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[The chemical control of disease vectors. Evaluation of new insecticides. Operational insecticides. New insecticides (author's transl)].

The chemical control of disease vectors which has been very successful during about 15 years is now faced with some difficulties due to the resistance of insects to the insecticides, to the decreasing number of candidate insecticides, to the increase of their price and to the legal restrictions concerning their safe use and their environmental inocuity. Since 1960, W.H.O. has carried out an evaluation programme to define the properties of new insecticides and to access their usefulness for public health. Through this programme several alternative insecticides have been selected and are now used in vector control operations. Although research continues on organophosphorous compounds and carbamates, it also includes the promising groups of pyrethroids and insect growth regulators. The present trend of vector control is to integrate various control techniques and to limit the use of insecticides to the control of the epidemiologically dangerous part of the vector population. This approach might prevent or delay the development of resistance.

Animals↗

PubMed1977

Insecticide solvents: interference with insecticidal action.

Several commercial solvent mixtures commonly used as insecticide carriers in spray formulations increase by more than threefold the microsomal N-demethylation of p-chloro N-methylaniline in midgut preparations of southern army-worm (Spodoptera eridania) larvae exposed orally to the test solvents. Under laboratory conditions, the same solvent mixtures exhibit a protective action against the in vivo toxicity of the insecticide carbaryl to the larvae. The data are discussed with respect to possible solvent-insecticide interactions occurring under field conditions and, more broadly, to potential toxicological hazards of these solvents to humans.

Enzyme Induction↗

PubMed2026

Genome-wide identification and expression profiling of CSP and OBP genes in Stictocephala bisonia reveals candidate genes potentially associated with insecticide response.

Stictocephala bisonia is an important invasive agricultural pest. Due to the frequent application of insecticides in its habitat, this species is under intense selection pressure. Chemosensory proteins (CSPs) and odorant-binding proteins (OBPs) are known to play key roles in insecticide resistance, but their specific functions in S. bisonia remain unclear. In this study, we identified a total of 22 SbisCSPs and 16 SbisOBPs based on the S. bisonia genome. To screen for candidate genes potentially linked to insecticide resistance, we adopted a multi-criteria screening strategy that integrated phylogenetic analysis, molecular docking with three insecticides, and tissue-specific expression profiling. Phylogenetic analysis identified several SbisCSPs and SbisOBPs clustering with genes known to be involved in insecticide resistance, serving as an initial evolutionary filter. Molecular docking results indicated that λ-Cyhalothrin exhibited the strong predicted binding affinity with most of SbisCSPs and SbisOBPs. Subsequent qPCR validation of seven prioritized candidates revealed distinct expression patterns: SbisCSP22 was highly expressed in adults and demonstrated strong binding affinity to all three insecticides tested, suggesting a potential role in mediating multi-insecticide response. Conversely, SbisCSP17 was significantly upregulated in larvae, clustered with genes known to mediate imidacloprid resistance, and exhibited strong binding affinity to imidacloprid. Given its larval-specific expression and the soil-dwelling behavior of larvae, we hypothesize that SbisCSP17 is a key candidate gene for larvae coping with soil-treated insecticides.

Animals↗

PubMed1976

Nonoxidative enzymes in the metabolism of insecticides.

Two major classes of enzymes, i.e., hydrolases and transferases, comprise all the nonoxidative enzymes, and together these enzymes catalyze a wide variety of biotransformations of insecticides. The hydrolytic enzymes involved in insecticide metabolism are carboxylesterase (EC 3.1.1.1), arylesterase alkylamidase, and DFPase (EC 3.8.2.1). Recent experimental evidence suggests that carboxylesterase enzyme(s), formerly known to hydrolyze malathion-type insecticides, can also catalyze hydrolysis of a variety of diversified insecticidal esters such as benzilic acid derivatives, carbanilate compounds, and pyrethroids. These organophosphate-sensitive esterases, with the exception of the enzyme which hydrolyzes malathion, are all present in microsomes. Similarly, the action of amidases now extends to those insecticidal compounds of their intermediates which contain an aminoformyl (N-CHO) moiety. Arylesterase and DFPase catalyze the P-anhydride bond cleavage of the leaving group, a major hydrolytic pathyway for organophosphate insecticides. Transferal enzymes which are presently know to metabolize insecticidal organophosphates are GSH-S-alkyltransferase (EC 2.5.1.12) and GSH-S-aryltransferase (EC 2.5.1.13). These enzymes cleave P-O-R (R = alkyl) or P-0-X (X = aromatic), with subsequent transfer of the R or X group to glutathione. Regarding the other conjugating enzymes, UDP-glucuronyltransferase (EC 2.4.L.17), UDP-glucosyltransferase (EC 2.4.1.35), and arylamine acetyltransferase (EC 2.3.1.5), much work is needed to understand their interactions with insecticidal compounds. There is some evidence that arylsulfotransferase (EC 2.8.2.1) MAY PLAY A PROMINENT ROLE IN THE CONJUGATIVE MECHANISMS OF INSECTS.

Amidohydrolases↗

PubMed1976

Nonoxidative enzymes in the metabolism of insecticides.

Two major classes of enzymes, i.e., hydrolases and transferases, comprise all the nonoxidative enzymes, and together these enzymes catalyze a wide variety of biotransformations of insecticides. The hydrolytic enzymes involved in insecticide metabolism are carboxylesterase (EC 3.1.1.1), arylesterase (EC 3,1.1.2), alkylamidase, and DFPase (EC 3.8.2.1). Recent experimental evidence suggests that carboxylesterase enzymes(s), formerly known to hydrolyze malathion-type insecticides, can also catalyze hydrolysis of a variety of diversified insecticidal esters such as benzilic acid derivatives, carbanilate compounds, and pyrethroids. These organo-phosphate-sensitive esterases, with the exception of the enzyme which hydrolyzes malathion, are all present in microsomes. Similarly, the action of amidases now extends to those insecticidal compounds or their intermediates which contain an aminoformyl (N--CHO) moiety. Arylesterase and DFPase catalyze the P--anhydride bond cleavage of the leaving group, a major hydrolytic pathway for organophosphate insecticides. Transferal enzymes which are presently known to metabolize insecticidal organophosphates are GSH-S-alkyltransferase (EC 2.5.1.12) and GSH-S-aryltransferase (EC 2.5.1.13). These enzymes cleave P--O--R (R = alkyl) or P--O--X (X = aromatic), with subsequent transfer of the R or X group to glutathione. Regarding the other conjugating enzymes, UDP-glucuronyltransferase (EC 2.4.1.17), UDP-glucosyltransferase (EC 2.4.1.35), and arylamine acetyltransferase (EC 2.3.1.5), much work is needed to understand their interactions with insecticidal compounds. There is some evidence that arylsulfotransferase (EC 2.8.2.1) may play a prominent role in the conjugative mechanisms of insects.

Amidohydrolases↗

PubMed1976

Insecticide movement following application to crevices in rooms.

The movement of chlorpyrifos and diazinon from cracks and crevices in empty dormitory rooms with and without forced air movement to houseflies and plates in non-target areas was studied. Aluminum pie plates in rooms with the high concentrations of an insecticide, no forced air movement, and at the earlier sampling interals contained more insecticide. Insecticides were not detectable at 48 hr. Increased housefly movement occurred simultaneously with the initiation of insecticide application in rooms with forced air and 1 min later in rooms with no forced air. Mortality of houseflies exposed during and at 5 hr after insecticide application was greater for males than females in all tests except one; at the high insecticide concentrations; and at successive time intervals through the 24-hr interval after their transfer from the treated rooms to holding rooms. Houseflies in cages near the ceiling, exposed to an insecticide, and forced air movement, exhibited greater mortality than those in cages on the floor, while the reverse was true for houseflies in rooms with no forced air movement.

Air Movements↗

PubMed1977

[Neurologic involvement caused by insecticides. Study of chronic manifestations in 13 cases].

The clinical study of 13 patients with chronic neurological manifestation induced by insecticides (organophosphorades and organochlorades compounds) is reported. Twelve patients were male and farmers and one was a saleslady. The authors adopted five conditions for diagnosis: frequent contact with insecticides, synaptomatology directly related to the compounds exposition, clinical and laboratorial exclusion of others pathologies, quickly improvement of the symptoms when the patients were away from their original environment and high levels of insecticides in blood and urine determination. The clinical data was not uniform and the manifestation include pure motor neuropathy, mixed sensory-motor neuropathy, mielopathy and cranial nerves palsies. No relationship could be established between the insecticides (type, frequency of number of exposition) to the clinical picture. The insecticides determination was positive (moderated or elevated levels) in all patients and in 40% of controls (traces). Eletromyographic studies showed a neuropathic pattern in the majority of cases and reduced motor nerve conduction velocities. The authors believe that insecticides determination has a relative value and others criterion must be used in the diagnosis of chronic illness caused by insecticides. They think that others factors can be related with the symptomatology (hypersensibility, malnutrition, previous sensibilization or cumulative effect).

Adult↗

PubMed2026

Bacillus thuringiensis pathogenicity islands encode regulatory circuits controlling insecticidal Cry toxin expression during vegetative growth.

Bacillus thuringiensis (Bt) produces insecticidal toxins, including Cry and Vip3 proteins, that are widely used for biological pest control. Cry proteins are classically expressed during sporulation under the control of sporulation-specific σ factors, whereas Vip3 is produced during vegetative growth, suggesting distinct regulatory pathways. Notably, many cry and vip3A genes are clustered within pathogenicity islands (PAIs), such as BtPAI-1. However, whether these PAIs also encode regulatory mechanisms coordinating toxin expression remains unclear. Here, we identify VipR, a BtPAI-1-encoded transcriptional regulator, as an activator of insecticidal gene expression during the vegetative phase in Bt strains HD-1 and CT-43. In these strains, VipR promotes the transcription of BtPAI-1 associated insecticidal genes, including vip3A and selected cry genes, resulting in premature Cry protein accumulation and increased insecticidal activity. In addition, VipR contributes to the vegetative-phase expression of the non-BtPAI-1 cry9Aa genes in strain BGSC 4AE1. Phylogenetic analysis revealed that vipR is widely distributed in one-third of Bt strains, and is strongly associated with PAIs. Futhermore, heterologous expression of vipR in BGSC 4J5 and HD-73 was sufficient to activate vegetative-phase transcription of some cry independently of sporulation-specific σ factor cascade. These results support a role for VipR in coordinating vegetative-phase expression of insecticidal genes in the Bt strains examined and suggest that BtPAI-1 can encode both insecticidal determinants and regulatory functions that influence their expression. These findings provide new insights into the regulatory architecture of Bt pathogenicity islands and may facilitate the engineering of strains with enhanced insecticidal activity.

Bacillus thuringiensis↗

PubMed1975

Insecticide susceptibility of some vector fleas and mosquitoes in Burma.

Rat fleas and mosquitoes are insect vectors of public health importance in Burma. Plague is endemic in Central Burma and DDT has been the principal insecticide used for its control to date. Dengue haemorrhagic fever, recently introduced and transmitted by Aedes aegypti, has been spreading to major towns since 1971. The rodents, Rattus rattus, R. exulans, Bandicota bengalensis, Mus musculus, as well as shrews were commonly caught during routine trapping in the country. Rattus norvegicus, prevalent in Rangoon City, is not found in Central Burma. The rat fleas, Xenopsylla cheopis and X. astia, were found to be infesting these rodents, the former being the principal vector of plague. Insecticide susceptibility tests have been carried out periodically in plague endemic areas and Rangoon since 1966 and it is now observed that rat fleas in most of these endemic towns and Rangoon Port are no longer susceptible to DDT. Subsequent rechecks in towns where fleas became resistance to DDT show that fleas are persistently resistant to the insecticide. Aedes aegypti is found to be highly prevalent both in rural and urban areas of almost every major town and townships below 900 meters. Insecticide susceptible tests on this mosquito in limited areas show that the mosquito is generally resistant to DDT but susceptible to other insecticides. With the development of DDT resistance in fleas, it is now necessary to change to an effective insecticide in the control of plague in Burma.

Aedes↗

PubMed1977

Insecticides, polychlorinated biphenyls and metals in African lake ecosystems. I. Hartbeespoort Dam, Transvaal and Voëlvlei Dam, Cape Province, Republic of South Africa.

Concentrations and distribution of chlorinated hydrocarbon insecticides, polychlorinated biphenyls (PCB's) and some metals were determined in two South African lakes, Hartbeespoort Dam and Voëlvlei Dam. Water, bottom sediments, aquatic plants, aquatic insects, fish, fish-eating birds and their eggs were collected. Insecticides and PCB's were analyzed by thin layer and gas chromatography and mass-spectrometry. Analysis of metals was accomplished with atomic absorption spectrophotometry. Metals included arsenic, cadmium, copper, mangenese, lead, zinc, and mercury. The insecticide residue most commonly found in both dams were DDE, DDD, DDT, and dieldrin. Hartbeespoort had higher levesl than Voëlvlei of insecticides and PCB's in all types of samples common to both lakes. Concentrations of PCB's in all types of samples common to both lakes. Concentrations of PCB's having six or more chlorines increased with an increase in the trophic level. Concentrations of PCB's in the brains of the African birds were greater than the average total concentration of insecticides while the opposite was true for carcasses. Biological magnification of insecticides and PCB's occurred in both lakes. Hartbeespoort Dam had higher levels than Voëlvlei for all metals examined in bottom sediments and birds, except for copper in bird carcasses. Mercury levels in bird carcasses ranged from 2- to 5-fold greater than in fish while lead concentrations ranged from 2- to 10-fold greater.

Animals↗

PubMed1977

Mutagenicity screening of five methyl carbamate insecticides and their nitroso derivatives using mutants of Salmonella typhimurium LT2.

The mutagenic activity of five methyl carbamate insecticides-carbaryl, baygon, BUX-Ten, landrin and methomyl-and their nitroso derivatives were investigated using histidine auxotrophs-his TA98, his TA100, his TA1535, his TA1537 and his TA1538--of Salmonella typhimurium LT2 derived by Ames. The methyl carbamate insecticides did not cause a signficant increase in the number of revertant colonies in any of the strains used. In contrast, the nitroso derivatives of the carbamate insecticides greatly increased the number of colonies on plates inoculated with strains his TA100 and his TA1535. We conclude that the nitroso derivatives of the tested methyl carbamate insecticides are potent mutagens; whereas, the parent insecticides are non-mutagenic.

Carbamates↗

PubMed1979

Assessment of insecticidal impact on the malaria mosquito's vectorial capacity, from data on the man-biting rate and age-composition.

The reduction in average age of a vector population after application of a residual insecticide is commonly interpreted under the implicit assumption that the vector population is uniformly exposed to the insecticide. This assumption maximizes the calculated impact of the insecticide on the vectorial capacity. An alternative assumption, namely that the vector population is composed of two subpopulations, one endophilic and exposed, the other exophilic and not exposed, leads to a much smaller calculated impact of insecticide on the vectorial capacity. This is illustrated with data collected before and after application of propoxur in the Garki District, Kano State, Nigeria. These data were also used to estimate, on the one hand, before spraying, the proportion of blood meals taken by Anopheles gambiae s.l. on man that are followed by rest indoors, and on the other hand, after spraying, the proportion exposed after the first blood meal, according to the model of non-uniform exposure; the two estimates agree fairly well. The discussion compares the models of uniform and non-uniform exposure in terms of plausibility and concludes that the latter is more realistic. It is therefore prudent to take it into account when evaluating the impact of insecticides on the transmission of malaria.

Anopheles↗

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↗

PubMed1978

Field desorption mass spectrometric analysis of organic compound residues in the environment. I--Organochlorine insecticides.

Field desorption mass spectrometry is applied to the positive identification of organochlorine insecticides and their related compounds residing in field soil environment. Additionally, standard field desorption mass spectra of these compounds are presented. Soil samples were collected in lettuce and spinach fields, and insecticides were extracted, cleaned up, and separated with thin-layer chromatography. Residue levels were measured by injecting the extract into a gas chromatography equipped with an electron capture detector. Residues of p,p'-DDT and dieldrin in field soil samples were clearly identified by field desorption mass spectrometry using the emitter dipping method. Moreover, mixed residues of these insecticides were simultaneously confirmed. However, residues of insecticides and their related compounds other than p,p'-DDT and dieldrin could not be characterized. All spectra of standard showed prominent [M].+, [M(35Cl(n-1), 37Cl)].+ and [M(35Cl(n-2, 37Cl2)].+ ions, and the [M(35Cl(n-1), 37Cl)].+ ion was the base peak in all spectra obtained.

Chromatography, Gas↗

PubMed1977

Nitrosated methylcarbamate insecticides: effect on the DNA of human cells.

Normal human skin cells were treated with six insecticide esters of N-methylcarbamic acid or their N-nitroso derivatives. The DNA of the cells was sedimented in alkaline sucrose gradients at various times after treatment. The insecticides used were aldicarb, baygon, BUX-TEN, carbofuran, landrin, and methomyl. Numerous single-strand breaks were apparent in the DNA of all the nitroso derivative-treated cells but not in the DNA of those treated with the parent insecticides. Since the effect of the nitroso derivatives on the DNA could be observed for at least 20 h after removal of the chemical from the cultures, the DNA repairing events normally occurring in human cells after damage initiated by these chemical agents was not repaired as UV-type DNA damage or ionizing-type DNA damage in human cells. These observations suggest that the human cellular DNA in vivo is irreversibly altered by nitrosated N-methyl carbamate insecticides resulting in numerous alkali-sensitive bonds.

Carbamates↗

PubMed1977

Detection and determination of organophosphorus insecticides in tissues by thin-layer chromatography.

The toxicological analysis of 12 common organophosphorus insecticides is described. Suitable methods for the extraction of organophosphorus insecticides from tissues are proposed. The detection, identification and estimation of these insecticides by thin-layer chromatography is described for 25 solvent systems and a series of chromogenic reagents. The distribution of insecticides in human body tissues in five cases of poisoning by ethyl parathion, malathion, dimethoate, sumithion and phosphamidon has also been studied.

Autopsy↗

PubMed1976

Naturally occurring insecticides.

Naturally occurring insecticides are abundant and varied in their effects, though but a few are articles of commerce. Even for these, pyrethrum, nicotine, rotenone, hellebore, ryania, and sabadilla, there is a paucity of information on mammalian toxicology and environmental effects. In general, these materials are characterized favorably by low acute toxicity and ready dissipation in nature. Unfavorable aspects of natural insecticides are the contained mixture of active and inactive components and the low active ingredient content on a crop yield basis pointing to a high unit cost. Natural insecticides can serve additionally as leads to unnatural mimics, of which the commercially successful synthetic pyrethroids are prime examples. The chemical nature, relationship of insecticidal activity to chemical structure, occurrence, production, and utilization, registered uses, metabolism, and insect and mammalian toxicity are reviewed.

Animals↗

PubMed1975

Metabolism of radiolabeled insecticides in insects and related arthropods: a critical study of various techniques.

The metabolism of radiolabeled insecticides in insects and acarina is studied largely by coupling radiotracer techniques with analytical methods, such as TLC, paper and column chromatography, gel-permeation chromatography, and enzymatic assays. These techniques in various combinations yield both the identification and quantification of the metabolites. Other analytical methods such as gas chromatography or IR spectrometry may also be used to obtain additional support for identification of metabolites. In the absence of authentic chromatographic standards, however, NMR and mass spectrometry are necessary in the identification of the unknown compound. The quantity of the radiolabeled insecticide administered should be within the toxicological range of the insect. Therefore, the dosage-mortality response of the insect using unlabeled material should be determined. A dose should be selected that keeps insect mortality to a minimum in order to avoid complications in the computation of the balance data. The radiolabeled insecticide is usually applied topically to the insect. Alternately, the material may be administered by dipping in a solution containing the radiolabeled compound or by exposure to filter paper impregnated with radiolabeled material. Administration of the radiolabeled material by the oral route presents several problems. Sterile rearing conditions are mandatory to avoid contamination of treated diet with microorganisms. Some knowledge of the insect's feeding rhythm is desirable so that the labeled diet is given at peak feeding time. Synthetic diets should be adjusted to pH 7.0. These precautions minimize degradation of the insecticide in the diet prior to consumption by the insect. Precise doses of radiolabeled materials may be administered by injection. The technique is mainly useful in metabolism studies of intermediate materials resulting from the biotransformation of the parent compound.

Animals↗