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Dosage-dependent effects of permethrin-treated nets on the behaviour of Anopheles gambiae and the selection of pyrethroid resistance.

Corbel V, Chandre F, Brengues C, Akogbeto M, Lardeux F, Hougard JM, Guillet P.

LIN-IRD, 911 Av, Agropolis, 34394 Montpellier, France. corbel mpl.ird.fr

BACKGROUND: The evolution and spread of pyrethroid resistance in Anopheles gambiae s.s, the major malaria vector in sub-Saharan Africa, is of great concern owing to the importance of pyrethroid-treated nets in the WHO global strategy for malaria control. The impact of kdr (the main pyrethroid-resistance mechanism) on the behaviour of An. gambiae is not well understood. The objective of this study was to determine whether high or low doses of permethrin differ in their resistance-selection effects. METHODS: The effect of permethrin treatment was assessed under laboratory conditions using the tunnel test technique against susceptible, heterozygous and homozygous genotypes. Experimental huts trials were then carried out in Benin to assess the level of personal protection conferred by nets treated with a variety of permethrin concentrations and their impact on the selection for kdr allele. RESULTS: Tunnel tests showed that nets treated with permethrin at 250 and 500 mg/m2 induced higher mortality and blood feeding reduction among susceptible and heterozygous (RS) females as compared to the lower concentration (100 mg/m2). The experimental hut trials showed that the best personal protection was achieved with the highest permethrin concentration (1,000 mg/m2). Mosquito genotyping revealed a non-linear relationship in the survival of kdr susceptible and resistant genotypes with permethrin dosage. Higher dosages (> or =250 mg/m2) killed more efficiently the RS genotypes than did lower dosages (50 and 100 mg/m2). CONCLUSION: This study showed that nets treated with high permethrin concentrations provided better blood feeding prevention against pyrethroid-resistant An. gambiae than did lower concentrations. Permethrin-treated nets seem unlikely to select for pyrethroid resistance in areas where the kdr mutation is rare and present mainly in heterozygous form.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15242513&dopt=Abstract permethrin Elimite



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Hapten and antibody production for a sensitive immunoassay determining a human urinary metabolite of the pyrethroid insecticide permethrin.

Ahn KC, Watanabe T, Gee SJ, Hammock BD.

Department of Entomology and UCD Cancer Research Center, University of California, Davis, California 95616, USA.

Permethrin is the most popular synthetic pyrethroid insecticide in agriculture and public health. For the development of the enzyme-linked immunosorbent assay (ELISA) to evaluate human exposure to permethrin, the glycine conjugate (DCCA-glycine) of a major metabolite, cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carboxylic acid (DCCA), of permethrin was established as the target analyte. Four different types of the cis- and trans-isomers of immunizing haptens were synthesized as follows: N-(cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carbonyl)glycine (hapten 3), N-(cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carbonyl)-4-amino-l-phenylalanine (hapten 5), N-(N-(cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carbonyl)glycine)amino-6-(2,4-dinitrophenyl)aminohexanoic acid (hapten 9), and N-(cis/trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-1-carbonyl)glycine-4-oxobutanoic acid (hapten 24). Sixteen polyclonal antibodies produced against each cis- or trans-hapten-thyroglobulin conjugate as immunogens were screened against numerous hapten-bovine serum albumin conjugates as coating antigens. Six ELISAs with both a heterologous hapten structure and a heterologous hapten configuration (cis/trans or trans/cis) between antibody and coating antigen showed a high sensitivity for the target analyte. The IC50 was 1.3, 2.1, and 2.2 microg/L for the trans-target analyte and 0.4, 2.3, and 2.8 microg/L for the cis-target analyte. The immunizing haptens, except for hapten 5, provided the target specific antibodies. Molecular modeling of the haptens supported the selection of reasonable immunizing haptens that best mimicked the target analyte. Hapten 5 was suitable as a coating antigen rather than as an immunogen since it had a different geometry. Very low cross-reactivities were measured to permethrin, its free metabolite (DCCA), PBA-glycine conjugate, and glycine. The ELISA will be optimized for the detection of total cis/trans-DCCA-glycine in human urine samples. Copyright 2004 American Chemical Society

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15264887&dopt=Abstract permethrin Elimite



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Lymphocyte DNA damage in rats exposed to pyrethroids: effect of supplementation with Vitamins E and C.

Gabbianelli R, Nasuti C, Falcioni G, Cantalamessa F.

Dipartimento di Biologia MCA Biology, Universita di Camerino, Via Camerini 2, MC 62032, Italy. rosita.gabbianelli unicam.it

Pesticides have been considered potential chemical mutagens. In fact, some studies show that various agrochemical ingredients possess mutagenic properties inducing mutations, chromosomal alterations or DNA damage. Experimental evidence shows a marked correlation between mutagenicity and carcinogenicity and indicates that short-term mutagenicity tests are useful for predicting carcinogenicity. The present study on rat exposed to two pyrethroids, cypermethrin and permethrin, showed different lymphocyte DNA damage depending on the type of pyrethroid, the dose, and the period of treatment. Data obtained from comet assay showed that oral treatment with 150 mg/kg body weight/day of permethrin (corresponding to 1/10 of LD50) for 60 days, induced a significant increase in all comet parameters. No lymphocyte DNA damage was measured after treatment with 25 mg/kg body weight/day of cypermethrin (corresponding to 1/10 of LD50) for the same period. A higher dose of permethrin (300 mg/kg body weight/day), for a shorter period (22 days), did not induce lymphocyte DNA damage, while supplementation with 200 mg/kg of Vitamins E and C protected erythrocytes against plasma membrane lipids peroxidation. Moreover, treatment with Vitamins E and C maintained the activity of glutathione peroxidase, which was reduced in the presence of permethrin, and reduced the osmotic fragility, which had increased following permethrin treatment.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15363578&dopt=Abstract permethrin Elimite



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Determination of pyrethroid residues in agricultural products by an enzyme-linked immunosorbent assay.

Park EK, Kim JH, Gee SJ, Watanabe T, Ahn KC, Hammock BD.

Department of Entomology and UCD Cancer Research Center, University of California, Davis, California 95616, USA.

To determine cypermethrin and permethrin in agricultural products, a competitive enzyme-linked immunosorbent assay (ELISA) method was employed. The matrix interferences were minimized by direct dilution of the extracts. No further cleanup was needed. A minimum matrix effect with a 1:10 dilution of white wine for cypermethrin and a 1:200 dilution of red and white wines, fruits, and vegetables for permethrin was found when phosphate-buffered saline containing 40% methanol was employed as the diluent. Good recoveries of spiked levels were observed. The mean percentage recoveries of cypermethrin spiked in white wine and permethrin spiked in red and white wines were 99.7, 74, and 78%, respectively. The mean percentage recoveries of permethrin spiked in apple, banana, cucumber, lettuce, onion, and peach were 99.2, 105, 70.2, 97.5, 94.4, and 89.4%, respectively. Validation of the ELISA method with permethrin-spiked lettuce and peach was carried out using gas chromatography with mass spectrometry, resulting in a good recovery and correlation.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15373394&dopt=Abstract permethrin Elimite



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Effects of permethrin on the salivary glands and neuroendocrine organs of unfed female Hyalomma (Hyalomma) dromedarii (Ixodoidea: Ixodidae).

Mohamed FS, Abbassy MM, Darwish ZE, Tetreault GE, Marzouk AS, Shoukry MA, Fryauff DJ, Beavers GM.

Vector Biology Research Program, U.S. Naval Medical Research Unit Number Three, Cairo, Egypt.

Permethrin-impregnated fabric has been shown to be an effective repellent against various tick species. However, some tick species are not repelled by this chemical. In Hyalomma dromedarii (Koch), permethrin exposure is reported to actually enhance the tick's attachment behavior. This study evaluated the histological effects of permethrin exposure on the salivary glands and neuroendocrine organs of unfed, virgin H. dromedarii ticks of uniform age. Three fabric treatments consisting of unwashed-untreated (control), washed after treatment (0.125 mg [AI] / cm2) and unwashed-treated were used after 5- and 10-min exposure times for unfed, unmated females. For all of the organs examined, the cellular structure of treated ticks differed from controls as evidenced by increases in cellular activity, as well as significant increases in the size of the cells of the organs under study (P < 0.05). These data conclusively demonstrate that an unexpected enhanced attachment response observed in this tick species after permethrin exposure is the direct result of increased neurosecretory and salivary gland activity induced by that exposure.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15535583&dopt=Abstract permethrin Elimite