Abstract
In Brazil, decades of dengue vector control using organophosphates and pyrethroids have led to dissemination of resistance. Although these insecticides have been employed for decades against Aedes aegypti in the country, knowledge of the impact of temephos resistance on vector viability is limited. We evaluated several fitness parameters in two Brazilian Ae. aegypti populations, both classified as deltamethrin resistant but with distinct resistant ratios (RR) for temephos. The insecticide-susceptible Rockefeller strain was used as an experimental control. The population presenting the higher temephos resistance level, Aparecida de Goiânia, state of Goiás (RR(95) of 19.2), exhibited deficiency in the following four parameters: blood meal acceptance, amount of ingested blood, number of eggs and frequency of inseminated females. Mosquitoes from Boa Vista, state of Roraima, the population with lower temephos resistance level (RR(95) of 7.4), presented impairment in only two parameters, blood meal acceptance and frequency of inseminated females. These results indicate that the overall fitness handicap was proportional to temephos resistance levels. However, it is unlikely that these disabilities can be attributed solely to temephos resistance, since both populations are also resistant to deltamethrin and harbour the kdr allele, which indicates resistance to pyrethroids. The effects of reduced fitness in resistant populations are discussed.
Highlights
Aedes aegypti (L., 1762) is a mosquito with wide geographic distribution, predominantly in tropical and subtropical regions (Jansen & Beebe 2010)
Insecticides still play a major role in the control of this mosquito, especially the organophosphate (OP) temephos which was the sole larvicide recommended for use in drinking water for a long period (Chavasse & Yap 1997)
The present study evaluated a series of life table parameters in two natural Ae. aegypti populations showing distinct levels of resistance to the OP temephos
Summary
Aedes aegypti (L., 1762) is a mosquito with wide geographic distribution, predominantly in tropical and subtropical regions (Jansen & Beebe 2010). The females feed preferentially on humans and are strongly associated with the urban environment (Gubler 2002, Ponlawat & Harrington 2005, Siriyasatien 2010) This species is considered the main dengue vector, both its global distribution and the number of dengue cases having expanded since the 1950s (Mackenzie et al 2004). OP binding to this enzyme impedes its function, resulting in continuous transmission of nerve impulses (Hemingway & Ranson 2000, Ranson et al 2004). Another major resistance mechanism is activation of insect xenobiotic detoxification pathways, known as metabolic resistance. Three groups of enzymes are involved in this process: esterases, glutathion-s-transferases and mixed function oxidases (Hemingway & Ranson 2000)
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