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PubMed2004

Insecticide resistance in Alabama and Florida mosquito strains of Aedes albopictus.

The susceptibility of four strains of Aedes albopictus (Skuse) to permethrin, deltamethrin, resmethrin, chlorpyrifos, malathion, propoxur, fipronil, imidacloprid, spinosad, and Bacillus thuringiensis variety israelensis (Bti) was determined. The HAmAal and MAmAal strains were collected in 2002 and 2003, respectively, from Huntsville and Mobile, AL, and the VBFmAal and SFmAal strains were collected in 1998 from Vero Beach and southern Florida, respectively. The HAmAal strain showed a 22-fold elevated level of resistance to deltamethrin compared with the susceptible Ikaken laboratory strain, whereas the VBFmAal strain showed a six-fold lower sensitivity to deltamethrin compared with Ikaken. However, comparison of resistance ratios for deltamethrin at LC50 and LC90 (21-fold) and the gradual slopes of dose-response curves indicated that the field population of this mosquito strain was heterogenous in response to deltamethrin. All four mosquito strains showed elevated levels of resistance to chlorpyrifos, with resistance ratios from 10 to 33. Nevertheless, except for the relatively low resistance to deltamethrin and chlorpyrifos, all mosquito strains showed a similar susceptibility or lower tolerance to the remaining insecticides tested compared with the susceptible Ikaken strain, even though some, such as permethrin, resmethrin, malathion, and Bti, have been used in the field for a long time, especially in Alabama. These results indicate that the development of resistance to insecticides in Ae. albopictus is slow and conventional insecticides, such as permethrin, resmethrin, malathion, and Bti, and relatively new insecticides, such as fipronil, imidacloprid, and spinosad, may all be valuable for the management of this important mosquito.

Aedes↗

PubMed2004

Microbial transformation of pyrethroid insecticides in aqueous and sediment phases.

Recent studies showed that synthetic pyrethroids (SPs) can move via surface runoff into aquatic systems. Fifty-six of SP-degrading bacteria strains were isolated from contaminated sediments, of which six were evaluated for their ability to transform bifenthrin and permethrin in the aqueous phase and bifenthrin in the sediment phase. In the aqueous phase, bifenthrin was rapidly degraded by strains of Stenotrophomonas acidaminiphila, and the half-life (t1/2) was reduced from >700 h to 30 to 131 h. Permethrin isomers were degraded by Aeromonas sobria, Erwinia carotovora, and Yersinia frederiksenii. Similar to bifenthrin, the t1/2 of cis- and trans-permethrin was reduced by approximately 10-fold after bacteria inoculation. However, bifenthrin degradation by S. acidaminiphila was significantly inhibited in the presence of sediment, and the effect was likely caused by strong adsorption to the solid phase. Bifenthrin t1/2 was 343 to 466 h for a field sediment, and increased to 980 to 1200 h for a creek sediment. Bifenthrin degradation in the inoculated slurry treatments was not greatly enhanced when compared with the noninoculated system. Therefore, although SP-degrading bacteria may be widespread in aquatic systems, adsorption to sediment could render SPs unavailable to the degraders, thus prolonging their persistence.

Adsorption↗

PubMed2001

Deltamethrin tolerance & associated cross resistance in Aedes aegypti from Mysore.

BACKGROUND & OBJECTIVES: The indiscriminate use of insecticides in public health and agriculture has led to the development of resistance to these insecticides in the vector mosquitoes. To understand the development of resistance to synthetic pyrethroids, selection studies on Aedes aegypti were done at Mysore. METHODS: Ae. aegypti collected from the field were subjected to selection experiment with deltamethrin for 16 generations in the laboratory. Cross resistance test was conducted against permethrin and fenvalerate. RESULTS: Tolerance level was found to increase by 333.83 folds in terms of its LC50 values. Cross resistance of this deltamethrin selected line was tested against permethrin and fenvalerate. The results show that the selected line has developed cross resistance as much as 5.19 and 5.92 folds respectively against permethrin and fenvalerate. INTERPRETATION & CONCLUSIONS: The findings show a continuous elevation in tolerance in Ae. aegypti with increase in deltamethrin selection pressure, and development of cross resistance to other insecticides of the same class. The natural or developed tolerance has its implications in the control of these mosquitoes.

Aedes↗

PubMed2001

Studies on the present status of insecticides resistance on mosquitoes using the diagnostic dosages in El-Fayium Governorate, a spot area of malaria in Egypt.

Insecticides susceptibility tests were conducted using the World Health Organization diagnostic doses on the adult and larvae of Anopheles pharoensis and Culex pipiens mosquitoes from Fayium Governorate in Egypt. Insecticides used were malathion, fenitrothion, temephos, diazinon, bromophos and fenthion from organophosphorous group and deltamethrin, permethrin and cypermethrin from synthetic pyrethroid group while propoxur was from carbamate group. Larvae of A. pharoensis were resistant to fenitrothion and susceptible to other insecticides used, while the adults were susceptible to malathion, deltamethrin, fenitrothion and premethrin. Larvae of C. pipiens were resistant to temephos, fenitrothion, bromophos and fenthion and susceptible to malathion, permethrin and diazinon, while the adults were resistant to fenitrothion, permethrin and propoxur and susceptible to deltamethrin, cypermethrin and malathion. These results are important for the success of the control programmes and monitoring the susceptibility status of vectors.

Animals↗

PubMed2004

Pediculosis and scabies.

Pediculosis and scabies are caused by ectoparasites; patients usually present with itching. Head and pubic lice infestations are diagnosed by the visualization of insects or viable nits (eggs). Primary treatment is topically administered 1 percent permethrin. Malathion is one alternative for treatment failures. The importance of environmental measures to prevent infestation is a matter of controversy. Pubic lice are treated the same as head lice, but this finding should prompt evaluation for other sexually transmitted diseases. Body lice infestation should be suspected when symptoms of generalized itching occur in persons who do not change or wash their clothing or bedding regularly; lice may be found in the seams of their clothing. Topically administered permethrin may help to eradicate body lice, but personal hygiene measures are essential for successful treatment. Classic scabies in adults can be recognized by a pruritic, papular rash with excoriations; in infants, small children, and the immunocompromised, the rash may include vesicles, pustules, or nodules. Primary treatment for scabies is permethrin cream and environmental measures are important to prevent recurrent infestation. Generalized crusted scabies is best treated with oral ivermectin.

Humans↗

PubMed2004

American Academy of Pediatrics guidelines for the prevention and treatment of head lice infestation.

The American Academy of Pediatrics (AAP) established diagnosis and treatment guidelines for pediculosis in 2002. Ideally, diagnosis should be based on the observation of a live louse. The presence of nits is also used by many people to positively diagnose an infestation, although a nit located farther from the scalp than 1 cm is unlikely to be viable. Other material on the scalp may be mistaken for nits, leading to misdiagnosis. Because lice are not associated with serious medical problems, the primary consideration of the AAP regarding treatment is the safety of pediculicides and other products used to treat head lice. From a pediatrician's perspective, no significant risk is acceptable. Over-the-counter (OTC) pyrethroid products (pyrethrin and permethrin) are commonly used by parents to treat their children and are generally considered safe for most people. Pyrethroids are not completely ovicidal, however, so a second application is required. Misuse and overuse of these products have contributed to the development of resistance. Prescription products include permethrin 5%, lindane, and malathion 0.5%. Resistance to permethrin 5% and lindane has been documented. In addition, lindane is associated with serious adverse events and should be used with caution only in a select population. Malathion 0.5% is about 98% ovicidal, and no resistance has been reported. Malathion is highly effective, but AAP guidelines note that the product is flammable and serious adverse effects can occur with ingestion. Very few cases of ingestion have occurred, and no reported cases of flammability, but children being treated with malathion should be carefully supervised, and this pediculicide should not be used unless treatment with OTC products has failed. AAP guidelines also state that no-nit policies in schools are detrimental, causing lost time in the classroom, inappropriate allocation of the school nurse's time for lice screening, and a response to infestations that is out of proportion to their medical significance. Accurate diagnosis, safe treatment options, and a common-sense approach to managing infestations in schools are recommended.

Animals↗

PubMed2004

Insecticide susceptibility and selection for resistance in a population of Aedes aegypti from Ratchaburi province, Thailand.

The insecticide susceptibility of Aedes aegypti larvae and adults from four areas of Ratchaburi Province, Thailand was investigated using World Health Organization standard procedures. The larvae of Ae. aegypti in all areas were found to be susceptible to temephos. The strain with the highest level of temephos resistance was subjected to temephos selection. The resistance ratios increased to 2.74-fold from their parental non selected strain after 5 generations of selection. For the adult of Ae. aegypti, the study was conducted to determine the effects of 0.75 % permethrin and 0.05 % deltamethrin impregnated paper selection on the strain having the highest with the highest LT50 level. The results showed the increase in the LT50 to 7.46 and 1.18-fold after the third selected generation with 0.75 % permethrin and 0.05 % deltamethrin respectively. Mortality rates after exposing adults to discriminating concentrations showed that field populations in Ratchaburi Province were resistant to permethrin and deltamethrin. Alternative non-chemical measures need to be used in new of the emergence of resistance in the mosquito population.

Journal Article↗

PubMed2006

Detection of insecticides resistance status in Culex quinquefasciatus and Aedes aegypti to four major groups of insecticides.

The resistance to various insecticides from 4 major groups (organochlorine, organophosphate, carbamate and pyrethroid) was investigated in a field strain of Culex quinquefasciatus from Baan Suan community, Nonthaburi province, Thailand by using a standard World Health Organization susceptibility test. The Baan Suan strain was completely resistant to DDT and highly resistant to deltamethrin, permethrin, fenitrothion and propoxur but this strain was still found to be highly susceptible to malathion. This strain displayed high resistance to cypermethrin since the result revealed that the resistance ratio of the 50% lethal concentration value (RR50) between the field and the laboratory strains (NIH strain) was 16. The study indicated that mosquitoes were resistant to almost all insecticide tested except malathion and this should be an alternative for Cx. quinquefasciatus control in this area. Moreover, Aedes aegypti, which is a main dengue vector in Baan Suan community was also tested with deltamethrin, permethrin and fenitrothion. The results showed that dengue mosquitoes are clearly resistant to permethrin and tolerant to deltamethrin, but was 100% susceptible to fenitrothion. The cause of insecticide resistance in Cx. quinquefasciatus may be due to the continuous use of insecticide for dengue vector control programme in Baan Suan community.

Aedes↗

PubMed1980

Residual toxicity of wall-sprayed organophosphates, carbamates and pyrethroids to mosquito Culex pipiens molestus Forskal.

Common house mosquito Culex pipiens molestus Forskal was used to test biologically the residual toxicity of 15 organophosphorus, 5 carbamate and 5 pyrethroid insecticide preparations sprayed on whitewashed or limewashed wall surfaces. The doses of 0.1 g and 1.0 g of active ingredient per 1 m2 of wall surface were used in this experiment. At the dose of 1 g/m2, organophosphates chlorpyriphos, diazinon, fenitrothion, malathion, pirimiphos-methyl and propetamphos, cambamates bendiocarb, dioxacarb, propoxur and promecarb, and pyrothroids bioresmethrin, decamethrin-permethrin and tetramethrin produced on whitewashed wall surfaces the residual toxicity persisting for at least four months. At the dose of 0.1 g/m2, a long-lasting residual toxicity persisting on whitewashed wall surfaces for at least two months was observed after bendiocarb, decamethrin, fenitrothion, permethrin, pirimiphos-methyl and propoxur application. The residual toxicity of organophosphates, carbamates except for bendiocarb and pyrethroids except for permethrin sprayed on limewashed wall surfaces was considerably shorter than on whitewashed surface.

Animals↗

PubMed1995

Susceptibility status of two species of Japanese encephalitis vectors to insecticides in the Thar desert, district Bikaner (Rajasthan).

Susceptibility tests were conducted on the adults of two species of Japanese encephalitis vectors viz., Culex pseudovishnui and C. tritaeniorhynchus against diagnostic doses of DDT, dieldrin, malathion, fenitrothion, propoxur and permethrin at different exposure duration. C. pseudovishnui was found susceptible to permethrin and resistant to dieldrin and propoxur while C. tritaeniorhynchus was found susceptible to permethrin and resistant to DDT, dieldrin, fenitrothion and propoxur. A verification, however, was required with other insecticides for both the species.

Animals↗

PubMed1993

The susceptibility of the Egyptian Phlebotomus papatasi to five insecticides.

Phlebotomus papatasi is the main vector of zoonotic cutaneous Leishmaniasis caused by L. major in nearly all the East Mediterranean Region. Generally speaking, control of any arthropod-borne disease should be directed against both the parasite and the vector. The present study was undertaken to establish a base line susceptibility levels of the Egyptian P. papatasi to five insecticides. These insecticides were: B H C and D D T (chlorinated hydrocarbon), permethrin (synthetic pyrethroides), malathion (Organophosphorus) and propoxur (carbamate). The results obtained revealed that the laboratory bred P. papatasi were more susceptible to the five insecticides than the wild caught ones. The insecticidal efficiency of the five insecticides based on LC50 was in the following descending order: propoxur, permethrin, BHC, DDT and malathion for laboratory bred flies and propoxur, permethrin, BHC, malathion then DDT for wild caught flies. The least LC50 was when using propoxur for both the wild caught flies (0.0014%) and laboratory bred ones (0.00043%). The least LT50 was when using propoxur for both the wild caught flies (4.8 seconds) and the laboratory bred flies (2.2 seconds).

Animals↗

PubMed1996

Current status of Anopheles stephensi response to various insecticides in some areas of the Thar desert.

Investigations on the current response of A. stephensi. to six insecticides viz. DDT, dieldrin, malathion, fenitrothion, propoxur and permethrin, were carried out in 3 districts i.e. Barmer, Jodhpur and Pali, of the Thar desert. The species was found resistant to DDT and dieldrin, partially resistant to malathion and susceptible to fenitrothion, propoxur and permethrin. Dieldrin and malathion resistance has been detected for the first time in the Thar desert. Lethal concentrations (LC50 & LC95) of DDT and dieldrin and lethal exposure times (LT50 & LT95) of malathion, fenitrothion, propoxur and permethrin have been determined. In some areas, the differences in LC50 and LT50 values of tested insecticides, except fenitrothion, were found statistically significant. Chi-square and regression tests have revealed the homogeniety and linear trend respectively in the response of A. stephensi to insecticides. The findings of the study indicate that organochlorine compounds can be used alternately in the spray operations.

Animals↗

PubMedDate not supplied

Pyrethroid decrease in central nervous system from nerve agent pretreatment.

We studied the effect of pyridostigmine bromide, a nerve agent prophylactic, on the central nervous system (CNS) uptake of [14C]permethrin, a pyrethroid insecticide, at scaled human-equivalent exposures in rats using accelerator mass spectrometry (AMS). AMS detects 14C at attomole sensitivities and determines the tissue distribution of 14C-labeled compounds. Pyridostigmine bromide in chow at 7.75 mg kg(-1) per day lowered the CNS tissue levels of permethrin, dosed at 4.75 microg kg(-1), in the CNS of rats by 30%. These results are inconsistent with hypothesized synergy of such compounds as a precursor to 'Gulf War syndrome'.

Animals↗

PubMed2005

Separation and aquatic toxicity of enantiomers of synthetic pyrethroid insecticides.

Synthetic pyrethroid insecticides are chiral compounds with multiple asymmetric positions. In this study, isomers of four commonly used pyrethroids were separated at the enantiomeric level by enantioselective high-performance liquid chromatography (HPLC), and differences between enantiomers in aquatic toxicity were characterized using individual isomers. Isomers of cis-bifenthrin and permethrin were completely resolved on a Sumichiral OA-2500-I column. All eight isomers of cypermethrin and cyfluthrin were completely separated on two chained Chirex 00G-3019-DO columns. Great differences were found between enantiomers in the acute toxicity to aquatic invertebrates Ceriodaphnia dubia or Daphnia magna. In cis-bifenthrin (cis-BF) and cis-permethrin (cis-PM), the 1R-cis isomer was 15-38 times more active than the 1S-cis enantiomer, while in trans-PM, the 1R-trans isomer was substantially more toxic than the 1S-trans enantiomer. In cypermethrin or cyfluthrin, two of the eight isomers, 1R-cis-alphaS and 1R-trans-alphaS, contributed for almost all the toxicity in the racemate, while the other six enantiomers were inactive. These results suggest that significant enantioselectivity occurs for pyrethroids in aquatic toxicity, and such enantiomeric differences must be considered when evaluating ecological effects of pyrethroid insecticides.

Animals↗

PubMed2001

Is attract-and-kill technology potent against insecticide-resistant Lepidoptera?

Attract-and-kill techniques, associating an attractant and a contact insecticide in a sticky formulation, are a new way of controlling Lepidopteran pests. Insecticide resistance may, however, limit the effectiveness and even the attractiveness of such formulations where resistance pleiotropic effects influence pheromone perception. We have tested this hypothesis on resistant codling moths Cydia pomonella (L) using a commercial formulation containing (E,E)-8,10-dodecadien-1-ol (codlemone), the major component of the sex pheromone, as an attractant and permethrin as toxicant. We first compared the attractiveness of codlemone in a wind tunnel and the contact toxicity of pyrethroids on males of one susceptible and of three strains selected for resistance to diflubenzuron, deltamethrin and azinphos-methyl. The dose-response relationships of males of susceptible and resistant strains to codlemone did not differ significantly. The deltamethrin-selected strain was the most resistant to pyrethroids, exhibiting 138-, 25- and 18-fold resistance ratios to deltamethrin, cypermethrin and permethrin, respectively. The efficiency of the attracticide formulation, applied successively on filter paper support, glass support and wood support, was estimated by recording the mortality delay of males after natural contact with the formulation in the wind tunnel. The deltamethrin- and diflubenzuron-resistant strains were significantly less affected than the susceptible strain by contact with the attracticide on the wooden support, exhibiting 58- and 2.3-fold greater LT50 ratios, respectively. Mortality of deltamethrin-resistant moths did not exceed 40% after 48 h. The LT50 value was significantly greater on filter paper support than on the two other supports. Surprisingly, the LT50 ratio of the deltamethrin-resistant strain was markedly higher on filter paper support (1021-fold), which was more absorbent, than on the glass support (31-fold). No sublethal effects in terms of pheromone response, mating or fecundity occurred in moths surviving contact with the attracticide. Choice of insecticides in attracticide formulations will be influenced by the resistance background of the target pests. Principles of insecticide resistance management may also be applied to attract-and-kill technology by alternating with other insecticides or control methods.

Animals↗

PubMed2002

Susceptibility of house flies (Diptera: Muscidae) exposed to commercial insecticides on painted and unpainted plywood panels.

House flies were collected from dairies in New York state and the levels of resistance to commercially available insecticide formulations were measured on painted and unpainted plywood panels. Dimethoate was ineffective on all surfaces. The wettable powder permethrin formulation was more toxic than the emulsifiable concentrate formulation. The wettable powder cyfluthrin formulation was also more toxic than the recently developed liquid formulation. In general, the best house fly control was obtained on flat latex painted plywood panels and the poorest control on gloss latex painted panels. It is highly unlikely that producers obtain adequate control with dimethoate and permethrin.

Animals↗

PubMed2003

The influence of lipophilicity and formulation on the distribution of pesticides in laboratory-scale sediment/water systems.

Pesticide reaching surface waters will be sorbed by sediment. This sorption process and the influence of pesticide formulation have been examined at 10 degrees C in small-scale systems having 2-cm depth of sediment and 8-cm overlying water stirred gently. Eight pesticides (triasulfuron, isoproturon, chlorotoluron, phenmedipham, difenoconazole, chlorpyrifos, pendimethalin and permethrin), spanning a range of physicochemical properties, were applied individually to the water. Sorption equilibrium was reached at between 15 and 30 days, the proportion of pesticide then in the sediment ranging from 20% for the acidic and therefore polar triasulfuron to 97% for the lipophilic permethrin; this behaviour was not influenced by formulation. Sorption coefficients measured in batch tests over 2 h gave good estimates of the equilibrium distribution. Some degradation was observed for all compounds over 90 days; for some compounds and formulations, enhanced degradation occurred after 20 to 60 days. It is concluded that lipophilicity is the chief determinant of pesticide distribution in sediment/water systems.

Algorithms↗

PubMed1983

Intoxication with four synthetic pyrethroids fails to show any correlation between neuromuscular dysfunction and neurobiochemical abnormalities in rats.

The neurological effects of four synthetic pyrethroids resmethrin, permethrin, cypermethrin, and deltamethrin have been investigated in the rat to establish whether there is a correlation between the clinical-functional status of the animal and peripheral nerve damage as measured biochemically. Neuromuscular dysfunction was assessed by means of the inclined plane test and peripheral nerve damage by reference to beta-glucuronidase and beta-galactosidase activity increases in nerve tissue homogenates from treated and control animals. A transient functional impairment was found in animals treated with any one of the four pyrethroids tested and in all cases this was maximal at the end of the 7 day subacute dosing regimen. Significant increases in beta-glucuronidase and beta-galactosidase were found 3-4 weeks after the start of dosing in the distal portion of the sciatic/posterior tibial nerves from permethrin, cypermethrin, and deltamethrin treated animal; but no changes were found in remesthrin-dosed animals. It is concluded therefore, that there is no direct correlation between the time-course of the neuromuscular dysfunction and the neurobiochemical changes. This suggests that these pyrethroids have at least two distinct actions--a short-term pharmacological effect and at near-lethal dose levels a more chronic neurotoxic effect that results in sparse axonal nerve damage.

Animals↗