Impact of environmental temperatures on resistance to organophosphate insecticides in Aedes aegypti from Trinidad.
OBJECTIVE
To examine the effects of increasing larval rearing temperatures on the resistance status of Trinidadian populations of Aedes aegypti to organophosphate (OP) insecticides.


METHODS
In 2007-2008, bioassays and biochemical assays were conducted on A. aegypti larvae collected in 2006 from eight geographically distinct areas in Trinidad (Trinidad and Tobago). Larval populations were reared at four temperatures (28 ± 2ºC, 32ºC, 34ºC, and 36ºC) prior to bioassays with OP insecticides (fenthion, malathion, and temephos) and biochemical assays for esterase enzymes.


RESULTS
Most larval populations reared at 28 ± 2ºC were susceptible to fenthion (>98% mortality) but resistant to malathion and temephos (< 80% mortality). A positive association was found between resistance to OP insecticides and increased activities of α- and β-esterases in larval populations reared at 28 ± 2ºC. Although larval populations reared at higher temperatures showed variations in resistance to OPs, there was a general increase in susceptibility. However, increases or decreases in activity levels of enzymes did not always correspond with an increase or decrease in the proportion of resistant individuals reared at higher temperatures.


CONCLUSIONS
Although global warming may cause an increase in dengue transmission, based on the current results, the use of insecticides for dengue prevention and control may yet be effective if temperatures increase as projected.
University of the West Indies, St. Augustine, Trinidad and Tobago.
Karen A
KA
Polson
William G
WG
Brogdon
Samuel C
SC
Rawlins
Dave D
DD
Chadee
D000330:Aedes / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D000818:Animals; D003715:Dengue / Q000517:prevention & control; D004950:Esterases / Q000032:analysis / Q000502:physiology; D005284:Fenthion / Q000494:pharmacology*; D057232:Global Warming; D006358:Hot Temperature; D019476:Insect Proteins / Q000032:analysis / Q000502:physiology; D007303:Insect Vectors / Q000187:drug effects* / Q000201:enzymology / Q000254:growth & development; D007305:Insecticide Resistance / Q000502:physiology; D007306:Insecticides / Q000494:pharmacology*; D007814:Larva / Q000187:drug effects / Q000201:enzymology; D008294:Malathion / Q000494:pharmacology*; D013045:Species Specificity; D000002:Temefos / Q000494:pharmacology*; D013696:Temperature; D014300:Trinidad and Tobago
D019476:Insect Proteins; D007306:Insecticides; D005284:Fenthion; D004950:Esterases; D000002:Temefos; D008294:Malathion