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PubMed1981

Insecticide levels in tissues associated with toxicity: a literature review.

Extensive residue studies have been done with most of the organochlorine insecticides. The brain is a reliable tissue to determine lethal or exposure residues of the persistent organochlorine insecticides. Fewer studies have been done with organophosphate residues. residues of organophosphate insecticides are useful indicators of poisoning in tissues of exposed animals. Metabolite determination and identification is a necessary consideration since metabolic activation is required for several of the organophosphate insecticides. No studies of tissue residue evaluation of carbamate insecticides are available.

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↗
PubMed1997

Susceptibility of Lutzomyia longipalpis (Diptera: Psychodidae) to selected insecticides in an endemic focus of visceral leishmaniasis in Venezuela.

A field population of Lutzomyia longipalpis from La Rinconada, Lara State, an endemic focus of visceral leishmaniasis in Venezuela, was tested for susceptibility to organochlorine (DDT 2%), carbamate (propoxur 0.01%), organophosphate (malathion 2%, fenitrothion 1%, and pirimiphos methyl 1%), and pyrethroid (deltamethrin 0.06%, lambdacyhalothrin 0.06%, and permethrin 0.2%) insecticides. Susceptibility to the insecticides tested was evaluated in the field population of L. longipalpis and compared with a laboratory reference strain. The (LT95) to propoxur and malathion insecticides for the field population was lower than the LT95 for the laboratory reference strain, demonstrating high susceptibility to these compounds. A low level of resistance at LT50 (< 3-fold) was found for fenitrothion, pirimiphos methyl, and permethrin insecticides, but no resistance was detected at LT95. No significant resistance at the LT50 and LT95 was detected for the pyrethroids deltamethrin and lambdacyhalothrin. The susceptibility levels of L. longipalpis to the insecticides tested are discussed in view of a future control program against endophilic vectors of leishmaniases based on the use of pesticides.

Animals↗
PubMed1998

Effect of insecticides on vital activity, hepatic enzymes and red blood cell acetyl cholinesterase activity of rabbits in Makkah.

Developing animals and invertebrate are markedly more sensitive to acute toxicity through exposure to insecticides. Varieties of insecticides are used for hygienic control in Makkah holy places. The present study examines the acute effects of commonly used insecticides in Makkah area. Rosfin as an organophosphorus, Airlen as a pyrethroid and Sulvac as a carbamate derivative were tested for their effects on vital activities, hepatic transaminases, serum triglycerides and acetyl cholinesterase activity of rabbits. The insecticides were tested in same and double concentration used for insect control by Makkah's municipal authorities. Compressed air was used as a source of pressure for spraying wooden boxes designed for habitation of animals during the experiments. There were no significant changes in vital activities of rabbits in both concentrations. However, serum glutamate pyuvate transaminase (SGPT) and serum glutamate oxaloacetate transaminase (SGOT) showed irregular changes (mild decrease or increase) in all groups, while triglyceride showed mild rise after six days exposure in case of double concentration. Acetyl cholinesterase showed mild increase in activity after five minutes incubation time, but there was unnoticed increase in activity after 15, 25, 35 and 45 minutes of incubation. In case of Airlen, the activity increased after five minutes of incubation and decreased thereafter. In conclusion, insecticides used in the holy places of Makkah area have no apparent effects on vital activity, acetyl cholinesterase activity and showed no significant effect on rabbit hepatic transaminases and serum triglyceride.

Acetylcholinesterase↗
PubMed1998

Laboratory simulation of splashes and spills of organophosphate insecticides on chemically protective gloves used in agriculture.

Agricultural workers rely on chemically protective gloves for protection from dermal exposure to insecticides. In Australia the most widely used gloves are manufactured from polyvinyl chloride or nitrile butadiene rubber. During insecticide application splashes and spills frequently occur on the external surfaces of gloves which may compromise the integrity of the membrane. Interaction of two organophosphate insecticides, chlorpyrifos (Lorsban 500 EC(R)) and diazinon (Jetdip(R)), with glove surfaces was investigated in laboratory conditions. The external surface of gloves was treated with concentrated insecticides for one minute and diluted and concentrated insecticides for 24, 36 and 48 hours and later examined by environmental scanning electron microscopy. Two classes of defects, cavities and convexities, were evident in the polyvinyl chloride gloves following all treatments, whereas cracking was significant in the nitrile butadiene rubber gloves after 24 hours. In addition, X-ray energy-dispersive microanalysis was used to evaluate chemical changes on the glove surfaces. Phosphorus and sulfur were useful indicators for organophosphate retention over specific time frames. Results corroborated the need for more robust chemically protective gloves to be developed for routine agricultural use.

Agricultural Workers' Diseases↗
PubMed2025

Coordinated regulation of glutathione S-transferases confers metabolic flexibility in multi-insecticide-resistant Frankliniella occidentalis (Pergande).

INTRODUCTION: The evolution of multi-insecticide resistance in insect pests threatens global food security. Although glutathione S-transferases (GSTs) are implicated in detoxification, the coordinated mechanism by which specific gene subfamilies interact to confer broad-spectrum resistance remains inadequately characterized. OBJECTIVE: To dissect the functional allocation and cooperation of GST subfamilies in multi-insecticide-resistant strains of Frankliniella occidentalis. METHODS: We integrated comparative genomics (20 GST genes cloned), transcriptomics (qRT-PCR), RNAi-mediated silencing, molecular docking (AutoDock Vina), and in vitro metabolism assays (UPLC-MS/MS) across susceptible and resistant thrips strains. RESULTS: The two resistant strains (NIL-R and FS-R) exhibited moderate to high resistance to five insecticides (chlorfenapyr, emamectin benzoate, spinetoram, spinosad, and thiamethoxam), accompanied by significantly elevated GSTs activity. Phylogenetic analysis indicates that GSTs include 10 conserved delta and 7 diverse sigma members. The sigma subfamily has undergone a marked expansion due to gene duplication. Delta (FoGSTd1, d4, and d9) and sigma (FoGSTs1, s2, and s6) genes were significantly up-regulated in the resistant strains. RNAi showed specialized functional allocation among GSTs: delta GSTs mediated resistance to spinosad and chlorfenapyr, sigma GSTs were responsible for thiamethoxam resistance, and notably, cooperation between these subfamilies contributed to resistance against emamectin benzoate and spinetoram. Molecular docking and in vitro metabolism assays of FoGSTd9 and FoGSTs1 proteins further supported the functional allocation and cooperative roles of GST subfamilies. CONCLUSION: Our results indicate that F. occidentalis may coordinate GST subfamilies to achieve metabolic flexibility in response to multi-insecticide pressure. This survival strategy, mediated by mechanistic functional allocation and cooperative interactions among subfamilies, may contribute to energy conservation and reduced adaptive costs. Disruption of this coordinated mechanism represents a potential approach for overcoming resistance in agricultural pest populations.

Animals↗
PubMed1964

THE SIGNIFICANCE OF DDT-IRRITABILITY TESTS ON MOSQUITOS: WITH AN ANNEX ON RESULTS OBTAINED WITH THE IRRITABILITY TEST METHOD RECOMMENDED BY THE WHO EXPERT COMMITTEE ON INSECTICIDES.

The author reviews various laboratory investigations of the effects of insecticides on mosquito behaviour. The only extensive data on this subject concern the effects of DDT on irritability. The measurement of this response is discussed, and information is collated on the factors affecting it, such as the type and state of the insecticide, the species and physiological state of the mosquito and environmental factors including temperature, humidity, light and crowding. The author concludes that, despite the numerous difficulties associated with this subject, a sound technique (such as that recommended by the WHO Expert Committee on Insecticides) should be adequate to detect inherent differences in irritability between mosquito colonies, of a magnitude likely to be important in practice.An annex describes tests carried out by the author on strains of two anopheline and four culicine species with the irritability test method recommended by the WHO Expert Committee on Insecticides. Four DDT-resistant strains were less irritated by DDT than normal colonies, the difference being significant in the two culicine resistant strains.

Animals↗
PubMed2002

Isolation and characterization of Bacillus cereus-like bacteria from faecal samples from greenhouse workers who are using Bacillus thuringiensis-based insecticides.

OBJECTIVES: Since the discovery of the insecticidal activity of Bacillus thuringiensis at the beginning of the twentieth century, this bacterium has been used increasingly against various insect pests. In spite of the extensive use of B. thuringiensis, only sporadic clinical case reports have been published. In recent years, the close relationship between B. thuringiensis and the human pathogen Bacillus cereus has been confirmed. In practice, only the insecticidal activity of B. thuringiensis distinguishes the two species. However, both species are composed of thousands of isolates with varying potential for causing adverse effects in humans. The aim of this study was to employ molecular biology methods for assessment of occupational exposure to B. thuringiensis-based biopesticides by determination of specific genetic information including plasmid profiles and random amplified polymorphic DNA (RAPD). METHODS: Faecal samples from 12 persons, working in Danish greenhouses, were collected for microbial analysis. Seven persons were using B. thuringiensis-based insecticides, whereas five persons were employed at greenhouses that did not use B. thuringiensis. The bacteria were isolated on B. cereus-specific solid substrate, and colonies were further identified using the polymerase chain reaction (PCR). The PCR method was used for the identification of the enterotoxin genes HblA and BceT. The expression of enterotoxins was detected with two commercial serological kits. Primers specific for 16S-23S spacer region were used to identify the bacteria as members of the B. cereus group. Several primers towards insecticidal genes have been used in order to further characterize the isolates as subspecies of B. thuringiensis. RESULTS: Two faecal samples from the B. thuringiensis-exposed greenhouse workers were positive for B. cereus-like bacteria. One isolate displayed intracellular crystalline inclusions characteristic of B. thuringiensis, production of and genes for B. cereus enterotoxins and it was PCR-positive for an insecticidal toxin primer set. RAPD profiles of the faecal isolate were identical to that of strains isolated from a commercial product. CONCLUSIONS: The methods applied have verified that the faecal isolate was identical to the B. thuringiensis isolate found in the biopesticide used. This is the first reported case of isolation of a bacterial biopesticide from human faeces. The biopesticide was shown to harbour and express enterotoxin genes. However, there is no evidence that this caused any adverse effects to the person from whom these bacteria were isolated.

Bacillus cereus↗
PubMed1986

The safety evaluation of bendiocarb, a residual insecticide for vector control.

The safety evaluation of bendiocarb, a carbamate insecticide for vector control is described. During the course of field studies data were collected to relate dermal exposure, absorption, excretion of metabolites, whole blood cholinesterase inhibition and clinical signs and symptoms. Studies were also carried out on blood sampling techniques for cholinesterase assay and on the effects of temperature and humidity on the dermal absorption of bendiocarb. It was shown that inhibition of blood cholinesterase by bendiocarb is rapidly reversible and routine cholinesterase monitoring of operators is therefore not necessary. It was also shown that dermal absorption of bendiocarb and probably other insecticides is facilitated under hot and humid conditions and special care must be taken with insecticide application at these times. The importance of effective training, adequate protective clothing and good personal hygiene in achieving safe application of insecticides in house-spraying programmes is stressed. It is concluded from these studies that bendiocarb is a safe insecticide for vector control when used with normal safety precautions and this has been confirmed in subsequent large-scale operational programmes.

Agriculture↗
PubMed2005

Insecticidal bacteria: an overwhelming success for invertebrate pathology.

The discovery and study of insecticidal bacteria, which began a little over a century ago, led to the development of commercial bacterial insecticides in the middle of the century that became the first successful and widely used microbial control agents. Most of these products were based on Bacillus thuringiensis, a bacterium that kills insects through the use of insecticidal proteins that subsequently became known as Cry proteins. While most of these products were only effective against lepidopteran pests, their success eventually led in the 1970s and 1980s to the discovery of strains effective against larvae of coleopteran pests and nematocerous dipterans, such as vector and nuisance mosquitoes and blackflies. The cloning in 1981 of the first gene encoding a Cry protein led to an explosion of basic and applied research that culminated in new strains of recombinant insecticidal bacteria and, even more importantly, the development, commercialization, and wide-scale deployment of insecticidal transgenic crops based on Cry proteins. This new and environmentally safe technology has revolutionized agricultural pest control, yielding a multibillion dollar industry that is paving the way to new types of plants that will dominate food and fiber production as the 21st century progresses. In this brief symposium paper, I provide an overview of some of the key work that led to this remarkable success.

Animals↗
PubMed1998

Residues of chlorinated hydrocarbon insecticides in human milk of Jordanian women.

A total of 411 milk samples were screened for the residues of the following chlorinated hydrocarbon insecticides using chromatographic methods: DDT insecticides (P,P'-DDT, P,P'-DDE, P,P'-DDD, O,P' -DDT); cyclodiene insecticides (aldrin, endrin, dieldrin, heptachlor, heptachlorepoxide, cis-and trans-chlordane); hexachlorocyclohexane (alpha-HCH, gamma-HCH) and hexachlorobenzene (HCB). The milk samples were obtained from lactating women selected randomly from five different geographical regions in Jordan. These regions were North and Middle Jordan Valley, Amman, Irbid and Zarqa. All of the studied insecticides were found to contaminate human milk in Jordan, but with high variations in the concentration and percentage of population occurrence. P,P'-DDE was the predominant contaminant occurring in 80.3% of studied population, followed by P,P'-DDT occurring in 53.5%. The regional results showed that the DDT residues were also the predominant contaminant in all regions and that the North and Middle Jordan Valley regions were the most affected. Infant's age (i.e. lactation period) had a significant inverse relationship with the concentration of insecticides in the milk fat.

Journal Article↗
PubMed2000

Secreted proteases from Photorhabdus luminescens: separation of the extracellular proteases from the insecticidal Tc toxin complexes.

Photorhabdus luminescens secretes both high molecular weight insecticidal toxin complexes and also a range of extracellular proteases into culture broth. Previous studies by others have suggested that insecticidal activity of the broth is associated with these proteases. However, by gene cloning and targeted knock-out, we have previously shown that oral insecticidal activity is associated with high molecular weight 'toxin complexes' (Tc) encoded by toxin complex or tc genes. Here we further clarify this distinction by biochemically separating the protease fractions away from the oral insecticidal activity of the Tc proteins. We purified three distinct protease fractions from the broth: one consisting of a single species of 55 kDa and two of several putatively related species of approximately 40 kDa. All of these clearly separate from the oral insecticidal activity associated with the high molecular weight Tc proteins and also show no effect on insect weight gain following injection into the haemocoel. Here we examine the substrate preferences and inhibitor profiles of these protease fractions and discuss their relationship with those previously described from other P. luminescens strains and phase variants.

Animals↗
PubMed2002

Novel Bacillus thuringiensis binary insecticidal crystal proteins active on western corn rootworm, Diabrotica virgifera virgifera LeConte.

A new family of insecticidal crystal proteins was discovered by screening sporulated Bacillus thuringiensis cultures for oral activity against western corn rootworm (WCR) larvae. B. thuringiensis isolates PS80JJ1, PS149B1, and PS167H2 have WCR insecticidal activity attributable to parasporal inclusion bodies containing proteins with molecular masses of ca. 14 and 44 kDa. The genes encoding these polypeptides reside in apparent operons, and the 14-kDa protein open reading frame (ORF) precedes the 44-kDa protein ORF. Mutagenesis of either gene in the apparent operons dramatically reduced insecticidal activity of the corresponding recombinant B. thuringiensis strain. Bioassays performed with separately expressed, biochemically purified 14- and 44-kDa polypeptides also demonstrated that both proteins are required for WCR mortality. Sequence comparisons with other known B. thuringiensis insecticidal proteins failed to reveal homology with previously described Cry, Cyt, or Vip proteins. However, there is evidence that the 44-kDa polypeptide and the 41.9- and 51.4-kDa binary dipteran insecticidal proteins from Bacillus sphaericus are evolutionarily related. The 14- and 44-kDa polypeptides from isolates PS80JJ1, PS149B1, and PS167H2 have been designated Cry34Aa1, Cry34Ab1, and Cry34Ac1, respectively, and the 44-kDa polypeptides from these isolates have been designated Cry35Aa1, Cry35Ab1, and Cry35Ac1, respectively.

Amino Acid Sequence↗
PubMed2004

Investigation of negative cross-resistance as a resistance-management tool for insecticide-treated nets.

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.

Animals↗
PubMed1999

Insecticidal activity of transgenic tobacco plants expressing both Bt and CpTI genes on cotton bollworm (Helicoverpa armigera).

Transgenic tobacco plants expressing both Bacillus thuringiensis (Bt) insecticidal protein and cowpea trypsin inhibitor (CpTI) genes was used to evaluate the insecticidal activity on the cotton bollworm (Helicoverpa armigera) compared with transgenic tobacco with Bt insecticidal protein gene alone. Mortality of first to third instar larvae fed on transgenic two genes tobacco for three days was significantly higher than that fed on transgenic Bt tobacco. First to fourth instar larvae fed on transgenic two genes tobacco continuously could not survive until pupation. Second instar larvae were fed on transgenic tobacco plants for three days and then were transferred to an artificial diet. The efficacy of transgenic two genes tobacco on mortality, larvae weight, percentage of pupation, and time to pupation were significantly higher than that of transgenic tobacco with Bt insecticidal protein gene alone. The results with transgenic tobacco as model plant were valuable for other crops both for the enhancement of insecticidal efficacy and for the delay of insect adaptation to transgenic Bt crops.

Animals↗
PubMed2005

[Efficient and permanent impact of two insecticides with the active ingredient, temephos, on mosquitoes (Diptera: Culicidae) larvae.].

The efficiency of two insecticides with the active ingredient, temephos (Tambro(R) 500 EC and Ekolarv(R) 500 EC), in laboratory and field conditions on Anopheles sacharovi Favre, and Culex pipiens (Linnaeus) larvae has been determined. Under laboratory conditions, it has been determined that both species are sensitive to insecticides. Under field conditions, 100% of larval mortality has been found even with the lowest (0.05 l/ha) of insecticide doses. It has been found that there was no difference in permanence of the effect of insecticides and their doses (p > 0.05). It has been found that insecticides used in mosquito control which contain the active ingredient temephos have to be used for a 20 day period under central Anatolia conditions.

English Abstract↗
PubMed2001

Sex-related differences in the tolerance of Oriental fruit moth (Grapholita molesta) to organophosphate insecticides.

In vivo toxicity assays have shown that organophosphate insecticides are less toxic to male than to female Oriental fruit moths Grapholita molesta. While male moths have higher levels of acetylcholinesterase and general esterase activities, female moth acetylcholinesterase enzymes are less sensitive to aromatic and aliphatic organophosphates than male enzymes. Elevated esterase and acetylcholinesterase activities in male moths explain their greater tolerance to aromatic and aliphatic organophosphates. Male and female acetylcholinesterase enzymes are equally tolerant to heteroaromatic organophosphates, the most widely used of this class of insecticides in G molesta control. This observation, in contrast to the greater sensitivity of male acetylcholinesterases to aromatic and aliphatic organophosphates, shows the potential for the evolution of insensitive target sites in male moths, which would increase male G molesta tolerance to these insecticides. Significant sex-linked differences in insecticide tolerance have not been reported previously in lepidopterans. The practical implications of the observed differences in tolerance in male and female G molesta question the practice of using pheromone traps to monitor populations of these moths in orchards.

Acetylcholinesterase↗
PubMed2003

Susceptibility of field populations of adult Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) and Eretmocerus sp (Hymenoptera: Aphelinidae) to cotton insecticides in Burkina Faso (West Africa).

Research was conducted in 14 cotton fields (3-10 ha) selected in seven localities (two fields per locality) in Burkina Faso, with the objectives of: (1) estimating Bemisia tabaci Gennadius (Homoptera: Aleyrodidae) population abundance, (2) assessing the levels of parasitism by Encarsia spp and Eretmocerus spp (Hymenoptera: Aphelinidae) and (3) estimating the susceptibilities of the pest and of an Eretmocerus sp to the insecticides currently sprayed on cotton. Yellow sticky cards and a leaf-turning technique were used to estimate adult B. tabaci population densities. Yellow sticky cards were also used to estimate the densities of adult Eretmocerus sp and the susceptibilities of B. tabaci to insecticides. Leaf disk techniques were used to estimate B. tabaci red eye nymph populations and parasitism by Encarsia spp and Eretmoceus spp was evaluated using stereo-microscopy. A leaf cage technique was used to estimate the susceptibilities of Eretmocerus sp to insecticides. A mean of 6.5-27.4 adult B. tabaci were trapped per yellow sticky card and 5.5 to > 34.9 were counted per leaf using the leaf turning technique. There were 0.14-13 Eretmocerus sp trapped per yellow sticky card. The levels of parasitism varied between 36 and 87% by the end of the season and parasitism by Eretmocerus sp predominated in most of the fields. The susceptibilities of B. tabaci and Eretmocerus sp varied from field to field and with the insecticide tested.

Animals↗