2001 SURVEY
FOR MOSQUITOES IN EASTERN SOUTH DAKOTA
In 2001, the
South Dakota Department of Health initiated a program to monitor mosquitoes
in South Dakota for the presence of the West Nile Virus. During the
first year (2001), a pilot survey was conducted at four sites (Brandon,
Brookings, Castlewood, and Watertown) in eastern South Dakota under the
direction of Drs. M.B. Hildreth (Department of Biology/Microbiology and
M.A. Catangui (Department of Plant Science) at South Dakota State University.
Two SDSU undergraduate students, Jeff Nolz and Kayla Zirpel (Department
of Biology/Microbiology), performed the collections and identified the
mosquitoes to the the species level. Dr. Paul Johnson (SDSU, Department
of Plant Science) assisted in some of the mosquito identifications and
provided comparative species from the South Dakota Entomological Museum.
Several South Dakota residents (Ms Peg Holmquest, Ms Donna Juffer, Mr.
& Mrs. Terry Drew) assisted in the collection of mosquitoes.
This pilot survey focused on the eastern part of the state because if the
West Nile Virus is ever found in South Dakota, it will likely appear in
the eastern side first. To collect mosquitoes, CDC miniture light
traps (J.W. Hock Inc., Gainesville, FL) were used without carbon-dioxide
baiting, beginning on July 3 and ending on August 2, 2001. The light
traps were equipped with an internal programmable photo-switch such that
the light and fan is turned on at dusk and and then off at dawn.
The traps were checked each morning and the mosquitoes were immediately
frozen in conventional freezers (approximately -20C). During
the same week, the mosquitoes were thawed briefly, identified and then
re-frozen at -70C. Frozen mosquiotes were sent to the S.D.
Department of Health on dry ice to be tested for the presence of the virus.
During this pilot study, a total of 2,045 mosquitoes were collected.
Only the results from Brookings and Watertown are shown below. Results
from this small collection showed that the most prominent species of mosquitoes
in eastern South Dakota were
Aedes vexans (88.2%), Culex tarsalis,
(5.2%),
and
Aedes dorsalis (4.9%). Less than 1% of the total mosquitoes
were Culex salinarius and Culiseta inornata.
West Nile Virus was not identified in any of the mosquitoes tested.
Collection Sites
Satellite
image provided by the USGS EROS Data Center.
Results
from each collection site:
Brookings
Watertown
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