Determination of insecticides' lethal concentrations and metabolic enzyme levels in Triatoma dimidiata / Determinación de concentraciones letales y niveles de enzimas metabólicas de insecticidas en Triatoma dimidiata

Abstract: Objective: The feasibility of the use of WHO impregnated paper and biochemical assays to determine lethal concentrations (LC50 and LC99) and insecticide metabolic enzyme levels of Triatoma dimidiata. Materials and methods: LC50 and LC99 were calculated with WHO papers impregnated at different concentrations of malathion, propoxur and deltamethrin; the percentage of insensitive acetylcholinesterase (iAChE); and the levels of esterases, glutathione S-transferases, and monooxygenases in laboratory nymphs of the first stage (5 to 7 days), were undertaken using the WHO biochemical assays. Results: Respectively the LC50 and LC99 µg/cm2 obtained for malathion were 43.83 and 114.38, propoxur 4.71 and 19.29, and deltamethrin 5.80 and 40.46. A 30% of the population had an iAChE, and only a few individuals had high P450 and β-eterase levels. Conclusion: Impregnated papers and biochemical tests developed by WHO for other insects, proved to be feasible methods in monitoring insecticide resistance and metabolic enzymes involved in T. dimidiata.

Resumen: Objetivo: La factibilidad de usar los papeles impregnados y ensayos bioquímicos según la OMS para determinar concentraciones letales (CL50 y CL99) y niveles enzimáticos en la resistencia a insecticidas en Triatoma dimidiata. Material y métodos: Se calcularon la CL50 y CL99 con papeles impregnados según la OMS a diferentes concentraciones de malatión, propoxur y deltametrina; el porcentaje de acetilcolinesterasa insensible (iAChE); y los niveles de esterasas, glutatión S-transferasas, y monooxigenasas en ninfas de laboratorio del estadio I (5-7 días) se determinaron usando los ensayos bioquímicos según la OMS. Resultados: Se obtuvieron las CL50 y CL99 µg / cm2 respectivamente para malatión 43.83 y 114.38, propoxur 4.71 y 19.29, y deltametrina 5.80 y 40.46. Un 30% de las chinches tuvo iAChE, y sólo pocos individuos tuvieron niveles superiores de P450 y β-eterasas. Conclusión: Los papeles impregnados y ensayos bioquímicos que describe la OMS para otros insectos demostraron ser métodos factibles para monitorear la resistencia a insecticidas y las enzimas metabólicas involucradas en T. dimidiata.

Resistencia a insecticidas en Aedes aegypti y Aedes albopictus (Diptera: Culicidae) de Tapachula, Chiapas, México / Insecticide resistance in Aedes aegypti and Ae. albopictus (Diptera: Culicidae) populations from Tapachula, Chiapas, Mexico

Resumen: Objetivo: Determinar la resistencia a insecticidas en Ae. aegypti y Ae. albopictus de Tapachula, Chiapas, México. Material y métodos: Se utilizaron ovitrampas para obtener huevos de mosquitos Aedes y se realizaron pruebas de susceptibilidad (CDC) y ensayos enzimáticos con la primera generación. Resultados: Aedes aegypti mostró resistencia a deltametrina, permetrina, malatión, clorpirifos, temefos y a bendiocarb (CARB), mientras que Aedes albopictus a malatión y en menor grado a cloripirifos, temefos, permetrina y deltametrina. Ambas especies mostraron altos niveles de enzimas como citocomo P450 y glutatión S-tranferasa, mientras que los niveles de esterasas variaron por especie y sitio muestreado. Se detectó acetilcolinesterasa insensible a insecticidas en ambas especies. Conclusión: En un hábitat urbano de Tapachula, Chiapas, México donde se aplica control con insecticidas Ae. aegypti y Ae. albopictus sólo son susceptibles al propoxur.

Abstract: Objective: To determine the insecticide resistance status of Ae. aegypti and Ae. albopictus from Tapachula, México. Materials and methods: Mosquito eggs were collected with the use of ovitraps and CDC susceptibility bioassays and biochemical assays were conducted to determine resistance levels and resistance mechanisms, respectively. Results: Ae. aegypti showed resistance to deltamethrin and permethrin (PYRs), malathion, chlorpyrifos and temephos (OP), and to bendiocarb (CARB), while Ae. albopictus showed resistance to malathion and to a lesser intensity to chlorypirifos, temephos, permethrin and deltamethrin. Both species showed high levels of P450 and GSTs, while levels of esterases varied by species and collection site. Altered acethilcholinesterase was detected in both species. Conclusion: In an urban habitat from Tapachula, Chiapas, Mexico where vector control using insecticides takes place, Ae. aegypti and Ae. albopictus are only susceptible to propoxur.

Assessment of nephrotoxicity and histopathological lesions of albino rats exposure to DD-force and baygon insecticides / Evaluación de la nefrotoxicidad y lesiones histopatológicas tras la exposición de ratas Albino a los insecticidas DD-Force y Baygon

Although studies suggest adverse effects of pesticides, human exposure to insecticides in homes is increasing and reports on their health effects are limited. The study investigated nephrotoxic effects of organo phosphate and carbamate insecticides, DD-Force and Baygon, in albino rats. Forty-five albino rats divided into groups were exposed to DD-Force (dichlorvos) or Baygon (propoxur) indoor insecticidein wooden boxes in separate exposure duration of 1, 2, 3 and 4 hours/day for 14 consecutive days. Serum and kidney tissue obtained after sacrifice were used to determine markers of renal damage and histopathological analysis, respectively. Exposure of rats to the insecticides showed duration-dependent significant increases (p<0.05) in serum levels of urea, uric acid and creatinine compared to control. However, rats exposed to DD-Force insecticide induced significantly higher levels of urea, uric acid and creatinine compared to Baygon (p<0.05). Histopathological lesions were observed in rats exposed to the insecticides, particularly in the exposure duration of 3 or 4 hours/day. These findings suggest that acute exposure to DD-Force and Baygonis nephrotoxic and may induce renal damage in rats.

Aunque los estudios sugieren efectos adversos de los pesticidas, la exposición humana a los insecticidas en los hogares está aumentando y los informes sobre sus efectos sobre la salud son limitados. Este estudio investigó los efectos nefrotóxicos de los insecticidas órgano fosfato y carbamato, DD-Force y Baygon, en ratas albinas. Cuarenta y cinco ratas albinas divididas en grupos fueron expuestas a DD-Force (diclorvos) o Baygon (propoxur) insecticidas de interior en cajas de madera en una duración de exposición separada de 1, 2, 3 y 4 horas / día durante 14 días consecutivos. Muestras séricas y de tejido renal obtenidas después del sacrificio se utilizaron para determinar los marcadores de daño renal y el análisis histopatológico, respectivamente. La exposición de las ratas a los insecticidas mostró aumentos significativos dependientes de la duración (p<0.05) en los niveles séricos de urea, ácido úrico y creatinina en comparación con el control. Sin embargo, las ratas expuestas al insecticida DD-Force indujeron niveles significativamente más altos de urea, ácido úrico y creatinina en comparación con Baygon (p<0.05). Se observaron lesiones histopatológicas en ratas expuestas a los insecticidas, particularmente en la duración de exposición de 3 o 4 horas/día. Estos hallazgos sugieren que la exposición aguda a DD-Force y Baygonis nephrotóxico y puede inducir daño renal en ratas.

Determinación de la sensibilidad a insecticidas organofosforados, carbamato y piretroides en poblaciones de Aedes aegypti Linneaus, 1762 ( Díptera: Culicidae ) de Panamá / Determining the status of susceptibility to organophosphate, carbamate and pyrethroids insecticides in populations of Aedes aegypti Linneaus, 1762 ( Diptera: Culicidae ) in Panamá

Introducción. Se llevó a cabo un estudio para determinar la sensibilidad de Aedes aegypti provenientes de regiones de alto riesgo de transmisión de dengue en Panamá, a insecticidas organofosforados, carbamatos y piretroides. Objetivo. Evaluar la sensibilidad a insecticidas piretroides, organofosforados y carbamatos en poblaciones de Ae. aegypti provenientes de ocho sitios pertenecientes a siete municipios de Panamá. Materiales y métodos. Se recolectaron poblaciones de Ae. aegypti en diferentes tipos de criaderos localizados en áreas urbanas y se criaron en condiciones controladas de laboratorio. Con la generación F 1 de cada una de las cepas se hicieron bioensayos de sensibilidad siguiendo la metodología estandarizada por la Organización Mundial de la Salud para larvas y adultos. Resultados. Las ocho cepas de Ae. aegypti resultaron sensibles a los insecticidas piretroides deltametrina, lambdacihalotrina y ciflutrina, el organofosforado fenitrotión y los carbamato propoxur y bendiocarb. Solo la cepa CHITRE resultó con resistencia moderada al insecticida deltametrina en larvas (FR 50 =5x). Sin embargo, en adultos resultó sensible. Conclusiones. Es necesaria la vigilancia periódica de la sensibilidad de las poblaciones de Ae. aegypti de los municipios evaluados, con el propósito de conservar en las poblaciones el carácter sensible a estos insecticidas. Los insecticidas aplicados para el control de Ae. aegypti pueden seguir siendo utilizados en los municipios evaluados, pero depende de la sensibilidad de los mosquitos en el área específica.

Introduction: We studied the susceptibility to organophosphate, carbamate and pyrethroid insecticides of Aedes aegypti from different regions of high transmission risk for dengue in Panama. Objective: To evaluate the susceptibility to organophosphate, carbamate and pyrethroid insecticides in Ae. aegypti from eight sites belonging to seven municipalities in Panamá. Materials and methods: We collected Ae. aegypti larval populations in different types of breeding sites located in urban areas. Insects were reared in laboratory control conditions. With the F 1 generation of each strain we performed susceptibility bioassays using WHO standardized methodology for larvae and adults. Results: The eight Ae. Aegypti strains were susceptible to the pyrethroid insecticides: deltamethrin, lambdacyhalothrin and cifluthrin, to the organophosphate fenitrothrion, and to the carbamates propoxur and bendiocarb. Only the CHITRE strain exhibited a moderate resistance to the insecticide deltamethrin in larvae (FR 50 =5x). However, adults were susceptible. Conclusions: It is necessary to perform periodic surveillance to evaluate the susceptibility of Ae. aegypti populations in the studied municipalities with the purpose of preserving their susceptible. The insecticides applied for Ae. aegypti control can still be used in the evaluated municipalities; however it will depend on the susceptibility of the mosquitoes in the specific area.

Estado de la susceptibilidad de poblaciones naturales / Susceptibility of natural populations of dengue vector to insecticides in Colombia

Introducción. La resistencia fisiológica de las poblaciones naturales de Aedes aegypti a los insecticidas de uso en salud pública, disminuye la eficacia del control químico utilizado para interrumpir la transmisión de dengue durante los brotes y epidemias. Objetivo. Determinar el estado de la susceptibilidad al carbamato propoxur, a los organofosforados adulticidas malatión y fenitrotión y al larvicida temefos, de 13 poblaciones naturales de Ae. aegypti en ocho municipios: una de Bucaramanga y dos de Sabana de Torres en el departamento de Santander; dos de Girardot y dos de La Mesa en Cundinamarca; dos de Villavicencio y dos de Puerto López en el Meta; una de San José del Guaviare, en Guaviare, y una de Florencia en Caquetá. Materiales y métodos. Las pruebas de susceptibilidad consistieron en bioensayos estandarizados de la Organización Mundial de la Salud (OMS), 1981, y botellas de los Centers for Disease Control and Prevention (CDC), 1998. Se aplicaron pruebas colorimétricas para determinar los niveles de enzimas como posibles responsables de la reducción de la susceptibilidad a insecticidas organofosforados y al carbamato propoxur. Resultados. Todas las poblaciones presentaron susceptibilidad a malatión y propoxur. Para el temefos, solo cuatro de las trece localidades evaluadas registraron susceptibilidad. Con respecto a los posibles mecanismos de desintoxicación enzimática, en siete de las once poblaciones naturales se registraron valores superiores al punto de corte para esterasas inespecíficas, solamente en Bucaramanga se presentó un incremento en las enzimas monooxigenasas del citocromo P450, pero en ninguna población se registró acetilcolinestarasa modificada. Conclusiones. La susceptibilidad generalizada a los organofosforados adulticidas evaluados, indica que el malatión, el insecticida más utilizado en Colombia para interrumpir la transmisión del dengue, sigue siendo eficaz. Las particularidades de los resultados de la resistencia fisiológica a insecticidas de las comunas de un mismo municipio, evidenciaron un fenómeno localizado de manera específica en espacio y tiempo.

Introduction. Physiological resistance of natural population of Aedes aegypti to insecticides contribute to the decreased efficacy of chemical control as a main control strategy during dengue outbreaks. Objective. The susceptibility status of Ae. aegypti was assessed for the carbamate propoxur, the adulticide malathion and the larvicide temephos on 13 natural populations of Ae. aegypti immature forms were taken from 8 Colombian localities. These included the following: Bucaramanga (1), Sabana de Torres (2), Girardot (2), La Mesa (2), Villavicencio (2), Puerto López (2), San José del Guaviare (1) and Florencia (1). Materials and methods. Susceptibility tests mainly consisted of the standardized bioassay outlined by WHO (1981) and CDC bottles (1998). Colorimetric tests were undertaken to determine enzyme levels possibly responsible for the reduction of susceptibility to organophosphate and carbamate insecticides. Results. All specimens demonstrated susceptibility to malathion and propoxur insecticides. Four of the 13 populations revealed susceptibility to the temephos larvicide. Seven of 11 populations showed a limited increase in values for nonspecific esterase enzymes. The Bucaramanga population was the only one which showed an increase in the cytochrome P450 monooxygenases enzymes. Neither population was found with modified acetilcolinesterase. Conclusions. The widespread susceptibility to organophosphates used as adulticides indicated that malathion, the most used insecticide in Colombia, remains effective in interrupting the transmission of dengue. Physiological resistance to insecticides occurring in communities of a single township proved to be a localized phenomenon.

Influence of joint exposure to diazinon, propoxur and bisphenol A on phagocytosis of RAW264.7 cell / 中华预防医学杂志

<p><b>OBJECTIVE</b>To explore the toxicity of joint exposure to diazinon, propoxur and bisphenol A on phagocytosis.</p><p><b>METHODS</b>Flow cytometer was employed to detect the influence of diazinon and bisphenol A, propoxur and bisphenol A in mixture (mixed according to ratio of IC(50)) on mouse macrophage RAW264.7 cells' function to phagocyte fluorescent microspheres, adopting the percentage of phagocytic cells (PP) and the phagocytic index (PI) as measurement indicators. The final concentrations of mixture of diazinon and bisphenol A were (0.4 + 0.1), (3.6 + 0.7), (36.2 + 7.2), (43.4 + 8.7), (52.1 + 10.4), (62.5 + 12.5), (75.0 + 15.0) µg/ml; while those of mixture of propoxur and bisphenol A were (0.2 + 2.0 × 10(-2)), (2.4 + 0.2), (23.7 + 2.0), (35.6 + 3.0), (53.3 + 4.4), (80.0 + 6.7), (120.0 + 10.0) µg/ml. Then based on the dose-response relationship, a 2 × 2 factorial design was then carried out among different doses of mixture with statistical significance to statistically evaluate the interaction between diazinon and bisphenol A, propoxur and bisphenol A.</p><p><b>RESULTS</b>After the joint exposure, compared to the control group (PP = (23.6 ± 2.2)%; PI = 0.36 ± 0.03), any dose of the mixture of diazinon and bisphenol A ((52.1 + 10.4), (62.5 + 12.5), (75.0 + 15.0) µg/ml) could significantly increase the levels of PP ((29.0 ± 1.4)%, t = 3.89, P < 0.05; (30.2 ± 2.3)%, t = 4.74, P < 0.05; (35.0 ± 3.4)%, t = 8.21, P < 0.05) and PI (0.43 ± 0.03, t = 3.86, P < 0.05; 0.41 ± 0.02, t = 2.95, P < 0.05; 0.46 ± 0.03, t = 5.34, P < 0.05); while that of propoxur and bisphenol A ((35.6 + 3.0), (53.3 + 4.4), (80.0 + 6.7), (120.0 + 10.0) µg/ml) reduced the levels of PP ((20.6 ± 1.1)%, t = -3.00, P < 0.05; (20.2 ± 1.0)%, t = -3.42, P < 0.05; (19.4 ± 1.3)%, t = -4.23, P < 0.05; (18.8 ± 2.1)%, t = -4.81, P < 0.05) and PI (0.31 ± 0.01, t = -4.75, P < 0.05; 0.31 ± 0.01, t = -4.58, P < 0.05; 0.30 ± 0.01, t = -4.92, P < 0.05; 0.27 ± 0.02, t = -7.80, P < 0.05) on the contrary. The 2 × 2 factorial design was carried out between the mixture of diazinon (60.0 µg/ml; PP = (28.5 ± 3.4)%; PI = 0.49 ± 0.07) and bisphenol A (12.0 µg/ml; PP = (35.7 ± 2.7)%; PI = 0.67 ± 0.07), and the mixture of propoxur (48.0 µg/ml ; PP = (28.1 ± 2.2)%; PI = 0.48 ± 0.04) and bisphenol A (4.0 µg/ml; PP = (34.4 ± 2.7)%; PI = 0.59 ± 0.07). The mixture of diazinon and bisphenol A (PP = (30.4 ± 1.4)%, F(interaction) = 6.22, P < 0.05; PI = 0.53 ± 0.03, F(interaction) = 7.35, P < 0.05) and the mixture of propoxur and bisphenol A (PP = (27.5 ± 4.1)%, F(interaction) = 4.56, P < 0.05; PI = 0.46 ± 0.08, F(interaction) = 11.13, P < 0.05) both showed a significant antagonistic interaction on phagocytosis of RAW264.7 cell.</p><p><b>CONCLUSION</b>It is suggested that the interactions between diazinon & bisphenol A and propoxur & bisphenol A both played the antagonistic role on phagocytic function of macrophages in vitro.</p>

Propoxur-induced acetylcholine esterase inhibition and impairment of cognitive function: Attenuation by Withania somnifera.

Propoxur (2-isopropoxyphenyl N-methylcarbamate) is widely used as an acaricide in agriculture and public health programs. Studies have shown that sub-chronic exposure to propoxur can cause oxidative stress and immuno-suppression in rats. Carbamates are also known to exhibit inhibitory effect on cholinesterase activity, which is directly related to their cholinergic effects. In the present study, the effect of Withania somnifera (Ashwagandha), a widely used herbal drug possessing anti-stress and immuno-modulatory properties was studied on propoxur-induced acetylcholine esterase inhibition and impairment of cognitive function in rats. Male Wistar rats were divided into four groups. Group I was treated with olive oil and served as control. Group II was administered orally with propoxur (10 mg/kg b.wt.) in olive oil, group III received a combination of propoxur (10 mg/kg b.wt.) and W. somnifera (100 mg/kg b.wt.) suspension and group IV W. somnifera (100 mg/kg b.wt.) only. All animals were treated for 30 days. Cognitive behaviour was assessed by transfer latency using elevated plus maze. Blood and brain acetylcholine esterase (AChE) activity was also assessed. Oral administration of propoxur (10 mg/kg b.wt.) resulted in a significant reduction of brain and blood AChE activity. A significant prolongation of the acquisition as well as retention transfer latency was observed in propoxur-treated rats. Oral treatment of W. somnifera exerts protective effect and attenuates AChE inhibition and cognitive impairment caused by sub-chronic exposure to propoxur.

Differences of acetylcholinesterase level in variety classes and strains of Culex pipiens pallens / 浙江大学学报·医学版

<p><b>OBJECTIVE</b>To investigate the diversity of acetylcholinesterase (AChE) activity in variety classes and strains of Culex pipiens pallens and provide a basis for the insecticide-resistance detection of mosquito by biochemical method.</p><p><b>METHODS</b>AChE insensitivity of single mosquito was determined, using acetythiocholine iodide (ATch) as the substrate, 5,5'-dithio-bis (2-nitrobenzoic acid) (DTNB) as the developer, and propoxur as the inhibitor.</p><p><b>RESULT</b>There were significant differences in AChE activity among the four types of IV instar larvae and 3-day-old adult female of sensitive strain mosquito (P<0.01). The AChE activity of the 3-day-old adult female was higher than that of IV instar larvae of the four types of sensitive strain mosquito (P<0.01). The AChE activity of anti-DDVP (Rd) and anti-propoxur (Rp) strains of Culex pipiens pallens was significantly higher than that of sensitive (S) strain (P<0.01), while the AChE activity of anti-cypermethrin (Rc) strain of Culex pipiens pallens was similar to that of S strain (P>0.05). The individual frequency of insensitive AChE of Rd and Rp strains of Culex pipiens pallens was significantly higher than that of sensitive (S) strain (P<0.01), while the individual frequency of insensitive AChE of Rc strain of Culex pipiens pallens was similar to that of S strain(P>0.05).</p><p><b>CONCLUSION</b>The AChE activity determination can be used to examine the insecticide-resistance of mosquito.</p>

Melatonin treatment prevents modulation of cell-mediated immune response induced by propoxur in rats.

The effect of melatonin, a major secretory product of the pineal gland, in attenuation of propoxur (2-isopropoxy phenyl N-methyl carbamate)-induced modulation of cell-mediated immune (CMI) response was studied in rats. Male Wistar albino rats were exposed to propoxur (a widely used pesticide) orally (10 mg/kg) and/or melatonin (10 mg/kg) orally for 4 weeks. CMI was measured by delayed-type hypersensitivity (DTH), leucocyte and macrophage migration inhibition (LMI and MMI) responses and estimation of cytokines TNF-alpha and IFN-gamma levels. Rats exposed to propoxur for 4 weeks showed significant decrease in DTH, LMI and MMI responses. Propoxur also suppressed TNF-alpha and IFN-gamma production significantly. Administration of melatonin alone caused a significant increase in DTH response. Although there were no changes in the LMI and MMI response, the cytokine levels were significantly increased, as compared to control. Co-administration of melatonin along with propoxur significantly nullified the effect of the pesticide on the CMI response, except DTH and reversed levels of cytokines to near control/normal values. Thus, melatonin treatment considerably attenuated immunomodulation caused by sub-chronic treatment of propoxur in experimental animals.

Evaluation of five local formulated insecticides against German cockroach [Blattella germanica L.] in southern Iran

The German cockroach, Blattella germanica L., is a serious household and public health pest worldwide. Control of this species has been very difficult to achieve. Toxicity of cypermethrin EC10%, deltamethrin EC5%, diazinon EC0.5%, lambda-cyhalothrin EC5% and Negon_ [permethrin+propoxur oil liquid1%] commercial formulations were investigated against adult males of German cockroaches collected from four hospitals of Bandar Abbas City, southern Iran, during 2006. These insecticides have been used for cockroach control in this city. The tests were carried out only on males by the glass jar contact method recommended by the WHO. Maximum mortality rates of 20, 35, 90, and 100% were obtained after one hour contact to label-recommended doses of cypermethrin, deltamethrin, lambad-cyhalothrin, diazinon and permethrin+propoxur insecticides, respectively. KT [50] results were different from 5.68 min for permethrin+propoxur mixture to 240.37 min for cypermethrin. German cockroach showed < 80 per cent mortality using three pyrethroid insecticides. It seems that the label-recommended concentrations of these insecticides were wrong and lower than WHO advised for cockroach control. For monitoring of resistance it is recommended to do more tests using the pure active ingredient of these insecticides

Deviation of negatively charged protein fractions in the trochophore and veliger larvae by the larvicidal action of baygon in freshwater pulmonate Gyraulus convexiusculus (Planorbidae).

In the present investigation egg capsules of Gyraulus convexiusculus were treated with different concentrations of baygon. A dose and duration dependent deviations in the number of negatively charged protein fractions in the trochophore and veliger larval stages were observed. It resulted into anomalies in the morphogenesis and organogenesis of corresponding larval stages. Most of the protein bands showed the decrease in the protein positive intensities in comparison to control. This suggested that baygon causes larval toxicity in Gyraulus convexiusculus.

Protective effect of melatonin against propoxur-induced oxidative stress and suppression of humoral immune response in rats.

Effect of melatonin in attenuation of propoxur induced oxidative stress and suppression of humoral immune response was studied in rats. Oral administration of propoxur (10 mg/kg) increased lipid peroxidation in serum after 28 days treatment. Superoxide dismutase, catalase and glutathione were also altered following propoxur exposure. In addition propoxur exposure markedly suppressed humoral immune response as assessed by antibody titre and plaque forming cell assay. Simultaneous treatment with melatonin (5 mg/kg, ip) markedly attenuated the effect of propoxur on (a) lipid peroxidation, (b) oxidative stress parameters and (c) immunotoxicity. Results have been discussed in the light of possible immunopotentiating and antioxidant effects of melatonin to understand the influence of oxidative stress on propoxur induced immunomodulation.

Efficacy of synthetic pyrethroid and propoxur aerosol in the control of German cockroaches (Dictyoptera: Blatellidae) in cookhouses.

BACKGROUND AND OBJECTIVES: A field trial was carried out in cookhouses in an urban area to evaluate the efficacy of synthetic pyrethroid (0.02% deltamethrin + 0.13% allethrin) and propoxur aerosols (2%) in the control of German cockroaches (Blatella germanica). METHODS: A total of six cookhouses were selected by simple random sampling method (two each for the two insecticide treatments and two for control). RESULTS: It was observed that 89.36-87.8 and 77.95-59.74% reductions were achieved with propoxur and synthetic pyrethroid treatment respectively by first week post-treatment. The reduction in propoxur treated areas by eight weeks post-treatment was 82.98-76.13%, whereas the reduction in the same time period in synthetic pyrethroid treated areas ranged from 14.36% to an increase in density by a phenomenal 157.86% in one of the treated sites. INTERPRETATION AND CONCLUSION: The study reports the efficacy of propoxur aerosol (2%) treatment over synthetic pyrethroid (0.02% deltamethrin + 0.13% allethrin) in the control of cockroach infestation in cookhouses in urban area.

Acute pancreatitis following propoxyfur (Baygon) ingestion.

Elevation of serum amylase and blood glucose is not uncommon following anticholinesterase poisoning. We report a young male who developed acute cholinergic crisis and acute pancreatitis following propoxyfur (Baygon) ingestion and recovered completely with conservative management.

Efficacy of Fipronil and Propoxur in the control of German cockroaches (Dictyoptera: Blatellidae).

A field trial for comparative evaluation of chemicals Fipronil gel, Propoxur spray and bait was carried out. The results in the Fipronil treated area indicate a reduction of 89%, 100% and 98% in cockroach infestation by days 7, 30 and 60, whereas the reduction in Propoxur spray treated area during the same period was 88%, 91% and 87% respectively. Propoxur bait was not found to be effective in reducing the cockroach infestation; rather a build up of the cockroach infestation was noticed in the treated site. The study reports the efficacy of Fipronil gel treatment over conventional insecticidal formulations in the control of cockroach infestation in cookhouses of urban households.

Resistencia a insecticidas en cepas de terreno de la especie Blattella germanica procedentes de Santiago de Cuba / Resistance to insecticides in Blattella germanica species strains from Santiago de Cuba

A study was conducted on the level of resistance to seven insecticides, namely, 3 organophosphate compounds (malathion, chlorpyrifos and pirimiphos-methyl), one carbamate (propoxur) and 1 pyrethroid (cypermethrin, deltamethrin and lambdacialotrine) of three field-collected strains of Blattella germanica (Linnaeus, 1767) from Santiago de Cuba. These strains showed high resistance levels to malathion, cypermethrin, deltamethrin and lambdacialotrine and low resistance to pirimiphos-methyl, and also they were susceptible to chlorpyrifos and propoxur. The levels of resistance to tested organophosphate insecticides such as malathion and pirimiphos-methyl and to pyrethroid compounds like cypermethrin, deltamethrin and lambdacialotrine may be related to the increased production of esterases as a mechanism of resistance. The value of frequency of the resistant genes for enzyme acetylcholinesterase was very low, therefore, the modified acetylcholinesterase is not involved in resistance to insecticides tested in the studied strains from Santiago de Cuba.

Insecticide cross-resistance spectra and underlying resistance mechanisms of Sri Lankan anopheline vectors of malaria.

Present status of insecticide resistance was investigated in two major vectors of malaria; An. culicifacies and An. subpictus, collected from a high malaria transmission area in Sri Lanka during 1996/1998. Adult and larval bioassays were carried out to obtain log-probit mortality lines for malathion, propoxur, permethrin and chlorpyrifos. Respective LD50 values were 4.45%, 0.002%, 0.16% and 0.001% for An. culicifacies and 0.66%, 0.004%, 0.004% and 0.04% for An. subpictus. Adults were also tested for WHO standard discriminating dosages of malathion, propoxur, permethrin, DDT, cypermethrin, deltamethlin and lambda cyhalothrin. Both populations were highly resistant to DDT. An. culicifacies was more resistant to malathion and An. subpictus was more resistant to chlorpyrifos. About 25% of both populations were resistant to permethrin. An. culicifacies was susceptible to propoxur, deltamethrin and lambda cyhalothrin and An. subpictus to cypermethrin and lambda cyhalothrin. Adult mosquitos were individually tested for their insecticide detoxifying enzyme activities and altered target-site, acetylcholinesterase. High general esterase activity indicated the presence of amplified esterase genes in both populations. Native gel electrophoresis resolved one elevated esterase isoenzyme, with high affinity to organophosphates, from each species. Malathion carboxylesterase mechanism was present in both populations. Higher glutathione-S-transferase activity was marked in An. subpictus. Synergistic studies showed the possible involvement of monooxygenases in resistance in both species. Acetylcholinesterase activity of approximately 80% of both populations was not inhibited by a standard dosage of propoxur. Low resistance to carbamates shows that the impact of agricultural pesticides is not significant in the development of resistance especially in An. culicifaies. Pyrethroids, other than permethrin, can be successfully used in vector control programs. Carbamates will be an alternative.

Propoxur selection of the adults of anopheles stephensi from minab, south of Iran

Anopheles stephensi is the main malaria vector in south of Iran. It has been known to be resistant to DDT, malathion and dieldrin. After appearance of resistance the area was treated with propoxur, at the rate of 2 g/m2 twice a year for 14 successive years. This species is still susceptible to propoxur. In order to forecast the possibility of development of propoxur resistance in An.stephensi, the females of this species were put under the pressure of propoxur for 14 generations in 1988. Fourteen generations of propoxur selection on the adult females of An.stephensi resulted in an increase in LT60 from 8.5 min to 24.30 minutes, i.e. 2.86 fold increase in tolerance