HomeMy WebLinkAboutMemo - Mail Packet - 6/28/2022 - Memorandum From Matt Parker Re: Summary Of West Nile Virus Technical Advisory Committee (Tac) Work / Background Of West Nile Virus
Natural Areas Department
1745 Hoffman Mill Road
PO Box 580
Fort Collins, CO 80522
970.416.2815
970.416.2211 - fax
fcgov.com/naturalareas
MEMORANDUM
DATE: June 22, 2022
TO: Mayor and City Councilmembers
FM: Matt Parker, Sr. Supervisor, Natural Areas
TH: Kelly DiMartino, City Manager
Tyler Marr, Interim Deputy City Manager
Mike Calhoon, Director, Parks
RE: Summary of West Nile Virus Technical Advisory Committee (TAC) Work / Background of
West Nile Virus
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Bottom Line:
West Nile Virus (WNV) is an ongoing threat to the health of community members. The City of Fort
Collins partners with the Larimer County Department of Health and Environment to mitigate the risk of
WNV through increasing public awareness, reducing mosquito larvae production, data collection, and
when necessary, applying adult mosquito control insecticide. The WNV Program was designed through
significant input from the US Centers for Disease Control and Colorado State University. This memo
outlines the City and County efforts, summarizes the off-season review of the WNV Technical Advisory
Committee, and provides a brief season outlook for 2022.
Background on the City s WNV Program
WNV is transmitted by two species of mosquito (as many as 12 species exist in the area), but the virus is
sustained in the region by the bird population. Through the summer weeks the virus presence amplifies
within the avian community presenting increased risk to humans. To mitigate this risk, the City funds a
program to educate community members on personal risk-reducing behaviors, reduce larval sources
and production, and collect weekly data on mosquito abundance and WNV infection rate. With a
program budget of approximately $360,000, over half is used to inspect and treat larval sites. The
remaining program budget is predominately used to develop a series of weekly datasets on species
abundance and infection rates, based upon a network of 53 traps throughout the community. Current
BFO offers intend to reestablish full funding allowing for complete season data coverage and aggressive
public outreach.
As this dataset represents the location and severity of WNV presence, it also represents a weekly
depiction of human risk of contracting WNV. This data is used to calculate an index value, or Vector
Index. Previous Councils have adopted a specific Vector Index threshold beyond which emergency funds
could be used, in conjunction with a recommendation from the LCDHE, for the application of adult
mosquito insecticide. To date, insecticide applications typically occur every other year, however last
year was a particularly active season as the data exceeded the Vector Index threshold three times,
2
resulting in three treatment applications. Despite the increased application, public concern as measured
by phone calls, emails, etc. was very limited. This may be attributed to the identification and treatment
of smaller zones.
Although mosquito production picks up with the rising river and warming temperatures, the species of
mosquitos transmitting WNV do not typically increase in abundance until later in the summer. In other
words, the mosquitoes currently pestering residents do not pose a WNV risk. The City s WNV Program is
not a nuisance mosquito program, rather a WNV mitigation effort. As the active WNV season begins in
late June, staff will provide weekly emails characterizing the current conditions and data.
The West Nile Virus Program has completed the annual off-season review process and is currently
beginning its operational season. If an adult mosquito application is scheduled, application specific
outreach will proceed as in past years.
TAC Off-Season Review Summary:
The annual review of the 2021 season focused on 1) early thoughts on how to expand trapping efforts to
reflect expansion of city footprint, particularly in the NE area of the city, and 2) sharing the breadth of
research conducted via the CSU OneHealth Institute aimed at minimizing the human and environmental
risk associated with WNV and its management. These studies represent novel potential solutions to
WNV-related issues, including treating WNV through ivermectin-treated bird seed, injecting DNA
barcode in larval feed to determine date and location of mosquito larvae production, and using past
WNV vector index data and weather data to develop improved models. As these studies gain funding
and continue to develop, additional information will be shared as appropriate.
Seasonal Outlook for WNV June through September:
Vector Disease Control International (WNV Program contractor) has hired staff and initiated their early
season process of training staff, identifying mosquito breeding areas, and treating larval populations as
necessary. Trapping and testing of mosquito populations began the week of June 6 and will continue
weekly through the week of September 12, 2022.
The National Oceanic and Atmospheric Administration (NOAA) climate prediction models indicate a
likelihood of hotter and drier than normal conditions through August. Hot and dry seasons can lead to
high presence of WNV as irrigation needs increase and birds and mosquitoes centralize on limited water
sources. Importantly, the long-term prediction models show warmer temperatures through September
and October. It is the nightly low temperatures that slow mosquito metabolism and induce the seasonal
decline in activity known as diapause. Higher overnight low temperatures are known to delay this
diapause, thereby potentially extending the mosquito season later into the calendar year.
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