2024-034 West Nile Virus 2024 Season Update September 20, 2024 Report No. 2024-034
INFORMAL STAFF REPORT
TO MAYOR AND CITY COUNCIL
SUBJECT:
Update on the City of Denton's 2024 Mosquito Season Risk Level and Mosquito Surveillance and
Response Plan process.
EXECUTIVE SUMMARY:
In May 2024, the City deployed traps at the beginning of mosquito season. The Mosquito
Surveillance and Response Plan (MSRP) outlines the City's process which includes five risk
levels. The city began the 2024 mosquito season at Risk Level 2 due to occurrence of West Nile
Virus (WNV) in mosquito pools in the previous season. On June 28, the City elevated to Risk
Level 3 with mosquito pools testing positive for West Nile Virus. On September 20, the City was
notified of a confirmed WNV human case within the City of Denton and elevated to Risk Level 4.
At Risk Level 4, the City will initiate necessary actions for ground-level spraying. To authorize
ground-level spraying, the City Council is required to take action on a Resolution. However, it is
at MSRP Risk Level 5 that ground-level spraying be part of the implemented vector control
actions.
BACKGROUND:
The City of Denton prepared the first Mosquito Surveillance and Response Plan (MSRP) in 2002
and has reviewed it annually. The last revisions were made in 2021 following the 2020 Mosquito
Season, which included ground-level spraying. Denton works with the University of North Texas
(UNT)to deploy, collect, and test mosquitoes across the city. Collected mosquitoes are sent to the
Texas Department of State Health Services (DSHS) for actual analysis of the West Nile Virus.
Additionally, the City works closely with Denton County to share mosquito trap locations as well
as WNV test results. An interactive map on the Denton County website integrates mosquito
trapping results from participating communities. Denton County is the Public Health Authority
and is the entity to be notified of any positive WNV human cases.
The City of Denton offers a limited supply of Bti briquettes (kill mosquito larva)to residents (two
per resident while supplies last) to assist in controlling the mosquito populations. Proof of
residency is required:
Customer Service, 601 E. Hickory St., Ste F, Monday-Friday 8 a.m. —5 p.m.
City of Denton Composting, 1100 S. Mayhill Rd., Tuesday-Saturday, 7 a.m. —3 p.m.
DISCUSSION:
The City of Denton began the 2024 Mosquito Season at Risk Level 2 — Enhanced Response
because of positive West Nile Virus (WNV) tests detected in 2023 mosquito pools within city
limits. On June 28, the City elevated to Risk Level 3 — Public Health Concern due to mosquito
September 20, 2024 Report No. 2024-034
pools being reported as positive for WNV by the Texas DSHS. On September 20,the City elevated
to Risk Level 4 - Public Health Warning due to notification from Denton County Public Health
of a confirmed WNV human case within the City of Denton.
At Risk Level 4, the probability of human outbreak is moderate to high and WNV is reported in
multiple mosquito pools with a single human case confirmed through laboratory testing. At Risk
Level 4, the City would continue enhanced efforts to promote source reduction and personal
protection.Possible breeding areas on City controlled property are treated regularly with larvicide.
In accordance with the City's Integrated Pest Management (IPM), we would proceed to use
Bacillus thuringiensis israelensis (Bti) and Spinosad products (bacterial insecticide). The City
would finalize all actions for implementing ground level spraying activities using ULV
applications of pyrethroids.
In Risk Level 5,laboratory testing would confirm human outbreak with multiple human cases. The
City would increase outreach efforts across the community and intensify larviciding efforts using
Bti in targeted areas. Larvidices containing Insect Growth Regulators (IGR) or pesticides such as
Spinosad may be applied at this time. Additionally, standing water in our City parks would be the
target of intense treatments. If the threat to human health is considered imminent, the City would
consider targeted adulticide applications using ground-based Ultra-Low Volume (ULV)
equipment. The decision to spray would be made by a Council Resolution prior to the first
application, for each mosquito season. ULV application should be implemented in the vicinity
(approximately 1 mile) of areas where positive human cases were detected.
The City of Denton last used ULV spraying in 2020,and that effort utilized Merus 3.09,an organic
pyrethrin product that does not contain petroleum distillates. Natural pyrethrins are a botanical
insecticide produced primarily by flowers from the chrysanthemum family.Merus 3.08 is Organic
Review Materials Institute (OMRI) and meets National Organic Program (NOP) standards for
adult mosquito control. The use of Merus 3.0®, or any organic-certified pesticides that may
become available, would continue to be used as the preferred option for ground-level spraying
operations in accordance with integrated pest management.
Spraying, if performed, uses city-owned spray equipment operated by a third-party licensed
contractor. Advanced community alerts of the spraying operation would include a news release,
social media messaging, website posts, text campaigns,phone calls, and road signs.
NEXT STEPS:
City Council should reach out to Michael Gange with any questions by Tuesday, Oct. 1. Staff are
preparing to bring a Resolution forward for Council consideration at the Tuesday, Oct. 15, 2024,
Council Meeting.
September 20, 2024 Report No. 2024-034
CONCLUSION:
The City of Denton has elevated to Risk Level 4 based on the positive WNV mosquito pools and
the confirmed human WNV case. This Report is an effort to clarify how the City elevated risk
levels and the necessary action of Council should ULV spraying be required within the City of
Denton. The current Risk Level, link to the mosquito trapping map, and other mosquito awareness
information may be round on the City's website.
STAFF CONTACT:
Michael A. Gange
Director of Environmental Services & Sustainability
Michael.gangekcityofdenton.com
(940) 349-7165
REOUESTOR: Staff Initiated.
STAFF TIME TO COMPLETE REPORT: 2 hours
PARTICIPATING DEPARTMENTS: Environmental Services&Sustainability,Marketing and
Communication, and City Manager's Office