Pyrethroids genetics

While the mechanism of resistance to various synthetic pyrethroids in flies has been elucidated in terms of physiology, biochemistry, and genetics, it seems that the resistance mechanism is mostly common to mosquitoes. 

Synthetic pyrethroids, avermectins, juvenile hormone mimics, biological pesticides 1985- Genetically engineered organisms... 

Famham, A.W. (1973). Genetics of resistance of pyrethroid-selected houseflies. Musca domestieti L. Bestir. Sci. 4, 513-520. 

Molecular Genetic Approach to the Study of Target-Site Resistance to Pyrethroids and DDT in Insects... 

A case in point is the unraveling of resistance to methyl parathion in the tobacco budworm, Heliothis virescens, which is a major pest of cotton as well as tobacco. In South Carolina, there is very severe, stable resistance. Although pyrethroid insecticides are very effective and there is no resistance to them in South Carolina at this time, it would be very useful to understand the genetic basis of methyl parathion resistance in case resistance to pyrethroids should arise in the future or spread eastward from Texas where it has been detected. Recent investigations with this pest will be described to illustrate certain mechanisms. 

Clearly the tobacco budworm is a highly adaptable species that possesses an impressive arsenal of natural physiological and biochemical defense mechanisms which can be brought to bear against a broad spectrum of xenobiotic compounds. Furthermore, recent laboratory studies have shown that the genetic traits of the pest also favor the development of significant levels of resistance to pyrethroids (36.371 when it is subjected to selection pressure. 

Controversy exists over the possible role of PB. Large doses of PB can cause bromide psychosis (Rothenberg et al. 1990). The literature is conflicted as to whether a genetic variation of butyrylcholinest-erase can cause a severe reaction to PB (Loewenstein-Lichtenstein et al. 1995 Lotti andMoretto 1995 Senecal and Osterloh 1990). PB also may act synergistically with A/,A/-diethyl-m-toluamide, or DEET, an insect repellent, and permethrin, a pyrethroid insecticide. DEET, PB, and permethrin in various combinations are more neurotoxic to hens than are these agents when administered alone (Abou-Donia et al. 1996). 

Reduced Na" channel sensitivity in pyrethroid-resistant head lice was first suggested by Hemmingway et al. (25). In pyrethroid-resistant head louse colonies from the US and the UK, resistance-specific two concomitant amino acid substitutions were commonly identified as kdr-VkQ mutations at DII S5 of para Na channel (26). Their analysis was based on a partial cDNA sequence of as many as 132 amino acid residues including Dll S3 and S6. Analysis of the whole coding sequence is a prerequisite for the development of molecular diagnosis or the study of the genetic origins of kdr-Vke mutations in head lice. 

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