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PubMed1995

Comparative toxicity of selected larvicides and insect growth regulators to a Florida laboratory population of Aedes albopictus.

Five organophosphates (OPs) (chlorpyrifos, chlorpyrifos methyl, fenthion, malathion, and temephos), 3 pyrethroids (bifenthrin, cypermethrin, and permethrin), and 2 microbial pesticides (Bacillus thuringiensis serovar.israelensis [B.t.i.] and Bacillus sphaericus) were tested as larvicides against a Florida Aedes albopictus population colonized in the laboratory. In addition, 3 insect growth regulators (IGRS) (diflubenzuron, methoprene, and pyriproxyfen) were evaluated. All OPs, except for malathion, were highly effective as indicated by low LC90s ranging from 0.0069 ppm (chlorpyrifos) to 0.026 ppm (fenthion); the larvae were considered tolerant to malathion (LC90 = 1.043 ppm). LC90 values of pyrethroids were: 0.0175 ppm (bifenthrin), 0.0079 ppm (cypermethrin), and 0.0031 ppm (permethrin). Commercial products of B.t.i., Vectobac and Bactimos were considered economically effective against Ae. albopictus larvae but products of B. sphaericus were ineffective (LC90s > 28 ppm). The IGRs showed exceptional activity. Pyriproxyfen (LC90 = 0.000376 ppm), was 2.23 and 21.5 times more toxic than diflubenzuron and methoprene, respectively. In general, toxicity ranking of chemicals and microbials tested was: IGRs > pyrethroids > OPs > microbials.

Aedes↗
PubMedDate not supplied

Evaluation of susceptibility status of Culex quinquefasciatus larvae to few organophosphorus insecticides based on logistic regression analysis.

A laboratory trial was carried out at Pune to evaluate the effectiveness of five types of larvicides viz. Malathion, Temephos, Fenthion, Dichlorvos and Fenitrothion against Culex quinquesfasciatus larvae. The expected number of mortality at various dose levels for the five types of insecticides were estimated separately using logistic regression model. Based on the fitted model, the estimated dose level corresponding to the 90 percent mortality (LC90) was obtained for each insecticide. Approximate 95 percent confidence intervals for the LC90 dose, in each case, has been provided. The analysis revealed that out of all the five types of insecticides included in the study, fenthion was the most effective. The estimated value of LC90 in this case was the lowest and is equal to 0.007 mg/L. The effectiveness of temephos, dichlorvos and fenitrothion was found to be approximately same and malathion was the least effective. The results were found to be comparable with that obtained under probit method.

Animals↗
PubMed1993

Comparative susceptibility of two Japanese encephalitis vectors from Mysore to six insecticides.

Larval populations of Culex tritaeniorhynchus and C. fuscocephala from Mysore city were tested for their susceptibility against two pyrethroids viz., cypermethrin and deltamethrin and four organophosphorus (OP) compounds viz., fenthion, fenitrothion, temephos and malathion. The investigations revealed that, among the pesticides tested, efficacy of pyrethroids was very high as compared to OP compounds. C. tritaeniorhynchus was found to be highly tolerant to all the insecticides used. It registered 4.0, 6.5, 17.0, 6.5, 14.0 and 1.5 times more tolerance than C. fuscocephala to cypermethrin, deltamethrin, fenthion, fenitrothion, temephos and malathion respectively in terms of the LC50 value. Further studies are needed to determine the development of resistance if any, by C. tritaeniorhynchus, an important JE vector in Karnataka.

Animals↗
PubMed1996

Toxicity of insecticides to Toxorhynchites splendens and three vector mosquitos and their sublethal effect on biocontrol potential of the predator.

Toxicity of six larvicides ie fenthion, temephos, malathion, deltamethrin, alphamethrin (Fendona), OMS 3031 and five adulticides ie malathion, fenitrothion, propoxur, deltamethrin, permethrin to Aedes aegypti, Culex quiquefasciatus, Anopheles stephensi and the predator, Toxorhynchites splendens was studied for evaluating safety margin. Concentrations of alphamethrin that killed 50% larvae of T. splendens were 53 and 12 times more than that which killed Cx. quinquefasciatus and Ae. aegypti. In case of deltamethrin, concentrations required to kill 50% larvae of T. splendens were 14 and 5 times more than that required against other two species. Other larvicides tested were equally toxic to both T. splendens and vector mosquitos. There was no significant difference in the toxicity of larvicides to T. splendens and An. stephensi. Deltamethrin was 25-132 times less toxic to adults of T. splendens in comparison to vector mosquitos. For other adulticides the range was 1-10. Immature developmental time of T. splendens was not affected by any of the insecticides tested. However, predation rate was lowered when larvae of Ae. aegypti previously exposed to fenthion and temephos were offered. Whereas, alphamethrin and OMS 3031 did not affect the feeding rate of the predator. There was a significant reduction in the pupal weight and pupation as a result of the predator feeding on the insecticide treated prey. There was a significant negative relationship between rate of pupation and dosage. The present study indicates that synthetic pyrethroids owing to their higher safety margin can be used in an integrated vector management program.

Aedes↗
PubMedDate not supplied

Ocular effects of organophosphates: a historical perspective of Saku disease.

Many publications, primarily of work performed in Japan, report findings in human populations of an increased incidence of myopia and of a more advanced visual disease syndrome (Saku disease), which reportedly correlated with increasing use of organophosphate pesticides in agriculture. Follow-up studies in animals performed in Japan using such agents as ethylthiometon, fenthion and fenitrothion demonstrate adverse effects of organophosphates on the visual system. The several ocular effects in question are dose dependent, ranging in severity from lenticular and electro-retinographic changes to the seemingly more serious histophysiological changes in such tissues as the ciliary body and retina. An important question arising from this work is that of the role of cholinesterase inhibition in the etiology of the effects. Studies currently in progress on particular organophosphates being conducted at EPA's research facility and by certain registrants of pesticides, which are in various stages of completion, appear to be substantiating much that has been reported in Japan. While animal studies clearly show that some organophosphates elicit ocular toxicity, there are many knowledge gaps with regard to effects in humans and the ocular toxicity in general, e.g. time and dose dependency, cholinesterase inhibition vs ocular effects and effects of routes of exposure. Consequently, the office is unable at this time to incorporate hazard assessment data with exposure assessment data or to perform risk assessments on organophosphates based on the ocular toxicity potential of this class of chemicals.

Animals↗
PubMed1980

Susceptibility of Brazilian samples of Boophilus microplus to organophosphorus acaricides.

This paper describes the susceptibility of various samples of Boophilus microplus from the southern region of Minas Gerais State in Brazil to the 4 commonest organophosphorus acaricides employed in the area. All samples showed some degree of resistance to each of the compounds used. The resistance factor varied from 1.42 to 132.90, being less in the case of dicrotophos fenthion than with chlorpyrifos and coumaphos.

Animals↗
PubMed1982

Sister-chromatid exchanges and cell-cycle delay in Chinese hamster V79 cells treated with 9 organophosphorus compounds (8 pesticides and 1 defoliant).

Significant increase of sister-chromatid exchanges (SCE) in V79 cells treated with 2 organophosphorus pesticides (OPP), fenthion and oxydemeton-methyl, was observed. The other 7 compounds (6 OPP and 1 defoliant) namely, amaze, azinphos-methyl, bolstar, DEF-defoliant, fensulfothion, monitor and nemacur caused no increase of SCE frequencies at the doses tested. All the compounds except fensulfothion and oxydemeton-methyl induced cell-cycle delay in varying degrees. Cell-cycle delay caused by an OPP was found to be dose-dependent. Based on these data as well as others reported, it would appear that OPP which induce no SCE increase and no or slight cell-cycle delay could be considered as good candidates to substitute the pesticides that have been found to be harmful to the environment.

Animals↗
PubMed1994

Interlaboratory cholinesterase determinations and the effect on the results of statistical evaluation of cholinesterase inhibition.

Cholinesterase activity is often a key parameter in the regulatory assessment of cholinesterase-inhibiting agents such as organophosphorous and carbamate pesticides. Thus, the nature and characteristics of the methodology involved in the measurement of plasma (PChe), erythrocyte (R Che), and brain (BChe) cholinesterase activity takes on a heightened degree of importance. In this study an interlaboratory comparison of cholinesterase activity as determined by various laboratories was conducted in order to assess the influence that different methodologies may have on the results of statistical evaluation of cholinesterase inhibition. RChe, PChe, and BChe from animals exposed to fenthion, a known cholinesterase inhibitor, were determined at 8 different laboratories with experience in cholinesterase determination. Seven different instruments and 5 different assay procedures were employed. Marked differences in both the magnitude of inhibition measured and its designation as a statistically significant difference often occurred between laboratories using both the same as well as different methods of cholinesterase analysis. These findings illustrate the importance of considering not only the sensitivity of a given method of analysis, but also the influence of inter- and intra-laboratory variation on statistically responsive aspects of the data profile itself (i.e., precision, sample size, etc.) when establishing regulatory levels (i.e., Reference Doses (RfDs), Health Advisory Levels (HALs), etc.) on the basis of a cholinesterase no-observed- or lowest-observed-effect level (NOEL, LOEL).

Analysis of Variance↗
PubMed2005

Toxicity assessment of pesticides to Pseudokirchneriella subcapitata under air-tight test environment.

This paper presents the toxicity data of seven pesticides including atrazine, parathion, dichlorvos, malathion, fenthion, 2-methyl-4-chlorophenoxyacetic acid, and pentachlorophenol on Pseudokirchneriella subcapitata based on a new algal toxicity testing technique conducted under air-tight environment. The dissolved oxygen production and the cell density were adopted as the response endpoints. Median effective concentrations (EC50) range from 0.0035 to 3.40 mg/L (DO production) and from 0.0067 to 3.12 mg/L (cell density). No-observed-effect concentration (NOEC) was determined using the Dunnett's test. NOEC values are with in the range of 0.001-1.20 mg/L. In general, the two test endpoints revealed similar sensitivities. From comparisons of literature data also based on Pseudokirchneriella subcapitata, it is clear that conventional batch tests tend to underestimate the toxicity of pesticides due to their open test environment. Closed-system tests, i.e., microplate test, respirometer test, and our BOD-bottle test, generally provide better assessment to the effects of pesticides. Data based on our test method reveals much higher toxicity (3-100 times) than that from the conventional batch tests. Furthermore, for organophosphorus insecticides, results from the present study show that Pseudokirchneriella subcapitata is less sensitive than Daphnia magna and rainbow trout, but is more susceptible than fathead minnow. The closed-system test applied in this study provides more adequate assessment for the toxicity of pesticides than the conventional batch tests.

2-Methyl-4-chlorophenoxyacetic Acid↗
PubMed2003

Effect of treatment on the dynamics of circulating hypodermin C in cattle naturally infested with Hypoderma lineatum (Diptera: Oestridae).

An antigen capture ELISA, using a murine monoclonal antibody recognising recombinant hypodermin C (rHyC), was used to evaluate the influence of early treatment with eprinomectin (Eprinex) or fenthion (Spotton) on the kinetics of circulating hypodermin C in calves naturally infested with Hypoderma lineatum. No viable larvae were collected from treated animals, whereas a variable number of warbles were found in control animals. Treatment provoked a decrease in circulating HyC levels that was significant 9 days post-treatment (p.t.). Circulating antigen levels in the treated cattle remained detectable for approximately 99 days p.t. In contrast, control animals had no detectable antigen at 64 days p.t., 42 days earlier than in the treated animals. These results suggest that larvae were either gradually killed, resulting in slow release of antigen or they were encapsulated, leading to the slow liberation of antigen. Kinetics of circulating HyC did not differ among the two insecticide treatments. Antibodies persisted, in all groups, throughout the 120-day study. These results suggest that the antigen capture ELISA will be useful as a technique for detecting successful treatment of cattle grub infestations and for the detection of new infestations in previously infested cattle.

Administration, Topical↗
PubMed1987

Neurotoxic effects of organophosphorus insecticides. An intermediate syndrome.

Acute neurotoxic effects during the cholinergic phase of organophosphorus insecticide poisoning and delayed neurotoxic effects appearing two to three weeks later are well recognized. We observed 10 patients who had paralysis of proximal limb muscles, neck flexors, motor cranial nerves, and respiratory muscles 24 to 96 hours after poisoning, after a well-defined cholinergic phase. The compounds involved were fenthion, monocrotophos, dimethoate, and methamidophos. Four patients urgently required ventilatory support. The paralytic symptoms lasted up to 18 days. A delayed polyneuropathy later developed in one patient. Three patients died. Electromyographic studies showed fade on tetanic stimulation, absence of fade on low-frequency stimulation, and absence of post-tetanic facilitation, suggestive of a postsynaptic defect. This neuromuscular junctional defect may have been the predominant cause of the paralytic symptoms, with neural and central components contributing to various degrees. Our patients appeared to have a distinct clinical entity (a so-called intermediate syndrome) that developed after the acute cholinergic crisis and before the expected onset of the delayed neuropathy.

Adult↗
PubMed1989

Toxic effects of organophosphates on nerve cell growth and ultrastructure in culture.

Organophosphates (OP) comprise one of the major classes of pesticides in use today. It is well accepted that the primary site of action of the OPs is at cholinergic synapses. However, it has been suggested that OPs may have direct neural effects as well. In this study, cultured chick dorsal root ganglia (DRG) were used to study the effect of fenthion (FEN), an OP pesticide, on isolated nerve cell growth and ultrastructure. Light microscopic evaluation revealed a dose-response relationship between the concentration of FEN (10(-2) M to 10(-5) M) and severity of morphologic changes. Cultured explants were treated with a lower concentration of FEN (10(-6) M) and morphologic alterations were compared to those observed in explants treated with 10(-6) M paraoxon, a more acutely toxic OP, or 10(-6) M neostigmine, a non-OP inhibitor of acetyl-cholinesterase. Based on both light and electron microscopy, neostigmine had no observed effect on cell morphology except for an inhibition of the extension of neurites by DRG cells. In contrast, explants treated with OPs exhibited a significant alteration in cell morphology. Initial lesions were observed first in the neurites and pseudopodia and consisted of vacuolization, loss of tubular structures, retraction of pseudopodia, and cell membrane disruption at the growth cone. Lipid accumulations were observed within the cytoplasm of treated cells. The effects of paraoxon on DRG cell morphology were significantly more severe than the effects of FEN, and lipid vacuoles observed in paraoxon-treated cells were several times larger than those observed in FEN-treated cells (5-10 microns in diameter vs. 0.5-1.0 microns in diameter). Results show that OPs have a direct effect on DRG nerve cells in culture, consistent with an alteration in cell membrane integrity. Cultured DRG cells can be useful in the evaluation of toxicologic effects.

Animals↗
PubMed1982

Prolonged toxicity of organophosphate poisoning.

A case of poisoning with a new organophosphate (fenthion) is reported in which the initial cholinergic crisis was delayed 5 days and recurred 24 days after ingestion. Psychosis was a persistent and sometimes singular manifestation. Because of the high lipid solubility of this pesticide, toxin analysis of repeated fat biopsies was an essential component of the management of this patient.

Adipose Tissue↗
PubMed1980

Insecticide resistance in field strains of Lucilia cuprina.

A survey was conducted in 1977-78 to determine the level of insecticide resistance in field strains of Lucilia cuprina from a wide area of Queensland. Discriminating dose data showed that all 19 strains tested were resistant to diazinon, dichlofenthion, fenthion-ethyl and chlorfenvinphos, but resistance factors in all strains were low, the highest being 18.9 for diazinon. Six strains showed no resistance to butacarb. A strain collected in 1967 and selected with diazinon for 117 generations, attained resistance factors of organophosphorus compounds far higher than those of the present field strains.

Animals↗
PubMedDate not supplied

Laval implant sutdies with Lucilia cuprina.

Semi-field studies, using the larval implant technique, show that sheep may be protected against resistant larvae of Lucilia cuprina by thorough jetting with chlorfenvinphos, diazinon, dichlofenthion and fenthion ethyl, but not bromophos ethyl, for the normal duration of waves of bodystrike in New South Wales. The standard method of assessing implant data is to be preferred to analyses based on average protection due to the extra time required for the latter procedure.

Animals↗
PubMedDate not supplied

Controlled release effect of insecticide microcapsules and their results in common household insect pest control.

Since 1978 we have prepared microencapsulated insecticides by complex coacervation and interfacial polymerization for household insect pest control, fenthion being the main core element. A series of tests have been conducted against mosquitoes (Culex pipiens quinquefasciatus), cockroaches (Periplaneta americana) and bedbugs (Cimex lectularius), and the results indicate that microencapsulation can prolong persistent effects by 2-12 times, enhance safety and subdue offensive odour. Furthermore, the production cost is comparatively low.

Animals↗
PubMed1994

Organophosphate poisoning: peripheral vascular resistance--a measure of adequate atropinization.

We report severe organophosphate poisoning complicated by hypotension and ischemic sequelae in two patients with pre-existing vascular disease. Both patients had a low total peripheral resistance and high cardiac output that were significantly reversed by doses of atropine in excess of those required to control other muscarinic symptoms. Cerebral infarcts and gangrene requiring a below knee amputation were complications of the poisonings. It is proposed that the ischemic complications are due to paradoxical vasoconstriction by acetylcholine at sites of endothelial injury. One patient, who had taken fenthion, also had a significantly delayed peak and prolonged, 2-3 week, systemic toxicity. We propose that stability of the plasma cholinesterase at 6 to 8 h after temporarily suspending oxime provides a rapid guide to the duration of therapy, especially in patients whose complications make clinical assessment difficult.

Acetylcholinesterase↗
PubMedDate not supplied

Topical insecticide treatments to protect dogs from sand fly vectors of leishmaniasis.

We compared the susceptibility of sand fly vectors to four topical insecticide treatments applied to domestic dogs, a reservoir of human leishmaniasis. Dogs were exposed to sand flies pretreatment and at 1 week, 1 month, and 2 months posttreatment. Sand fly bloodfeeding and survival rate of both fed and unfed flies were significantly reduced by the permethrin, deltamethrin, and fenthion treatments, but diazinon had no effect. The survival rate of bloodfed sand flies was reduced by up to 86% with deltamethrin collars. The antifeeding effect suggests that deltamethrin collars may be recommended to dog owners to protect their pets from sandfly- borne diseases. The combined effects on sand fly feeding and survival indicate that epidemiologic, community-based trials are warranted to test whether deltamethrin collars could reduce the incidence of canine and, hence, human leishmaniasis.

Administration, Topical↗