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Background: Malaria is endemic in most parts of Afghanistan and insecticide-based vector control measures are central in controlling the disease. Insecticide resistance in the main malaria vector Anopheles stephensi from Afghanistan is increasing and attempts should be made to determine the underlying resistance mechanisms for its adequate management. Methods: The contents of cytochrome P450s, esterases, glutathione S-transferases (GSTs) and acetylcholine esterase (AChE) activities were measured in the Kunar and Nangarhar populations of An. stephensi from Afghanistan and the results were compared with those of the susceptible Beech strain using the World Health Organization approved biochemical assay methods for adult mosquitoes. Results: The cytochrome P450s enzyme ratios were 2.23- and 2.54-fold in the Kunar and Nangarhar populations compared with the susceptible Beech strain. The enzyme ratios for esterases with alpha-naphthyl acetate were 1.45 and 2.11 and with beta-naphthyl acetate were 1.62 and 1.85 in the Kunar and Nangarhar populations respectively compared with the susceptible Beech strain. Esterase ratios with para-nitrophenyl acetate (pNPA) were 1.61 and 1.75 in the Kunar and Nangarhar populations compared with the susceptible Beech strain. The GSTs enzyme ratios were 1.33 and 1.8 in the Kunar and Nangarhar populations compared with the susceptible Beech strain. The inhibition of AChE was 70.9 in the susceptible Beech strain, and 56.7 and 51.5 in the Kunar and Nangarhar populations. The differences between all values of the enzymes activities/contents and AChE inhibition rates in the Kunar and Nangarhar populations were statistically significant when compared with those of the susceptible Beech strain. Conclusions: Based on the results, the reported resistance to pyrethroid and organophosphate insecticides, and tolerance to bendiocarb in the Kunar and Nangarhar populations of An. stephensi from Afghanistan are likely to be caused by a range of metabolic mechanisms, including esterases, P450s and GSTs combined with target site insensitivity in AChE. [ABSTRACT FROM AUTHOR]

Background: Culex pipiens play an important role in transmission of infectious diseases. Vector control by chemical pesticides, leads inevitably to resistance development. Understanding the underlying resistance mechanisms can help improve the control programmes and insecticide resistance management., Methods: The total contents of cytochrome p450s and the activities of glutathione S-transferases, alpha- and beta-esterases and inhibition rates of acetylcholine esterase (by propoxur) were measured in the field population of Cx. pipiens collected from Sari County, North of Iran, in 2016 and the results were compared with those of the laboratory susceptible strain according to the biochemical assay methods of WHO for adult mosquitoes. Independent sample t -test was used to compare the mean values of enzyme activities/contents between filed and laboratory susceptible populations., Results: The enzyme ratio of cytochrome p450s, alpha- and beta-esterases in the field population was 2.07, 3.72 and 1.36 respectively when compared with the results of the laboratory population. Although not statistically significant, the mean GSTs activities in the field population was marginally less than the laboratory population (ER=0.92). Acetylcholinesterase was insensitive to propoxur in 62.82% of the individuals of the tested field population. There was a significant difference (P< 0.05) between all values of the activities/contents of the enzyme in the field population except for GSTs compared with the laboratory susceptible strain. The highest enzyme activity was related to alpha esterase., Conclusion: The present study showed a range of metabolic mechanisms, comprising p450s and esterases combined with target site insensitivity of AChE, contributing to organophosphate, carbamate and pyrethroid resistance in the field population of Cx. pipiens ., (Copyright© Iranian Society of Medical Entomology & Tehran University of Medical Sciences.)

Mosquitoes are important vectors of human and animal diseases. This study updates current knowledge on fauna, dominance, and distribution of mosquitoes in Mazandaran Province, Northern Iran, to inform disease control effort. Larval collections, using standard dippers or droppers, and adult collections, using total catches, shelter pits, CDC light traps, and human landing catches, were performed monthly in 30 villages across 16 counties, from May to December 2014. Ovitraps, baited with hay infusion as oviposition attractants or stimulants for Aedes (Stegomyia) mosquitoes, were installed in each village and inspected weekly for eggs. Lactophenol and Berlese media were used for preserving and mounting specimens. Overall, 36,024 mosquito specimens (19,840 larvae and 16,184 adults) belonging to 4 genera and 20 species were morphologically identified. The dominance and distribution indices showed that Culex pipiens s.s. was the eudominant species with a constant distribution of larvae (D = 69.07%, C = 100%) and adults (D = 31.86%, C = 100%), followed by Cx tritaeniorhynchus (D = 38.14%, C = 100%) and Anopheles maculipennis s.l. (D = 11.05%, C = 100%) as adults. Aedes vexans was the dominant (7.85%) species, but it had a sporadic (20%) distribution. Culex torrentium and Culiseta morsitans were added as the new species to the checklist of mosquitoes in Mazandaran Province. Due to the potential role, Cx. pipiens s.s. as a vector of various pathogens, further ecological studies are recommended.