Pyrethroids resistance mechanism

Gunning. R.V, Easton. C.S., Balle, M.E. and Ferris, LG. (1991). Pyrethroid resistance mechanisms in Australian Helicovcrpti armtgera. Pestic. Sci. 33,473-490. 

CYP6D1 of the housefly (Musca domestica) has been found to hydroxylate cyper-methrin and thereby provide a resistance mechanism to this compound and other pyrethroids in this species (Scott et al. 1998 see also Chapter 12). Also, this insect P450 can metabolize plant toxins such as the linear furanocoumarins xanthotoxin and bergapten (Ma et al. 1994). This metabolic capability has been found in the lepi-dopteran Papilio polyxenes (black swallowtail), a species that feeds almost exclusively on plants containing furanocoumarins. 

Resistance mechanisms associated with changes in toxicokinetics are predominately cases of enhanced metabolic detoxication. With readily biodegradable insecticides such as pyrethroids and carbamates, enhanced detoxication by P450-based monooxygenase is a common resistance mechanism (see Table 4.3). 

In some resistant strains, both types of resistance mechanism have been shown to operate against the same insecticide. Thus, the PEG87 strain of the tobacco bud worm (Heliothis virescens) is resistant to pyrethroids on account of both a highly active form of cytochrome P450 and an insensitive form of the sodium channel (Table 4.3 and McCaffery 1998). 

The other major mechanism of pyrethroid resistance found in some field strains of Heliothis virescens was enhanced detoxication due to a high rate of oxidative detoxication, mediated by a form of cytochrome P450 (McCaffery 1998). Some strains, such as PEG 87, which was subjected to a high level of field and laboratory selection, possessed both mechanisms. Other example of pyrethroid resistance due to enhanced detoxication may be found in the literature on pesticides. 

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. 

Yasutomi K, Takahashi M (1989) Insecticidal resistance of Culex tritaeniorhynchus in Chinen, Okinawa Prefecture, with special reference to the mechanism of pyrethroid-resistance. Jpn JSanitZool 40 315-321... 

Kasai S, Komagata O, Itokawa K, Kobayashi M, Tomita T (2010) Mechanisms of pyrethroid resistance in adult Aedes aegypti. Med Entomol Zool 61(Suppl) 46... 

Several human carboxylesterases have been cloned, sequenced and expressed. These human carboxylesterases are important in the hydrolysis of certain pesticides such as the pyrethroids. In certain strains of insects that are resistant to malathion, the resistance mechanism is associated with a higher level of a carboxylesterase, which detoxifies malathion (Figure 10.10D). 

Sequestration in insects This is another resistance mechanism in which GSTs were found to be involved in pyrethroid resistance. Kostaropoulos et al. (2001) have reported that GST confers protection against deltamethrin by binding to the insecticide in the yellow mealworm ijenebrio monitor). 

Pyrethroids are widely used to control many agriculturally and medically important insect pests. Due to intensive use of pyrethroids in pest control, many pest populations have developed resistance to these compounds. One major mechanism of pyrethroid resistance, conferred by the knock down resistance gene (Mr), is reduced target site (sodium channel) sensitivity to DDT and pyrethroids. Studies on the molecular basis of Mr and Mr-type resistance in various insects are enhancing our understanding of the structure and function of insect sodium channels and the molecular interaction between insect sodium channels and pyrethroids. In this chapter, I will review recent advances in... 

The wide spectrum of pyrethroid resistance in these populations, which involves permethrin, fenvalerate, flucythrinate, cypermethrin, deltamethrin, and cyhalothrin, the relative lack of synergism by p. b. (52) or DEF, and the presence of DDT as well as methoxychlor resistance (52), suggest that this resistance is due to the site insensitivity mechanism kdr. Interestingly, some evidence of behavioral resistance was also detected. It was observed that pyrethroid-resistant flies tended to... 

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