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PubMed1962

Assessment of the residual toxicity to Anopheles gambiae of the organophosphorus insecticides Malathion and Baytex.

As part of a WHO programme to evaluate possible substitutes for the chlorinated hydrocarbons to which anopheline mosquitos in many countries have become resistant, two organophosphorus insecticides, malathion and Baytex, were tested as residual sprays on various types of surface against Anopheles gambiae adults in experimental huts at Magugu in Tanganyika. The long-lasting toxicity of both insecticides on relatively impervious surfaces was confirmed, but-as is the case with the chlorinated hydrocarbons-shorter persistence was obtained on sorptive surfaces. As most of the mosquitos rested on the roof, its surface was of much greater importance than the wall surface in determining kill; trials with naturally entering mosquitos indicated that where the roof was of grass malathion was to be preferred to Baytex. Observations confirmed that control huts attracted far more mosquitos than the treated huts and that the insecticide vapour apparently masked the human odour.

Animals↗

PubMed1964

HEMATOLOGICAL DISORDERS FOLLOWING EXPOSURE TO INSECTICIDES.

The medical literature dealing with hematological disorders following exposure to insecticides (chiefly chlorinated hydrocarbons and organic phosphorus compounds) is briefly reviewed. The development of blood dyscrasias as a consequence of exposure to insecticides is considered unlikely. Reported cases are few in number and often involve persons with little contact with these materials. It is often impossible to prove (or to disprove) a cause-and-effect relation in the individual case. Pointers which may be of assistance in evaluating this relationship are described. Purpura as a result of allergic vascular changes after exposure to insecticides is also discussed.

Agranulocytosis↗

PubMed1965

POST-TREATMENT REACTIONS IN CATTLE DURING EXTENSIVE FIELD TESTS OF SYSTEMIC ORGANOPHOSPHATE INSECTICIDES.

Treatment, grub infestation, and post-treatment reaction data is given for 11,537 range-managed beef cattle, of all age classes, treated for grub and louse control with various systemic organophosphate insecticides during the period 1956 to 1964. Two cows died from perforation of the throat during administration of Trolene boluses. Of 6,858 calves, 71 showed adverse reactions with 4 dead. Of 4,679 cattle over one year of age, 3 showed adverse reactions with one death. No typical organophosphate poisoning occurred. One death resulted from a paraplegic reaction and necropsy showed spinal nerve damage of the type often associated with the presence of H. bovis grubs in the spinal canal. Seventy-three reactions, with 4 deaths, were of a bloat-salivation type, and necropsies of 3 indicated anaphylaxis, the other an extensive pharyngeal - esophageal necrosis. Reactions were directly associated with grub abundance. Other stress factors coincident to insecticide treatment, such as Bang's vaccination and dehorning, did not enhance reactions, and incipient coccidiosis did not predispose to reactions, nor did insecticide treatment increase susceptibility to coccidiosis. It is concluded that the observed adverse reactions resulted from the killing of grubs situated in the animal tissues.

Animals↗

PubMed1955

Nozzles of insecticide sprayers; comments from the point of view of malaria control.

Certain performance characteristics of the insecticide-sprayer nozzle tip and its relationship to the pressure regulator are discussed.After analysing the effectiveness of residual spraying at various pressures, the author concludes that low-pressure application would best attain the pattern and rate of insecticide discharge laid down by the WHO Expert Committee on Insecticides.

Humans↗

PubMedDate not supplied

Insecticide treated nets: impact on vector populations and relevance of initial intensity of transmission and pyrethroid resistance.

Insecticide treated bednets locate a deposit of a quick-acting insecticide of low human toxicity between a sleeper and host-seeking mosquitoes. Thus a chemical barrier is added to the often incomplete physical barrier provided by the net. Treated nets may be considered as mosquito traps baited by the odour of the sleeper. Trials in Assam, Tanzania and elsewhere have shown that when a whole community is provided with treated nets, so many mosquitoes of anthropophilic species are killed by contact with the nets that the density and/or sporozoite rate of the vector population is reduced. In order to gain this "mass" or community effect, in addition to widespread personal protection, and thus to achieve the full potential of the treated net method, a high per cent coverage of the community is needed. This suggests that organised free provision of treated nets, comparable to a house spraying programme, is likely to be more cost-effective than trying to market nets and insecticide to very poor rural people. In areas with high malaria transmission, where acquisition of immunity to malaria is very important, it has been argued that vector control (without vector eradication) could, in the long run, make the situation worse by preventing the normal build-up of immunity. However, our data from Tanzania do not support this idea--3-4 years after provision of nets (which are re-treated annually) young children are still showing clear health benefits; older children are not "paying" for this by showing worse impact of malaria. There is less malaria morbidity in a highland area where malaria transmission is about 15x less intense than in a nearby lowland area. The per cent impact of treated nets malaria morbidity in both area was very similar. At present only pyrethroids are used for net treatment which suggested that emergence of pyrethroid resistance would have a disastrous effect. However, in West Africa, where there is now a high frequency of the kdr resistance gene in Anopheles gambiae, it is reported that treated nets continue to have a powerful impact on vector populations. In Tanzania, pyrethroid resistance has not been detected in malaria vectors, but it has emerged in bedbugs after seven years use of treated nets.

Animals↗

PubMed2005

Adult and larval insecticide susceptibility status of Culex quinquefasciatus (Say) mosquitoes in Kuala Lumpur Malaysia.

The susceptibility of Culex quinquefasciatus to chemical insecticides in two field sites in Kuala Lumpur was evaluated using the WHO standard susceptibility test. Less then 7 days old female mosquitos, reared from wild caught females were exposed to discriminating dosages of insecticides at recommended exposure periods. The larval bioassay were conducted using the multiple concentrations and the LC50 value was determined. The results indicated that cyfluthrin is the most effective among all the insecticides tested with LT50 value of 29.95 min and 28.59 min, for the strain from Ampang Hill and Pantai Dalam, respectively. It was surprisingly to note that both these field strains showed 0% mortality when tested against malathion and DDT. The LC50 value indicated that both strains were highly resistant to malathion with resistance ratio of 17,988 folds and 14,053 folds, respectively. This concludes that resistance at larval stages is extremely high compared to adult stages.

Animals↗

PubMedDate not supplied

[The seasonal changes in the resistance and irritability to insecticides in malarial mosquitoes in Karakalpakia].

Primary observations on insecticide resistance and irritability in Anopheles martinius and An. pulcherrimus were carried out in Karakalpakia. Both the species were completely susceptible to malathion and fenitrothion, and An. pulcherrimus was also susceptible to propoxur and DDT. An. martinius had a moderate resistance to DDT, which decreased by the autumn, and initial stage of resistance to propoxur probably based on knockdown mechanism. In both the species irritability was to DDT high, and was lower to malathion, propoxur and especially fenitrothion. During the season, irritability to the four insecticides was decreasing in An. pulcherrimus, and in An. martinius; it was high in April but became moderate or low in July and then began to grow again reaching the initial high level in November. No relation between the seasonal changes of irritability and rounds of insecticide spraying was noticed. It is supposed that a genetically and physiologically stipulated mechanism of the seasonal variability of irritability exists in mosquito populations.

Animals↗

PubMed1978

Resistant level of houseflies to six kinds of synthetic insecticides in Malaysia.

The resistant level of the houseflies to six kinds of insecticides, DDT, Resmethrin, DDVP, Baytex, Sumithion and Diazinon, was examined on the seven strains collected in Malaysia. It was found that their susceptibility is rather higher than that of the Takatsuki strain which is a standard strain in Japan. However, their susceptibility to Sumithion was the same or slightly lower than that of the Takatsuki strain. The resistant level to five of six kinds of insecticides was the highest in the strain of Cameron Highland. The values were close to Singh's data in 1973, and this means that the resistance of the houseflies to the insecticides is increasing in Malaysia.

Animals↗

PubMed1989

[Insecticide resistance in the Musca domestica populations of the GDR 1976-1988].

Data have been compiled concerning insecticide-resistance in native populations of Musca domestica from 10 districts of the GDR for the period between 1976 and 1988. The insecticides tested were trichlorfon, dimethoate, bromophos, and trichlophenidine, i.e. those insecticides commonly used in house fly control on animal production farms. Pyrethrum and permethrin were also tested. Since the test strains were frequently selected in connection with control failures, the data may not be representative for all populations. But they allow some conclusions concerning the development of resistance. A stage of development has been reached which required a departure from the exclusive use of conventional procedures (residual spraying of surfaces with persistent contact pesticides). Intensified research on non-chemical or special chemical methods is urgently needed.

Animals↗

PubMed1967

Insecticide-resistance in Culex pipiens fatigans.

The three main subspecies of the Culex pipiens complex-pipiens, fatigans and molestus-have similar "normal" levels of susceptibility to insecticides. C. p. fatigans larvae resemble those of anopheline mosquitos in sensitivity to dieldrin, but are more resistant to DDT; the adults are unusually resistant to chlorinated insecticides, but do not differ greatly from other species of mosquito in susceptibility to organophosphorus compounds.There is evidence of conversion of DDT to DDE in C. p. fatigans and other mosquitos, but this may well not be the only cause of resistance. Dieldrin-resistance in C. p. fatigans involves cross-resistance to HCH, but at a considerably lower level; the mechanism of resistance is still obscure. Resistance to organophosphorus insecticides has been observed; the cross-resistance to diazinon indicates that the mechanism is not solely one of carboxy-esterase detoxication.Mechanisms of inheritance of resistance have been investigated. The most recent results indicate the monofactorial inheritance of resistance by a single pair of nearly dominant genes on chromosome 2 for DDT-resistance and by a single pair of genes on chromosome 3 with intermediate dominance for HCH dieldrin-resistance.

Africa↗

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↗

PubMed1996

Susceptibility status of Phlebotomus papatasi and Sergentomyia punjabaensis (Diptera:Psychodidae) to some insecticides in district Bikaner (Rajasthan).

Susceptibility tests were carried out on the females of two species of sandflies viz. Phlebotomus papatasi and Sergentomyia punjabaensis against six insecticides viz. DDT, dieldrin (organochlorines); malathion, fenitrothion (organophosphates); propoxur (carbamate) and permethrin (synthetic pyrethroid) in district Bikaner, Rajasthan. A concentration and time dependent effect was observed with insecticides for both the species. P. papatasi was found resistant to DDT, dieldrin and propoxur while susceptible to malathion, fenitrothion and permethrin. However, S. punjabensis was found susceptible to all the insecticides tested. LC50 and LT50 value estimated for DDT and dieldrin for P. papatasi and S. punjabaensis were found to be 2.2 and 0.3% x 1 hr and 1.45 and 0.032% x 15 min. respectively.

Animals↗

PubMed1996

[3 combinations of esterases and their relation with the resistance to organophosphate, carbamate, and pyrethroid insecticides in Culex quinquefasciatus Say, 1823 (Diptera: Culicidae) in Cuba].

The possible relationship between different patterns of esterases and the resistance to various types of insecticides was analyzed by bioassays, biochemical tests, and electrophoresis carried out in a population of Culex quinquefasciatus from Camagüey and in three colonies obtained from it by family selection. The original population was heterogeneous and presented 8 combinations of esterases in polyacrylamide gel. A3A6B6, B1B6 and B1A6B6 were the most frequent of them and characterized each selected colony. Every studied colony, including the parental one, showed different levels of resistance to diverse insecticides. Only the resistance to propoxur showed less variation. In every colony it seems to exist a combination of resistance mechanisms; however, the differences found in tests with DEF synergized insecticides show that the different bands of zymograms may represent esterases contributing in a different way to resistance.

Animals↗

PubMed1998

Novel insecticidal peptides from Tegenaria agrestis spider venom may have a direct effect on the insect central nervous system.

Fractionation of venom from an agelenid spider, Tegenaria agrestis, resulted in the isolation of a family of three peptides with potent insecticidal activity. These peptide toxins, TaITX-1, -2, and -3, whose sequences were revealed from cloned cDNAs, each consist of 50 amino acid residues, six of which are cysteines. They appear to be amidated at their C-termini and exhibit greater than 90% sequence identity. Unlike other reported spider toxins, the TaI toxins are processed from precursors containing no propeptide sequences. In lepidopteran larvae and corn rootworm beetles, the insecticidal Tegenaria toxins caused an unusual excitatory symptomatology with 50% paralytic doses ranging from 0.23 to 2.6 nmol/g. In a series of electrophysiological experiments performed in house fly larvae, these toxins caused an elevated rate of firing from central nervous system neurons. No significant effects were found when any peripheral sensory or motor systems were examined. Thus, it appears that the TaI toxins may act in a fashion not previously reported for insecticidal peptide toxins; they may act directly on the insect central nervous system.

Amino Acid Sequence↗

PubMed2002

Surfactant-mediated capillary electrochromatography with octadecyl-silica- packed capillary columns for the separation of nonpolar compounds. Case of pyrethroid insecticides.

Capillary electrochromatography (CEC) with octadecyl-silica-packed capillary columns was evaluated in the separation of nonpolar compounds, e.g., pyrethroid insecticides, using surfactant-rich mobile phases. This novel concept is referred to as surfactant-mediated capillary electrochromatography (SM-CEC), and is based on including a charged surfactant, namely sodium di-2-ethylhexyl sulfosuccinate (DOSS), in the mobile phase. Under these conditions, DOSS plays the role of a slowly moving pseudostationary phase so that solutes are partitioned between a mobile phase, a fixed stationary phase and a slowly moving pseudostationary phase. The SM-CEC system was investigated with pyrethroid insecticides over a wide range of DOSS and acetonitrile concentrations in the mobile phase. Pyrethroid insecticides, which are very hydrophobic solutes consisting of geometric isomers and diastereomers, were better resolved in SM-CEC than in straight CEC.

Acetonitriles↗

PubMed2001

Optimum timing of insecticide applications against diamondback moth Plutella xylostella in cole crops using threshold catches in sex pheromone traps.

Field trials were conducted in cabbage (Brassica oleracea var capitata), cauliflower (B oleracea var botrytis) and knol khol (B oleracea gongylodes) crops at two different locations in Karnataka State (India) to optimize the timing of insecticide applications to control the diamondback moth, Plutella xylostella, using sex pheromone traps. Our results indicate that applications of cartap hydrochloride as insecticide during a 12-24 h period after the pheromone traps had caught on average 8, 12 and 16 males per trap per night in cabbage, cauliflower and knol khol, respectively, were significantly more effective than regular insecticide sprays at 7, 9, 12 or 15 days after transplantation. This was demonstrated by estimation of the mean number of eggs and larvae per plant, the percentage of holes produced, as well as the marketable yield of the three crops at each location. A good correlation between the immature stages, infestation level, the estimated crop yield and the number of moths caught in pheromone traps was also found, indicating the usefulness of pheromone-based monitoring traps to predict population densities of the pest.

Animals↗

PubMed2001

The discovery of indoxacarb: oxadiazines as a new class of pyrazoline-type insecticides.

The evolution of the insecticidal pyrazoline moiety that was originally discovered in 1972 has led to the discovery of a new crop insecticide, indoxacarb, which is the first commercialized pyrazoline-type sodium-channel blocker. Both monocyclic and fused-tricyclic pyrazolines and pyridazines, as well as structurally related semicarbazones were examined prior to the discovery of analogous tricyclic oxadiazines which had similarly high activity as well as favorable environmental dissipation rates and low toxicity to non-target organisms. The eventual leading candidate, DPX-JW062, was originally obtained as a racemic molecule, but a chiral synthesis was developed which produces material that is 50% ee in the insecticidal (+)-S-enantiomer (DPX-MP062, indoxacarb).

Animals↗

PubMed1984

Adaptation of insects to insecticides.

Insects have successfully adapted to most insecticides by becoming resistant to them. This adaptation, of recent origin, has evolved rapidly and independently in a large number of species and is of serious economic and medical importance. The origins of resistance are still obscure, but resistance is assumed to be pre-adaptive, arising through recurrent mutation of existing alleles. However, in at least one well-researched case it probably originated by gene duplication. Resistance can be monofactorial or multifactorial. When several independent mechanisms confer resistance to the same group of insecticides the order in which these mechanisms are selected may reflect their effectiveness in protecting insects from the toxic effects of the different compounds. Our concept of resistance is changing as insects continue to adapt to the insecticide-containing environment. Criteria for defining resistance in both fundamental and practical terms are re-examined here in the light of recent work.

Adaptation, Biological↗