Update of Mosquitoes, Disease Surveillance, and Susceptibility Testing in Jacksonville

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Update of Mosquitoes, Disease Surveillance, and
Susceptibility Testing in Jacksonville

• Marah Clark, Entomologist
• Jacksonville Mosquito Control

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Arboviral Update

• 66,500 mosquitoes collected from NJLT in 2007
• Seroconversions
• Human Cases 0
• Sentinel 2, 1 EEE and 1 WN at same site
• Horses 0
• Dead Birds 0
• Mosquito pools 0

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Bottle Bioassay in Duval County

• Testing Laboratory Resistance of
• Culex quinquefasciatus to Dibrom

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Objective

• Dibrom has been applied by aircraft for over 30
  years in Duval County
• Culex quinquefasciatus is a vector species
• Evidence suggests that aerial adulticiding is not
  efficacious in controlling Culex in Jacksonville
  (2004 CDC collections after aerial spray
  application)
• Is there any significant resistance by wild Culex
  quinquefasciatus to Dibrom?

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Procedure

• Review bottle bioassay protocol, including
  documentation on preparing Dibrom test solution.
• www.pherec.org/memoranda/procedure.html
• Collect and rear native mosquitoes
• Collected in larval stage from select catch
  basins
• Reared using artesian well water and pulverized
  dog food
• Obtain Dibrom sample from chemical stored on site

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Appropriate Test Solution Concentration

• Diagnostic concentration of 25 ug/mL Naled
• 1mL of test solution used to prepare 4 bottles
  for each test
• 1mL of ethanol used to prepare 2 control bottles
  for each test
• Mosquitoes aspirated and introduced to bottles
• Number of dead mosquitoes recorded every 15
  minutes, until 100 mortality obtained

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Percent Mortality, May 2007
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Percent Mortality, December 2007
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Conclusions

• Culex quinquefasciatus collected in Jacksonville
  displayed uniform susceptibility to Dibrom
  concentrate
• Consistency of how the test is conducted is
  important to maintain statewide standards
• County continues to see uniform susceptibility,
  though further testing is warranted

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Next Question

• If resistance is not a problem, is correct
  concentration being applied for the area?
• What may be other causes that would prevent
  effective control?
• Mosquito behavior minimizes vulnerability
• Weather (humidity, wind, temp., etc.)
• Mission timing (dusk versus dawn)
• Aerosol equipment, technique

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Notes/Future Tests

• Bottle Bioassay results indicate resistance only.
  They will not point toward appropriate field
  application rates.
• Bottle concentration is 2 X LC95 and is designed
  to create a kill situation.
• Plans to run pre- and post- season tests for
  resistance in Culex species to Dibrom
• Run permethrin tests for Culex species pre- and
  post- season
• Attempt to conduct a Dose Response Curve using
  Log Dose Probit (LDP) to infer appropriate
  concentrations for both Cx. nigripalpus and Cx.
  quinquefasciatus