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PubMed2006

Pyrethroid insecticides: advances and challenges in biomonitoring.

Pyrethroid insecticides have a wide variety of applications throughout the world. They are structurally diverse chemicals that are synthetically derived from naturally occurring pyrethrin insecticides. Significant advances in analytical chemistry have led to the development of biomarkers of exposure to pyrethroids, and these methods are currently being applied to study exposure in the general population. This article reviews the chemistry and toxicology of pyrethroid insecticides, with an emphasis on the development of biomarkers to assess environmental exposure. Future challenges in the application of these biomarkers in epidemiological studies are explored, as is a need for improved understanding of the toxicokinetics of pyrethroids in humans.

Biomarkers↗
PubMed2002

Acute ingestion poisoning with insecticide formulations containing the pyrethroid permethrin, xylene, and surfactant: a review of 48 cases.

BACKGROUND: Forty-eight patients poisoned with insecticide formulations containing permethrin (a Type I pyrethroid insecticide), xylene, and surfactants are reported here. These patients were diagnosed and treated in the Chang Gung Memorial Hospital in Taiwan from January 1987 to June 1999. Ten patients ingested permethrin in error and 38 patients attempted suicide. Gastrointestinal tract signs and symptoms were most common (35/48; 73%), and included sore throat, mouth ulcerations, dysphagia, epigastric pain, and vomiting. Pulmonary abnormalities were documented in 29% (14/48) of patients. Aspiration pneumonitis occurred in eight patients, including onefatal case. Pulmonary edema was observed in two patients. Sixteen patients (33%) had central nervous system involvement including confusion (6/48; 13%), coma (10/48; 21%), and seizures (4/48; 8%). Cardiovascular symptoms in 3/48 (7%) patients were limited to arrhythmias and shock. Mild renal and hepatic dysfunction was found in 5/48 (10%) and 3/48 (6%) of patients, respectively. Leukocytosis occurred in 16 patients (33%) but was not associated with infection. Only one death occurred during this 12.5-year period. CONCLUSION: Poisoning caused by ingesting insecticides containing permethrin, xylene, and surfactant manifests primarily gastrointestinal tract symptoms and signs. The involvement of the central nervous system and lungs were less common, but clinically more significant. The relative contributions of the 20% permethrin, 70% xylene, and 10% surfactant to these toxic manifestations, however, is uncharacterized.

Adult↗
PubMed1989

Monitoring for insecticide resistance in field-collected strains of the German cockroach (Dictyoptera: Blattellidae).

Forty-five field-collected strains of German cockroaches, Blattella germanica were tested for resistance to 12 different insecticides by the time-mortality response method in comparison with a known susceptible strain. Only low to moderate resistance to diazinon, chlorpyrifos, and acephate was detected. Resistance to malathion was widespread; about half of the strains tested showed high resistance. High resistance to the carbamates propoxur and bendiocarb also occurred. High resistance was uncommon with propoxur, but about 35 strains were highly resistant to bendiocarb. High resistance to pyrethrins was observed in about of the strains tested. Resistance to the pyrethroids allethrin, permethrin, phenothrin, fenvalerate, and cyfluthrin was detected in some of the strains examined. All of the strains tested were susceptible to one or more of the insecticides used. These results indicate that, although resistance is a serious problem in this species, satisfactory control should be possible by selection of an appropriate insecticide.

Animals↗
PubMed1990

Quantitative genetic tools for insecticide resistance risk assessment: estimating the heritability of resistance.

Quantitative genetic studies of resistance can provide estimates of genetic parameters not available with other types of genetic analyses. Three methods are discussed for estimating the amount of additive genetic variation in resistance to individual insecticides and subsequent estimation of the heritability (h2) of resistance. Sibling analysis and offspring-parent regression permit direct estimates of h2 by comparing the resistance phenotypes of individuals of known relatedness. Threshold trait analyses, performed on data from selection experiments, provide estimates of realized heritability. Procedures are outlined for predicting changes in resistance to insecticides based on h2 estimates. Quantitative genetic theory is examined as it relates to resistance and resistance as a quantitative trait; quantitative genetic methods also are unique in providing estimates of genetic correlations between traits. Comments are included on estimates of genetic correlation between resistance and phenotypic traits (e.g., development time) and how they may be used to predict changes in the genetic aspects of phenology that result from insecticide applications (i.e., to predict how the reproductive capacity of future generations will differ from that of the treated generation).

Analysis of Variance↗
PubMed1991

Dot-blot test for identification of insecticide-resistant acetylcholinesterase in single insects.

A test was developed to detect the presence of insecticide-resistant acetylcholinesterase (AChE) in single insects based on the quasipermanent binding of proteins onto blotting membranes. The method is simple, sensitive, requires inexpensive equipment, and produces a permanent record of results. AChE activity is revealed by the Karnovsky & Roots staining technique in the presence of propoxur, or after exposure of the membrane to paraoxon and rinsing with water. We chose insecticide concentrations that inhibited the sensitive AChE while allowing detectable residual activity of the resistant AChE to remain. By comparing the staining of insecticide-treated and control membranes, susceptible and resistant genotypes for the AChE gene could be distinguished in laboratory strains of mosquitoes (Culex spp. and Anopheles albimanus Wiedemann) and the house fly (Musca domestica L.). Resistant AChE from mosquitoes was less susceptible both to propoxur and paraoxon than the corresponding sensitive AChE, whereas resistant AChE from house fly was less susceptible mainly to paraoxon. The technique worked well for mosquito adults and house fly heads but not for mosquito larvae. Blotted AChE did not show detectable loss of activity during storage of the membranes for 3 wk at 25 degrees C. Storage is an important asset of the technique because transportation of live insect material to the laboratory may not be necessary.

Acetylcholinesterase↗
PubMed1991

Comparative toxicity of seven insecticides to immature stages of Musca domestica (Diptera: Muscidae) and two of its important biological control agents, Muscidifurax raptor and Spalangia cameroni (Hymenoptera: Pteromalidae).

The toxicity of seven insecticides was evaluated against unparasitized Musca domestica L. pupae and pupae parasitized by Muscidifurax raptor Girault & Sanders or Spalangia cameroni Perkins, two important biological control agents. Only pyrethrins + piperonyl butoxide (Pyrenone) was less toxic to M. raptor compared with house flies. Conversely, all of the insecticides except crotoxyphos were less toxic to S. cameroni compared with house flies. A plateau in the tetrachlorvinphos bioassay line for S. cameroni suggested that this colony had approximately 45% resistant individuals. The selectivity observed between immature stages of house flies and M. raptor or S. cameroni is different from that reported against adult stages of these same species, suggesting that selectivity of an insecticide varies considerably between different life stages.

Animals↗
PubMed1994

Efficacy of Brahman breeding in the management of insecticide-resistant horn flies (Diptera: Muscidae) on beef cattle.

The efficacy of Brahman breeding used as an alternative tactic to manage insecticide-resistant populations of adult horn flies, Haematobia irritans irritans (L.), was determined. Concentration-mortality bioassays done at Booneville and Hope, AR, in 1988 and 1989, respectively, showed that horn fly populations were resistant to diazinon, pirimiphos methyl, tetrachlorvinphos, and methoxychlor. Data showed loss of field efficacy for coumaphos and delnav. Mean horn fly counts on Braham cows were significantly lower than on Angus cows for all sampling dates in 1989 and 1990. Mean fly counts on Brahman x Angus cows were approximately intermediate to the two purebred mean fly counts. Brahman breeding caused significant reductions in the number of organophosphate-resistant horn flies, which had been equal to or greater than that obtained from continued spraying with organophosphate insecticides. The Brahman x Hereford cows, which have one-eighth greater Brahman breeding than the Brangus cows, had fewer horn flies on 48 of 56 sampling dates in 1988-1990 and significantly fewer flies on 37 sampling dates. The effectiveness of Brahman breeding in causing lower numbers of insecticide-resistant horn flies significantly increased as the percentage of Brahman breeding increased.

Animals↗
PubMed1996

Insecticide susceptibility of cat flea (Siphonaptera: Pulicidae) pupae.

Studies were conducted to investigate what protective nature the cocoon and nylon carpeting has against the performance of insecticides directed at cat flea, Ctenocephalides felis (Bouché), pupae developing in carpet. The following 5 combinations of life stages and substrates were used in these tests were: (1) larvae that pupated in carpet, (2) cocoons placed in carpet, (3) naked pupae placed in carpet, (4) cocoons placed on filter paper, and (5) naked pupae placed on filter paper. These studies evaluated the performance of chlorpyrifos, microencapsulated chlorpyrifos, propetamphos, permethrin, and linalool. When averaged over all insecticides, the mean controls of cocooned pupae placed in carpet and cocooned pupae placed on filter paper were 37.2 and 26.7%, respectively, whereas that of naked pupae placed in carpet was only 13.7%. Additional tests conducted using chlorpyrifos revealed that mortality was 23 and 42% higher, respectively, whenever pupae in cocoons and naked pupae were treated in glass dishes without filter paper. These studies demonstrate that the debri-coated cocoon is not a barrier to insecticide penetration, and that pupae appeared to be protected inside the carpet matrix. Additional studies demonstrated that control of pupae developing in carpet was maximized at lower application pressures. The mean control of pupae with chlorpyrifos at 0.7 kg/cm2 pressure was 77.2%, yet applications at 1.7 kg/cm2 resulted in only 23.3% control.

Animals↗
PubMed1998

Interaction of insecticides, entomopathogenic nematodes, and larvae of the western corn rootworm (Coleoptera: Chrysomelidae).

Chemical insecticides and entomopathogenic nematodes have been independently used to suppress corn rootworm damage in maize. We report on the mortality response of larvae of the western corn rootworm, Diabrotica virgifera virgifera LeConte, to the combined treatment with 1 of 3 insecticides (terbufos, fonofos, and tefluthrin) and the entomopathogenic nematode Steinernema carpocapsae Weiser (Mexican strain). Corn rootworm mortality with combinations of the insecticides terbufos or fonofos and S. carpocapsae was typically additive for the 2 agents. Evidence of antagonism between these agents was sometimes observed. The combination of tefluthrin with S. carpocapsae frequently resulted in a synergistic response and a 24% average increase in expected mortality. The influence of the tefluthrin appears to be isolated to an effect on the rootworm larvae. Synergism also was observed when tefluthrin was combined with the nematode Heterorhabditis bacteriophora Poinar (Lewiston strain). The combined use of tefluthrin with an entomopathogenic nematode may offer an integrated approach to increase the efficacy of entomopathogenic nematodes for insect control.

Animals↗
PubMed2003

Emergence of adult northern and western corn rootworms (Coleoptera: Chrysomelidae) following reduced soil insecticide applications.

A 3-yr investigation was conducted in commercial corn, Zea mays (L.), fields in eastern South Dakota to determine how reduced application rates of planting-time soil insecticides would influence temporal emergence patterns and survival of northern and western corn rootworms, Diabrotica barberi Smith and Lawrence, and D. virgifera virgifera LeConte, respectively. Beetle emergence was monitored at 2-d intervals throughout the entire adult emergence period of three growing seasons from corn plots treated with planting-time applications of labeled (1X) and reduced (0.5 and 0.75X) application rates of terbufos, tefluthrin, and chlorethoxyfos. No consistent insecticide- or rate-related impacts on mean total emergence per trap were recorded for any of the compounds investigated. However, terbufos applications resulted in a 52% reduction in the number of beetles captured per trap, 53% reduction in maximum rate of adult emergence, and a 59% reduction in overall rate of emergence over time for male D. virgifera during 1994. Terbufos also significantly extended the time required for emergence to peak and linear emergence of female D. virgifera to end in 1994. Tefluthrin applications delayed onset, end, and time of maximum emergence of female D. barberi by 9.9, 14.1, and 12 d, respectively, during 1993. Tefluthrin also reduced emergence rates over time for male (38%) and female (46%) D. barberi during 1994. Overall, application rate was inconsequential regarding total emergence, seasonal emergence pattern, or level of plant protection provided for all insecticides we tested in this 3-yr investigation. Our findings demonstrate that, if properly applied, the reduced application rates used in this study provide adequate root protection and will not significantly impact the biology of these pest species.

Animals↗
PubMed2003

Field and laboratory tests of new insecticides against the apple maggot, Rhagoletis pomonella (Walsh) (Diptera: Tephritidae).

Laboratory bioassays and field tests were conducted to compare the effectiveness of the new insecticides, imidacloprid, indoxacarb, pyriproxyfen, spinosad, thiacloprid, and thiamethoxam, against apple maggot. The activity ranking of the compounds in reducing oviposition in laboratory bioassays was: imidacloprid, 95% reduction at 11 ppm > thiamethoxam, 91% and thiacloprid, 89% reduction at 100 ppm > spinosad, 98% reduction at 316 ppm > indoxacarb, 80% reduction at 1000 ppm > pyriproxyfen, 0% reduction at 38 ppm. In laboratory bioassays, the only insecticides that were toxic to flies at concentrations equal to or below the recommended field rates were imidacloprid, (50% of flies at 11 ppm), spinosad (90% of flies at rates > 10 ppm), and thiamethoxam (approximately 50% of flies at 32 ppm). In field trials, thiacloprid was the only material that consistently controlled apple maggot fruit infestation that was comparable to standard treatments of organophosphate insecticides. Spinosad applied at weekly intervals, and indoxacarb applied as biweekly sprays provided adequate control of apple maggot damage when infestation levels in the field were low, but were not effective in preventing damage in small plots when apple maggot pressure was high.

Animals↗
PubMed2004

Contact and leaf residue activity of insecticides against the sweet Corn pest Euxesta stigmatias (Diptera: Otitidae).

Damage by Euxesta stigmatias Loew larvae to sweet corn renders the ears unmarketable. This report evaluates the efficacy of insecticides labeled for armyworm control in Florida sweet corn against E. stigmatias adults. Tests were performed in controlled settings by using direct contact and dried plant residues of esfenvalerate, cyfluthrin, lambda-cyhalothrin, chlorpyrifos, methyl parathion, methomyl, and thiodicarb. Direct application of all insecticides except thiodicarb quickly killed or caused incapacitating sublethal affects (uncoordinated movement, uncontrolled twitching, and hyperextension of mouthparts and ovipositor) to > 75% of the flies. Low rates (0.56 kg [AI]/ha) of chlorpyrifos and methyl parathion provided the most efficient control, killing 100 and 93%, respectively, within 2 h of direct contact. Low rates of pyrethroids induced low mortality but high sublethal effects that together immobilized nearly 100% of adults within 1 h of exposure. Mortality reached 95% within 2 h of direct contact in flies treated with high rates of pyrethroids. Methomyl killed as many as 94%, but required 24 h to reach this level after direct treatment. Residues on dipped leaves and field-treated plants of all tested insecticides except methyl parathion were less effective at killing adults compared with direct contact tests. Pyrethroid residues (particularly cyfluthrin) on field planted sweet corn induced significantly higher levels of sublethal effects (57-70%), and for a longer period of time, compared with materials in the other classes of chemistry.

Animals↗
PubMed2005

Insecticidal effect of NeemAzal against three stored-product beetle species on rye and oats.

The insecticidal effect of the azadirachtin-based insecticide, NeemAzal, was examined against adults of Rhyzopertha dominica (F.), Sitophilus oryzae (L.), and Tribolium confusum Jacquelin du Val in rye, whole oats, and peeled oats. The insecticide was applied at three dose rates, which were equivalent to 50, 100, and 200 ppm of azadirachtin A. Adults of the above-mentioned species were exposed to the treated grains at 25 degrees C and 65% RH, and mortality was assessed after 24 h, 48 h, 7 d, and 14 d of exposure. Then, all adults were removed, and the treated substrate remained at the same conditions for an additional 45 d. After this interval, the grains were checked for progeny production. In all species and commodities tested, mortality increased with the increase of dose and exposure interval, except for T. confusum on whole and peeled oats. For R. dominica, NeemAzal was more effective on oats than on rye and peeled oats. In contrast, at rates > or = 100 ppm, azadirachtin was equally effective against S. oryzae on whole rye and oats, where mortality was 100% after 7 and 14 d of exposure, respectively. NeemAzal was not very effective against T. confusum where adult mortality was low, even after 14 d of exposure at the highest rate. For all species, significantly less progeny were recorded in the treated grains than in the untreated grains, with the exception of T. confusum on oats where offspring was significantly reduced only at the highest rate.

Animals↗
PubMed2000

Integration of repellents, attractants, and insecticides in a "push-pull" strategy for managing German cockroach (Dictyoptera: Blattellidae) populations.

"Push-pull" is a behavior manipulation strategy in which behavior-modifying stimuli are integrated with a pest control agent. We evaluated the efficacy of an insecticide bait in combination with attractants ("pull"), repellents ("push"), or both ("push-pull") using a hydramethylnon-based bait, feces-contaminated surfaces as an attractant, and methyl neodecanamide-treated surfaces to repel cockroaches. Both adult males and first-instar German cockroaches, Blattella germanica (L.), chose shelters nearest the attractant-treated surfaces and farthest from the repellent-treated surfaces. Food consumption was highest from food nearest the preferred shelters, and mortality was highest when the insecticide bait was near the preferred shelter. These patterns were more apparent in first instars than in adults. Our results from large arena studies in the laboratory show that the push-pull strategy can be used to displace pests from resources or commodities that are to be protected, and simultaneously lure the pest to an attractant source coupled with a pest control agent. Concentrating cockroaches into a limited area should facilitate the precision-targeting of the pest population and promises to reduce insecticide use.

Animals↗
PubMed1986

Reye's syndrome and spruce budworm insecticide spraying in Maine, 1978-1982.

Studies have associated insecticides used for spruce budworm control with Reye's syndrome. In Maine, spruce budworm insecticide spraying began in 1954, and an annual spray program was started in 1972. Reye's syndrome incidence information (1978-1982), obtained from hospital discharge data, death certificates, and reports to the Bureau of Health, was compared with the geographic distribution of spruce budworm insecticide spraying. No association between Reye's syndrome and spruce budworm spraying was found, although some geographic clustering of Reye's syndrome cases was observed.

Aerosols↗
PubMed2005

Acetylcholinesterase/paraoxonase interactions increase the risk of insecticide-induced Parkinson's disease.

Exposure to agricultural insecticides, together with yet incompletely understood predisposing genotype/phenotype elements, notably increase the risk of Parkinson's disease. Here, we report findings attributing the increased risk in an insecticide-exposed rural area in Israel to interacting debilitating polymorphisms in the ACHE/PON1 locus and corresponding expression variations. Polymorphisms that debilitate PON1 activity and cause impaired AChE overproduction under anticholinesterase exposure were strongly overrepresented in patients from agriculturally exposed areas, indicating that they confer risk of Parkinson's disease. Supporting this notion, serum AChE and PON1 activities were both selectively and significantly lower in patients than in healthy individuals and in carriers of the risky polymorphisms as compared with other Parkinsonian patients. Our findings suggest that inherited interactive weakness of AChE and PON1 expression increases the insecticide-induced occurrence of Parkinson's disease.

Acetylcholinesterase↗
PubMed2005

Insect glutathione transferases and insecticide resistance.

Glutathione transferases (GSTs) are a diverse family of enzymes found ubiquitously in aerobic organisms. They play a central role in the detoxification of both endogenous and xenobiotic compounds and are also involved in intracellular transport, biosynthesis of hormones and protection against oxidative stress. Interest in insect GSTs has primarily focused on their role in insecticide resistance. GSTs can metabolize insecticides by facilitating their reductive dehydrochlorination or by conjugation reactions with reduced glutathione, to produce water-soluble metabolites that are more readily excreted. In addition, they contribute to the removal of toxic oxygen free radical species produced through the action of pesticides. Annotation of the Anopheles gambiae and Drosophila melanogaster genomes has revealed the full extent of this enzyme family in insects. This mini review describes the insect GST enzyme family, focusing specifically on their role in conferring insecticide resistance.

Animals↗
PubMed1989

Response of insecticide-resistant and susceptible houseflies (Musca domestica) to a commercial granular bait formulation containing methomyl.

Female houseflies (Musca domestica L.) from a susceptible and a multi-insecticide-resistant strain were used to evaluate the relative toxicity of an insecticide bait formulation of the carbamate insecticide methomyl. Individual flies were allowed to feed on bait granules for an unrestricted period or for 5 s. Resistant flies took longer than susceptible flies to initiate a feeding response. When allowed to feed continuously, those from the resistant strain spent longer feeding than susceptible ones. The time taken to knock-down (KD), including feeding times, was significantly greater for resistant than susceptible flies (P less than 0.001), but once the proboscis was withdrawn from the granule there was no difference in KD times between the strains. All flies from both strains were knocked down, and only a very small number of resistant and susceptible flies recovered. The toxic effects of methomyl on flies which were restricted to a 5 s feed ranged from no observed effect to KD in less than 1 min. After feeding for 5 s, 81% of resistant and 98% of susceptible flies developed signs of methomyl poisoning. More resistant than susceptible flies recovered from KD, giving final mortalities of 46% and 88% respectively. With both feeding regimes, some flies of both strains which had apparently recovered from KD had lost their ability to fly. Observations have also shown that 8% of resistant flies may have been repelled by methomyl granules. The implication of these results on the survival of M. domestica in intensive animal units following exposure to methomyl bait is also discussed.

Animals↗