Evaluating Mosquitoes for Insecticide Resistance
Centers for Disease Control and Prevention
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 About this course

 Disease Vectors

 Strategies for Resistance Management

 Bottle Bioassay
 Larval Bioassay
 Microplate Assay
 Interpretation of Results

 Case Studies

 Links and resources

 Companion Materials

 (Glossary Explained)This term is defined in the glossary.
Larval Bioassay > Running the Assay
  1. Aspirate 15 to 25 mosquito larvae into each beaker. Use a number you can easily count with accuracy as the mosquitoe larvae swim about. With practice you can test many more mosquitoes than in your first few assays. It is best if you collect all of the mosquitoes together in a pipette and introduce them into the bottle at once; this will reduce the amount of additional water that is added to the beaker and minimize possible contaminates/organic material from the larval water. In the case of especially organic rearing water, larvae may first be transferred into clean water prior to sampling.
  1. Examine the beaker to be sure all mosquitoes survived the transfer process. Especially avoid exuviae, which can be easily confused with dead larvae.
    all exuvae and pupae as necessary.
  1. Start a timer and record how many mosquitoes are dead or alive (whichever is easier to count) every 15 minutes until all are dead or 1.5 - 2 hours have elapsed. Tapping the beaker or gently touching the larvae with a stirring rod or other small instrument works well to identify larvae that are still alive. You may want to continue for a total of 2 hours when working with Malathion or Fenthion as these chemicals tend to take longer to kill mosquitoes than pyrethroids, for example.
    * Dead larvae will either sink to the bottom of the beaker or float to the top.
  1. After all larvae are dead or 2 hours have passed, recount the total number of mosquitoes in each beaker. To get an accurate count, empty the beaker through a screen to collect the larvae and count the total.

    Calculate the percent mortality for each 15-minute interval.

    Plot percent mortality (y axis) against time (x axis) using a probability scale for the percent mortality. If probability paper or a suitable statistical computer program is unavailable, a standard graphical plot is a good substitute.


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This page last reviewed July 3, 2001

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