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Susceptibility of Musca domestica and Chrysomya megacephala to Permethrin and deltamethrin in Thailand.

Susceptibility to permethrin and deltamethrin was assessed in the house fly, Musca domestica L., and blow fly Chrysomya megacephala (F.). The laboratory strain of M. domestica was captured in Muang District (downtown), Chiang Mai, northern Thailand, and the field strains were collected from Muang District, two agricultural areas of Hang Dong District and San Khampaeng District. These strains displayed susceptibility to both permethrin and deltamethrin insecticides, with LD50 values of 0.0049, 0.0019, 0.0003, and 0.0005 microg/fly and 0.1058, 0.0185, 0.1251, and 0.0981 microg/fly, respectively. Tests on the laboratory strain of C. megacephala and the field strains collected from four areas of Chiang Mai (Muang District [downtown], two agricultural areas of Hang Dong District, and San Khampaeng District) and the wooded area near the National Forest revealed slightly lower susceptibility compared with house fly, with LD50 values of permethrin equal to 0.0028,0.0027,0.0024, 0.0007, and 0.0034 microg/fly and of deltamethrin equal to 0.0461, 0.0267,0.1327,0.1151, and 0.0244 microg/fly. These results indicated that the adult populations of both fly species were susceptible to both insecticides.

Animals↗

Comparative study of permethrin 1% creme rinse and lindane shampoo for the treatment of head lice.

The efficacy and safety of permethrin 1% creme rinse and lindane shampoo were compared for the treatment of head lice (Pediculus humanus var. capitis). A total of 1040 patients in the Nezahualcoyotl community of Mexico City representing 296 family groups were enrolled and randomized to treatment, with one patient in each family designated as the index patient. Among index patients 98% treated with permethrin and 76% treated with lindane were louse-free 2 weeks after treatment (P less than 0.001). Comparable results were found with nonindex patients as well. Mild dermal reactions, such as pruritus or erythema, occurred in 1.2% of permethrin-treated patients and 2.6% of lindane-treated patients. There were no reports of central nervous system adverse effects or conjunctivitis.

Administration, Topical↗

Genetic mapping of genes conferring permethrin resistance in the malaria vector, Anopheles gambiae.

Resistance to permethrin in an East African population of the major malaria vector, Anopheles gambiae is multifactorial. A mutated sodium channel allele and enhanced insecticide metabolism contribute to the resistance phenotype. We used microsatellite markers to scan the genome for quantitative trait loci (QTL) associated with permethrin resistance. Two major and one minor QTL were identified. The first QTL, rtp1, colocalizes with the sodium channel gene on chromosome 2L thus further supporting the importance of mutations in this gene in conferring permethrin resistance. The second two loci are located on the third chromosome and one of these, rtp2, flanks a large cluster of cytochrome P450 genes. Further detailed mapping of these regions will help elucidate the molecular mechanisms of metabolic resistance to insecticides.

Animals↗

Efficacy of permethrin-impregnated curtains for malaria vector control.

Preliminary results obtained by the use of permethrin-impregnated curtains against the Afrotropical malaria vectors Anopheles gambiae Giles s.l. and An.funestus Giles are reported and discussed. Field trials were carried out in villages near Ouagadougou, Burkina Faso. Houses were provided with curtains made from 100% cotton netting, impregnated with permethrin at the dose of 1 g a.i./m2, to cover the doorway, the window(s) and the space under the eaves. Entomological data collected during the period 1985-86 showed residual permethrin activity for about a year, and almost complete prevention of indoor-resting mosquitoes. Increased exit-rate and mortality-rate of house-entering malaria vectors were also obtained. Utilization of this malaria vector control method in primary health care programmes is advocated.

Animals↗

The influence of permethrin-impregnated bednets and mass drug administration on the incidence of Plasmodium falciparum malaria in children in Sabah, Malaysia.

A small-scale trial was carried out in the Upper Kinabatangan district of Sabah, Malaysia, to determine the effect of using permethrin-impregnated bednets on malaria transmission. A total of 306 nylon bednets with cotton borders, impregnated at a dose estimated to have been 0.062 g permethrin/m2 of nylon netting, were distributed to 139 households in five villages. At the time of distributing bednets, mass drug administration with Fansidar plus primaquine was also administered to the human population to clear all parasitaemias due to Plasmodium falciparum Welch. In another village, for comparison, mass drug administration was the only intervention. After intervention measures in December 1984 and January 1985, the parasite rates in children declined in all villages during the first month, significantly more in the villages with impregnated bednets than in the control, thus proving that the nets had an impact on malaria. However, after about 2 months, parasite rates started to increase again. After 4-6 months, parasite rates in the villages with bednets approached the rate in the control village without nets. The increase in parasite rates was paralleled by a significant deterioration in the quality, physical condition and the degree of non-utilization of bednets. Entomological evaluation proved the efficacy of permethrin-impregnated nets for controlling Anopheles balabacensis Baisas and other anophelines. Bioassays (1 h exposure) of permethrin-impregnated bednets gave 100% mortality initially and 44-61% mortality after 85-106 days. Mosquito collections in treated bednets were significantly reduced for at least 217 days. The project failed to achieve prolonged suppression of malaria transmission for a combination of entomological, sociological and practical reasons which are discussed in relation to the objectives and implementation of future bednet studies.

Animals↗

Reduced susceptibility to permethrin and its relationship to DDT resistance in larvae of Anopheles stephensi.

Permethrin selection of DDT resistant Anopheles stephensi Liston mosquito larvae produced a reduction in susceptibility to knockdown (2 h exposure) of 17-fold, but only 1.6-fold to kill (24 h exposure). Genetic analysis, incorporating visible mutant markers, was interpreted as indicating that, through multigenic inheritance, several interacting genetic factors were collectively responsible for reduced larval susceptibility to knockdown. These were maintained together only under selection pressure, as the effect was lost quickly in the absence of selection or with outcrossing. The 30-40-fold DDT-resistance found in the parental strain was barely altered by permethrin selection, suggesting no relationship with the major source of DDT resistance. This was confirmed in single family studies. Some evidence for an additional tolerance to DDT was found to be associated with reduced larval susceptibility to permethrin.

Animals↗

Evaluation of permethrin-impregnated mosquito-nets against mosquitoes in China.

In Yishan County, Guangxi Province, China, where malaria and Brugian filariasis are transmitted by vectors belonging to the Anopheles hyrcanus Pallas group, a study was conducted from June to November 1986 to evaluate the effectiveness of permethrin-impregnated mosquito bednets to reduce man/vector contact. In three experimental villages a total of 246 mosquito nets were treated with permethrin EC at a dosage of 0.5 g/m2. Control bioassays (1 h exposure) of treated nets gave up to 100% mortality of Armigeres subalbatus (Coquillett), Anopheles sinensis Wiedemann and Culex tritaeniorhynchus Giles for up to 19 weeks. During 5 months evaluation in the villages, permethrin-impregnated mosquito-nets reduced the number of mosquitoes found inside nets by 99.3% for Culex quinquefasciatus Say, by 94.4% for Anopheles sinensis Wiedemann and by 75% for Anopheles lesteri anthropophagus Xu & Feng. This measure could thus be considered an appropriate means of controlling vectors in villages.

Animals↗

Efficacy of mosquito nets treated with permethrin in Suriname.

In the rain-forest of Suriname, where malaria is endemic, 95% of the Maroons (who call themselves bush-negroes) and all Amerindians use mosquito nets made of cotton cloth or, less frequently, nylon or cotton gauze over their hammocks or beds. Bush-negroes usually wash their nets weekly; Amerindians wash nets at 1-4 month intervals. Females of the principal local malaria vector, Anopheles darlingi Root, were seen blood-feeding through cotton cloth netting (at 22.30-23.30 hours) on a person sleeping in a hammock; others fed successfully after the net was opened in the morning. Cotton cloth impregnated with permethrin at a rate of 0.5 g/m2 killed all An. darlingi females exposed for 2 min, but after the material had been washed twice in soapy water the bioassay mortality fell to only 21.4%. Exit traps on a hut with a single sleeper protected by a permethrin-impregnated net yielded 185 An. darlingi females (12% blood-fed) in 74 nights, compared with 276 females (19% blood-fed) from another hut with a sleeper using an untreated net on the same nights (P less than 0.001). No An. darlingi females remained resting alive indoors in these huts during the daytime, and very few were found dead on the floor in the mornings (one treated, seven untreated). The 24 h mortality rate for those collected in exit traps was 58.4% for the test hut and 27.1% for the control hut (P less than 0.001). Bioassays of permethrin-treated cotton cloth using laboratory-reared sugar-fed Culex quinquefasciatus Say females showed that sprayed nets were less effective than nets impregnated by soaking (at equivalent dosages of 0.16-1.34 g/m2 measured by chemical assay) and confirmed that washing causes severe decline in insecticidal activity. The feasibility of local mass treatment of mosquito nets is discussed.

Animals↗

Permethrin-impregnated bednets: behavioural and killing effects on mosquitoes.

Permethrin-treated pieces of netting and simulated bednets were evaluated against Anopheles gambiae Giles and Aedes aegypti (L.) in the laboratory. When female mosquitoes were allowed to feed on a human arm through pieces of impregnated netting fastened at the end of tubes, doses above 2 g/m2 were required to stop blood-feeding of both An. gambiae and Ae. aegypti. A much lower dose prevented Ae. aegypti from feeding on mice through impregnated netting. When mosquitoes were released in a room and a human subject sat under a permethrin-impregnated (0.2 g/m2) bednet with an arm pressed against the net (mesh 1.5 mm), mosquitoes failed to bite through the net. All the mosquitoes trying to bite through or entering the net through holes cut in it were knocked down within 30 min of release and ultimately died. Permethrin-impregnated wide-mesh (4 or 8 mm) bednets similarly prevented entry and caused high mortality-rates of An. gambiae.

Aedes↗

Permethrin-impregnated bednets reduce nuisance arthropods in Gambian houses.

The prevalence of bedbugs (Cimex hemipterus L.), chicken ticks (Argas persicus Oken) and headlice (Pediculus capitis De Geer) was surveyed in a rural area of The Gambia. At the beginning of the study 37.5% of children's beds were infested with bedbugs and 3.9% with chicken ticks, whilst the prevalence rate of pediculosis in children under 10 years old was 28.8%. Both bedbugs and headlice were clustered within compounds. Headlice prevalence increased with hair length and they were more common on girls than boys. Following this cross-sectional survey all bednets in the sixteen hamlets were either dipped in permethrin or a placebo. About 4 months later it was found that bedbugs and chicken ticks had disappeared from homes in which the bednets had been impregnated with permethrin. There was no reduction in hamlets with placebo-treated bednets. The rate of acquiring headlice between the two surveys was reduced by 91.1% in children who slept under insecticide-treated bednets compared with children with placebo-treated bednets. There were also significantly fewer day-flying and crawling insects, except earwigs, in homes of children who slept under insecticide-treated bednets compared with those with placebo-treated nets. These additional benefits of permethrin-treated bednets should contribute to their widespread acceptance and utilization by the community for personal protection.

Animals↗

Impact of permethrin impregnated bednets on child mortality in Kassena-Nankana district, Ghana: a randomized controlled trial.

A community-based randomized, controlled trial of permethrin impregnated bednets was carried out in a rural area of northern Ghana, between July 1993 and June 1995, to assess the impact on the mortality of young children in an area of intense transmission of malaria and no tradition of bednet use. The district around Navrongo was divided into 96 geographical areas and in 48 randomly selected areas households were provided with permethrin impregnated bednets which were re-impregnated every 6 months. A longitudinal demographic surveillance system was used to record births, deaths and migrations, to evaluate compliance and to measure child mortality. The use of permethrin impregnated bednets was associated with 17% reduction in all-cause mortality in children aged 6 months to 4 years (RR = 0.83; 95% CI 0.69-1.00; P = 0.05). The reduction in mortality was confined to children aged 2 years of younger, and was greater in July-December, during the wet season and immediately after (RR = 0.79; 95% CI 0.63-1.00), a period when malaria mortality is likely to be increased, than in the dry season (RR = 0.92, 95% CI 0.73-1.14). The ready acceptance of bednets, the high level of compliance in their use and the subsequent impact on all-cause mortality in this study has important implications for programmes to control malaria in sub-Saharan Africa.

Bedding and Linens↗

Comparison of crotamiton 10% cream (Eurax) and permethrin 5% cream (Elimite) for the treatment of scabies in children.

Permethrin 5% cream (Elimite) was approved as a treatment for scabies by the U.S. Food and Drug Administration in September 1989. In a double-blinded, randomized study, it was compared with crotamiton 10% cream (Eurax) for the treatment of scabies in children 2 months to 5 years of age. Two weeks after a single overnight treatment, 14 (30%) of 47 children were cured with permethrin 5% cream, in contrast to only 6 of 47 (13%) of subjects treated with Eurax. Four weeks after treatment the figures were 89% and 60% cured for the two agents, respectively. In 10 of the 19 patients whose treatment failed, the condition became worse after therapy. The difference in efficacy in favor of permethrin was significant (P = 0.002). That agent also demonstrated greater effectiveness in reducing pruritus and secondary bacterial infections. Elimite offers a safe, efficacious, and cosmetically elegant alternative to Eurax in the treatment of scabies in children.

Administration, Topical↗

A field trial to determine the effect of fly control using permethrin on milk yields in dairy cattle in the UK.

Permethrin, applied by knapsack sprayer or spray arch, was used to control flies on cattle in two dairy herds in the United Kingdom. The spray washes were applied at nominal rates of 0.5 litre of 0.1 per cent permethrin per animal and 1.0 litre of 0.05 per cent permethrin per animal respectively. The individual milk yields of two groups of cows were recorded before and after treatment. In both cases there was a significant increase in milk yield after treatment. The mean yield per cow per day during the trial period rose by 0.8 kg in one group and by 1.0 kg in the other group, after treatment. Assessments were made throughout the trial of the level of infestation of Stomoxys calcitrans, Haematobia irritans and non-biting flies.

Animals↗

No effect of albumin on the dermal absorption rate of hydrocortisone 21-butyrate, permethrin or diflunisal in the isolated, single-pass perfused rabbit ear.

Rabbit ears were single-pass perfused with a buffer solution containing either 6% hetastarch or 5% bovine serum albumin. Hydrocortisone 21-butyrate (5 mM), diflunisal (17 mM) or permethrin (33 mM) was added to isopropyl myristate with 5% polyethylene, and applied to about 40% of the epithelial surface area of the ear. Hydrocortisone 21-butyrate or permethrin were not found in the effluent with hetastarch or albumin. Following cutaneous ester hydrolysis, the appearance rate of hydrocortisone was about 4 pmol/min per cm2 in the hetastarch- or the albumin-containing buffer solution. No hydrolysis of permethrin was detected; the appearance rate of 3-phenoxybenzyl alcohol with 3-phenoxybenzoic acid corresponded to the absorption rate of the substrate impurities. During ex vivo perfusion of intact skin, serum albumin in the perfusion fluid may not enhance the appearance rate of xenobiotics in the effluent following dermal application when the distribution coefficient n-octanol/water is > 2,000 or when the xenobiotic is ionized at physiological pH. In general, for all substances investigated with our perfusion model thus far, the appearance rates decreased with rising distribution coefficient (n-octanol/buffer pH 7.4). High lipophilicity hinders the release from isopropyl myristate and the penetration through the skin.

Administration, Cutaneous↗

Reduced bio-efficacy of permethrin EC impregnated bednets against an Anopheles gambiae strain with oxidase-based pyrethroid tolerance.

BACKGROUND: Insecticide-treated nets (ITNs) are an integral component of malaria control programmes in Africa. How much pyrethroid resistance in malaria vectors will impact on the efficacy of ITNs is controversial. The purpose of this study was to evaluate knockdown and killing effects of ITNs on a metabolic-based resistant or tolerant malaria vector strain. METHODS: Bio-efficacy of 500 mg/m2 permethrin EC treated bednets was assessed on the OCEAC laboratory (OC-Lab) strain of Anopheles gambiae s.s.. This strain is resistant to DDT and tolerant to pyrethroids, with elevated mixed function oxidases. The Kisumu reference susceptible strain of A. gambiae s.s. was used as control. Nets were impregnated in February 1998 and used by households of the Ebogo village. Then they were collected monthly over six months for Bio-assays (WHO cone test). Knockdown and mortality rates were compared between the OC-Lab and the Kisumu strains, by means of the Mantel-Haenszel chi-square test. RESULTS: During the whole trial, permethrin EC knockdown rates were impressive (mostly higher than 97%). No significant difference was observed between the two strains. However, the mortality rates were significantly decreased in the OC-Lab strain (40-80%) compared with that of the Kisumu strain (75-100%). The decrease of killing effect on the OC-Lab strain was attributed to permethrin EC tolerance, due to the high oxidase metabolic activity. CONCLUSION: These data suggested an impact of pyrethroid tolerance on the residual activity of ITNs. More attention should be given to early detection of resistance using biochemical or molecular assays for better resistance management.

Animals↗

Effects of methoprene and permethrin on paedogenetic larvae of Heteropeza pygmaea and Mycophila speyeri (Diptera: Cecidomyiidae).

The effects of methoprene and permethrin on larvae of Heteropeza pygmaea Winnertz and Mycophila speyeri (Barnes), two Cecidomyiid species of paedogenetic insect mushroom pest, were investigated in sterile culture at concentrations of 0.1-100 micrograms/g. The two highest concentrations of permethrin caused complete mortality of M. speyeri but only low mortality of H. pygmaea. The main sublethal effects of permethrin on both species were reduced fecundity and reduced mother-larval width. Methoprene had only sublethal effects on both species. At all doses, methoprene caused an increase in H. pygmaea generation time but a reduction in hemipupal width and fecundity according to dosage. The effects on M. speyeri were similar but more severe.

Animals↗

Variation in susceptibility of Diadegma insulare (Hymenoptera: Ichneumonidae) to permethrin.

Six field populations of the parasitoid Diadegma insulare (Cresson) were collected from Mexico and the United States and tested for their susceptibility to permethrin by using a glass-vial residue bioassay. Significant differences existed in susceptibility, with one population significantly more susceptible than the other five. Susceptibility of D. insulare increased when they were reared for several generations in the greenhouse in the absence of selection. D. insulare was less suceptible to permethrin than the adult stage of its host, Plutella xylostella (L.), from a laboratory colony, but more susceptible than those hosts collected from a commercial field. Our data suggest that a field population of D. insulare appeared to increase its tolerance to permethrin much more slowly than P. xylostella.

Animals↗

Suppression of mosquito (Diptera: Culicidae) and black fly (Diptera: Simuliidae) blood feeding from Hereford cattle and ponies treated with permethrin.

The blood feeding of mosquitoes and black flies from Hereford cattle and ponies treated with commercial formulations of permethrin was evaluated using an animal enclosure trap sample system that allowed comparison of insect blood-feeding levels between treated and nontreated animals. Blood feeding of both Aedes dorsalis Meigen and A. melanimon Dyar from heifers treated with pour-on concentrate and whole body spray treatments was reduced significantly by 79-88% at 4 d posttreatment, with apparent but not significant reductions of 61-68% at 11 d posttreatment. Simulium bivittatum Malloch and S. griseum Coquillett blood feeding was reduced significantly by 96% to >99% at 4 d posttreatment, but apparent reductions of 30-87% at 11 d posttreatment were not significant. Blood feeding of S. bivittatum from ponies treated with a permethrin fly wipe was reduced significantly by 98 and 87% at 1 and 7 d posttreatment, respectively. No evidence of treatment-induced mortality was observed for recently blood-fed female mosquitoes or black flies captured from treated animals and held for 24 h. The potential benefit of using permethrin to protect livestock from insect-transmitted pathogens was estimated with a model based on level of host attack, pathogen infection rate in the vector, and suppression of blood feeding. Suppression of blood feeding by 90% is predicted to prevent the exposure of a host to a pathogen for up tolO d at 1,000 insect feedings per d when the vector population infection rate is one insect per 1,000. If insect feedings are lower (100/d) and the insect infection rate remains at one per 1,000, protection is predicted for 100 d. In contrast, a 90% suppression of blood feeding is predicted to provide protection for less than 1 d at 1,000 feeding per day and a vector infection rate of one insect per 100.

Aedes↗