Thiamethoxam Resistance in the House Fly, Musca domestica L.: Current Status, Resistance Selection, Cross-Resistance Potential and Possible Biochemical Mechanisms.

Hafiz Azhar Ali Khan,Waseem Akram,Javaid Iqbal,Unsar Naeem-Ullah,Marcelo Gustavo Lorenzo

doi:10.1371/journal.pone.0125850

Abstract

The house fly, Musca domestica L., is an important ectoparasite with the ability to develop resistance to insecticides used for their control. Thiamethoxam, a neonicotinoid, is a relatively new insecticide and effectively used against house flies with a few reports of resistance around the globe. To understand the status of resistance to thiamethoxam, eight adult house fly strains were evaluated under laboratory conditions. In addition, to assess the risks of resistance development, cross-resistance potential and possible biochemical mechanisms, a field strain of house flies was selected with thiamethoxam in the laboratory. The results revealed that the field strains showed varying level of resistance to thiamethoxam with resistance ratios (RR) at LC50 ranged from 7.66-20.13 folds. Continuous selection of the field strain (Thia-SEL) for five generations increased the RR from initial 7.66 fold to 33.59 fold. However, resistance declined significantly when the Thia-SEL strain reared for the next five generations without exposure to thiamethoxam. Compared to the laboratory susceptible reference strain (Lab-susceptible), the Thia-SEL strain showed cross-resistance to imidacloprid. Synergism tests revealed that S,S,S-tributylphosphorotrithioate (DEF) and piperonyl butoxide (PBO) produced synergism of thiamethoxam effects in the Thia-SEL strain (2.94 and 5.00 fold, respectively). In addition, biochemical analyses revealed that the activities of carboxylesterase (CarE) and mixed function oxidase (MFO) in the Thia-SEL strain were significantly higher than the Lab-susceptible strain. It seems that metabolic detoxification by CarE and MFO was a major mechanism for thiamethoxam resistance in the Thia-SEL strain of house flies. The results could be helpful in the future to develop an improved control strategy against house flies.

Highlights

Sanitation and hygiene are the basic measures in the management of house flies, Musca domestica L., in and around livestock facilities
In contrast to insecticides which are applied as residual sprays for premises treatment, the chances of resistance development are low to those applied as baits [3]
The results of insecticidal bioassays revealed varying levels of resistance to thiamethoxam in different house fly strains when compared with the Lab-susceptible reference strain (Table 1)

Summary

Introduction

Sanitation and hygiene are the basic measures in the management of house flies, Musca domestica L., in and around livestock facilities. These measures could be applied by managing or eliminating the animal feces which play a significant role in the breeding of house flies. Insecticides in the neonicotinoid class (e.g., imidacloprid, thiamethoxam) are synthetic derivatives of nicotine, an alkaloid compound present in the leaves of many plants. These insecticides exert their toxic effects via interactions with nicotinic acetylcholine receptors of the insect nervous system and are used extensively in the management of insect pests of agricultural and public health importance [5]. Thiamethoxam is the first commercial insecticide from the subclass thianicotinyl of neonicotinoids, which is usually used as a seed, foliar and soil treatment in agricultural operations, and as a bait against house flies [4]

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