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A 3 1/2-year-old girl had a Pthirus pubis infestation of the scalp, neck, eyelashes, back, and pubic area. The child's body, including the scalp, was treated with a 1% permethrin cream rinse formulation for 10 minutes. The treatment was repeated after 10 days. The eyelashes were treated by application of the permethrin solution with a cotton-tip swab.
The recommendation to use personal protection measures (PPMs) to prevent arthropod-related diseases and nuisance bites is a common element of travel medicine consultation.1-3 Prevention of arthropod-related casualties is especially important to the military, given the often intense exposure of service members to biting arthropods and the threat of personnel losses to mission success. In the 1980s, 75% deet (N,N-diethyl-m-toluamide) was the US military-issue insect repellent for use on skin and clothing. Collaboration between military and civilian researchers led to the implementation in 1991 of the current US military system of PPMs which has three components: topical application of 33% extended-duration deet, treatment of field uniforms with permethrin, and proper wearing of field uniforms.4-6 Compared to military-issue 75% topical deet, 33% extended-duration deet prevents bites up to three times longer (as long as 12 hours), is less greasy, and has lower plasticizing properties. Field uniforms treated with the contact toxicant, permethrin, are also necessary to minimize bites from crawling arthropods such as ticks and chiggers. Implementation of all three components of this system is a safe and effective means of reducing the threat posed by biting arthropods.7 We conducted a questionnaire survey to assess the degree of deployed soldiers' knowledge of the US military's system of PPMs and use of PPMs in general. Survey results may promote the development of better ways to advise and teach military and civilian travelers about the proper use of PPMs given the multitude of available products and practices.
Pyrethroid insecticides are among the most commonly used classes of insecticides worldwide, but their endocrine disrupting activities remain unclear. Therefore, in the present study, we examined the estrogenic activities of pyrethroid insecticides in E-screen and competition binding assays. In addition, we measured estrogen receptor (ER) protein and pS2 mRNA levels in human breast cancer cells (MCF-7 BUS) to clarify the mechanism of their estrogenicity. Seven pyrethroid insecticides (bioallethrine, cypermethrin, deltamethrin, fenvalerate, permethrin, sumithrin, and tetramethrin) were tested because of their worldwide usage. In addition, 17beta-estradiol was tested as a positive control. As expected, 17beta-estradiol significantly increased MCF-7 BUS cell proliferation at concentrations of 10(-11) M and above. Of the pyrethroid insecticides tested, only sumithrin increased MCF-7 BUS cell proliferation in a dose-dependent manner; the maximum induction of cell proliferation was observed at a dose of 10(-5) M. In the anti-estrogenic activity test, bioallethrin, fenvalerate, and permethrin significantly inhibited 17beta-estradiol-induced MCF-7 BUS cell proliferation at 10(-6) M, a concentration comparable to the effective dose (10(-9) M) of ICI 182,780, a pure ER antagonist. However, none of the pyrethroid insecticides competitively inhibited the binding of [(3)H]estradiol to rat uterus ERs in competition binding assays. Both 17beta-estradiol (10(-10) M) and sumithrin (10(-5) M) decreased the levels of cytosolic ERalpha and ERbeta protein expression significantly as compared with the vehicle control. In addition, 17beta-estradiol (10(-10) M) increased pS2 mRNA expression markedly, and sumithrin significantly increased pS2 mRNA levels in a dose-dependent manner. The other six compounds tested in the present study did not affect ER protein levels or pS2 mRNA levels. These results suggest that certain pyrethroid insecticides may be considered to be estrogen-like chemicals that act through pathways other than direct ER binding, and may function as endocrine modulators in both wildlife and humans.
OBJECTIVES: The theoretical maximum intake values of pesticides by body weight (TMI) were estimated for school children and the differences in district and age-group were compared. Furthermore TMI values for children (7-11 years old) were calculated from Japanese National Nutrition Survey (NNS) data. Our TMI values for school children were compared with those from NNS data and evaluated to assess whether our values were appropriate for use in the calculation of theoretical maximum of daily intake (TMDI) of the pesticides. METHODS: The TMI values of pesticides for children were estimated using the intake amounts of agricultural products calculated from school lunch data in three elementary school districts (in Hyogo, Tokyo and Yamagata prefectures) and the survey of data from meals at home. Furthermore, TMI values for children (7-11 years old) were estimated from NNS data relating to agricultural products intake. Target pesticides for TMI calculations were chlorpyrifos, cyhalothrin, fenbutatin oxide, malathion, meltribuzin, oxamyl, permethrin and vamidothion. RESULTS: TMI of malathion from school lunch data corresponded to 58% of ADI and was too large for exposure from one meal in comparison to other pesticides (8-24%). Our estimations of TMI of chlorpyrifos, cyhalothrin, oxamyl and vamidothion in the school lunches were smaller than those from the NNS data. However TMI of malathion calculated from the school lunch data was larger than that from the NNS data. TMI of fenbutatin oxide, meltribuzin and permethrin from the school lunch data were similar to those from the NNS data. CONCLUSIONS: The TMI values for children in three districts depended upon the agricultural products used in school lunches. Even though the survey methods differed between the NNS's and our data, the TMI values closely corresponded. We concluded that the school lunch data might compensate for the lack of NNS data in order to estimate more appropriate TMDI for children's ingestion of agricultural products.
To investigate genetic variation and seasonal fluctuation in susceptibility to insecticides, natural populations of Drosophila melanogaster were collected from Katsunuma in mid summer and late fall for two consecutive years. After isofemale lines of each population collected in each season had been established in a laboratory, the susceptibility of each line to five insecticides, including permethrin, malathion, prothiophos, fenitrothion, and DDT, was examined. Lines of each population exhibited the broad ranges of variation in susceptibility to all chemicals. Comparison between populations in different seasons indicated that genetic variation in susceptibility to organophosphates fluctuated in consistency with the population size, in which the susceptibility increased in fall. In addition, highly significant correlations were observed among responses to organophosphates, and the correlations also fluctuated with seasons. On the other hand, genetic variation in susceptibility to permethrin and DDT was less fluctuated. These results suggest that not only a common resistance factor for organophosphate resistance but also different resistance factor(s) for each insecticide could be involved within a natural population, and that the fluctuation observed in the susceptibility to organophosphates could be associated with fitness costs of organophosphate resistance factor(s).
BACKGROUND: We previously reported widespread insecticide exposure during pregnancy among inner-city women from New York City. Here we report on a pilot intervention using integrated pest management (IPM) to reduce pest infestations and residential insecticide exposures among pregnant New York City African-American and Latina women (25 intervention and 27 control homes). METHODS: The IPM consisted of professional cleaning, sealing of pest entry points, application of low-toxicity pesticides, and education. Cockroach infestation levels and 2-week integrated indoor air samples were collected at baseline and one month postintervention. The insecticides detected in the indoor air samples were also measured in maternal and umbilical cord blood collected at delivery. RESULTS: Cockroach infestations decreased significantly (p = 0.016) after the intervention among intervention cases but not control households. Among the intervention group, levels of piperonyl butoxide (a pyrethroid synergist) were significantly lower in indoor air samples after the intervention (p = 0.016). Insecticides were detected in maternal blood samples collected at delivery from controls but not from the intervention group. The difference was significant for trans-permethrin (p = 0.008) and of borderline significance (p = 0.1) for cis-permethrin and 2-isopropoxyphenol (a propoxur metabolite). CONCLUSION: To our knowledge, this is the first study to use biologic dosimeters of prenatal pesticide exposure for assessing effectiveness of IPM. These pilot data suggest that IPM is an effective strategy for reducing pest infestation levels and the internal dose of insecticides during pregnancy.
Verandah trap huts in a Tanzanian village were used to assess the effectiveness of impregnated bednets and curtains in preventing hut entry and feeding by, and in killing of, Anopheles gambiae and An. funestus. Permethrin, deltamethrin, lambdacyhalothrin and pyrethrum were used for impregnation of damaged or undamaged bednets, sisal eaves curtains or bed curtains made of polypropylene fibre. The performance of the three synthetic pyrethroids did not differ statistically significantly, except that on a damaged net permethrin was better at preventing feeding. Sisal eaves curtains deterred mosquitoes from hut entry but did not kill those that had entered. In assessing damaged nets and curtains it must be recognised that anything less than the best vector control may have no appreciable impact on holoendemic malaria.
Twelve families, 26 genera, and 30 identifiable spider species were found in surveys conducted in apple orchards of western Oregon. The Salticidae, Linyphiidae, Clubionidae, Philodromidae, and Theridiidae comprised 85.56% ofthe total spiders collected. The most common species in order of abundance were Metaphidippus aeneolus Curtis, Spirembolus mundus Chamberlin & Ivie, Cheiracanthium inclusum (Hentz), Philodromus spectabilis Keyserling, Eris marginata (Walckenaer), and Theridion lawrencei Gertsch & Archer. Individuals of these species were collected in 50-60% of the samples and were most abundant in the month of August. The Bacillus thuringiensis-based insecticides, DiPel (100 Million International Units/100 liters) and MVP (250 ml/100 liters), summer oil (0.5-1.0 liter/100 liters), the insect growth regulator (IGR) diflubenzuron (3-12 g/100 liters), and organophosphate Phosmet (6-60 g/100 liters) were generally harmless (P > 0.05) to these spider species. Full field rates of organophosphate azinphosmethyl (25 g/100 liters) and carbamate carbaryl (60 g/100 liters) were slightly to moderately harmful (25-75% mortality). These insecticides at reduced rates (azinphosmethyl 2.5-5.0 g and carbaryl 12 g/100 liters) applied alone or in combination with DiPel and MVP, had a negligible effect. Full rates of pyrethroids esfenvalerate (2.5 g/100 liters) and permethrin (4.0 g/100 liters) were moderately to highly harmful (50-75% mortality) and their reduced rates (esfenvalerate 0.25-0.50 g and permethrin 0.4-0.8 g/100 liters) were selective to the spiders.
Chemical analysis (high-performance liquid chromatography) and bioassay demonstrated the presence of compounds that seem to be components of the Ixodes scapularis arrestment pheromone. Only two purines, guanine and xanthine, were found in acidified saline extracts made from cast skins after molting of fed nymphs, fed larvae, and fecal/excretory exudates deposited by unfed adults on substrates in their environment. The ratio of guanine to xanthine was 10.6:1 in an extract from the nymphal skins versus 0.95:1 in an extract from the larval skins. Guanine, xanthine, and traces of a third purine, tentatively identified as 8-azaguanine, were found in extracts made from filter paper strips or washings from glass vials contaminated with tick feces and excreta left by unfed adults. 8-azaguanine may be a product of microbial degradation of the other purines rather than a natural product from the ticks. Low concentrations of ammonia also were detected in saline extracts of excreta from feeding ticks. Hematin also was found in NH4OH extracts of the black fecal/excretory exudates deposited by the unfed ticks. Hematin was tentatively identified by comparison of spectra with that of the authentic standard. Bioassays demonstrated a strong positive arrestment response to cast skins found to contain a mixture of guanine and xanthine and to black fecal/excretory exudates containing guanine, xanthine, the putative 8-azaguanine, and hematin. A Noldus video tracking system using a CCD video camera and Ethovision Pro tracking software showed statistically significant increases in the frequency of visits to the treated zone versus the control. Ticks were significantly more likely to assemble in response to the tick exudates within as little as 3 h compared with the controls. Previous bioassay studies also showed strong positive responses to guanine, xanthine, other purines, and hematin. Comparisons with the arrestment pheromones of other tick species are described. The inclusion of the pheromone components in a permethrin-impregnated oily matrix, Last Call, increased the lethal activity of the product to 95% compared with only 65% in the formulation with permethrin alone. More detailed knowledge of I. scapularis arrestment pheromone may be useful for improving the efficacy of this tick-killing technology even further.
Resistance management for insecticide-treated nets (ITNs) remains a challenge. Options are limited, because a safe and highly active insecticide with a persistence of several months is required. These criteria have only been met by pyrethroids, although organophosphates (OPs) and carbamates have been considered as alternatives for impregnation of eave curtains. It has been observed that some pyrethroid-resistant mosquito strains show increased OP susceptibility over pyrethroid-susceptible strains (i.e., negative cross-resistance). The current study investigated whether this phenomenon applies to a range of mosquito species and strains, because a mixture or rotation strategy for resistance management could then be envisaged. Adult female mosquitoes from laboratory strains of Anopheles stephensi Liston, Anopheles gambiae Giles, and Culex quinquefasciatus Say were tested in World Health Organization susceptibility test kits. For An. stephensi, the highly pyrethroid-resistant DUB 234 strain showed the same level of resistance to malathion as the pyrethroid-susceptible DUB S. The malathion-resistant ST MAL strain was as susceptible to pyrethroids as the insecticide-susceptible BEECH. For An. gambiae, the malathion tolerance of the previously pyrethroid-resistant RSP strain was significantly higher than that of the insecticide-susceptible KWA. For Cx. quinquefasciatus, selection of the QUINQ strain with permethrin abolished preexisting resistance to the OP malathion as pyrethroid resistance increased, rendering the strain more susceptible to malathion than PEL SS. Some indication of negative cross-resistance to malathion was found for the permethrin-resistant MUHEZA strain. The occurrence of negative cross-resistance seems dependent on the history of insecticide selection and is not generally applicable. Resistance management for ITNs will need to use mechanisms other than negative cross-resistance to be effective.
Runoff and surface-water effluents commonly contain suspended solids. Adsorption to suspended particles and the associated dissolved organic matter (DOM) may significantly decrease the freely dissolved concentration of a hydrophobic compound and, hence, its availability to aquatic organisms. In the present study, we evaluated phase distribution and bioaccumulation of two synthetic pyrethroids, bifenthrin and permethrin, in water samples containing suspended solids from different source sediments. Uptake of [14C]bifenthrin or [14C] permethrin by Daphnia magna after 24 h consistently decreased with increasing levels of suspended solids in the range of 0 to 200 mg/L. The trend of decrease was closely mimicked by pesticide accumulation on polydimethylsiloxane (PDMS) fibers exposed under the same conditions, and the ratio of body residues in D. magna to the concentration detected in the PDMS fiber was consistently around 2.4. Regression analysis showed that the pesticide adsorbed on particles or DOM was completely unavailable to D. magna for uptake during the 24-h exposure. The relative contribution of particles and DOM to the reduced bioavailability depended on the organic matter content and the texture of the source sediment. The influence from particles was predominant for sandy sediments, but contribution from DOM became comparable to or even greater than particles when the organic matter content of the source sediment was 1% or greater. The inhibitory effects of suspended solids on bioavailability should be considered when monitoring runoff and surface-water effluents for synthetic pyrethroids. The proposed PDMS method is simple and inexpensive, and it may serve as an effective option for obtaining ecotoxicologically relevant concentrations.
Permethrin is probably the most effective topical treatment for scabies. There is little microbial resistance to the drug, and it is highly effective. Toxicity is limited to occasional contact dermatitis. Similarly, oral ivermectin 200 micrograms/kg is extremely effective. Oral administration eliminates the need to be certain that medication has been applied properly. Toxicity has been very limited. It is not available in the US for human use in scabies at this time. The toxicity of most of other treatments that are available has not been studied carefully. Sulphur 6% in petrolatum is recommended as safe, but there are no good studies to confirm this. Sulphur is probably the medication of choice when cost is the overriding concern. Crotamiton and benzyl benzoate are probably safe, but are not as effective as permethrin. Lindane has some potential CNS toxicity if used incorrectly, and must be used carefully on damaged skin to avoid excessive absorption. It is important to stress that all household and sexual contacts must be treated, whether or not they have symptoms. Proper application of topical medications must be achieved, including under the fingernails, and up to the edge of all body orifices.
Dermal penetration of 14C-labeled carbaryl, parathion, DDT, dieldrin and permethrin was compared in American roaches, tobacco hornworms, Japanese quail, grass frogs and mice. Insecticides were absorbed more quickly in mice (one exception) while entry into insects was generally slow. The half time penetration rates for carbaryl ranged from 6 min for frogs to 4600 min for roaches. Whereas permethrin penetrated easily into insects, other insecticides showed generally slower penetration into target organisms. Carbaryl tended to penetrate most rapidly in all species except roaches, while DDT and dieldrin tended to penetrate slowly in all organisms tested. Distribution of insecticides in the blood and liver of Japanese quail and grass frogs was surprisingly low. Insect species tended to show higher amounts in hemolymph than most other species. Excretion of radioactivity was relatively low in the frog in these experiments but was high in the quail for rapidly-metabolized compounds.
A clinical study was performed in 21 dogs to evaluate the efficacy of selamectin for the treatment of naturally acquired infection of sucking lice (Linognathus setosus [L.setosus]) in dogs. Each dog was randomly assigned to one of two treatment groups. One group was treated with selamectin applied topically at a mean dosage of 7.9 mg/kg. The other group was treated with permethrin applied topically at a mean dosage of 85.7 mg/kg. At day 42 posttreatment, all animals remaining in the study (10 treated with selamectin and six with permethrin) were clear of lice. In both groups, the reduction in lice counts from pretreatment values to day 42 was statistically significant at P< or =0.0001. Selamectin applied topically appeared to be effective against L. setosus infection in dogs.
Five organophosphates (OPs) (chlorpyrifos, chlorpyrifos methyl, fenthion, malathion, and temephos), 3 pyrethroids (bifenthrin, cypermethrin, and permethrin), 1 phenyl pyrazole (fipronil), 2 microbial pesticides (Bacillus thuringiensis serovar. israelensis [B.t.i.] and Bacillus sphaericus), and 3 insect growth regulators (IGRs) (diflubenzuron, methoprene, and pyriproxyfen) were evaluated against field-collected Culex quinquefasciatus larvae from urban Dhaka, Bangladesh. The LC90 values of all OPs, except for temephos (LC90 = 0.0096 ppm), were high, ranging from 0.13 ppm (fenthion) to 2.882 ppm (chlorpyrifos methyl). Pyrethroid LC90 values were 0.021 ppm (bifenthrin), 0.00061 (cypermethrin), and 0.017 ppm (permethrin). Fipronil exhibited a superior activity with LC90 value of 0.000896 ppm. Technical powders of B.t.i. and B. sphaericus (VectoBac TP and VectoLex TP) were considered highly effective against the Cx. quinquefasciatus larvae. The IGRs also were effective with pyriproxyfen (LC90 = 0.0011 ppm), being 3 times and 47 times more active than diflubenzuron (LC90 = 0.0034 ppm) and methoprene (LC90 = 0.052 ppm), respectively. In general, toxicity ranking of chemicals and microbials tested was phenyl pyrazole > IGRs > pyrethroids > microbials > OPs.
A study was conducted to compare responses of male and female Aedes aegypti (Linn.) and Aedes taeniorhynchus (Wiedemann) to 9 olfactory repellents in the World Health Organization insecticide irritability test system. An irritant insecticide (permethrin) and a control were included for comparison. Aedes aegypti exhibited significantly more takeoffs than Ae. taeniorhynchus, and female mosquitoes exhibited significantly more takeoffs than males. Permethrin induced significantly more takeoffs than the control, but olfactory repellents did not. Certain 2- and 3-factor interactions of test materials, species, and sexes were statistically significant. This study supports a previous conclusion that the World Health Organization test method does not measure contact repellency (irritancy) and olfactory repellency equally.
A collection of Aedes aegypti from Tortola, British Virgin Islands, with a high level of temephos resistance (46.8-fold at the 95% lethal concentration [LC95]) was selected to higher resistance with temephos in the laboratory. After 13 generations of pressure, the temephos resistance ratio increased to 180.6 (LC95), whereas in the absence of selection pressure the resistance ratio declined to 8.5. Relatively low levels of resistance or cross-resistance to other organophosphate and carbamate insecticides, and a high level of resistance to the pyrethroid permethrin were also observed. Synergism tests implicated detoxifying esterases in temephos resistance and the presence of elevated esterase activity was confirmed by biochemical tests; however, no evidence was found of insensitive acetylcholinesterase. Mendelian crosses indicated that temephos resistance was inherited as a monofactorial trait. The presence of high levels of temephos and permethrin resistance in Ae. aegypti has important implications for Aedes control programs.
OBJECTIVE: The research was to survey potential dermal exposure and inhalation exposure of operators to preservative fluids used in industrial timber pre-treatment. RESULTS: Surveys in 1996-98 produced 64 data points. These were taken from 54 sites, and involved 57 timber pre-treatment process operators. Of the data, 38 related to copper chromium arsenic preservative used in vacuum-pressure processes, 19 to solvent-based preservative in double vacuum processes and 7 to water-based preservative in double vacuum processes. Treatment cycle times, preservative concentrations, treatment load sizes and quantities of preservative used per cubic metre of timber are reported. Preservative deposition patterns were similar for all treatments, with about 90% on the legs, and most of the remainder on the arms and chest. The results are quoted as mg preservative preparation (as opposed to active substance), expressed as mg per treatment cycle and mg per minute. Water-based products in vacuum-pressure processes (38 data) showed potential dermal exposure in the range 547-132,000 mg per cycle with a median value 3960 mg per cycle (median cycle time 3 h). Water-based products in double vacuum processes (7 data) showed a range 59-8750 mg per cycle with a median value 4260 mg per cycle; and solvent-based products in double vacuum processes (19 data) showed a range 7.5-449 mg per cycle with a median value 119 mg per cycle (median cycle time 1 h for double-vacuum processes). Contamination of work clothing occurred in nearly all surveys, with around 10% penetration of the preservative as estimated by a sampling patch mounted inside the operator's coveralls. Contamination was measured inside the operator's gloves in nearly all surveys. Wearing fresh gloves was found to reduce exposure to arsenic by 71% and to permethrin by 37%. Contamination on socks was measured and found to be less frequent for double vacuum than for vacuum-pressure processes. Exposure by inhalation for vacuum-pressure processes expressed as preservative, showed a range of 0.06-7.96 mg/m3, with a median value of 1.07 mg/m3, time-weighted average exposure over one or two treatment cycles. Exposure was detected in 68% of the vacuum-pressure process surveys. There was evidence for aerosol generation on transporting timber treated with water-based preservative. For double vacuum processes, two non-zero results only were found, both for water-based preservatives. Aerosols within treatment vessels were found to have dispersed 2.5 min after opening the door. Pilotstudy biological monitoring data for urinary chromium, arsenic, and permethrin metabolites are quoted with reference to creatinine. There are tentative conclusions relating to up take via the skin.