HomeMy WebLinkAboutIR 8793INFORMAL REPORT TO CITY COUNCIL MEMBERS NO- 8793
To the Mayor and Members of the City Council
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Pagel of 2
t 0• SUBJECT: UPDATE ON MOSQUITOES
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At the July 25, 2006 Pre - Council Meeting, Council requested an update on the City's activities related
to mosquitoes and specifically asked if the City had any plans to implement a spraying program. The
purpose of this Informal Report is to describe the City's ongoing mosquito sampling, disease
surveillance and public education efforts, provide data describing the threat and occurrence of West
Nile Virus (WNV) within Fort Worth, and describe the City's current position on spraying initiatives.
Mosquito sampling, disease surveillance and public education
Beginning in 2002, with the emergence of West Nile Virus as a new health threat to this part of the
country, the City's Public Health Department has participated in a countywide disease surveillance
system aimed at identifying mosquito pools where West Nile Virus is present. Numerous sampling
sites throughout the city are administered during warm - weather months, with mosquito samples
routinely submitted for laboratory testing. Mosquitoes are tested for the presence of West Nile Virus,
St. Louis encephalitis and other vector -borne diseases.
When a mosquito sample tests positive, or a human WNV case is reported, public health department
personnel respond as follows:
• Conduct an environmental scan of the area to determine if there are opportunities to larvicide
standing pools or ponds of water on public property and /or educate property owners with
mosquito - friendly environments on their property.
• Disseminate educational materials targeting businesses, churches, schools, neighborhood
associations in the area to promote personal protection and source reduction and educate
them of the relatively small risk of exposure.
• Perform enhanced mosquito sampling in the area.
The Fort Worth Public Health Department continues to recommend personal protection, prevention
and source reduction strategies (rather than spraying for adult mosquitoes) as an effective means to
reduce the risk of human exposure to WNV.
West Nile Virus Data
According to recently published research data, less than 1% of individuals bitten by a mosquito
infected with West Nile Virus will experience illness to the extent that medical attention is sought.
Eighty percent will have no symptoms and a little over 19% will have mild symptoms for which
medical attention will not be sought. Those most at risk are the elderly, the very young and those with
compromised immune systems.
Through August 2, 2006 there has been one confirmed human WNV case in Fort Worth and two
additional cases currently being investigated. Below is a table detailing reported Fort Worth WNV
data for the past few years.
F1111
ISSUED BY THE CITY MANAGER
FORT WORTH, TEXAS
INFORMAL REPORT TO CITY COUNCIL MEMBERS NO. 8793
To the Mayor and Members of the City Council
�'ATEiy�O
Page 2 of 2
s_
• •- SUBJECT: UPDATE ON MOSQUITOES
i.
"a"
Year
# of WNV Human
Cases
# of WNV Positive
Mos uito Pools
# of WNV Mosquito
Pools Sampled
2006 Year -To -Date
1
4
47
2005
2
8
153
2004
1
2
115
2003
3
32
150
Spraying Policies
The Fort Worth mosquito monitoring, surveillance and education program stresses source reduction
and personal protection. The distribution of environmentally - friendly larvicide is used in locations
where mosquito larvae are reported. However, spraying pesticide for adult mosquitoes will not occur
unless the surveillance program finds the West Nile Virus present in sufficient quantity to be an
increased threat to human health. Spraying for mosquitoes will temporarily reduce the number of
adult mosquitoes in the immediate vicinity. However, the toxins used in spraying have side effects
that generally outweigh the limited positive impact. First, spraying will not rid the city of mosquitoes.
The chemical must make direct contact with the insect to kill it, making it difficult to destroy
mosquitoes in grass, bushes, trees, backyards or wooded areas not easily accessed with spraying
equipment. Moreover, the chemicals have no residual effects and do nothing to kill mosquito larvae
thriving in stagnant water. Secondly, spraying for mosquitoes may give residents a false sense of
security. The risk of someone being infected with West Nile Virus might then increase if fewer people
decide to follow personal protection and /or source reduction strategies. Thirdly, adding potentially
harmful chemicals to the environment can have unwanted secondary effects. The City has lakes
which have fishing bans or restrictions tied to pesticides. Finally, thousands of Fort Worth residents
living with respiratory problems such as asthma would be in danger of an onset triggered by the
pesticides. After weighing the potential hazard to the general population against the limited benefits
of pesticide application, the current no -spray policy was adopted.
By comparison, the following nearby cities are currently routinely spraying for mosquitoes in their
communities: Dallas, Haltom City, Hurst, North Richland Hills, Richland Hills, Irving and Coppell.
Other cities who have adopted a spraying policy similar to Fort Worth's include: Arlington, Grapevine,
Bedford, Mansfield, Southlake, Colleyville, Denton, and White Settlement. There is no reliable data
suggesting that routine spraying reduces the risk of human exposure to WNV. There have been other
human cases reported in 2006 in Tarrant County from cities where routine spraying does occur.
The staff will continue the current program of mosquito monitoring, disease surveillance, and public
education unless the City Council would like a further review of this strategy. Should you have any
questions, please feel free to contact Dan Reimer, Public Health Director at (817) 871 -7201.
Charles R. Boswell
City Manager
ISSUED BY THE CITY MANAGER
FORT WORTH, TEXAS