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II. Strategies for
Resistance Management
- Resistance
surveillance should be conducted in association with surveillance for
control efficacy.
Otherwise, the significance of changes in susceptibility cannot be determined.
- The initial
step in resistance surveillance is to establish a baseline for susceptibility
in the mosquito population. The population need not be fully susceptible
to establish this initial benchmark. Subsequent surveillancecan thus
detect changes in the resistance level of the population.
- A correlation
between changes in control efficacy and resistance profile should be
observed before resistance should be considered. Control failure can
result from many factors other than resistance.
- Once
an increase in resistance level is observed that correlates with a decline
in control efficacy, the mechanism of the resistance should be determined.
Some mechanisms affect efficacy of other insecticides or even other
insecticide classes through cross-resistance. Some resistance mechanisms
allow greater choice of alternative strategies than others.
- The
resistance problem should be mapped spatially. Most resistance problems
are highly focalized and may only be of significance to control in only
a restricted area of a program's region of responsibility.
- Choices
at this point include:
- Continuing
with the current compound until an unacceptable level of control
is obtained.
- Switching
to an insecticide that is unaffected by the resistance.
- Relying
more on breeding source reduction.
- Using
focal spraying to reduce selection for resistance in the larger
mosquito population.
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