Exposure to Insecticides Modifies Gene Expression and DNA Methylation in Hematopoietic Tissues In Vitro.

The evidence supporting the biological plausibility of the association of permethrin and malathion with hematological cancer is limited and contradictory; thus, further studies are needed. This study aimed to investigate whether in vitro exposure to 0.1 µM permethrin and malathion at 0, 24, 48 and 72 h after cell culture initiation induced changes in the gene expression and DNA methylation in mononuclear cells from bone marrow and peripheral blood (BMMCs, PBMCs). Both pesticides induced several gene expression modifications in both tissues. Through gene ontology analysis, we found that permethrin deregulates ion channels in PBMCs and BMMCs and that malathion alters genes coding proteins with nucleic acid binding capacity, which was also observed in PBMCs exposed to permethrin. Additionally, we found that both insecticides deregulate genes coding proteins with chemotaxis functions, ion channels, and cytokines. Several genes deregulated in this study are potentially associated with cancer onset and development, and some of them have been reported to be deregulated in hematological cancer. We found that permethrin does not induce DNA hypermethylation but can induce hypomethylation, and that malathion generated both types of events. Our results suggest that these pesticides have the potential to modify gene expression through changes in promoter DNA methylation and potentially through other mechanisms that should be investigated.

Low concentrations of permethrin and malathion induce numerical and structural abnormalities in KMT2A and IGH genes in vitro.

Pesticides are commonly used worldwide and almost every human is potentially exposed to these chemicals. Exposure to pesticides such as permethrin and malathion has been associated with hematological malignancies in epidemiological studies. However, biological evidence showing if these chemicals induce genetic aberrations involved in the etiology of leukemia and lymphoma is missing. In our previous work, we have shown that a single high exposure (200 µm, 24 hours) of permethrin and malathion induce damage in genes associated with hematological malignancies in peripheral blood mononuclear cells analyzed by interphase fluorescence in situ hybridization (FISH). In the present study, we assessed by FISH whether exposure to low concentrations (0.1 µm, 72 hours) of permethrin and malathion induce aberrations in KMT2A and IGH genes, which are involved in the etiology of leukemia and lymphoma. Peripheral blood mononuclear cells were exposed to the chemicals, and damage in these genes was assessed on interphases and metaphases. We observed that both chemicals at low concentration induced structural aberrations in KMT2A and IGH genes. A higher level of damage was observed in KMT2A gene with malathion treatment and in IGH gene with permethrin exposure. We also observed numerical aberrations induced by these chemicals. The most frequent aberrations detected on interphase FISH were also observed on metaphases. Our results show that permethrin and malathion induce genetic damage in genes associated with hematological cancer, at concentrations biologically relevant. In addition, damage was observed on dividing cells, which suggests that these cells maintain their proliferation capacity in spite of the genetic damage they possess.

Physiological selectivity and activity reduction of insecticides by rainfall to predatory wasps of Tuta absoluta.

In this study, we carried out three bioassays with nine used insecticides in tomato crops to identify their efficiency against tomato leaf miner Tuta absoluta, the physiological selectivity and the activity reduction of insecticides by three rain regimes to predatory wasps Protonectarina sylveirae and Polybia scutellaris. We assessed the mortality caused by the recommended doses of abamectin, beta-cyfluthrin, cartap, chlorfenapyr, etofenprox, methamidophos, permethrin, phenthoate and spinosad to T. absoluta and wasps at the moment of application. In addition, we evaluated the wasp mortality due to the insecticides for 30 days on plants that did not receive rain and on plants that received 4 or 125 mm of rain. Spinosad, cartap, chlorfenapyr, phenthoate, abamectin and methamidophos caused mortality higher than 90% to T. absoluta, whereas the pyrethroids beta-cyfluthrin, etofenprox and permethrin caused mortality between 8.5% and 46.25%. At the moment of application, all the insecticides were highly toxic to the wasps, causing mortality higher than 80%. In the absence of rain, all the insecticides continued to cause high mortality to the wasps for 30 days after the application. The toxicity of spinosad and methamidophos on both wasp species; beta-cyfluthrin on P. sylveirae and chlorfenapyr and abamectin on P. scutellaris, decreased when the plants received 4 mm of rain. In contrast, the other insecticides only showed reduced toxicity on the wasps when the plants received 125 mm of rain.

Genotoxic and mutagenic effects of permethrin in mice: micronuclei analysis in peripheral blood erythrocytes.

Pyrethroids such as permethrin are synthetic compounds widely used in the agriculture of many countries to combat plagues and in domestic products, such as acaricides. Not so long ago these chemicals were characterized as non-toxic for non-target organisms; however, recent studies have showed that these compounds could present toxic potential for many organisms. In this sense, this study presents genotoxic and mutagenic potential of permethrin administered intraperitoneally in mice under artificial conditions by the use of micronucleus assay in the peripheral blood of these animals. The mice were divided into five groups: group I = negative control (distilled water), group II = positive control (cyclophosphamide), group III = 30% of permethrin LD(50) (96 mg/kg), group IV = 50% of permethrin LD(50) (160 mg/kg), and group V = 80% of permethrin LD(50) (256 mg/kg). The peripheral blood was collected 24, 48, and 72 h after treatment. Results showed that all the tested permethrin dosages presented genotoxic and mutagenic effects 24 h after treatment, which would contradict the classification of this chemical product as moderately toxic, i.e., unable to cause damages to the cell DNA.

Degenerative process and cell death in salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi-engorged female exposed to the acaricide permethrin.

Ticks are ectoparasites of great medical and veterinary importance around the world and synthetic chemicals such as permethrin have been used for their control. This study provides a cytochemistry analysis of both degenerative and cell death processes in salivary glands of the brown dog tick Rhipicephalus sanguineus semi-engorged females exposed to 206, 1,031, and 2,062 ppm of permethrin. The results presented herein demonstrate that permethrin is a potent chemical acaricide that would act on the glandular tissue's morphophysiology in this tick species by eliciting severe changes in the acinus shape, intense vacuolation of the acinar cells' cytoplasm, marked glandular tissue disorganization, culminating in an advanced degenerative stage with consequent formation of many apoptotic bodies (cell death). In addition, permethrin induced major changes in the acinar cells' nucleus, such as a change both in its shape and size, chromatin marginalization, nuclear fragmentation, and appearance of picnotic nuclei, especially when the highest concentrations of the product were used. Thus, permethrin induced early degeneration of this tissue characterized by significant changes in the structure of acinar cells and production of enzymes related to the cell death process, in addition to interfering directly in the genetic material of these cells.

Droplet size and efficacy of an adulticide-larvicide ultralow-volume formulation on Aedes aegypti using different solvents and spray application methods.

BACKGROUND: When cases of dengue are reported or the density of adult Aedes aegypti (L.) becomes too high, ultralow-volume (ULV) application of insecticides is the recommended control method. The droplet size of an aerosol insecticide influences its efficiency in killing adult mosquitoes. Many studies have been carried out to determine the optimum droplet size that maximises vector control efforts, but only a few have determined droplet-size spectra for specific equipment using different solvents and comparing thermal and non-thermal aerosols. RESULTS: The present study showed that the droplet size for a water-based adulticide-larvicide formulation was larger than for the same formulation diluted in gasoil or biodiesel. No significant differences in adult mortality were observed between sprayers and solvents, but efficacy decreased with distance from the sprayer nozzle. Adult emergence inhibition was more than 90% when using water as a solvent for both thermal and cold foggers, and the efficacy did not decrease with distance from the sprayer nozzle. On the other hand, oil-based solvents became less effective with distance. CONCLUSION: The use of water as a solvent with both thermal and cold foggers improves the efficacy of the studied formulation containing permethrin as adulticide and pyriproxyfen as larvicide in scaled-up assays. Moreover, it reduces the environmental impact and costs of spraying by comparison with formulations using oil solvents.

Hormetic responses of a stinkbug predator to sublethal doses of pyrethroid.

Stressors can affect reproduction and longevity by impacting endocrine and immune systems but they may increase life span and stimulate reproduction. The effects of sublethal doses of permethrin topically applied on third instar nymphs of Podisus distinctus (Heteroptera: Pentatomidae) was evaluated. The weight of females survival of nymph and adults, number of eggs and nymphs/females of P. distinctus were higher when exposed to lower doses of permethrin. On the other hand, the exposition to the 0.131, 1.315 and 13.15 ppb showed positive effects on the oviposition periods, number of egg masses and longevity of P. distinctus females.

Cytotoxic effects of permethrin in salivary glands of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi-engorged females.

Because of the medical and veterinary importance of ticks and the wide use of synthetic chemical substances such as permethrin (active ingredient of Advantage® Max3 - Bayer)for their control, this study evaluated the effects of different concentrations (206, 1031 and 2062 ppm) of the acaricide on the salivary glands of Rhipicephalus sanguineus semi-engorged females. Results showed that permethrin is a potent substance that acts morpho-physiologically in the tick glandular tissue, causing changes in the acini shape intense vacuolation in acinar cells, and disruption of the tissue by cell death process, with subsequent formation of apoptotic bodies, especially at higher concentrations, thus precluding the accurate identification of different types of acini. Importantly, it is demonstrated that permethrin acts on salivary gland tissue, as well as affecting the nervous system, accelerating the process of glandular degeneration, and interfering with the engorgement process of female ticks, preventing them from completing the feeding process.

Cytotoxic effects of permethrin in oocytes of Rhipicephalus sanguineus (Acari: Ixodidae) fully engorged females: I. Direct or indirect action of the acaricide in germ cells?

Given the wide use of synthetic chemicals to control ticks, this study evaluated the effects of the permethrin pyrethroid on oocytes of Rhipicephalus sanguineus fully engorged females in order to examine whether this compound, in addition to the proven neurotoxic effect, also acts directly on germ cells. The results revealed that permethrin effectively inhibits and/or interrupts the reproductive process of R. sanguineus. Exposed oocytes exhibited prominent structural changes such as altered shape of cells and germ vesicle (oocyte nucleus), cytoplasmic vacuolation, and decrease of yolk granules. The composition of the latter, however, was not altered. These findings confirm those already reported by Roma et al. (Food Chem Toxicol 48:825-830, 2010) demonstrating that permethrin acts on germ cells of R. sanguineus via direct absorption from the hemolymph by pedicel cells, or by the oocyte plasmic membrane. On the other hand, these results contradict studies reporting that acaricides act exclusively on the nervous systems of ticks and that all the changes in other organs are a result from the indirect action of these chemical compounds, because blocking of the nervous system would compromise the normal metabolism of other organs (dependent on sensory information).

Insecticide survival and behavioral avoidance in the lacewings Chrysoperla externa and Ceraeochrysa cubana.

Insecticide impact on non-target species, such as insect predators and parasitoids, is an ever-growing concern in agriculture and recent studies have been shifting focus from lethal to sub-lethal effects since they may prevail in field conditions, although more difficult to assess. Synthetic insecticides are the main concern, but the recent spread of biopesticide use in agriculture draws attention, particularly the main botanical insecticide currently in use - azadirachtin. Here we assessed the lethal and behavioral sub-lethal response of predatory larvae of the lacewing species Chrysoperla externa and Ceraeochrysa cubana to two frequently used synthetic insecticides, malathion and permethrin, and to the bioinsecticide azadirachtin. The recommended field concentration of the synthetic insecticides led to low survival time of lacewing larvae from both species, in contrast with azadirachtin. However, all three compounds led to 100% mortality of the lacewing larvae from both species. Insecticide repellence (i.e., avoidance without contact) was similar for both synthetic insecticides in both species, but azadirachtin was a stronger repellent for C. externa, but not C. cubana. In addition, insecticide irritability (i.e., avoidance after contact) occurred in both lacewing species to all three insecticides tested. The notion that natural compounds are safer than synthetic compounds to non-target species is refuted in the present study, which also detected significant irritability to all of the insecticides regardless of their origin, and species-specific repellence elicited particularly by azadirachtin. Therefore, bioinsecticides should not be exempted from risk assessment, and non-target sub-lethal effects should not be neglected when considering potential insecticide use in agriculture.

Decreased sperm motility in rats orally exposed to single or mixed pesticides.

The Brazilian Agency of Sanitary Vigilance (ANVISA) conducted a study that demonstrated the presence of residues of several pesticides in fresh fruits and vegetables that were available for purchase by the general populace. In order to evaluate potential adverse health effects of low-level exposure to agrochemicals, the reproductive toxicity of the pesticides dicofol, dichlorvos, permethrin, endosulfan, and dieldrin was evaluated in rats dosed with these chemicals individually or as mixtures. Sixty male Lewis rats (6 wk old, 200 x g) were randomly allocated to 8 groups: (1) control group, received basal diet; (2) 5 groups designated a to e received the diet containing each pesticide individually, at the respective effective doses: lowest-observed-adverse-effect level (LOAEL) for dieldrin and endosulfan, lowest-observed-effect level (LOEL) for dicofol, and lowest effect level (LEL) for dichlorvos and permethrin, respectively, depending on the published data; (3) effective dose group, which received a mixture of pesticides added to basal diet at the respective doses reported to produce adverse effects; and (4) low dose group, which received a pesticide mixture added to the basal diet, where each pesticide was at its no-observed-effect level (NOEL). After 8 wk of treatment, reproductive parameters were evaluated. Sperm morphology, daily sperm production (DSP), sperm transit time through the epididymis, hormonal levels, and histopathological evaluation of testis and epididymis did not differ significantly among the groups. However, sperm motility was significantly decreased in animals that received a mixture of dieldrin, endosulfan, dicofol, dichlorvos, and permethrin, as well as in the group receiving dicofol alone. Exposure to the individual pesticides endosulfan, dichlorvos, and permethrin did not markedly affect sperm motility. The impairment of sperm motility in the mixture of pesticides at the NOEL level indicates that reproductive effects not seen with individual pesticides may occur in presence of several pesticides due to an additive effect. However, the pesticide mixtures did not appear to affect DSP or spermatogenesis despite reduced sperm motility.

Permethrin-induced morphological changes in oocytes of Rhipicephalus sanguineus (Acari: Ixodidae) semi-engorged females.

The permethrin, active ingredient of the Advantage(R) Max3--Bayer, has been widely used in the chemical control of ticks. These ectoparasites are one of the most important animal groups that cause serious damage to their hosts. This study evaluated the toxic effects of permethrin in oocytes of Rhipicephalus sanguineus semi-engorged females subjected to four treatments: group I (control--distilled water), group II (206 ppm of permethrin), group III (1031 ppm of permethrin) and group IV (2062 ppm of permethrin). Results demonstrated that permethrin is a potent chemical agent causing major structural changes in oocytes, such as emergence of large vacuolated cytoplasm regions, reducing the amount of yolk granules and decreasing the size of oocytes, culminating with cell death. As reported in the literature, these oocytes changes, besides affect the tick nervous system, also drastically reduce or prevent the reproduction process in females of R. sanguineus ticks subjected to this compound.

Permethrin-induced ultrastructural changes in oocytes of Rhipicephalus sanguineus (Latreille, 1806) (Acari: Ixodidae) semi-engorged females.

Currently, the most effective method for tick control is by the use of chemical acaricides such as permethrin (active ingredient of the Advantage(®) Max3 acaricide, Bayer), a pyrethroid with neurotoxic action. However, data about its effect on other tick systems, such as glandular and reproductive, are still scarce. This study provides ultrastructural details of the toxic effects induced in oocytes of semi-engorged Rhipicephalus sanguineus females exposed to 206, 1031, and 2062 ppm of permethrin. The results showed that permethrin is an effective acaricide by inhibiting and/or neutralizing the tick reproductive process since oocytes of treated ticks presented major structural changes such as cytoplasm vacuolation, disruption of both membranes and cell organelles, leading to cell death. Data also showed that even in low concentrations permethrin induced changes in germ cells, making them non-viable. The defense mechanisms used by oocytes against the action of permethrin in the attempt of recovering the cellular integrity and of ensuring the viability of these cells were also described in this study.

Aerial and tidal transport of mosquito control pesticides into the Florida Keys National Marine Sanctuary

This project was undertaken as the initial monitoring program to determine if mosquito adulticides applied along the Florida Keys cause adverse ecological effects in the Florida Keys National Marine Sanctuary (FKNMS). The study monitored the distribution and persistence of two mosquito adulticides, permethrin and dibrom (naled), during three separate routine applications by the Florida Keys Mosquito Control District. The approach was to determine if toxic concentrations of the pesticides entered the FKNMS by aerial drift or tidal transport. The amount of pesticide entering the FKNMS by way of aerial drift was monitored by collection on glass fiber filter pads, set on floats in a grid pattern on either side of the FKNMS. Permethrin was recovered from filter pads on the leeward side for each of the three applications, ranging from 0.5 to 50.1 microg/m(2) throughout the study. Tidal current transport was monitored by collection of surface and subsurface water samples at each grid site. Tidal transport of naled and dichlorvos (naled degradation product) was apparent in the adjacent waters of the FKNMS. These compounds were detected in subsurface, offshore water at 0.1 to 0.6 microg/1, 14 hr after application. Permethrin was not detected in offshore water samples; however, concentrations ranging from 5.1 to 9.4 microg/l were found in surface water from the canal system adjacent to the application route. Comparison of the observed environmental concentrations with toxicity data (permethrin LC-50, 96 hr for Mysidopsis bahia = 0.02 microg/l) indicated a potential hazard to marine invertebrates in the canals with possible tidal transport to other areas

Aerial and tidal transport of mosquito control pesticides into the Florida Keys National Marine Sanctuary.

This project was undertaken as the initial monitoring program to determine if mosquito adulticides applied along the Florida Keys cause adverse ecological effects in the Florida Keys National Marine Sanctuary (FKNMS). The study monitored the distribution and persistence of two mosquito adulticides, permethrin and dibrom (naled), during three separate routine applications by the Florida Keys Mosquito Control District. The approach was to determine if toxic concentrations of the pesticides entered the FKNMS by aerial drift or tidal transport. The amount of pesticide entering the FKNMS by way of aerial drift was monitored by collection on glass fiber filter pads, set on floats in a grid pattern on either side of the FKNMS. Permethrin was recovered from filter pads on the leeward side for each of the three applications, ranging from 0.5 to 50.1 microg/m(2) throughout the study. Tidal current transport was monitored by collection of surface and subsurface water samples at each grid site. Tidal transport of naled and dichlorvos (naled degradation product) was apparent in the adjacent waters of the FKNMS. These compounds were detected in subsurface, offshore water at 0.1 to 0.6 microg/1, 14 hr after application. Permethrin was not detected in offshore water samples; however, concentrations ranging from 5.1 to 9.4 microg/l were found in surface water from the canal system adjacent to the application route. Comparison of the observed environmental concentrations with toxicity data (permethrin LC-50, 96 hr for Mysidopsis bahia = 0.02 microg/l) indicated a potential hazard to marine invertebrates in the canals with possible tidal transport to other areas.

Evolution of resistance under insecticide selection pressure in Culex pipiens quinquefasciatus (Diptera, Culicidae) from Martinique.

Population surveys of Culex pipiens quinquefasciatus carried out in 1991 and 1999 were compared with data collected in 1990 before the beginning of the control program against this mosquito. Larval samples collected in 1999 displayed resistance to the four tested insecticides: permethrin, propoxur, temephos, and chlorpyrifos. Temephos resistance ratio at LC50 (RR50) ranged between 8.1- and 42-fold compared with 2.9- and 4.6-fold in 1990, and chlorpyrifos RR50 ranged between 8.6- and 123-fold compared with 6.4- and 19-fold in 1990. This increased resistance to organophosphorus insecticides was associated with a sharp decrease of susceptible genotypes at two loci (Ester and ace-1), as well as to an allele replacement at the Ester locus.

Prevalence and levels of permethrin resistance in Pediculus humanus capitis De Geer (Anoplura: Pediculidae) from Buenos Aires, Argentina.

Permethrin has been used extensively for control of Pediculus humanus capitis De Geer (Anoplura: Pediculidae) in Argentina since 1990, resulting in the development of resistance to this and other pyrethroids. This resistance was first detected in some field populations in 1997. A survey for resistance in Buenos Aires in 2001 revealed significant resistance levels in lice on children at 24 of 26 (92.3%) schools. When compared with a previously unexposed reference population, resistance ratios (RRs) obtained by exposing the insects to filter papers impregnated with permethrin ranged from 2 to 60 in 10 (39%) of the schools. RRs in the remaining 14 (61%) populations were too great to not be measured with the filter paper method (RR > 88.7). As an alternative, we used topical applications of 0.1 microl of acetone solution of permethrin on the dorsal abdomen of adults and third instars. This topical method, which has not been previously reported for head lice, was capable of quantifying higher levels of resistance. Highly resistant populations had RRs from 162.5 to 655.2. When applied to populations with low and intermediate levels of resistance, results from the filter paper and topical application methods were highly correlated, and RRs from topical application were higher than those from the filter paper method. Results from the combination of the two methods indicated that head lice among Buenos Aries school children are highly resistant to permethrin, and the resistance is widespread.

Survey of resistance to permethrin and diazinon and the use of a multiplex polymerase chain reaction assay to detect resistance alleles in the horn fly, Haematobia irritans irritans (L.).

A field survey was conducted in 2001 to evaluate resistance to pyrethroid and organophosphate (OP) insecticides on horn flies, Hematobia irritans irritans (L.), from seven ranches in the state of Tamaulipas, Mexico, and from three locations in central Texas. Filter papers impregnated with either technical permethrin or diazinon were used to measure the levels of resistance to pyrethroids and OPs. A multiplex polymerase chain reaction (PCR) assay was used on individual horn flies from these field populations to detect the presence of the kdr and super-kdr alleles associated with pyrethroid resistance, and a mutated alphaE7 esterase allele associated with OP resistance. Relative to a susceptible laboratory (Kerrville) strain, horn flies from Mexico exhibited 5.1- to 28.3-fold resistance to permethrin at the LC50, and 23.8- to 136-fold resistance at the LC90. Horn flies from Texas ranches exhibited only two- to five-fold resistance. All field populations of the horn fly were highly susceptible to diazinon, and no mutant alphaE7 esterase alleles were detected. The super-kdr allele was found only in a single fly from a ranch in Mexico. Results of PCR assays showed that the kdr allele was present at various frequencies in field populations of horn flies. A gender-related bias in distribution of kdr genotypes was found in horn flies from Mexico, but not in horn flies from Texas. The overall kdr allelic frequencies in horn flies from Mexico were 23.2-37.8% higher in females than in males. Regression analysis revealed a significant correlation between kdr allelic frequencies and the levels of knockdown resistance to permethrin among the horn fly populations studied. The results validate the role of the PCR-based molecular assay as a diagnostic tool in monitoring resistance to pyrethroids and also provide useful information on population genetics of horn fly resistance to pyrethroids and OPs.

Susceptibility of Haematobia irritans (Diptera: Muscidae) to permethrin in dairies in Aguascalientes, Mexico.

The purpose of this study was to conduct a survey for the susceptibility of the horn fly, Hematobia irritans (L.), populations to permethrin on dairy cattle from Aguascalientes, Mexico. Samples of populations of horn flies at 25 dairies were exposed to two discriminating doses (2.5 and 6.0 microg/cm2) on permethrin-treated filter papers and the percentage of mortality was compared with that of a susceptible strain treated with same doses of permethrin. The results show that there was a difference in the mortality from two discriminating doses and the mortality of the susceptible strain. Therefore, horn fly populations at all dairies tested in Aguascalientes, Mexico, were susceptible to permethrin. This insecticide, as well as other pyrethroids, could continue to be used to provide satisfactory control of horn flies in the study region.