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 METHODS Data were gathered from two sources: a bibliographic review of studies published from 1985 to 2017, and unpublished data produced by our team within the MoReNAa between 1998 and 2012.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.

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.