Elimite
An episode of resistance to permethrin in larvae of Simulium squamosum (Diptera: Simuliidae) from Cameroon, after 3 1/2 years of control.

Hougard JM, Escaffre H, Darriet F, Lochouarn L, Riviere F, Back C.

Centre Pasteur du Cameroun, Yaounde.

Because of the biting nuisance from females of Simulium squamosum, a 30 km section of the Sanaga River (Cameroon) was treated since 1987 with permethrin for the control of larval populations. In 1990, resistance to permethrin occurred in a small proportion of the larvae, with a resulting 2-4x increase of the LC95 for dead larvae (moribund larvae considered as live). In 1991, after a 6-month interruption of the treatments, susceptibility to permethrin returned to the initial level, and was similar to the susceptibility of S. squamosum larvae from a non-treated section of the Sanaga. In the context of a small-scale control program, resistance to permethrin can be reversible, and it can be avoided by rotation with other types of insecticides such as Bacillus thuringiensis serovar, israelensis.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1431861&dopt=Abstract permethrin Elimite



Elimite
Cytogenetic effects of permethrin in cultured human lymphocytes.

Barrueco C, Herrera A, Caballo C, de la Pena E.

Centro Nacional de Sanidad Ambiental, Instituto de Salud Carlos III, Majadahonda, Madrid, Spain.

The pyrethroid insecticide permethrin was tested for its ability to induce sister chromatid exchanges (SCE), micronuclei (MN) and structural chromosome aberrations (CA) in cultured human peripheral blood lymphocytes. Permethrin was tested in the range of 5-500 micrograms/ml in the absence and in the presence of a rat liver activation system (S9 mix). Small elevations in the SCE frequencies were found and even though statistically significant may have no biological meaning, the more so since there was no dose-effect relationship. Permethrin induced both MN and CA when it was evaluated in the absence of a metabolic activation system. Nevertheless, it cannot be said that S9 mix suppressed the activity in itself. The effect of permethrin seemed to be time of exposure dependent. Permethrin could be characterized as a S-phase independent agent with greater potential for inducing chromosomal damage than sister chromatid exchanges.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1474919&dopt=Abstract permethrin Elimite



Elimite
Laboratory and field trials of permethrin-treated cotton used as nesting material to control fleas (Insecta: Siphonaptera) on cricetid rodents.

Beard ML, Maupin GO, Craven RB, Montman CE, Barnes AM.

Bacterial Zoonoses Branch, U.S. Department of Health and Human Services, Fort Collins, Colo. 80522.

Upholstery cotton treated with four different concentrations (0.25-2.0%) (2,500-20,000 ppm) of an aqueous permethrin solution, used as nesting material by white mice, was laboratory-tested against the potential plague vectors Oropsylla montana (Baker), Thrassis bacchi (Rothschild), and Orchopeas howardi (Baker) and found highly effective (P less than 0.001) for 1 yr. Similarly treated cotton gauze was tested under ambient and 75% RH and was found to be highly effective (P less than 0.001) in both environments for 1 yr. A separate test determined that the LD50 of permethrin-treated cotton was less than 10 ppm. Cotton tested with 0.5% permethrin and distributed under field conditions to cricetid rodents for use as nesting material was found to be highly effective (P less than 0.001 as a pulicide for greater than 4 mo when tested during winter in Larimer County, Colo. Permethrin-treated cotton was less successful in controlling fleas on cricetid rodents during the summer months in a New Mexico hyperendemic plague area.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1495054&dopt=Abstract permethrin Elimite



Elimite
Permethrin transfer from treated cloth to the skin surface: potential for exposure in humans.

Snodgrass HL.

Toxicology Division, U.S. Army Environmental Hygiene Agency, Aberdeen Proving Ground, MD 21010-5422.

Permethrin is an agricultural insecticide of great interest to the military because of its repellency toward disease-bearing insects when impregnated into uniforms. However, migration of the substance from clothing to the skin surface is of toxicological importance. To quantitate leaching from treated clothing, studies were performed in which swatches of fabric impregnated with 14C-labeled permethrin were applied to the backs of rabbits for 1 wk. Permethrin migration was quantitated by measuring the fate of the 14C label. Conditions that could affect leaching and/or absorption were also evaluated, that is, varying environments, the presence of sweat, different fabric types, and the effects of prelaundering. Results showed that fabric treated with permethrin at a rate of 0.125 mg/cm2 lost the substance to the skin surface at an average rate of 0.49%/d. At the end of the 7-d exposures in rabbits, about 3.2% of the available permethrin had reached the skin, 2% having been recovered from excreta (absorbed) and 1.2% remaining on the skin surface. Prelaundering the treated fabric had little effect on migration rate, nor did the other variables tested. Exposure dose to humans from wearing permethrin-treated (0.125 mg/cm2) military clothing is predicted to be 6 x 10(-4) mg/kg/d.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1542137&dopt=Abstract permethrin Elimite



Elimite
Permethrin and dimethyl phthalate as tent fabric treatments against Aedes aegypti.

Schreck CE.

U.S. Department of Agriculture, Medical and Veterinary Entomology Research Laboratory, Gainesville, FL 32604.

Tests were conducted to determine the persistence of compounds applied to tents to protect against mosquitoes. Interiors of 2 camping tents were treated by the manufacturer--one with the repellent dimethyl phthalate (DMP) and one with the insecticide permethrin. A third tent was untreated. Tents were set up outdoors and exposed to weathering for one year. Weekly tests were conducted by releasing Aedes aegypti into the tents, then recording knockdown (KD) and biting behavior during a 3-h period. Weather data were collected 24 h/day during the study. Year-long mean KD of mosquitoes exposed in the tent to permethrin was 58.6%, to DMP 2.7% and the control 0.9%. Mean biting was 11.9, 43.8 and 58%, respectively. Under constant exposure to weathering, the permethrin-treated tent gave best results with average protection from bites greater than 96% for 9 months (DMP was less than 31%). Although preliminary, the data suggest permethrin would be effective as a tent treatment to reduce annoyance of mosquitoes.

Online source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1787396&dopt=Abstract permethrin Elimite