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Autosomal sex-associated pyrethroid resistance in a strain of house fly (Diptera: Muscidae) with a male-determining factor on chromosome three.

Mechanisms and genetics of resistance to pyrethroid insecticides were investigated in a strain of house fly (ASPR) collected from a cattle ranch in Miyagi, Gunma Prefecture, Japan. Flies were selected in the laboratory with the pyrethroid insecticide permethrin. Both sexes were resistant to pyrethroids; however, females were 22- to 245-fold more resistant than males. Permethrin resistance could be partly suppressed by the monooxygenase inhibitor piperonyl butoxide in females, but not in males. In this strain, sex was determined by a male factor on the third autosome. The relationship of the autosomal male factor to the lower resistance levels observed in the males and the mechanisms of resistance expressed in each sex are discussed.

Animals↗

Pyrethroid resistance and synergism in a field strain of the German cockroach (Dictyoptera: Blattellidae).

A field-collected strain of the German cockroach, Blattella germanica (L.), was highly resistant to 10 pyrethroid insecticides (cyfluthrin, cyhalothrin, cypermethrin, fenvalerate, esfenvalerate, fluvalinate, permethrin, resmethrin, sumithrin, tralomethrin) based on topical applications and comparison with a known susceptible strain. Resistance ratios ranged from 29 to 337. In general, pyrethroid compounds with an alpha-cyano functional group were more toxic than those lacking this moiety, but resistance ratios were similar for both classes of compound. The metabolic inhibitors DEF and PBO were tested for synergism in conjunction with cypermethrin (alpha-cyano) and permethrin (non alpha-cyano). Application of synergists resulted in partial elimination of resistance, suggesting that the basis of resistance involves enhanced metabolism as well as target site insensitivity. These results suggest that pyrethroid insecticides may have a very short functional life in German cockroach control unless they are used judiciously.

Animals↗

Development of diagnostic concentrations for insecticide resistance monitoring in soybean looper (Lepidoptera: Noctuidae) larvae using an artificial diet overlay bioassay.

Diagnostic concentrations for several standard and experimental insecticides were determined for a laboratory reference strain of soybean looper, Pseudoplusia includens (Walker), using an insecticide diet overlay bioassay to evaluate the relative susceptibility of field (P) and F1 generations of four field-collected strains of third-, fourth-, and fifth-instar soybean loopers in 1996 and 1997. Diagnostic concentrations were defined as concentrations that killed 90-95% of the susceptible individuals and were 5 ppm for permethrin, 1,300 ppm for thiodicarb, 60 ppm for chlorfenapyr, 5 ppm for emamectin benzoate, and 60 ppm for spinosad. Field strains exhibited significantly greater percentage survival than the laboratory reference strain in the permethrin bioassays in 1996 and 1997 in both the P and F1 generation bioassays and in the thiodicarb bioassays in 1997. Larvae exposed to diagnostic concentrations of the experimental insecticides chlorfenapyr, emamectin benzoate, and spinosad usually did not exhibit significantly higher percentage survival than the reference strain.

Animals↗

Evaluation of host-targeted acaricide for reducing risk of Lyme disease in southern New York state.

A 2-yr evaluation of a commercial product designed to reduce the risk of Lyme disease by delivering permethrin-treated cotton to white-footed mice (Peromyscus leucopus) was conducted at three sites in Westchester County, N.Y., an area where Lyme disease is endemic. We examined the numbers of host-seeking nymphal Ixodes dammini Spielman, Clifford, Piesman & Corwin, the numbers of larval I. dammini infesting mice, and the proportion of nymphs infected with Borrelia burgdorferi, the causative agent of Lyme disease. The density of nymphs collected by drag sampling did not differ between treatment and control areas in the first year for either a woodland or recreational site. In the second year, no significant decrease in the density of nymphs was observed in the treatment areas compared with the control areas. Numbers of larvae on 67 mice captured on treatment and control grids did not differ for woodland and recreational sites, but significantly fewer larvae were found on mice captured at the residential treatment site. The percentage of host-seeking ticks infected with spirochetes did not differ between treatment and control sites in any habitat for either year. The use of permethrin-treated cotton did not measurably reduce the numbers of I. dammini or the proportion of ticks infected with spirochetes at our study sites.

Animals↗

Acaricide susceptibility of immature Ixodes scapularis (Acari: Ixodidae) as determined by the disposable pipet method.

The disposable pipet method was used to establish baseline dose-mortality data for immature stages of Ixodes scapularis Say for carbaryl, esfenvalerate, cyfluthrin, and permethrin. Permethrin and cyfluthrin were most toxic to both nymphs and larvae, followed in order by esfenvalerate and carbaryl, based on LD50 and LD90 values. Larvae were substantially more susceptible than nymphs to each compound.

Animals↗

Resistance to organophosphorus and pyrethroid insecticides in Culex pipiens (Diptera: Culicidae) from Tunisia.

Resistance to the organophosphates temephos and chlorpyrifos, the carbamate propoxur, the pyrethroid permethrin, and the organochloride DDT was investigated in Tunisian populations of Culex pipiens pipiens (L.) collected between 1990 and 1996. Resistance to temephos was uniformly low, reaching 10-fold in the most resistant population. In contrast, resistance to chlorpyrifos was highly variable, reaching the highest level (> 10,000-fold) recorded worldwide. The chlorpyrifos-resistant populations also were highly resistant to propoxur. Some populations also showed high resistance to permethrin (up to 5,000-fold) and moderate resistance to DDT (approximately 20-fold). Bioassays conducted in the presence of synergists showed that increased detoxification had only a minor role in resistance, although several over-produced esterases known to be involved in organophosphate resistance were detected. To better understand the factors influencing the distribution of resistance in Tunisia, the polymorphism of genes involved in organophosphate resistance (i.e., over-produced esterases and insensitive acetylcholinesterase) was investigated in relation to the genetic structure of populations studied by analyzing the electrophoretic polymorphism of "neutral" genes. Over the area studied, and despite a high level of gene flow, resistance genes showed a patchy distribution. Results are discussed in relation to the selection pressure caused by insecticide treatments.

Alleles↗

Characterization of pyrethroid resistance and susceptibility to coumaphos in Mexican Boophilus microplus (Acari: Ixodidae).

Two patterns of pyrethroid resistance were characterized from Boophilus microplus (Canestrini) collected in Mexico. One was characteristic of a kdr mutation and the other involved esterase and cytochrome P450 enzyme systems. Very high resistance to permethrin, cypermethrin, and flumethrin, not synergized by TPP and PBO and high resistance to DDT, characterized the kdr-like pattern found in the Corrales and San Felipe strains. Esterase and cytochrome P450-dependent resistance was found in the Coatzacoalcos strain. It was characterized by resistance to permethrin, cypermethrin, and flumethrin, synergized by TPP and PBO, but no resistance to DDT. The Coatzacoalcos strain also showed 3.6-fold resistance to the organophosphate coumaphos. This factor appeared to be independent of pyrethroid resistance. Pyrethroid resistance patterns found in Mexico were similar to those found earlier in Australia. The significance of pyrethroid and coumaphos resistance to the U.S. cattle fever tick quarantine is discussed.

Animals↗

Baseline susceptibility of a laboratory strain of Pediculus humanus humanus (Anoplura: Pediculidae) using a modified World Health Organization testing protocol.

The World Health Organization (WHO) protocol for determining resistance in body lice, Pediculus humanus humanus (L.), requires holding lice for long periods, which makes successful execution of the test difficult in field settings. The purpose of this study was to modify the WHO test procedure to make the holding period of lice shorter and the handling of lice easier. Susceptible lice from a laboratory colony were placed in a petri dish containing a paper that had been treated with an insecticide solution. After 6 h, the petri dish was turned on its side and lightly tapped on the table. Lice that were unable to cling to the paper were counted as knocked down. The KD50 in mg (AI)/ml of the insecticide solution used to treat the papers was as follows: lindane 0.060, permethrin 0.115, d-phenothrin 0.554, and malathion 1.008. If the diagnostic dose is set at 2 times the KD99, for this test procedure the diagnostic doses and WHO equivalent dose would be lindane, 0.368 mg (AI)/ml (WHO 0.132%); permethrin, 0.498 mg (AI)/ml (WHO 0.206%); d-phenothrin, 2.680 mg (AI)/ml (WHO 1.107%); and malathion, 5.212 mg (AI)/ml (WHO 2.020%).

Animals↗

Mutagenic activity in synthetic pyrethroids in Salmonella typhimurium.

Four pyrethroids, allethrin, resmethrin, permethrin and fenvalerate, were tested for mutagenicity in bacterial reversion assay systems with seven strains (TA1535, TA100, TA1538, TA98, TA1537, TA97 and TA104) of Salmonella typhimurium. Our results show that three pyrethroids, namely resmethrin, permethrin and fenvalerate, were not found to be mutagenic in S. typhimurium in the presence or absence of a rat liver activation system. Allethrin was found to be mutagenic with TA100, TA104 and TA97 strains and required metabolic activation (S9 mix) in order to show its activity, mainly with TA100 and TA104 strains.

Allethrins↗

Effect of temperature on toxicity of three pyrethroids to horn flies.

Predictive models describing best-fit regression equations for per cent mortality of horn flies as a function of temperature were determined for each of three pyrethroid insecticides (fenvalerate, flucythrinate and permethrin) over the temperature range 20-35 degrees C. Susceptible horn flies, Haematobia irritans (L.), were exposed to c. an LC70 dose of each pyrethroid using a residue-on-glass method. This technique used confined exposure in chambers with temperatures of 20, 25, 30 and 35 degrees C. Within this range, mortality was greatest at 25 degrees C with all three insecticides. Estimated temperature-mortality equations for each pyrethroid revealed different responses of horn flies to each of these insecticides. Horn flies exposed to flucythrinate demonstrated a linear mortality response that varied inversely with temperature. The response to permethrin was described by a quadratic equation, while the response to fenvalerate was best fitted by a cubic equation.

Animals↗

A self-medicating applicator for control of ticks on deer.

A self-medicating applicator for killing ticks on deer and domestic ungulates by passive transfer of acaricides during feeding is described. The applicator consists of a barrel divided into a food bin (above) and a sealed self-contained acaricide reservoir (below) with a vertical, centrally-located ceramic column that extends from the reservoir into the food bin. Acaricide is drawn up the column from the sealed reservoir by absorption. Animals attracted to the food in the device acquire the acaricide during feeding when they contact the uppermost portion of the column. White-tailed deer (Odocoileus virginianus) readily utilize the applicator in penned and natural conditions. In a field study, examination of hunter-killed deer demonstrated that animals from a treated site were infested with many fewer Ixodes scapularis (3.4 +/- 1.1) than those from a control site (10.8 +/- 3.0). Chromatographic analysis of hair samples revealed traces of permethrin on three of the four animals examined, suggesting use of applicators by these deer. In a study using penned goats (Capra hircus) infested with Amblyomma americanum ticks, treatment efficacy reached 86.4% within 4 days of exposure to the applicators. Visual observations confirmed that all animals used the applicators. Gas chromatographic analysis of goat hair samples indicated that permethrin was detectable on all of the treated animals exposed to the device.

Animals↗

Control and eradication of chelonian tick infestations, with particular reference to vectors of heartwater.

Studies using the African tortoise tick (Amblyomma marmoreum) and leopard tortoises (Geochelone pardalis) demonstrated that cyfluthrin and permethrin were safe and efficacious acaricides for control of Amblyomma ticks on tortoises. A protocol was developed that successfully eradicated an A. sparsum infestation from a tortoise breeding facility in Florida. It involved treatment of all tortoises with a permethrin formulation, followed by treatment of the premises with a cyfluthrin formulation. Sentinel tortoises were later placed on the treated premises to establish successful tick eradication.

Animals↗

Systematic review of clinical efficacy of topical treatments for head lice.

OBJECTIVES: To collect and evaluate all trials on clinical efficacy of topical treatments for head lice. DESIGN: Systematic review of randomised trials identified from following data sources: Medline, International Pharmaceutical Abstracts, Science Citation Index, letters to key authors and companies, and hand search of journals. SETTING: Trials in schools or communities. SUBJECTS: Patients infested with lice. MAIN OUTCOME MEASURE: Cure rate (absence of live lice and viable nits) on day 14 after treatment. RESULTS: Total of 28 trials were identified and evaluated according to eight general and 18 lice specific criteria. Of the 14 trials rated as having low to moderate risk of bias, seven were selected as they used the main outcome measure. These seven trials described 21 evaluations of eight different compounds and placebo (all but two evaluations were of single applications). Only permethrin 1% creme rinse showed efficacy in more than two studies with the lower 95% confidence limit of cure rate above 90%. CONCLUSIONS: Only for permethrin has sufficient evidence been published to show efficacy. Less expensive treatments such as malathion and carbaryl need more evidence of efficacy. Lindane and the natural pyrethrines are not sufficiently effective to justify their use.

Administration, Topical↗

Synthetic pyrethroid insecticides: a dermatological evaluation.

Synthetic pyrethroids are lipophilic insecticides whose biological activity seems to be directly related to their chemical structure. In this investigation differences in cutaneous sensation were detected by human participants between synthetic pyrethroids with a cyano group in the (S)-configuration of the 3-phenoxybenzyl alcohol of their molecular structure (fenvalerate) and those that do not (permethrin). A strong relation was noted between insecticidal potency and degree of induced cutaneous sensation for the alpha-cyano and non-cyano pyrethroids, with a prominent difference between the two. No sensation was observed by any of the same participants on topical exposure to the inert ingredients of these agents. A linear correlation between concentration and degree of induced dysaethesia was observed for both pyrethroids. Regressing the cutaneous sensation on the common logarithm of concentration resulted in a regression equation of Y = 84.0 + 31.0X1 for fenvalerate and Y = 27.5 + 15.8X1 for permethrin. A highly efficacious therapeutic agent for pyrethroid exposure was noted to be dl-alpha tocopherol acetate. An impressive degree of inhibition of paraesthesia resulted from the topical application of vitamin E acetate, with a therapeutic index of almost 100%.

Dose-Response Relationship, Drug↗

Resistance of the red poultry mite to pyrethroids in France.

The resistance of Dermanyssus gallinae, the red poultry mite, to a pyrethroid acaricide, permethrin, and to an organophosphate, dichlorvos, was examined on five French poultry farms which had experienced problems in controlling mite populations and on one farm with no problems. The concentration of permethrin required to kill 50 per cent of the mites on the five farms was between eight and 40 times the concentration required on the control farm. In contrast, no resistance to dichlorvos was detected. This is the first description of resistance to a pyrethroid in D gallinae in France.

Animals↗

Metabolites of pyrethroid insecticides in urine specimens: current exposure in an urban population in Germany.

Pyrethroids are important insecticides used in agriculture, forestry, horticulture, and in the home. In humans, they are rapidly metabolized and renally eliminated. In numerous studies, pyrethroid metabolites have been detected in urine after occupational exposure to insecticides. In this study, we used a new, reliable, easy, and sensitive analytical method to assess the internal pyrethroid exposure of an urban population without exposure to pyrethoids at home or at work (children and adults). A total of 1,177 persons took part in this investigation, including 331 children under 6 years of age and 247 children between 6 and 12 years of age. None of them reported exposure to pyrethroids at home or at work. Accordingly, the levels of permethrin found in household dust from their homes were lower than expected (median < limit of detection; 95th percentile, 4.8 mg/kg; maximum value, 19 mg/kg). Urine specimens were analyzed for cis-3-(2,2-dibromo-vinyl)-2,2-dimethylcyclo-propanecarboxylic acid (Br(2)CA), cis- and trans-3-(2,2-dichlorovinyl)-2,2-dimethylcyclopropane-carboxylic acid (cis-Cl(2)CA and trans-Cl(2)CA), and 4-fluoro-3-phenoxybenzoic acid (F-PBA) using a gas chromatographic method with mass-selective detection. The limit of detection for pyrethroid metabolites was between 0.1 and 0.2 microg/L. trans-Cl(2)CA was detected in 65% of the urine specimens tested, cis-Cl(2)CA was detected in 30%, and Br(2)CA and F-PBA were found in 19% and 16%, respectively, of the urine specimens. The urinary metabolite levels in children did not differ from those in adults, and there was no correlation between the levels of metabolites and indoor exposure to permethrin in household dust. Moreover, no seasonal correlations could be found. The 95th percentile levels in urine specimens were as follows: Br(2)CA, 0.30 microg/L; cis-Cl(2)CA, 0.51 microg/L; trans-Cl(2)CA, 1.43 microg/L; F-PBA, 0.27 microg/L. Background exposure to pyrethroids was found in the general population; it seems to be caused by the uptake of pyrethroids with the diet. This hypothesis needs to be tested in duplicate diet studies combined with biomonitoring. As long as representative data are lacking, however, the rounded 95th percentile values obtained in our study may be used as reference values for pyrethroid metabolites in urine samples from the population in Germany; 95th percentile values for children and adults are as follows: Br(2)CA, 0.3 microg/L; cis-Cl(2)CA, 0.5 microg/L; trans-Cl(2)CA, 1.5 microg/L; and F-PBA, 0.3 microg/L.

Adolescent↗

Effect of insecticides on the diamondback moth (Lepidoptera: Plutellidae) and its parasitoid Diadegma insulare (Hymenoptera: Ichneumonidae).

Studies were conducted to evaluate the toxicity of insecticides to adult Diadegma insulare (Cresson) and its host the diamondback moth, Plutella xylostella (L.). Leaf-dip and direct-dip bioassays for diamondback moth larvae and residual bioassays for adults of diamondback moth and D. insulare were used to assess mortalities. Larval mortalities at field rates were significantly higher with carbaryl, permethrin, spinosad, and tebufenozide when compared with Bacillus thuringiensis, or imidacloprid in the larval-dip bioassay 72 h after treatment. In the leaf-dip and residual bioassays, both permethrin and spinosad caused 100% mortalities to diamondback moth larvae and adults, respectively, 72 h after treatment. Of all the materials tested, only B. thuringiensis and tebufenozide were not toxic to D. insulare 24 h after treatment. Spinosad was not toxic to D. insulare 30 min after treatment. However, 100% mortality was observed 8 h after treatment.

Animals↗

Pupation site selection of cat fleas (Siphonaptera: Pulicidae) in various carpet types and its influence on insecticide efficacy.

Pupation sites of cat flea, Ctenocephalides felis (Bouché), larvae were determined in three styles of nylon and one style of wool carpet. Nylon saxony carpet had 59.3% of pupae at the top of the pile and 40% at the base of the pile. In nylon contract carpet, 55.2% of pupae were found at the top, 42.6% in the middle, and only 2.2% at the base of the pile. Nylon loop carpet contained 59.2% of pupae at the base, 25.5% in the middle, and 15.3% in the top of the pile. Wool loop carpet had 92.4% at the base and 3.8% both in the middle and top of the pile. Bioassays comparing the control of pupae manually placed at the base of carpets to that in carpets with natural pupation showed that control of pupae in the latter was 39-68% higher. Pupal control after natural pupation was greatest in nylon saxony and nylon contract carpets and lowest in nylon loop and wool loop carpets. Additional studies demonstrated that vacuuming provided the same level of pupal control on nylon saxony carpet as a spray application of permethrin to the carpet surface. Therefore, pupae that survived chemical and mechanical control treatments in nylon saxony carpet probably pupated away from the surface of the pile. Application of permethrin to the base of nylon saxony carpet did not significantly increase control. Future bioassays with cat flea pupae in carpet should be performed after natural pupation and consider carpet make and style.

Animals↗