRAY PESTICIDES (also called ADULTICIDES)
All of these communities have mosquito control programs in place that include come level of: surveillance, testing, selective larviciding and public education. In addition, they have used adulticides in 2002 and 2003 as a regular part of their program.
1.) Dallas, Dallas County, TX, (population 2,218,899) 3.53 per 100K
2.) Nashville, Davidson County, TN,(population 569,891) .34 per 100K,
(2003 budget $180K about $55-75K of it was spent on spraying, 502 Sq. Miles, staff=3 full-time)
3.) Memphis, Shelby County, TN, (population 897,472) 5.57 per 100K
4.) Baltimore County, MD, (population 754,292) 2.25 per 100K
5.) Savannah, Chatham County, GA, (population 232,048) 3.88 per 100K
6.) Columbus/Franklin County, OH, (population 1,068,978) 1.21 per 100K
7.) Baltimore City, MD, (population 651,154) 2.46 per 100K
AVERAGE West Nile Cases per 100K=1.37 per year
USE NO PESTICIDES (also called ADULTICIDES)
All of these communities have mosquito control programs in place that include some level of: surveillance, testing, selective larviciding and public education. Some also have door-to-door teams in place to deal with problem areas.
1.) Ft. Worth, Tarrant County, TX (population 1,446,219) 1.87 per 100K
2.) Charlotte/ Mecklenburg County, NC (population 695,454) .57 per 100K,
(budget $150K, 526 Sq. Miles, staff=1 full-time year round and 10 seasonal technicians)
3. Cincinnati/Hamiton County, OH, (population 845,303) 3.55 per 100K
4.) Fulton County (metro Atlanta), GA, (population 816,006) 1.59 per 100K
5.) Montgomery County, MD, (population 873,341) 1.83 per 100K
6.) Washington, DC, (population 572,059) 6.46 per 100K
(budget $193 K, 61 Sq. Miles, 3-4 seasonal technicians) They say, “Spraying does trigger asthma attacks and can trigger allergy attacks.”
7.) DeKalb County, GA, (population 665,865) .75 per 100K,
(budget $270K, 268 Sq. Miles, staff=10 full-time seasonal technicians)
AVERAGE West Nile Cases per 100K=1.19 per year
Local note: Murfreesboro does not spray Murfreesboro/Rutherford, County*, TN, (population 182,023) 1.08 per 100K
CONCLUSION: The data shows that there is no significant difference in the cases of West Nile virus in communities that spray adulticides compared to those that don’t but use other methods of mosquito control. Therefore, the risks and the costs of adulticiding do not outweigh the benefits.
The risks must always be weighed against the benefits. The benefits of adulticiding in these cities in the United States are not apparent in examination of these data.
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Original No Spray Nashville page with analysis of the 14 cities can be found here.
See related information at Why Other Cities Have Chosen Not to Spray.