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Flea (Siphonaptera:Ceratophyllidae, hystrichopsyllidae) and tick (Acarina:Ixodidae) control on wood rats using host-targeted liquid permethrin in bait tubes.

The efficacy of a liquid permethrin-treated bait tube controlling fleas and ticks on Mexican wood rats, Neotoma mexicana Baird, was evaluated during a 1-yr study in north-central Colorado. Results indicated that the bait tubes were effective for reducing flea and tick infestations on wood rats. The effects of treatment persisted throughout the study, despite the fact that bait tubes were replenished with bait and permethrin only during the first 4 mo (4 replenishments). Our results suggest that these bait tubes provide an effective, economical, and environmentally acceptable means of controlling vectors of flea or tick-borne diseases, although slight modifications of the basic bait tube design might be required to maintain the effectiveness of the tube under different ecological conditions.

Animals↗

Efficacy of a reduced application time of Ovide lotion (0.5% malathion) compared to Nix creme rinse (1% permethrin) for the treatment of head lice.

Our objective was to conduct a randomized, investigator-blinded evaluation of the pediculicidal and ovicidal activity of a reduced application time (20 minutes) of Ovide (0.5% malathion) compared to Nix (1% permethrin) in a south Florida population infested with Pediculus humanus capitis. Either Ovide or Nix was applied according to the label instructions. However, Ovide application time was reduced to 20 minutes. At day 8, subjects with live lice were re-treated with the same product and procedure as on day 1. Ovicidal and pediculicidal efficacy were evaluated at days 8 and 15. A subject free of lice and viable eggs at day 15 was considered to be a treatment success. Percent efficacy was calculated using the number of subjects free of lice and viable eggs per total number of subjects treated. We found that a 20-minute application of Ovide was significantly more pediculicidal and ovicidal (98%) compared to Nix (55%) at day 15 (p < 0.0001). The percentage of Ovide subjects who required treatment at day 8 was half that of the Nix group. The reinfestation rate was 0% with Ovide and 33% with Nix. In conclusion, a 20-minute treatment with Ovide, instead of the approved 8- to 12-hour application, cured 40 of 41 subjects (98%), demonstrating superior efficacy to Nix. The poor efficacy of Nix confirms the resistance of head lice to permethrin in south Florida.

Adolescent↗

Experimental hut trials of permethrin-impregnated mosquito nets and eave curtains against malaria vectors in Tanzania.

Permethrin impregnated netting was tested against Tanzanian populations of Anopheles arabiensis Patton, An.gambiae Giles and An.funestus Giles in experimental huts fitted with traps to catch samples of the mosquitoes existing during the night. Treated bednets killed some mosquitoes and increased the tendency of survivors to exit during the night. Treated cotton did not perform so well as treated nylon bednets. An impregnated bednet in which holes had been cut, to simulate a torn net, reduced the number of mosquitoes which fed and survived approximately as well as an intact untreated net. Treated curtains around the eaves of experimental huts did not perform so well as bednets but caused considerable reductions in the number of mosquitoes which fed and survived. However, there was no such effect when treated netting was placed around the eaves of a dwelling house. When one child slept under a treated net and another slept outside the net in the same hut, the number of bites on the latter child was less than if neither child had been under a net. Various aspects of the applicability of permethrin impregnated nets on a community basis are discussed.

Animals↗

Seasonal abundance and biting behaviour of Anopheles punctulatus and An. koliensis in Malaita Province, Solomon Islands, and a trial of permethrin impregnated bednets against malaria transmission.

Seasonal abundance of the malaria vectors Anopheles punctulatus Dönitz and An.koliensis Owen in Bilimanu, an isolated inland village with forty-two houses in Malaita Province of the Solomon Islands, was monitored over 28 months by means of all-night landing/biting catches at one site during June 1985 to September 1987. Totals of 1250 An.punctulatus and 141 An.koliensis were collected, the latter being the largest number of this species ever caught at any locality in the Solomons. Bednets impregnated with permethrin 0.5 g/m2 were introduced in December 1986 to be used at night by all 190 villagers for protection against malaria vectors. Bioassay tests with An.punctulatus blood-fed females exposed under nets for 10 min resulted in 100% mortality up to 50 weeks post-impregnation. For An.punctulatus, the main vector species, the mean catch (indoors + outdoors) per man hour was 2.9 (range 0.7-13.2) before a cyclone on 19 May 1986, and, 0.66 (0.2-2.7) after the cyclone. The vector survival rates were usually high before the cyclone, but erratically lower thereafter for An.punctulatus. An.koliensis disappeared after the cyclone. Both An.punctulatus and An.koliensis consistently showed higher rates of biting man indoors than outdoors and their diel biting cycle showed a peak around midnight. Outdoors, the parous proportion of An.punctulatus was twice the nulliparous, and nearly so indoors. Following intervention with permethrin-treated bednets, the mean catch of An.punctulatus fell to 0.35 per man-hour (monthly range 0-1.5). The Plasmodium falciparum malaria infection rate reduced from 10% pre-intervention to zero in September 1987, 9 months after intervention, and then rose again.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

The impact of permethrin-impregnated bednets on malaria vectors of the Kenyan coast.

The effects of introducing permethrin-impregnated bednets on local populations of the malaria vector mosquitoes Anopheles funestus and the An.gambiae complex was monitored during a randomized controlled trial at Kilifi on the Kenyan coast. Pyrethrum spray collections: inside 762 households were conducted between May 1994 and April 1995 after the introduction of bednets in half of the study area. All-night human bait collections were performed in two zones (one control and one intervention) for two nights each month during the same period. PCR identifications of An.gambiae sensu lato showed that proportions of sibling species were An.gambiae sensu stricto > An.merus > An.arabiensis. Indoor-resting densities of An.gambiae s.l. and the proportion of engorged females decreased significantly in intervention zones as compared to control zones. However, the human blood index and Plasmodium falciparum sporozoite rate remained unaffected. Also vector parous rates were unaltered by the intervention, implying that survival rates of malaria vectors were not affected. The human-biting density of An.gambiae s.l., the predominant vector, was consistently higher in the intervention zone compared to the control zone, but showed 8% reduction compared to pre-intervention biting rates-versus 94% increase in the control zone. Bioassay, susceptibility and high-performance liquid chromatography results all indicated that the permethrin content applied to the nets was sufficient to maintain high mortality of susceptible vectors throughout the trial. Increased rates of early outdoor-biting, as opposed to indoor-biting later during the night, were behavioural or vector composition changes associated with this intervention, which would require further monitoring during control programmes employing insecticide-treated bednets.

Animals↗

Anopheles gambiae gonotrophic cycle duration, biting and exiting behaviour unaffected by permethrin-impregnated bednets in The Gambia.

Permethrin-impregnated bednets protect children against malaria in The Gambia, where Anopheles gambiae complex mosquitoes are the main vectors of malaria. However, no effect has been found on mosquito density, parous rates or sporozoite rates in An.gambiae sensu lato populations; only a reduction in the numbers of mosquitoes resting indoors in rooms with treated bednets. A possible explanation for this paradox is that exposure to treated bednets leads to changed vector behaviour such as a shift in biting time, a diversion to biting outdoors instead of indoors, to biting animals instead of humans, or to increased duration of the gonotrophic cycle. To investigate these possibilities, we observed the biting and existing behaviour of An.gambiae in ten pairs of villages, in half of which the residents used permethrin-treated bednets. The possible influence of treated bednets on the gonotrophic cycle length was evaluated by mark-release-recapture experiment. No significant difference was found between villages with treated and untreated bednets in the indoor/outdoor ratio of human biting, in mean biting times or in human blood indices of An.gambiae females found resting indoors in the mornings. The proportions of unfed, fed or gravid An.gambiae females collected in exit traps, and the number of females exiting showed no significant differences between rooms with treated and untreated bednets. Indications for a gonotrophic cycle length of 2 days were found. No evidence for any change in duration of the gonotrophic cycle in relation to exposure to treated bednets was found, although the number of recaptures was low in the villages with treated bednets. Since equal numbers of infective An.gambiae were found in villages with treated or untreated bednets, and no changes in mosquito behaviour were detected, we cannot account for how children are protected against malaria by treated bednets. One possibility is that mosquitoes divert to bite other hosts, including adults.

Animals↗

Field assessment of permethrin in the control of sheep headfly disease.

Three groups of sheep, gimmers, ewes with lambs and rams, were sprayed at fortnightly intervals from June to September 1980 with a 0.1 per cent emulsion of permethrin in an attempt to control damage caused by Hydrotaea irritans. Complete prevention of damage was not achieved but the number of sheep affected and the severity of lesions present in affected sheep was significantly reduced in comparison with untreated control groups. Permethrin treatment was also judged to be valuable in the management of rams with head wounds. Variation in susceptibility with age was noted, gimmers being the most severely affected and a breed variation was apparent in the rams which was related to the character of horn present.

Animals↗

Inhibition of trans-permethrin hydrolysis in human liver fractions by chloropyrifos oxon and carbaryl.

Permethrin, a pyrethroid insecticide, is one of several deployment-related chemicals that have been suggested as causative agents for Gulf War related illnesses. Hydrolysis of trans-permethrin (tPMT) is a major route of detoxication and a potential locus for interactions with chemicals with similar use patterns. This study examined the potential inhibitory effects of chlorpyrifos, carbaryl, pyridostigmine bromide and the insect repellent N,N-diethyl-m-toluamide (DEET) on tPMT hydrolysis in human liver fractions. Although chlorpyrifos was not inhibitory, its toxic metabolite, chlorpyrifos oxon, strongly and irreversibly inhibited tPMT hydrolysis at low concentrations (cytosolic and microsomal Ki values of 3 and 16 nM, respectively). Carbaryl, a known anticholinesterase agent, showed non-competitive inhibition kinetics, with Ki values two orders of magnitude higher than those for chlorpyrifos oxon. Although DEET was much less effective than either chlorpyrifos oxon or carbaryl, equimolar concentrations inhibited up to 45% of tPMT hydrolysis. Pyridostigmine bromide showed no inhibitory effects. This study suggests that interaction potential between organophosphorus and pyrethroid insecticides should be considered in safety assessments when both insecticides are deployed simultaneously.

Carbaryl↗

Cost-benefit analysis of ivermectin, permethrin and benzyl benzoate in the management of infantile and childhood scabies.

In the US, 6% sulfur in petrolatum has been the most frequently administered treatment for infantile scabies. It appears to be safe but there is no literature containing a large series of patients on which to base that determination. In the UK, benzyl benzoate is the approved product. Benzyl benzoate is rarely used in the US at the present time. 5% Permethrin is an excellent substitute and has many advantages. It appears to be quite safe in infants, although it is more expensive than other products. It remains present on the skin for several days, therefore protecting against reinfestation. Ivermectin is a systemic drug which is assumed to be safe in infants, although it requires repeated doses and does not protect against reinfestation. In the opinion of the author, 5% permethrin is the best treatment for scabies in infants and young children.

Administration, Cutaneous↗

Effect of permethrin-impregnated nets on exiting behavior, blood feeding success, and time of feeding of malaria mosquitoes (Diptera: Culicidae) in western Kenya.

The impact of permethrin-treated bednets on the feeding and house entering/exiting behavior of malaria vectors was assessed in two studies in western Kenya. In one study, matched pairs of houses were allocated randomly to receive bednets or no bednets. Exiting mosquitoes were collected in Colombian curtains hung around half of each house; indoor resting mosquitoes were collected by pyrethrum spray catches. The number of Anopheles gambiae Giles and An. arabiensis Patton estimated to have entered the houses was unaffected by the presence of bednets; Anopheles funestus Giles was less likely to enter a house if bednets were present. Anopheles gambiae and An. funestus were less likely to obtain a blood meal and significantly more likely to exit houses when bednets were present. No difference was detected in An. arabiensis rates of blood feeding and exiting. In a second experiment, hourly night biting collections were done on 13 nights during the rainy season to assess whether village-wide use of permethrin-treated bednets caused a shift in the time of biting of malaria vectors. A statistically significant shift was detected in the biting times of An. gambiae s.l., although the observed differences were small. No change was observed in the hourly distribution of An. funestus biting. Our study demonstrated that, at least in the short-term, bednets reduced human-vector contact and blood feeding success but did not lead to changes in the biting times of the malaria vectors in western Kenya.

Animals↗

Failure of a permethrin treatment regime to protect cattle against bluetongue virus.

Holstein heifers in a confined feedlot setting on a southern California dairy were either sprayed individually along the ventral midline using 0.2% permethrin (250 ml/animal) (two pens) or were not treated (two pens). Treatments (n = 6 dates) were applied every 2 wk during the peak fall bluetongue virus transmission season (22 August-29 October). Animals seronegative for bluetongue virus antibodies at the initial bleeding on 15-18 September (n - 106 in the treatment pens and n = 117 in the control pens) were bled again for testing 2 mo later (12-13 November). Seroconversion rates were not significantly different: 56% for the treated animals and 48% for the controls (P > 0.2). The area has many essentially contiguous, confinement dairies with wastewater ponds that produce large numbers of Culicoides sonorensis Wirth & Jones, the primary bluetongue virus vector. Further, these dairies presumably provided a large reservoir of virus-infected cattle to infect vectors in the immediate area. Under these severe virus challenge conditions, permethrin applied at 2-wk intervals failed to reduce exposure to bluetongue virus.

Animals↗

Comparative efficacy and persistency of permethrin in Olyset net and conventionally treated net against Aedes aegypti and Anopheles stephensi.

The efficacy of the Olyset net was compared to a net treated conventionally with permethrin 10% emulsifiable concentrate at the World Health Organization recommended dose. The nets were assessed under laboratory conditions against the mosquito vectors Aedes aegypti and Anopheles stephensi. Knockdown efficacy for the Olyset net was assessed after the first 10 washings and then after the 15th and 20th washings. Data were not collected for the conventionally treated netting after 5 washings because the conventional treatment was no longer effective. The results of the study indicate permethrin effectively persisted on Olyset net for at least 20 washings, confirming the regeneration of pesticide after each wash.

Aedes↗

Control of northern fowl mite with permethrin and fenvalerate, two synthetic pyrethroid compounds.

Trials were conducted to evaluate the efficacy of permethrin and fenvalerate, two synthetic pyrethroid compounds, for the control of the northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), on White Leghorn hens. Fenvalerate at .0125%, .025%, and .05% active ingredient (ai) were as effective as carbaryl at .5% ai for 56 days posttreatment. Permethrin at .01%, .025%, and .05% ai were as effective, or better than, malathion at .27% ai for 56 days posttreatment. All treatments were applied to the birds as high pressure sprays.

Animals↗

The effectiveness of polyvinyl chloride plastic bands impregnated with permethrin as a control for the northern fowl mite, Ornithonyssus sylviarum (Canestrini and Fanzago), infesting caged laying chickens.

Caged White Leghorn hens were used to study the effectiveness of polyvinyl chloride (PVC) bands impregnated with 10% permethrin (50 mg/active ingredient/band) for control of the northern fowl mite (NFM), Ornithonyssus sylviarum (Canestrini and Fanzago). The PVC bands were attached two ways, either to the leg of the bird or to the cage floor. Leg band treatments included one, two, three, four, and six birds banded (one band per bird) per cage of six birds. Cage band treatments included one, two, and four PVC strips attached to the cage floor. The attachment of PVC bands to cages was very effective in controlling NFM. Birds in the treatment with four bands attached to the cage floor were essentially mite free for the duration of the 19-week test. Based on this test, the leg banding technique does not seem to be as effective or practical for controlling NFM on caged layers as is attachment of the bands to the cage floor. The use of permethrin-impregnated PVC bands or strips attached to the floor of poultry cages shows promise for effective NFM control and for relieving stress on birds resulting from conventional spraying or dusting treatments.

Animals↗

The effectiveness of permethrin-impregnated bed nets against malaria for migrant workers in eastern Thailand.

A randomized, double-blind, field trial was carried out to compare the effectiveness of permethrin-treated bed nets with that of untreated nets as a method of malaria control for migrant workers in eastern Thailand. The study was conducted using 261 subjects in eastern rural areas that are known to be highly endemic for multidrug-resistant Plasmodium falciparum infection. One hundred twenty-six subjects used treated nets, while 135 used untreated nets. During the 35 weeks of observation, 23 subjects using treated nets and 33 workers using untreated nets developed 28 and 51 episodes of malaria, respectively (P = 0.029). The reduction in risk per subject due to treated nets was 0.06. The residual effects of permethrin were tested using a World Health Organization standard bioassay. Anti-mosquito activity was found to be present in the nets for more than 16 months. We conclude that because of the failure of the development of safe, effective, long-lasting prophylactic agents, integrating the use of impregnated nets with large-scale primary health care programs may be a partially effective method for controlling malaria in eastern Thailand.

Adult↗

Factory-based permethrin impregnation of uniforms: residual activity against Aedes aegypti and Ixodes ricinus in battle dress uniforms worn under field conditions, and cross-contamination during the laundering and storage process.

The factory-based permethrin coating technique has only recently been developed. Consequently, no data are available on residual activity, laundering, and weathering resistance in impregnated battle dress uniforms (BDUs) worn under military deployment conditions, or on the cross-contamination potential of such uniforms. Herein, factory-impregnated BDUs worn-out during military deployment to Afghanistan were investigated for residual permethrin concentration, residual efficacy against arthropod vectors, and cross-contamination during laundering and storage. When compared with BDUs subjected to 50 defined washings using the U.S. Insect/Arthropod Repellent Fabric Treatment method, no significant differences in efficacy were observed against Aedes mosquitoes, but remaining knockdown activity in Ixodes ticks was significantly better in polymer-coated BDUs. BDUs impregnated by the polymer-coating method were found to be effective for the life of the uniform, ensuring protection of soldiers in the field from arthropod vectors, while causing less cross-contamination than those treated by the Insect/Arthropod Repellent Fabric Treatment method.

Afghanistan↗

[Laboratory evaluation of alpha-cypermethrin insecticide efficacy on Anopheles gambiae populations of Côte d'Ivoire resistant to permethrin and deltamethrin].

Susceptibility tests were carried out in laboratory conditions to evaluate the efficacy of alpha-cypermethrin (a synthetic pyrethroid never used in Côte d'Ivoire) for malaria vector control. Five wild populations of Anopheles gambiae originating from M'bé, Yaokoffikro, Korhogo, Kafiné and Daola and two laboratory reared strains (Kisumu susceptible and Kou permethrin resistant selected strain) were tested. The diagnostic dosage of alpha-cypermethrin for the sensitive strain Kisumu was 2.5 x 10(-3)%. A comparative study of the susceptibility of samples of wild populations of An. gambiae was carried out according to the WHO standard susceptibility test. Impregnated papers with 4% DDT, 0.25% permethrin, 0.025% deltamethrin and 0.0025% alpha-cypermethrin were used. The results showed that except for mosquitoes from M'bé, all the other populations were resistant to these insecticides. Bioassays were carried out with alpha-cypermethrin at the operational dosage of 20 mg a.i./m2 on the same population and laboratory reared strains. The results showed the efficacy of this insecticide on both the Kisumu strain and the population from M'bé, a maintained efficacy for the Daloa, Kafiné and Korhogo mosquito populations, but the wild anopheline population from Yaokoffikro clearly appeared fully resistant.

Animals↗

[Protective effect of clothing impregnated with permethrin against D. reticulatus and D. marginatus in an open biotope of central western France].

During the period of major tick activity, in April and May 1998, in the Saint-Maixent l'Ecole area of Poitou, a comparative study was carried out in order to evaluate the protective effect of garments impregnated with permethrin cis/trans 25/75. Three groups of soldiers made up respectively of 208, 218 and 427 men were involved for 2 or 3 days in this experiment. Respectively 107, 107 and 215 wore impregnated uniforms. Out of a total of 319 ticks, 3 were lxodes ricinus, 305 Dermacentor marginatus and 11 D. reticulatus. There was a significant difference in both the intensity (number of ticks per individual, P < 0.0001) and prevalence (number of individuals with ticks, P < 0.001) of ticks on individuals between impregnated and non impregnated uniforms. The repellent effect of permethrin on ticks was observed at the site of preferential tick attachment (normally the head of the host for these two species of Dermacentor in France) where the number of ticks was significantly lower in impregnated uniforms.

Animals↗