The P450-Monooxygenase Activity and CYP6D1 Expression in the Chlorfenapyr-Resistant Strain of Musca domestica L.

The house fly Musca domestica L. is one of the most common insects of veterinary and medical importance worldwide; its ability to develop resistance to a large number of insecticides is well known. Many studies support the involvement of cytochrome P-450-dependent monooxygenases (P450) in the development of resistance to pyrethroids, neonicotinoids, carbamates, and organophosphates among insects. In this paper, the monooxygenase activity and expression level of CYP6D1 were studied for the first time in a chlorfenapyr-resistant strain of house fly. Our studies demonstrated that P450 activity in adults of the susceptible strain (Lab TY) and chlorfenapyr-resistant strain (ChlA) was 1.56-4.05-fold higher than that in larvae. In females of the Lab TY and ChlA strains, this activity was 1.53- and 1.57-fold higher, respectively (p < 0.05), than that in males, and in contrast, the expression level of CYP6D1 was 21- and 8-fold lower, respectively. The monooxygenase activity did not vary between larvae of the susceptible strain Lab TY and the chlorfenapyr-resistant strain ChlA. Activity in females and males of the ChlA strain exceeded that in the Lab TY strain specimens by 1.54 (p = 0.08) and 1.83 (p < 0.05) times, respectively, with the same level of CYP6D1 expression. PCR-RFLP analysis revealed a previously undescribed mutation in the promoter region of the CYP6D1 gene in adults of the Lab TY and ChlA strains, and it did not affect the gene expression level. The obtained results show that the development of resistance to chlorfenapyr in M. domestica is accompanied by an increase in P450-monooxygenase activity without changes in CYP6D1 expression.

Molecular analysis of acetylcholinesterase gene in field-collected populations of Musca domestica (Diptera: Muscidae) in Northwestern Iran.

Nowadays, pyrethroid (Py) insecticides are commonly used against household insect pests and housefly. The combination of Py and organophosphates (OP) are also utilized to combat these insects. The resistance status of Iranian housefly populations to them and carbamate (CB) insecticides is uncertain. This study investigates the presence of acetylcholinesterase (AChE) mutations related to the resistance of Musca domestica to OP and/or CB insecticides in Northwestern Iran. Nucleotides 1041-1776, based on their positions in the ACE gene of aabys strain, were amplified and sequenced in houseflies collected from West Azerbaijan, Gilan, and Ardebil Provinces, Iran. Among 12 single-nucleotide polymorphisms detected, 3 mismatches were found at nucleotides 1174 (T/A, G), 1473 (G/T, C), and 1668 (T/A), leading to amino acid substitutions in V260L, G342A/V, and F407Y positions with various combinations. Genotyping results showed that 85% of specimens had at least one of these substitutions. In addition, the Iranian housefly population was composed of 5 insensitive and sensitive alleles. For the first time, the current study reports the presence of V260L, G342A, G342V, and F407Y substitutions in M. domestica specimens collected from Northwestern Iran. The selection of multiple alleles in field populations might be due to the application of various pesticides/insecticides during extended periods in the region. These molecular levels signify the presence of control problems in the area and the need for developing effective control strategies for such populations.

Impact of Insecticides at Sublethal Concentrations on the Enzyme Activities in Adult Musca domestica L.

Nowadays, the use of pesticides is, as before, the most common way to control arthropod plant pests and the ectoparasites of animals. The sublethal effects of pesticides on insects can appear at different levels, from genetics to populations, and the study of these effects is important for a better understanding of the environmental and evolutionary patterns of pesticidal resistance. The current study aimed to assess the sublethal effects of chlorfenapyr and fipronil on the activities of detoxifying enzymes (carboxylesterase-CarE, acetylcholinesterase-AChE, glutathione-S-transferase-GST, and cytochrome P450 monooxygenase-P450) in adults Musca domestica L. The insects were exposure to insecticides by a no-choice feeding test and the enzyme activities and the AChE kinetic parameters were examined in female and male specimens at 24 h after their exposure. According to Tukey's test, the CarE activity was statistically significantly decreased by 29.63% in the females of M. domestica after an exposure to chlorfenapyr at a concentration of 0.015% when compared to the controls (p ≤ 0.05). An exposure to the sublethal concentration of fipronil (0.001%) was followed by a slightly decrease in the specific activity (33.20%, p ≤ 0.05) and the main kinetic parameters (Vmax, Km) of AChE in females in comparison with the control values. The GST and P450 activities had not significantly changed in M. domestica males and females 24 h after their exposure to chlorfenapyr and fipronil at sublethal concentrations. The results suggest that the males and females of M. domestica displayed biochemically different responses to fipronil, that is a neurotoxin, and chlorfenapyr, that is a decoupler of oxidative phosphorylation. Further research needs to be addressed to the molecular mechanisms underlying the peculiarities of the insect enzyme responses to different insecticides.

Endectocides as a complementary intervention in the malaria control program: a systematic review.

BACKGROUND: Malaria is the most common vector-borne disease transmitted to humans by Anopheles mosquitoes. Endectocides and especially ivermectin will be available as a vector control tool soon. The current review could be valuable for trial design and clinical studies to control malaria transmission. METHODS: PubMed/MEDLINE, Scopus, Web of Science, and Science Direct were searched for original English published papers on ("Malaria chemical control" OR "Malaria elimination" OR "Anopheles vector control" OR "Malaria zooprophylaxis") AND ("Systemic insecticides" OR "Endectocides" OR "Ivermectin"). The last search was from 19 June 2019 to 31 December 2019. It was updated on 17 November 2020. Two reviewers (SG and FGK) independently reviewed abstracts and full-text articles. Data were extracted by one person and checked by another. As meta-analyses were not possible, a qualitative summary of results was performed. RESULTS: Thirty-six published papers have used systemic insecticides/endectocides for mosquito control. Most of the studies (56.75%) were done on Anopheles gambiae complex species on doses from 150 µg/kg to 400 µg/kg in several studies. Target hosts for employing systemic insecticides/drugs were animals (44.2%, including rabbit, cattle, pig, and livestock) and humans (32.35%). CONCLUSIONS: Laboratory and field studies have highlighted the potential of endectocides in malaria control. Ivermectin and other endectocides could soon serve as novel malaria transmission control tools by reducing the longevity of Anopheles mosquitoes that feed on treated hosts, potentially decreasing Plasmodium parasite transmission when used as mass drug administration (MDA).

Efficacy of acetamiprid and fipronil fly baits against the housefly (Musca domestica L.) under laboratory conditions.

BACKGROUND: The housefly Musca domestica L. (Diptera: Muscidae) is permanent pests in livestock facilities. High fly density in livestock and poultry farms can increase the risks of economic loss and public health. Treatment with toxic baits is one of the methods for housefly control. However, development of resistance to insecticides makes it difficult to manage of flies. Anti-resistance strategies include the use of multiple pesticides with different modes of action. AIM: This study was conducted to estimate the efficacy of neonicotinoid acetamiprid and phenylpyrazole fipronil, applied alone or in the mixture, against adults of M. domestica and to evaluate the efficacy of fly bait formulations containing acetamiprid and fipronil under laboratory conditions. MATERIALS AND METHODS: The adult flies, M. domestica of laboratory strain, were used in laboratory bioassays. The efficacy of acetamiprid and fipronil as technical substances, when applied alone and in the mixture, against adult flies was tested by no-choice feeding bioassays. The insecticidal efficacy of bait formulations (wet powder) with acetamiprid or fipronil or their mixture was tested against flies by choice feeding bioassays. The probit analysis was used to calculate lethal concentrations of insecticides, and the χ2 test was used to analyze the interaction between fipronil and acetamiprid in the mixture. RESULTS: Fipronil was more toxic to adults of M. domestica than acetamiprid in laboratory tests. Lethal concentrations for 50% mortality (95% confidence interval) of flies were 0.0159% (0.0124-0.0205) of acetamiprid and 0.000119% (0.000039-0.0002640) of fipronil. The mixture containing fipronil at concentration 0.005% and acetamiprid at concentration 0.05% had the additive effect on fly mortality. CONCLUSION: The results of laboratory feeding bioassays indicate that the mixture of fipronil and acetamiprid might have a potential to use in toxic bait formulations against houseflies.