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Guatemala
Focal Nature
of Insecticide Resistance in Guatemala and Its Change with Time.
Purpose
- To demonstrate
use of biochemical assay techniques to investigate multiple resistance.
- To show
how these methods may be used to document the presence of resistance
foci.
- To illustrate
how resistance levels and mechanisms may differ at specific locations
within a control area.
- To illustrate
how enhanced levels of insecticide resistance enzymes may be associated
with areas of more extensive agricultural use of insecticides.
Background
| In
1985-1989, Anopheles albimanus mosquito populations from the
Pacific Coast of Guatemala showed evidence of elevated esterase and
insensitive acetylcholinesterase resistance mechanisms. The insensitive
acetylcholinesterase resistance mechanism was originally selected
by the carbamate insecticide propoxur. This resistance crossed to
the organophosphate insecticide fenitrothion. Carbamate-selected cross-resistance
between carbamates and organophosphates is known from a number of
insect species. Collection of biochemical resistance data from all
over the country revealed some interesting trends regarding resistance. |
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| Figure
1: Map showing the 21 collection sites in Guatemala; at
least 200 mosquitoes were collected from each location
(total collection, 9417). |
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| Data |
| Figure
2. Biochemical (microplate) assay data for the elevated esterase resistance
mechanism in agricultural and non-agricultural regions of Guatemala.
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| Figure
3. Biochemical (microplate) assay data for the insensitive acetylcholinesterase
resistance mechanism showing areas within the same state with dramatically
different resistance levels. |
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4. Biochemical (microplate) assay data for the elevated esterase resistance
mechanism showing areas within the same state with dramatically different
resistance levels. |
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Conclusions
- Both
the high esterase and the insensitive acetylcholinesterase resistance
mechanisms occurred at much higher frequency in areas of intensive agriculture.
- Resistance
was focal, with locations near each other sometimes showing highly variable
resistance levels.
- Biochemical
methods allow detailed comparison of resistance levels over a large
geographic area.
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