Simultaneous determination of spinosad, temephos, and piperonyl butoxide in animal-derived foods using LC-MS/MS.

Pesticides, which are used as plant protection products, can enter the food chain, and exposure to these xenobiotics can cause a wide array of health problems in humans. Therefore, the objective of the present study was to develop an analytical method for the simultaneous determination of residual spinosad (sum of spinosyn A and D), temephos and piperonyl butoxide in porcine muscle, egg, milk, eel, flatfish and shrimp (sampling period: February to June 2018) using liquid chromatography-triple quadrupole tandem mass spectrometry (LC-MS/MS). The target analytes were extracted with a combination of acidified acetonitrile and ethyl acetate and subsequently purified with original QuEChERS kits (composed of magnesium sulfate and sodium chloride) as well as n-hexane. All analytes were separated on a reversed-phase analytical column using a mobile phase of (A) 0.1% formic acid containing 10 mm ammonium formate in distilled water and (B) methanol. Good linearity (R2 ≥ 0.980) was achieved over the tested concentration range (3.5-35 µg/kg for spinosyn A; 1.5-15 µg/kg for spinosyn D; 5-50 µg/kg for temephos and piperonyl butoxide) in matrix-matched standard calibrations. Fortified samples at three spiking levels yielded recoveries in the range of 71-105% with relative standard deviations ≤9.2%. The applicability of the method was evaluated via evaluating samples collected from a large wholesale market located in Seoul, and none of the samples contained any of the target analytes. In conclusion, the current approach is simple, efficient and reliable and can successfully determine the residual levels of spinosad, temephos and piperonyl butoxide in complex animal-derived food products.

Resistance to temephos and deltamethrin in Aedes aegypti from Brazil between 1985 and 2017

BACKGROUND Aedes aegypti populations in Brazil have been subjected to insecticide selection pressures with variable levels and sources since 1967. Therefore, the Brazilian Ministry of Health (MoH) coordinated the activities of an Ae. aegypti insecticide resistance monitoring network (MoReNAa) from 1999 to 2012. OBJECTIVES The objective of this study was to consolidate all information available from between 1985 and 2017 regarding the resistance status and mechanisms of Brazilian Ae. aegypti populations against the main insecticide compounds used at the national level, including the larvicide temephos (an organophosphate) and the adulticide deltamethrin (a pyrethroid). METHODS Data were gathered from two sources: a bibliographic review of studies published from 1985 to 2017, and unpublished data produced by our team within the MoReNAa between 1998 and 2012. A total of 146 municipalities were included, many of which were evaluated several times, totalling 457 evaluations for temephos and 274 for deltamethrin. Insecticide resistance data from the five Brazilian regions were examined separately using annual records of both the MoH supply of insecticides to each state and the dengue incidence in each evaluated municipality. FINDINGS Ae. aegypti resistance to temephos and deltamethrin, the main larvicide and adulticide, respectively, employed against mosquitoes in Brazil for a long time, was found to be widespread in the country, although with some regional variations. Comparisons between metabolic and target-site resistance mechanisms showed that one or another of these was the main component of pesticide resistance in each studied population. MAIN CONCLUSIONS (i) A robust dataset on the assessments of the insecticide resistance of Brazilian Ae. aegypti populations performed since 1985 was made available through our study. (ii) Our findings call into question the efficacy of chemical control as the sole methodology of vector control. (iii) It is necessary to ensure that sustainable insecticide resistance monitoring is maintained as a key component of integrated vector management. (iv) Consideration of additional parameters, beyond the supply of insecticides distributed by the MoH or the diverse local dynamics of dengue incidence, is necessary to find consistent correlations with heterogeneous vector resistance profiles.

Water use practices limit the effectiveness of a temephos-based Aedes aegypti larval control program in Northern Argentina.

BACKGROUND: A five-year citywide control program based on regular application of temephos significantly reduced Aedes aegypti larval indices but failed to maintain them below target levels in Clorinda, northern Argentina. Incomplete surveillance coverage and reduced residuality of temephos were held as the main putative causes limiting effectiveness of control actions. METHODOLOGY: The duration of temephos residual effects in household-owned water-holding tanks (the most productive container type and main target for control) was estimated prospectively in two trials. Temephos was applied using spoons or inside perforated small zip-lock bags. Water samples from the study tanks (including positive and negative controls) were collected weekly and subjected to larval mortality bioassays. Water turnover was estimated quantitatively by adding sodium chloride to the study tanks and measuring its dilution 48 hs later. PRINCIPAL FINDINGS: The median duration of residual effects of temephos applied using spoons (2.4 weeks) was significantly lower than with zip-lock bags (3.4 weeks), and widely heterogeneous between tanks. Generalized estimating equations models showed that bioassay larval mortality was strongly affected by water type and type of temephos application depending on water type. Water type and water turnover were highly significantly associated. Tanks filled with piped water had high turnover rates and short-lasting residual effects, whereas tanks filled with rain water showed the opposite pattern. On average, larval infestations reappeared nine weeks post-treatment and seven weeks after estimated loss of residuality. CONCLUSIONS: Temephos residuality in the field was much shorter and more variable than expected. The main factor limiting temephos residuality was fast water turnover, caused by householders' practice of refilling tanks overnight to counteract the intermittence of the local water supply. Limited field residuality of temephos accounts in part for the inability of the larval control program to further reduce infestation levels with a treatment cycle period of 3 or 4 months.

Studies on persistence of temephos in sandy loam soil under field and laboratory conditions.

Persistence of temephos was studied in soils under field and laboratory conditions in sandy loam soil to evaluate the effect of moisture and formulations on persistence. The insecticide was applied as 50 EC and 1 % S.G. granules @1 kg a.i. ha-1 on surface of the soil' and residues were determined spectrophotometrically. The soil was fortified separately with dilute emulsion of EC and suspension of granular formulation at 5 ppm level and incubated at different moisture levels at 25:1:1 degrees C for 90 days. The residues of temephos from both the formulations persisted upto 55 days in soil when applied @1 kg a.i. ha(-1). In 40 days 92 and 91.43 per cent temephos was dissipated from soil treated with EC and granular formulations, respectively. There was no leaching or downward movement of the toxicant beyond 7.5 cm. The half-life of temephos under field condition for EC and granular formulations were 18.14 and 20.44 days, respectively. Statistically, there was no significant effect of two formulations of temephos on its persistence. But at three different moisture conditions viz. airdry, field capacity and sub-merged, the difference was significant at 5% level.

Métodos de insensibilizaçäo de suinos e seus efeitos na qualidade da carne / Effects os stunning methods on the quality of pigmeat

Os principais métodos de insensibilizaçäo de suínos, aplicados nos países desenvolvidos, em caráter obrigatório e com uso permitido no Brasil, säo revistos em suas características básicas e viabilidade industrial. Enfase é dada quanto à influência da insensibilizaçäo sobre a qualidade da carne, considerando as alteraçöes de suas propriedades e os efeitos nos aspectos sensorial e de processamento. Ainda säo discutidos a relaçäo entre concentraçöes de catecolaminas e metabolismo animal, contraçöes musculares, fraturas ósseas, pontuaçöes hemorrágicas e custos como fatores relevantes que interferem na qualidade da carne e na seleçäo de método de insensibilizaçäo mais adequado

Studies on the effect of translocation of chemical insecticides in Eicchornia host plant on Mansonia mosquitos--a potential control method.

A novel method for the control of Mansonia larvae was developed and tested. In this method, foliar absorption and translocation of a chemical insecticide, monocrotophos, a known systemic insecticide was studied in the Eicchornia plant. Acetone solution of the insecticide was painted onto leaves of the plant. At daily intervals, stems were severed and divided into equal sections which were introduced into bowls. Larvae of Aedes aegypti were tested for the presence of monocrotophos. It was found that translocation of the insecticide occurred at different rates in the stems and in some plants the chemical was also released into the surrounding water. Based on these results, 2 insecticides namely, monocrotophos and temephos were painted onto leaves of the host plant and their translocation to the root and water environment was examined by testing with Mansonia and Aedes aegypti larvae. The results again confirmed the translocation process and it was found that the insecticides were secreted into the surrounding water, thereby killing the larvae. However, in leaves painted with permethrin (synthetic pyrethroid) or flufenoxuron (chitin synthesis inhibitor), such a process was not detected. The potential of this new concept in Mansonia larval control is examined.

Sensitivity and accuracy of a bio-assay for the determination of the concentration of residual pesticide in natural water bodies.

Determination of pesticide levels in natural water bodies requires complex chemical methods not always available in tropical countries where such control programmes are implemented. Apart from chemical methods, effectiveness of treatment can be estimated by mortality of target and non-target species. But the latter criteria do not permit a good appraisal of dispersion and residual activity of pesticide. We propose here a simple and cheap bio-assay adaptable to water-borne vector or intermediate host control programmes. Results obtained with the bio-assay were compared with those obtained with gas liquid chromatography, a standard chemical method.

Residual concentration and efficacy of three temephos formulations for control of larval Aedes aegypti.

The residual concentration and efficacy of Abate 5CG (impregnated in celatom granules) and plaster pellets impregnated with either Abate 4E or technical temephos were compared against late 3rd-instar Aedes aegypti larvae. Both plaster pellet formulations resulted in 100% larval mortality during the 6-wk test, compared with 2 wk for a similar level of mortality for the celatom formulation. The maximum temephos concentration in water treated with the celatom formulation occurred 30 min after treatment at 0.071 ppm. Temephos concentration of water treated with the 4E plaster formulation peaked at 12 h at 0.148 ppm while the concentration of the technical plaster formulation peaked at 48 h at 0.30 ppm.

Fate and toxicity of temephos applied to an intertidal mangrove community.

The distribution, persistence, and toxicity of the mosquito larvicide temephos was monitored following aerial applications to an intertidal mangrove community in Lee County, Florida. The amount of temephos penetrating to the mangrove floor ranged from 15 to 70% of the amount entering the upper leaf canopy, with 50-60% of that applied remaining on the mangrove leaves. Rainfall caused an additional influx of temephos from the leaves to the mangrove floor. Residues were detected in intertidal water at 2 h, but not 4 h after application. However, temephos was observed to persist in simulated tidal pools and on mangrove leaves for up to 72 h and in oysters for up to 48 h after application. Marine organisms placed in cages at 3 test sites and a control site were monitored for toxic effects. Mortality among natural mosquito larvae was simultaneously monitored. Mysids (Mysidopsis bahia) exhibited a significant mortality at one site during 1 of 3 applications monitored; however, no correlation was observed between mortality and temephos concentration in water. No significant mortality was observed for the other organisms, which included: brown shrimp (Panaeus aztecus), grass shrimp (Palaemonetes pugio), juvenile snook (Centropomis undecimalis) and sheepshead minnow (Cyprinodon variegatus).

Uptake of the mosquito larvicide Temefos by the salt marsh snail, New Jersey--1973-1974.

Uptake of the mosquito larvicide temefos (Abate) by the salt march snail (Melampus bidentatus Say) in New Jersey was measured by gas-chromatographic analysis. Measurable quantities of temefos were found in the snails within 1 day after the first treatment with a 2% granular formulation but 3 weeks elapsed before uptake occurred following treatment with a temefos emulsion. Residues in the snails exposed to the granular formulation were generally more than 10 times higher than those in snails exposed to the emulsion although application rates of the granular formulation were only about three times higher than those of the emulsion. Residues in snails exposed to the emulsion fell below detectable levels less than 3 weeks after cessation of treatments although measurable amounts were found in snails exposed to the granular formulation for more than 5 weeks after the last treatment. The persistence of temefos in M. bidentatus suggests the potential for its movement through food webs exposed to the granular formulation.

Storage and analysis of samples of water, fish, and mud from environments contaminated with abate.

Methods for extraction, cleanup, and analysis of samples of water, mud, and fish containing trace quantities of Abate have been developed. Water was extracted by high-speed stirring of 10 ml of hexane in a 300-ml sample. The extracts were evaporated and analyzed by gas chromatography with a limit of detection of 0.00003 ppm. Dried mud samples were extracted by shaking with acetone. An aliquot of the acetone extract was diluted with water and the Abate extracted into 10 ml of hexane by high-speed stirring. The extracts were analyzed by gas chromatography. Fish were extracted with methylene chloride, cleaned up on a silica gel column, and analyzed by gas chromatography. The limit of sensitivity of the methods for mud and fish was found to be 0.001 ppm. Fish samples were stored for 3 weeks in 10% formalin containing 5% sodium thiosulfate without significant loss of Abate residues. A biological magnification of greater than 100 was observed in fish exposed to Abate for 16 hr at concentrations of 0.02 and 0.002 ppm.

Spatial distribution of insecticide resistance in Caribbean populations of Aedes aegypti and its significance

To monitor resistance to insecticides, bioassays were performed on 102 strains of the dengue vector Aedes aegypti (L.) from 16 countries ranging from Suriname in South America and throught the chain of Caribbean Islands to the Bahamas, where the larvicide temephos and the adulticide malathion have been in use for 15 to 30 years. There was wide variation in the sensitivity to the larvicide in mosquito populations within and among countries. Mosquito strains in some countries such as Antigua, St. Lucia, and Tortola had consistently high resistance ratios (RR) to temephos, ranging from 5.3 to 17.7. In another group of countries-e.g., Anguilla and Curacao-mosquitoes had mixed levels of resistance to temephos (RR=2.5-10.6), and in a third group of countries, including St. Kitts, Barbados, Jamiaca, and Suriname, mosquitoes had consistently low levels of resistance to temephos (RR=1-4.6) (P<0.05). On occasion significantly different levels of resistance were recorded from neighboring A. aegypti communities, which suggests there is little genetic exchange among populations. The impact of larval resistance expressed itself as reduced efficacy of temephos to kill mosquitoes when strains were treated in the laboratory or in the field in large container environments with recommended dosages. Although a sensitive strain continued to be completely controlled for up to 7 weeks, the most resistant strains had 24 percent survival after the first week. By week 6, 60 percent to 75 percent of all resistant strains of larvae were surviving the larval period. Responses to malathion in adult A. aegypti varied from a sensitive population in Suriname (RR=1.3) to resistant strains in St. Vincent (RR=4.4), Dominica (RR=4.2), and Trinidad (RR=4.0); however, resistance was generally not on the scale of that observed to temephos in the larval stages and had increased only slightly when compared to the levels that existed 3 to 4 years ago. Suggestions are made for a pesticide usage policy for the Caribbean region, with modifications for individual countries. This would be formulated based on each country's insecticide-resistance profile. Use of physical and biological control strategies would play a more critical role than the use of insecticides (AU)