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PubMed2002

Outbreaks of forest defoliating insects in Japan, 1950-2000.

In Japan, several forest-defoliating insects reach outbreak levels and cause serious defoliation. Stand mortality sometimes occurs after severe defoliation. However, in general, tree mortality caused by insect defoliation is low because of the prevailing moist climate in Japan. Evergreen conifers are more susceptible to tree mortality as a result of insect defoliation whereas deciduous broad-leaved trees are seldom killed. Insect defoliation occurs more frequently in man-made environments such as among shade trees, orchards, and plantations than in natural habitats. Outbreaks of some defoliators tend to occur in stands of a particular age: e.g. outbreaks of the pine caterpillar, Dendrolimus spectabilis Butler (Lepidoptera: Lasiocampidae) occur more frequently in young pine plantations. In contrast, defoliation caused by outbreaks of lepidopterous and hymenopterous pests in larch plantations is more frequent with stand maturation. There is a relationship between outbreaks of some defoliators and altitude above sea level. Most outbreaks of forest defoliators were terminated by insect pathogens that operated in a density-dependent fashion. Since the 1970s, Japan has been prosperous and can afford to buy timber from abroad. More recently, there has been an increasing demand for timber in Japan, that coincides with a huge demand internationally, so that the country will need to produce more timber locally in the future. The increasing pressure on the forestry industry to meet this demand will require more sophisticated methods of pest control coupled with more sustainable methods of silviculture.

Animals↗
PubMed2003

Comparative analysis of microsatellite loci in four fruit fly species of the genus Ceratitis (Diptera: Tephritidae).

The possibility to cross-species amplify microsatellites in fruit flies of the genus Ceratitis was tested with the polymerase chain reaction (PCR) by analysing 23 Ceratitis capitata (Wiedemann) microsatellite markers on the genomic DNA of three other economically important, congeneric species: C. rosa (Karsch), C. fasciventris (Bezzi) and C. cosyra (Walker). Twenty-two primer pairs produced amplification products in at least one of the three species tested. The majority of the products were similar, if not identical in size to those expected in C. capitata. The structures of the repeat motifs and their flanking sequences were examined for a total of 79 alleles from the three species. Sequence analysis revealed the same repeat type as the homologous C. capitata microsatellites in the majority of the loci, suggesting their utility for population analysis across the species range. A total of seven loci were differentially present/absent in C. capitata, C. rosa, C. fasciventris and C. cosyra, suggesting that it may be possible to differentiate these four species using a simple sequence repeat-based PCR assay. It is proposed that medfly-based microsatellite markers could be utilized in the identification and tracing of the geographical origins of colonist pest populations of the four tested species and in the assessment of their risk and invasive potentials; thereby assisting regulatory authorities in implementing quarantine restrictions and other pest control measures.

Alleles↗
PubMed2005

Host-plant finding by the asparagus fly, Plioreocepta poeciloptera (Diptera: Tephritidae), a monophagous, monovoltine tephritid.

The role of various olfactory and visual stimuli was studied in host-plant finding by the asparagus fly Plioreocepta poeciloptera (Schrank), a monophagous monovoltine tephritid causing serious damage to asparagus spears. Volatiles released by asparagus plants were extracted by diethyl ether after cryotrapping concentration, and identified by gas chromatography-mass spectrometry. Twelve of the 13 compounds identified were tested using electroantennography to measure the response of the fly. Behavioural response was analysed using two different flight tunnels according to circadian rhythm, age and sex of adults, presence of the plant and of different coloured lures, presence of a male congener, or exposure to four pure asparagus odour compounds that elicited responses in electroantennography, i.e. hexanal, (E)-2-hexenal, (Z)-2-hexen-1-ol and decanal. Data showed that males locate the host plant more quickly than females. Females are attracted mainly by the blend of plant odour and male pheromone. Both sexes respond to a complex of stimuli only during the afternoon. These findings will be helpful in developing new and effective approaches to control this pest insect.

Animals↗
PubMed1989

Evaluation and regulation of pesticides in drinking water: A Canadian approach.

Pesticides are registered in Canada under the authority of the Pest Control Products Act, administered by the Department of Agriculture. Pre-market registration requirements include submission of extensive toxicology data in order to allow evaluation of potential human hazards which may be associated with exposure to pesticides. Drinking water guidelines in Canada, although under provincial jurisdiction, are generally recommended by the federal government with collaboration of provincial authorities. In 1987, 42 pesticides were selected for development of guidelines for drinking water. When complete, the 42 pesticides will represent approximately 80% of all agricultural pesticides utilized in Canada, based on active ingredient weight sold. As do many other regulatory agencies, the Department of National Health and Welfare uses two different approaches to derive health-based guidelines or maximum acceptable concentrations of pesticides in drinking water. The threshold approach assumes that there is a dose below which no adverse effect will occur. This threshold level is closely related to the experimentally determined no observed adverse effect level and, when divided by an appropriate uncertainty or safety factor, forms the basis for the establishment of the maximum acceptable concentration. The second approach is the non-threshold or risk assessment approach and this assumes that these is some probability of harm at any level of exposure. This latter approach is generally utilized for chemicals believed to be capable of causing cancer and has not been used for any of the existing 29 pesticide drinking water guidelines developed in Canada.

Canada↗
PubMed1999

Mycopesticide production by fermentation: potential and challenges.

The agriculture industry is in need of novel biopesticides and development of large-scale production of mycopesticide, either fungal cells themselves or cell-free fungal components. The identification of a fungal strain with pesticide activity, and its improvement, is the primary step in developing infective propagules such as conidia, blastospores, chlamydospores, oospores, and zygospores as well as in preparing hydrolytic enzyme mixtures. This review discusses various parameters for submerged and solid state fermentation to produce fungal structures, particularly of mycoparasitic and entomopathogenic species that are prospective candidates for use as mycopesticides. The understanding of the molecular aspects of fungus-fungus and fungus-insect interactions, the role of hydrolytic enzymes especially chitinases in the killing process, and the possible use of chitin synthesis inhibitors are the prime areas of research aimed at making fungi more effective either singly or in combination as mycopesticides.

Animals↗
PubMedDate not supplied

Combined exposure to DEET (N,N-diethyl-m-toluamide) and permethrin: pharmacokinetics and toxicological effects.

Permethrin and DEET are concurrently used for pests control inside homes, in public places, and in military shelters. Combined exposure to these compounds produced greater biochemical, behavioral, and metabolic alterations in animals compared to each individual compound. Concurrent application of DEET and permethrin induced urinary excretion of 3-nitrotyrosine and 8-hydroxy-2'-deoxyguanosine, markers of DNA damage and oxidative stress in rats, increased the release of rat brain mitochondrial cytochrome c, disrupted the blood-brain barrier (BBB) in rats, decreased m2 muscarinic acetylcholine receptor ligand binding density in rat brain, increased urinary excretion of 6 beta-hydroxycortisol, a marker CYP3A4 induction, altered sensorimotor and locomotor activities in rats, and changed in vivo and in vitro metabolism and pharmacokinetic profiles of the individual compound. These findings show that more research is needed to examine adverse effects of the combined use of DEET and permethrin on other biochemical/physiological system(s) and to predict mechanistic pathways for these effects, particularly mechanism of action at cellular and molecular levels and alterations of genes transcription.

Animals↗
PubMedDate not supplied

Determination of the reference dose for chlorpyrifos: proceedings of an expert panel.

Chlorpyrifos is an extensively used organophosphate insecticide with numerous agricultural crop and urban pest control uses. Dow AgroSciences, one of the manufacturers of chlorpyrifos, convened a panel of toxicology and medical experts to consider the available scientific literature (both published papers and unpublished reports from Dow AgroSciences) on chlorpyrifos with respect to determining the acute and chronic toxicological reference doses (RfD) for chlorpyrifos. The most sensitive effect observed in the body of animal and human studies on chlorpyrifos is the inhibition of the various cholinesterases. In animal studies chlorpyrifos is not carcinogenic, teratogenic, or mutagenic. Reproductive toxicity studies indicate some effects on postnatal survival, but these effects were seen at doses higher than maternal toxic dose levels. There are no clinical signs of cholinergic toxicity below 70% inhibition of brain cholinesterase. Cognitive or behavioral defects are not observed until substantial brain cholinesterase inhibition occurs. There are no indications that chlorpyrifos caused delayed neurotoxicity at dose levels below twice the oral LD50. The panel members stated that plasma cholinesterase was an inappropriate endpoint for the RfD. They recommended that brain, erythrocyte cholinesterase depression and clinical signs were appropriate as endpoints for the RfD. Plasma cholinesterase should be used only as an indicator of exposure. After a thorough review of the experimental animal literature, it was determined that the chlorpyrifos repeated-exposure RfD based on application of a 100-fold uncertainty factor on the no observed adverse effects level (NOAEL) for brain cholinesterase inhibition or on a 10-fold uncertainty factor on the NOAEL for erythrocyte cholinesterase inhibition is 0.01 mg/kg/d. Based on the human volunteer studies, which indicate a repeated-dose NOAEL of 0.1 mg/kg/d for erythrocyte cholinesterase inhibition, and then using a 10-fold uncertainty factor, the RfD is again 0.01 mg/kg/d. In this human volunteer study on d 9 (last day) of administration, 1 individual in the 0.1 mg/kg/day dose group was removed from the study due to a "cold" (runny nose, blurred vision, and a feeling of faintness). He was asymptomatic 12 h later. To some degree this diagnosis is supported by the hematology, since lymphocyte counts were reduced and neutrophil counts were increased markedly, indicating a possible inflammatory reaction on d 8 of dosing, clearing by posttreatment d 5. In the absence of any indication of erythrocyte cholinesterase inhibition and with plasma cholinesterase inhibition being greater in two of the four other individuals treated at the same dose level, these signs and symptoms are unlikely to have been induced by cholinesterase inhibition. The panel concluded that the symptoms this individual displayed were not an appropriate endpoint for the RfD. The single-exposure reference dose can be based on the human data. No erythrocyte cholinesterase inhibition or clinical signs of toxicity were observed after a single oral dose of 0.5 mg/kg. Utilizing a 10-fold uncertainty factor, the single-dose RfD is 0.05 mg/kg.

Animals↗
PubMed2005

JWA--a novel environmental-responsive gene, involved in estrogen receptor-associated signal pathway in MCF-7 and MDA-MB-231 breast carcinoma cells.

The pyrethroid insecticide fenvalerate and the organophosphorus insecticide phoxim are now the most widely used agents for indoor pest control in China. Fenvalerate was shown to mimic estrogenic activity, whereas phoxim did not induce similar effects. Our previous studies demonstrated that JWA, a novel retinoic acid-inducible and cytoskeleton-associated gene, is also a potential environmental-responsive gene with increased expression to oxidative and heat-shock stresses. In the present study, the influence of both fenvalerate and phoxim was examined on the expression of JWA in MCF-7 (ER+) and MDA-MB-231 (ER-) human breast carcinoma cell lines. Concentrations of 0.01, 1, and 100 micromol/L of fenvalerate or phoxim were selected to treat both MCF-7 and MDA-MB-231 cells at 1, 3, and 5 d, respectively. The MTT results only showed that fenvalerate stimulated MCF-7 cell proliferation. Western blot assay was employed to detect the expressions of JWA and heat-shock proteins (hsp27 and hsp70). The results showed that after treatment with fenvalerate, both JWA and hsp70 showed similar expression patterns in the both cell lines; however, all the expression patterns of JWA, hsp27, and hsp70 were evidently reversed between ER+ and ER- cells. In addition, phoxim-treated cells showed a concentration-dependent relationship in JWA expression at all time points. These results suggest that JWA has similar functions with respect to hsp27 and hsp70, and might be a novel signal molecule in estrogen receptor-related signal transduction pathways in mammalian cells.

Breast Neoplasms↗
PubMed1984

A teratology study of carbaryl and malathion mixtures in rat.

Recently, much controversy has developed in relation to the use of pesticides alone and in mixtures. Mixtures are used as a more efficient method of pest control. Carbaryl and malathion are one of many combinations used today. A limited amount of work has been done with these two pesticides in relation to their teratogenic potential. This study examined the teratological parameters of carbaryl and malathion in combination compared to the effect of the individual insecticides. Formulation grade carbaryl (0, 1, 10, and 100 mg/kg), formulation grade malathion (1 and 50 mg/kg), and a formulation grade mixture of carbaryl/malathion (1/1 and 50/50 mg/kg) were administered daily by gavage for 3 mo prior to and throughout gestation. Dams were sacrificed on d 20 of gestation, and the fetuses were examined for external, skeletal, and visceral malformations. Significant decreases in dam weight gain during pregnancy and a slight decrease in the number of implantations and number of live fetuses per dam were observed with the 100-mg/kg carbaryl group and were further reduced in both combination doses. The combination dose groups showed a significant reduction in placenta weight. No increases were seen in skeletal or visceral anomalies for the individual treatment groups; however, an increase in external hemorrhagic spots was observed with malathion at 50 mg/kg and the high-dosage mixture group.

Abnormalities, Drug-Induced↗
PubMed1994

Mammalian toxicology of organophosphorus pesticides.

Organophosphorus compounds have been utilized as pesticides for almost five decades. They continue to be used as insecticides, helminthicides, ascaricides, nematocides, and to a lesser degree as fungicides and herbicides. While they have been and continue to be extremely useful in agricultural pest control throughout the world, their extensive use has led to numerous poisonings of nontarget species, including many human fatalities. The primary acute mammalian toxicity associated with exposure to organophosphorus pesticides results from inhibition of the enzyme acetylcholinesterase. However, other toxicities, some of which are life-threatening but not related to acetylcholinesterase inhibition, have been observed following exposure to certain organophosphorus compounds. The focus of the current review is to summarize the known effects, both cholinergic and noncholinergic, of organophosphorus pesticides in mammals. Included in this summary is a discussion of the metabolic activation of organophosphorus pesticides, since this process plays a critical role in mediating the acute toxicities of many of these pesticides.

Animals↗
PubMed2000

Central nervous system toxicity and early peripheral neuropathy following dermal exposure to methyl bromide.

CASE REPORT: We describe a case of early peripheral neuropathy and central nervous system toxicity as a result of acute predominantly dermal exposure to methyl bromide. A 32-year-old male was admitted after an accidental predominantly dermal exposure to methyl bromide while fumigating soil for pest control. The patient suffered dermal burns and vesicles on the upper and lower limbs. One week following exposure, he developed progressive weakness of the lower limbs, ataxia, paresthesiae of both legs and the left arm, hyperactive tendon reflexes in the lower limbs, and left Babinski sign. Nerve conduction velocity testing was compatible with axonal neuropathy. The patient recovered gradually from his burns. Three months postexposure he showed no signs of central nervous system toxicity, but the peripheral neuropathy was still present. DISCUSSION: Neurological effects primarily referable to the central nervous system following severe inhalation of methyl bromide have frequently been reported. The patient described in this study developed an unusual early peripheral neuropathy following dermal exposure. Peripheral neuropathy can be an outcome of methyl bromide intoxication, but is usually a late sequela of acute central nervous system toxicity or an aftereffect of repetitively inhaled chronic exposure. In this case, exposure to methyl bromide through abraded skin caused early peripheral neuropathy and central nervous system toxicity.

Administration, Cutaneous↗
PubMed2001

Issues in public health entomology.

Public health entomology focuses on the population biology of vector-borne infections, seeking to understand how such pathogens perpetuate over time and attempting to devise methods for reducing the burden that they impose on human health. As public health entomology passes its centennial, a series of pervasive research themes and spirited debates characterize the discipline, many reflecting a tension between field and laboratory research. In particular, institutional support for population-based research and training programs has fallen behind that for those using modern lab-based approaches. Discussion of modes of intervention against vector-borne infections (such as deployment of genetically modified vectors, the role of DDT in malaria control, host-targeted acaricides for Lyme disease risk reduction, and truck-mounted aerosol spraying against West Nile virus transmission) illustrates the discipline's need for strengthening population-based research programs. Even with the advent of molecular methods for describing population structure, the basis for anophelism without malaria (or its eastern North American counterpart, ixodism without borreliosis) remains elusive. Such methods have not yet been extensively used to examine the phylogeography and geographical origins of zoonoses such as Lyme disease. Basic ecological questions remain poorly explored: What regulates vector populations? How may mixtures of pathogens be maintained by a single vector? What factors might limit the invasion of Asian mosquitoes into North American sites? Putative effects of "global warming" remain speculative given our relative inability to answer such questions. Finally, policy and administrative issues such as the "no-nits" dictum in American schools, the Roll Back Malaria program, and legal liability for risk due to vector-borne infections serve to demonstrate further the nature of the crossroads that the discipline of public health entomology faces at the start of the 21st Century.

Animals↗
PubMed1990

Occupational and environmental hygiene assessment of fumigations with methyl bromide.

Use of methyl bromide for pest control fumigation may result in adverse exposure to three populations: the actual fumigators; other workers not actually involved in the fumigation; and the general public in the vicinity. The risk of exposure of these three target populations in Switzerland was investigated. The methodology was a combination of occupational hygiene surveys, including a preliminary hazard analysis, with a comprehensive assessment of the safety and health systems in use based on the 'Management Oversight and Risk Tree' (MORT) method [Knox and Eicher, MORT User's Manual, Revision 2. DOE 76-45/4 (1983)]. The target populations most concerned depend on the type of fumigation. Fumigators risk severe accidental exposure although they usually wear personal protection devices. In soil and chamber fumigation, workers not involved in the fumigation may undergo high exposure (75-100 pm for 1 h), far greater than the usual time-weighted average and short-term occupational exposure limits (5-20 ppm range). Occupants of premises adjoining the fumigated buildings may also be exposed to significant concentrations (25-50 ppm for 0.1-2 h). Problems originate mainly from a lack of management controls, failure to apply an appropriate code of practice and the use of personnel who are not properly qualified and trained.

Air Pollutants↗
PubMed2000

Should we take measurements at an intermediate design point?

It is well known that, for estimating a linear treatment effect with constant variance, the optimal design divides the units equally between the two extremes of the design space. If the dose-response relation may be nonlinear, however, intermediate measurements may be useful in order to estimate the effects of partial treatments. We consider the decision of whether to gather data at an intermediate design point: do the gains from learning about nonlinearity outweigh the loss in efficiency in estimating the linear effect? Under reasonable assumptions about nonlinearity, we find that, unless sample size is very large, the design with no interior measurements is best, because with moderate total sample sizes, any nonlinearity in the dose-response will be difficult to detect. We discuss in the context of a simplified version of the problem that motivated this work-a study of pest-control treatments intended to reduce asthma symptoms in children.

Journal Article↗
PubMed1999

Actographic analysis of the effects of an esterase inhibitor on male moth responses to sex pheromone.

The effects of 3-octylthio-1,1,1-trifluoropropan-2-one (OTFP), a trifluoromethyl ketone that inhibits antennal esterases, on male Mamestra brassicae responses to the main pheromone component have been investigated using an actograph. This actograph used a movement detector based on the Doppler effect. The signal from the detector was digitalized and analysed on a PC microcomputer to quantify male activity. When added to the air flowing through the observation chamber, OTFP inhibited the responses of male moths to the pheromone. The number of males responding to the pheromone and the intensity of the response were decreased by OTFP. The latency of the response was increased and its duration decreased. These effects on the kinetics of the behavioural response cannot be directly correlated to the inhibition of pheromone catabolism by OTFP and other targets must be involved. The high level of inhibition of behaviour observed in presence of OTFP demonstrates the interest of trifluoromethyl ketones as mating disruption agents for pest control.

Acetone↗
PubMedDate not supplied

Determination of dialkyl phosphates in human urine using gas chromatography-mass spectrometry.

Organophosphates are used as pesticides in agriculture and pest control. They are metabolized to dialkylphosphates, which are excreted in urine. Determination of these metabolites is useful for assessing human exposure to organophosphates. This publication describes a new, reliable, and very sensitive analytical procedure for quantitating dimethylphosphate (DMP), diethylphosphate (DEP), O,O-dimethylthiophosphate (DMTP), O,O-diethylthiophosphate (DETP), O,O-dimethyldithiophosphate (DMDTP), and O,O-diethyldithiophosphate (DEDTP) in human urine. The analytes are extracted from acidified urine into a mixture of diethylether and acetonitrile. Dibutylphosphate serves as internal standard. Derivatization is performed using pentafluorobenzylbromide at 40 degrees C overnight. After further liquid-liquid extraction, analysis is carried out by gas chromatography-mass spectrometry. The limits of detection are 5 microg/L urine for DMP and 1 microg/L for the other five metabolites. Using the new procedure, 54 spot urine samples from persons in the general population in Germany were analyzed. Nearly every sample contained DMP, DEP, and DMTP, and the median values (95th percentiles) of the concentrations were 30 microg/L (105 microg/L), 4 microg/L (21 microg/L), and 22 microg/L (174 microg/L), respectively. DETP and DMDTP were found in lower concentrations.

Environmental Monitoring↗