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Regular monitoring of insecticide resistance among vector mosquitoes and their mechanism are very important for formulation of effective vector control measures. Insecticide resistance developed due to metabolic resistance which is mediated by the enhanced production of different detoxifying enzymes resulting in sequestration or biodegradation of insecticides. Present study was designed to assess any evidence of metabolic resistance among four major JE vectors - Cx. tritaeniorhynchus, Cx. vishnui, Cx. pseudovishnui, and Cx. gelidus from northern districts of West Bengal, India. A total of 92 adults per species of JE vectors in each study districts were analysed to measure the activity/levels of acetylcholinesterase (AChE), non-specific esterase (ESTs), glutathione-S-transferases (GSTs), and cytochrome P450s mono-oxygenase (CytP450s) according to WHO protocol. A significant increase in mean AChE activity without propoxur were observed among most of the JE vector species. All four species showed significantly elevated AChE activity with propoxur, except Cx. gelidus of Darjeeling and Uttar Dinajpur. More than 70% of Cx. tritaeniorhynchus showed homozygous resistant (RR) genotype to propoxur-inhibited residual activity of AChE but Cx. gelidus, Cx. pseudovishnui and Cx. vishnui showed either homozygous sensitive (SS) or heterozygous resistant (RS) genotype. More than 50% and 80% population of all species showed an elevated level of both alpha, beta ESTs and GSTs. CytP450s activity was also higher among all species. The present study suggests that the development of resistance against different classes of insecticides among four major JE vector species is becoming a matter of concern that should be monitored closely.

The insecticides imidacloprid (IMI), a neonicotinoid, and propoxur (PRO), an N-methylcarbamate compound, are pesticides widely used throughout the world. Although they are not used together to combat pests, both are often found in freshwater near agricultural areas. Thereby, the goal of this study was to evaluate the additive effects of IMI and PRO mixtures at environmental concentrations in relation to isolated compounds on Rhamdia quelen, a neotropical fish. The fish was exposed to IMI (0.11 µg/L), PRO (0.039 µg/L), or Mix (0.11 µg/L IMI plus 0.039 µg/L PRO) during 96 h. Glutathione S-transferase (GST), superoxide dismutase (SOD), catalase (CAT), acetylcholinesterase (AChE) activities were determined. To verify oxidative damage thiobarbituric acid reactive substances (TBARS), protein carbonyl (PC), reactive oxygen species contents (ROS), antioxidant capacity against peroxides (ACAP) were determined in gills, liver, brain and muscle. The results shows that a mixture of these pesticides at environmental concentrations inhibited acetylcholinesterase activity in the brain and induced oxidative damage in all analyzed tissues. These results reinforce the hypothesis that mixture of contaminants present in environment could induce additive or synergistic effects on fish species.

Different species of Culex mosquitoes are present in high numbers in many other countries in addition to sub-Saharan Africa and Asian countries. Culex mosquitoes are serious nuisance which also transmit a range of pathogens including several viruses such as West Nile virus, Saint Louis encephalitis, and Rift Valley fever, as well as parasites such as avian malaria, and filarial worms. In Ethiopia, unlike Anopheles mosquitoes, little effort was given to study habitat, species composition, blood meal sources and insecticide susceptibility status of Culex mosquitoes. Therefore, this study aimed to assess the species composition, their blood meal source and insecticide susceptibility status of Culex mosquitoes to some of selected insecticides in Jimma town southwest Ethiopia. Culicine mosquito larvae were collected using a standard dipper (by dipping) from a range of breeding sites and reared to adults. Species identification was carried out using standard keys. Bioassay tests were performed on adults to assess the susceptibility of Culex mosquitoes to insecticide-impregnated papers with Dichlorodiphenyltrichloroethane (DDT (4%), mlathion (5%), bendiocarb (0.1%), propoxur (0.1%), deltamethrin (0.05%) and pirimiphos-methyl (0.25) following World Health Organization Pesticide Evaluation Scheme (WHOPES) guideline. Moreover, 184 blood fed (BF) Culex mosquitoes were collected using aspirator from indoor and outdoor resting and assayed to assess blood meal sources using Enzyme-Linked Immunosorbent Assay (ELISA). The result of the study showed that among the collected Culex moquitoes, two species were identified as Culex quinquefasciatus and Cx antennatus whereas the remaining one could not be identified to species level. Culex mosquitoes were found to be resistant to DDT, malathion, bendiocarb, propoxur, and deltamethrin whereas susceptible to pirimiphos-methyl. The blood meal source analysis using Enzyme-Linked Immunosorbent Assay (ELISA) showed higher blood source of human (33.2%) than bovine (15.2%). Thus, the observed resistance to the most of the insecticides coupled with higher human blood meal source calls further studies to be carried out in Culex mosquito populations of Ethiopia.

Vector-borne diseases pose serious threat to life and socio-economic status of an individual and application of insecticides has always been a prime strategy to control the vectors. However, with frequent use of insecticides the vectors develop resistance towards the same. It is therefore necessary to evaluate the resistance status of vectors against such chemicals for proper management of vector-borne diseases. As such, field populations of Culex quinquefasciatus a vector of lymphatic filariasis were collected 3 districts of West Bengal and mortality percentage was studied against 6 insecticides. Quantitative assay of major detoxifying enzymes was also studied to unveil their association with insecticide resistance and the presence of mutation in the voltage-gated sodium channel (L1014F) was also evaluated. This study showed multiple resistance to all of the insecticides used i.e., deltamethrin, lambdacyhalothrin, permethrin, DDT, propoxur and malathion). The presence of high frequency of L1014F mutant allele and enhanced enzyme activity may indicate their involvement in the development of insecticide resistance.

BackgroundAedesborne viral diseases, notably dengue, are increasingly reported in Cameroon withAedes aegyptibeing a major vector. Data on insecticide resistance of this vector and underlying mechanisms needed for outbreak preparedness remain scarce in Cameroon. Here, we present the nationwide distribution of insecticide resistance inAe. aegyptiand investigate the potential resistance mechanisms involved.MethodsImmature stages ofAe. aegyptiwere collected between March and July 2017 in 13 locations across Cameroon and reared until G1/G2/G3 generation. Larval, adult bioassays, and piperonyl butoxide (PBO) synergist assays were carried out according to World Health Organization guidelines. F1534C mutation was genotyped using allele specific polymerase chain reaction in field collected adults (Go) and the polymorphism of the sodium channel gene was assessed. Theχ2test was used to compare the mortality rate between bioassays with insecticides only and bioassays after preexposure to PBO synergist.ResultsLarval bioassay revealed that all the three populations tested with temephos were susceptible. Adult bioassays showed a good level of susceptibility toward both pyrethroids tested, 0.25% permethrin and 0.05% deltamethrin, with six out of 10 populations susceptible. However, two populations (Douala and Edéa) were resistant (deltamethrin [73.2–92.5% mortality], permethrin [2.6–76.3% mortality]). The resistance to 4% dichlorodiphenyltrichloroethane was observed in four out of 10 populations tested (16.8–87.1% mortality). Resistance was also reported to carbamates including 0.1% propoxur (60.8–87.1% mortality) and to 0.1% bendiocarb (82.9% mortality). All populations tested were fully susceptible to 1% fenitrothion. A partial recovery of susceptibility was observed in the pyrethroid resistant population of Douala after pre-exposed to PBO suggesting the implication of cytochrome P450 monoxygenases permethrin resistance. Genotyping and sequencing detected the F1534Ckdrmutation in the two pyrethroid resistant locations of Edéa and Douala, with allelic frequency of 3.3% and 33.3% respectively. However, the high genetic diversity of the sodium channel gene supports the recent introduction of this mutation in Cameroon.ConclusionsThis study revealed the contrasting resistance profiles to insecticides ofAe. aegyptipopulations in Cameroon suggesting that, instead of a unique nationwide control approach, a regionally adapted strategy will be needed to control this vector. The localised distribution of the F1534Ckdrmutation supports this region-specific control strategy.

Background In the Republic of Congo, with two massive outbreaks of chikungunya observed this decade, little is known about the insecticide resistance profile of the two major arbovirus vectors Aedes aegypti and Aedes albopictus. Here, we established the resistance profile of both species to insecticides and explored the resistance mechanisms to help Congo to better prepare for future outbreaks. Methods Immature stages of Ae. aegypti and Ae. albopictus were sampled in May 2017 in eight cities of the Republic of the Congo and reared to adult stage. Larval and adult bioassays, and synergist (piperonyl butoxide [PBO]) assays were carried out according to WHO guidelines. F1534C mutation was genotyped in field collected adults in both species and the polymorphism of the sodium channel gene assessed in Ae. aegypti. Results All tested populations were susceptible to temephos after larval bioassays. A high resistance level was observed to 4% DDT in both species countrywide (21.9–88.3% mortality). All but one population (Ae. aegypti from Ngo) exhibited resistance to type I pyrethroid, permethrin, but showed a full susceptibility to type II pyrethroid (deltamethrin) in almost all locations. Resistance was also reported to 1% propoxur in Ae. aegypti likewise in two Ae. albopictus populations (Owando and Ouesso), and the remaining were fully susceptible. All populations of both species were fully susceptible to 1% fenitrothion. A full recovery of susceptibility was observed in Ae. aegypti and Ae. albopictus when pre-exposed to PBO and then to propoxur and permethrin respectively. The F1534C kdr mutation was not detected in either species. The high genetic variability of the portion of sodium channel spanning the F1534C in Ae. aegypti further supported that knockdown resistance probably play no role in the permethrin resistance. Conclusions Our study showed that both Aedes species were susceptible to organophosphates (temephos and fenitrothion), while for other insecticide classes tested the profile of resistance vary according to the population origin. These findings could help to implement better and efficient strategies to control these species in the Congo in the advent of future arbovirus outbreaks.

Background Aedes aegypti were found developing in the water in open public drains (drain-water, DW) in Jaffna city in northern Sri Lanka, a location where the arboviral diseases dengue and chikungunya are endemic. Methods Susceptibilities to the common insecticides dichlorodiphenyltrichloroethane (DDT), malathion, propoxur, permethrin and deltamethrin and activities of the insecticide-detoxifying enzymes carboxylesterase (EST), glutathione S-transferase (GST) and monooxygenase (MO) were compared in adult Ae. aegypti developing in DW and fresh water (FW). Results DW Ae. aegypti were resistant to the pyrethroids deltamethrin and permethrin, while FW Ae. aegypti were susceptible to deltamethrin but possibly resistant to permethrin. Both DW and FW Ae. aegypti were resistant to DDT, malathion and propoxur. Greater pyrethroid resistance in DW Ae. aegypti was consistent with higher GST and MO activities. Conclusions The results demonstrate the potential for insecticide resistance developing in Ae. aegypti adapted to DW. Urbanization in arboviral disease-endemic countries is characterized by a proliferation of open water drains and therefore the findings identify a potential new challenge to global health.

Background Dengue is a serious public health problem worldwide, including in Selangor, Malaysia. Being an important vector of dengue virus, Aedes aegypti are subjected to control measures which rely heavily on the usage of insecticides. Evidently, insecticide resistance in Ae. aegypti, which arise from several different point mutations within the voltage-gated sodium channel genes, has been documented in many countries. Thus, this robust study was conducted in all nine districts of Selangor to understand the mechanisms of resistance to various insecticides in Ae. aegypti. Mosquitoes were collected from dengue epidemic and non-dengue outbreak areas in Selangor. Methods Using the Center for Disease Control and Prevention (CDC) bottle assays, the insecticide resistance status of nine different Ae. aegypti strains from Selangor was accessed. Synergism tests and biochemical assays were conducted to further understand the metabolic mechanisms of insecticide resistance. Polymerase chain reaction (PCR) amplification and sequencing of the IIP-IIS6 as well as IIIS4-IIIS6 regions of the sodium channel gene were performed to enable comparisons between susceptible and resistant mosquito strains. Additionally, genomic DNA was used for allele-specific PCR (AS-PCR) genotyping of the gene to detect the presence of F1534C, V1016G and S989P mutations. Results Adult female Ae. aegypti from various locations were susceptible to malathion and propoxur. However, they exhibited different levels of resistance against dichlorodiphenyltrichloroethane (DDT) and pyrethroids. The results of synergism tests and biochemical assays indicated that the mixed functions of oxidases and glutathione S-transferases contributed to the DDT and pyrethroid resistance observed in the present study. Besides detecting three single kdr mutations, namely F1534C, V1016G and S989P, co-occurrence of homozygous V1016G/S989P (double allele) and F1534C/V1016G/S989P (triple allele) mutations were also found in Ae. aegypti. As per the results, the three kdr mutations had positive correlations with the expressions of resistance to DDT and pyrethroids. Conclusions In view of the above outcomes, it is important to seek new tools for vector management instead of merely relying on insecticides. If the latter must be used, regular monitoring of insecticide resistance should also be carried out at all dengue epidemic areas. Since the eggs of Ae. aegypti can be easily transferred from one location to another, it is probable that insecticide-resistant Ae. aegypti can be found at non-dengue outbreak sites as well. Electronic supplementary material The online version of this article (10.1186/s13071-019-3472-1) contains supplementary material, which is available to authorized users.

Background Sri Lanka has been malaria-free since 2013 but re-introduction of malaria transmission by infected overseas travelers is possible due to a prevalence of potent malaria vectors. Knowledge of the insecticide resistance status among Anopheles vectors is important if vector control has to be reintroduced in the island. The present study investigated the insecticide susceptibility levels and resistance mechanisms of Anopheles sundaicus (sensu lato) (previously classified as Anopheles subpictus species B) an important malaria vector in the Jaffna Peninsula and it surroundings in northern Sri Lanka after indoor residual spraying of insecticides was terminated in 2013. Results Species-specific PCR assays identified An. sundaicus (s.l.) in four locations in the Jaffna and adjacent Kilinochchi districts. Bioassays confirmed that An. sundaicus (s.l.) collected in Kilinochchi were completely susceptible to 0.05% deltamethrin and 5% malathion and resistant to 4% dichlorodiphenyltrichloroethane (DDT), whereas those from Jaffna were relatively susceptible to all three insecticides. Kilinochchi populations of An. sundaicus (s.l.) showed significantly higher glutathione S-transferase activity than population from Jaffna. However, Jaffna An. sundaicus (s.l.) had significantly higher Propoxur-resistant acetylcholinesterase activity. Activities of non-specific esterases and monooxygenases were not significantly elevated in An. sundaicus (s.l.) collected in both districts. Conclusions The susceptibility to malathion and deltamethrin in An. sundaicus (s.l.) suggests that they can be still used for controlling this potential malaria vector in the Jaffna Peninsula and adjacent areas. Continuing country-wide studies on other malaria vectors and their insecticide susceptibilities are important in this regard.

A total of 39 strains ofAnopheles stephensi, an important urban malaria vector, were collected from various parts of India and maintained in the insectary for this study. Based on the egg-float ridge number, 19 strains were classified into ecological variants and 32 strains were exposed to chlorpyrifos and propoxur to investigate their resistance status. Filter paper containing freshly laid eggs was taken, the ridge numbers on the floats were counted under the microscope, and strains were classified into ecological variants. Of the 19 strains, 18 were of ‘type form’, with ridge numbers ranging from 15 to 21. The Papareddipalya (PRP) strain belonged to the ‘intermediate form’, with 14 to 17 ridge numbers. Larval bioassays were carried out according to the procedure of the WHO. For chlorpyrifos, the lowest LC50value was 0.00107 mg/l (Padmanabhanagar strain) and the highest value was 0.0403 mg/l (GOA-A strain). Furthermore, the lowest LC90value was 0.00368 mg/l (Delhi strain) and the highest was 0.1746 mg/l (GOA-A strain). For propoxur, the lowest LC50value was 0.00029 mg/l (Goraguntepalya strain) and the highest value was 0.0037 mg/l (JP Nagar strain). Moreover, the lowest LC90value was 0.00094 mg/l (Goraguntepalya strain) and the highest value was 0.0115 mg/l (JP Nagar strain). The tolerance values ranged from 1.26 to 37.68 for chlorpyrifos and from 1.34 to 12.77 for propoxur. All the type forms were from urban and semi-urban locations, and the intermediate strain was from a semi-urban location. The bioassay results indicated that the strains ofAn. stephensiwere more susceptible to propoxur than to chlorpyrifos.

Background Aedes albopictus (Skuse) is an invasive mosquito that has become an important vector of chikungunya, dengue and Zika viruses. In the absence of specific antiviral therapy or a vaccine, vector management is the sole method available for reducing Aedes-induced disease morbidity. Determining the resistance status of Ae. albopictus to insecticides and exploring the resistance mechanisms is essential for future vector control planning. Methods Aedes albopictus larvae and pupae were sampled from six sites (two sites each from urban, suburban and rural) in Guangzhou. The resistance bioassays were conducted against Bacillus thuringiensis israelensis (Bti): deltamethrin, propoxur and malathion for larvae; and deltamethrin, DDT, propoxur and malathion for adults. P450 monooxygenase (P450s), glutathione S-transferase (GSTs) and carboxylesterase (COEs) activities of adult mosquitoes were measured. Mutations at the knockdown resistance (kdr) gene were analyzed, and the association between kdr mutations and phenotypic resistance was tested. Results Adult bioassays revealed varied susceptibility against DDT, deltamethrin and propoxur in the six Ae. albopictus populations. Significantly lower mortality rates were found in urban populations than suburban and rural populations. Urban mosquito populations showed resistance against DDT, deltamethrin and propoxur, while one rural population was resistant to DDT. All populations tested were susceptible to malathion. Larval bioassays results indicated that all populations of Ae. albopictus were sensitive to the larvicide Bti and malathion. Resistance to deltamethrin and propoxur was common in larval populations. The F1534S and F1534 L mutations were found to be significantly associated with deltamethrin resistance. Biochemical assays indicated elevated detoxification enzyme activities in the field mosquito populations. Conclusions Aedes albopictus populations in Guangzhou, especially in urban areas, have developed resistance to the commonly used insecticides, primarily DDT and deltamethrin. This finding calls for resistance management and developing counter measures to mitigate the spread of resistance. Electronic supplementary material The online version of this article (10.1186/s13071-017-2581-y) contains supplementary material, which is available to authorized users.

Dengue and chikungunya are important arboviral infections in the Andaman Islands. Competent vectors viz. Aedes aegypti and Aedes albopictus are widely prevalent. The most effective proven method for interrupting the transmission of these arboviruses is vector control, mediated through insecticides. Currently, DDT and temephos are the insecticides used for vector control in these islands. Lack of information on susceptibility necessitated assessing the susceptibility profile of A. aegypti and A. albopictus. F1 generation of adult and larvae were assayed, and LT50 and LT90 values were interpreted following the World Health Organization (WHO) protocol. Adults were found resistant to DDT-4 % while susceptible to dieldrin-0.4 %. Against organophosphates, both showed resistance to fenitrothion but susceptible to malathion-5 %. Both species showed resistance to carbamate and bendiocarb-0.1 % while susceptible to propoxur-0.1 %. Of the four synthetic pyrethroids, both were susceptible to deltamethrin-0.05 %, while resistant to permethrin-0.75 %, lambdacyhalothrin-0.05 % and cyfluthrin-0.15 %. Larvae of both species showed resistance to temephos at 0.02 mg/L but susceptible to malathion at 1 mg/L and fenthion at 0.05 mg/L. Currently, there is no prescribed WHO dose for adult-insecticide susceptibility testing. The emergence of resistance to DDT and temephos in the vector population poses a challenge to the on-going vector control measures. The results highlight the need for monitoring resistance to insecticides in the vector population. Impetus for source reduction and alternative choices of control measures are discussed for tackling future threat of arboviral infections in these islands.

Background Indoor residual spraying is one of the key vector control interventions for malaria control in Ethiopia. As malaria transmission is seasonal in most parts of Ethiopia, a single round of spraying can usually provide effective protection against malaria, provided the insecticide remains effective over the entire malaria transmission season. This experiment was designed to evaluate the residual efficacy of bendiocarb, pirimiphos-methyl, and two doses of propoxur on four different wall surfaces (rough mud, smooth mud, dung, and paint). Filter papers affixed to wall surfaces prior to spraying were analyzed to determine the actual concentration applied. Cone bioassays using a susceptible Anopheles arabiensis strain were done monthly to determine the time for which insecticides were effective in killing mosquitoes. Results The mean insecticide dosage of bendiocarb applied to walls was 486 mg/m2 (target 400/mg). This treatment lasted 1 month or less on rough mud, smooth mud, and dung, but 4 months on painted surfaces. Pirimiphos-methyl was applied at 1854 mg/m2 (target 1000 mg/m2), and lasted between 4 and 6 months on all wall surfaces. Propoxur with a target dose of 1000 mg/m2 was applied at 320 mg/m2, and lasted 2 months or less on all surfaces, except painted surfaces (4 months). Propoxur with a target dose of 2000 mg/m2, was applied at 638 mg/m2, and lasted 3 months on rough mud, but considerably longer (5–7 months) on the other substrates. Conclusions It would appear that the higher dose of propoxur and pirimiphos-methyl correspond best to the Ethiopian transmission season, although interactions between insecticide and the substrate should be taken into account as well. However, the insecticide quantification revealed that the dosages actually applied differed considerably from the target dosages, even though care was taken in the mixing of insecticide formulations and spraying of the walls. It is unclear whether this variability is due to initial concentrations of insecticides, poor application, or other factors. Further work is needed to ensure that target doses are correctly applied, both operationally and in insecticide evaluations. Electronic supplementary material The online version of this article (10.1186/s12936-017-2122-3) contains supplementary material, which is available to authorized users.

New and improved strategies for malaria control and prevention are urgently needed. As a contribution to an optimized personal protection strategy, a novel long-lasting insecticide and repellent-treated net (LLIRN) has been designed by binding combinations of permethrin plus N,N-diethyl-m-toluamide (DEET), or insect repellent 3535 (IR3535), and etofenprox plus DEET, onto fibres of bed net fabric employing a new multi-layer polymer-coating technique. Protective repellent efficacy, toxicological effectiveness and residual activity of 12 LLIRN types have been evaluated by laboratory testing against adult Aedes aegypti. The novel multi-layer LLIRN design allowed simultaneous embedding at concentrations up to 5,930 mg/m(2) for DEET, 3,408 mg/m(2) for IR3535, 2,296 mg/m(2) for permethrin and 2,349 mg/m(2) for etofenprox, respectively. IR3535 layers prevented co-binding of additional pyrethroid-containing polymer layers, thus making pyrethroids plus DEET LLIRNs an ideal combination. All LLIRNs revealed synergistic insecticidal effects which, when measured against concentration controls of the isolated compounds, were significant in all LLIRN types designed. DEET in DEET plus permethrin LLIRNs significantly (p 0.0001) reduced the concentration-dependent permethrin 100 % knockdown (KD) time from 55 to 75 %, the corresponding 100 % kill time (p 0.0001) from 55 to 64 %. DEET in DEET plus etofenprox LLIRNs reduced the dose-specific 100 % knockdown (KD) time of etofenprox from 42 to 50 % (p = 0.004), the 100 % kill time from 25 to 38 % (p 0.0001). Permethrin or etofenprox did not influence spatial repellency of DEET or IR3535 on LLIRNs. Vice versa, DEET and IR3535 increased spatial and excitatory repellency and reduced landing and probing frequency on LLIRNs resulting in strongly enhanced biting protection, even at low concentrations. One hundred percent biting and probing protection of stored LLIRNs was preserved for 83 weeks with the 5,930 mg/m(2) DEET and 2,139 mg/m(2) etofenprox LLIRN, for 72 weeks with the 5,002 mg/m(2) DEET and 2,349 mg/m(2) etofenprox LLIRN, for 63 weeks with the 3,590 mg/m(2) DEET and 1,208 mg/m(2) permethrin LLRN, and for 61 weeks with the 4,711 mg/m(2) DEET and 702 mg/m(2) etofenprox LLIRN. Because 100 % bite protection with up to 75 % quicker contact toxicity of pyrethroids were documented, synergistic toxicological and repellent effects of multi-layer polymer-coating LLIRNs may overcome LLIN-triggered selection pressure for development of new kdr- and metabolic pyrethroid resistances while simultaneously increasing protective efficacy also against kdr- and metabolic pyrethroid-resistant mosquitoes substantially due to the repellent-induced effects of LLIRNs thus indicating that this approach is a promising new candidate for future bed net, curtain, and window screen impregnation aiming at optimized prevention from mosquito-borne diseases.

The present study was undertaken to investigate the effects of organophosphate and carbamate insecticides namely, temephos and propoxur respectively, on the life history of Anopheles stephensi Liston (Culicidae) under laboratory conditions. The late third instar larvae of the mosquito were exposed to sublethal concentrations of temephos and propoxur at LC(10), LC(30) and LC(50), respectively, and adult survivors were evaluated for fitness parameters. Sublethal effects were also evaluated in subsequent generations. Fecundity, egg hatchability, sex ratio, adult longevity and morphology of gonads were the end points studied and compared to the untreated control. Adverse changes in developmental traits were mainly observed in fecundity, egg hatchability and sex ratio. However, significant differences in adult longevity were observed in the insecticide-exposed population. Pleiotropic effects through prolonged larval duration and enhanced longevity of adults were observed. Morphology of gonads in the insecticide-exposed population was severely affected and is represented by rudimentary and atrophied testes, and the size of the vas deferens was very much reduced when compared to that of the control. In another set of experiments, circadian rhythm (for pupation and adult emergence) of LC(10), LC(30) and LC(50) values to abovementioned insecticides exposed to late third instar larvae was studied. Pupation and adult emergence rhythms were found to be disturbed with an increase in concentrations of insecticides when compared to that of untreated control.

Reversed electrode polarity stacking mode (REPSM) coupled to micellar electrokinetic chromatography (MEKC) was employed for the simultaneous determination of carbamate insecticide residues in fruit juice samples. A mixture of the studied insecticides (i.e., methomyl, propoxur, carbofuran, carbaryl, isoprocarb, and promecarb) in 10 mmol L−1 phosphate buffer (pH 7.0) was introduced into the capillary tube by hydrodynamic injection at 0.5 psi for 30 s followed by removal of the sample matrix at −15 kV for 0.5 min. The analytes were successfully separated within 8 min using 10 mmol L−1 borate buffer containing 60 mmol L−1 sodium dodecyl sulfate at pH 9.5, and photodiode array detection at 205, 214, and 225 nm. The REPSM–MEKC gave stacking enhancement factors of about 4–13, compared to that without stacking. The limits of detection were in the range 0.01–0.10 mg L−1, which is acceptable with respect to the maximum residue limits. Good precisions were obtained with relative standard deviation lower than 1.8% (for migration time) and 10% (for peak area). The recoveries for most fruit juice samples were acceptable (>80%). No contamination of the studied carbamates was observed in any sample. The proposed method is simple and effective for preconcentration and removal of matrix interferences in a single step for the determination of the studied carbamate insecticides.

A facile procedure was described for the hapten design of the N-methylcarbamate insecticide propoxur. Two new haptens of propoxur (hapten 1a and hapten 1b) were synthesized by introducing appropriate spacers in the pesticide aromatic moiety of the analyte molecular structure. First, the propoxur reacted with nitric acid to yield the intermediate product. Then hapten 1a was prepared via the reduction of the intermediate product, and hapten 1b was formed by the acylation of hapten 1a with succinic anhydride. In addition, we have also developed a simple method to prepare hapten 2 for the pyrethroid insecticide cyhalothrin, which only requires two steps including the reactions of nitration and reduction. Three haptens were coupled to carrier proteins to prepare the corresponding artificial antigens. The molecular structures of these three haptens were identified by 1H NMR and MS, and those of the artificial antigens were confirmed by UV-vis.

Carbamate pesticides like propoxur have been shown to adversely affect memory and induce oxidative stress on both acute and chronic exposure. The present study was designed to explore the modulation of the effects of propoxur over cognitive function by progesterone (PROG) and 4'-chlorodiazepam (4CD). Cognitive function was assessed using step-down latency (SDL) on a passive avoidance apparatus, transfer latency (TL) on a plus maze and spatial navigation test on Morris water maze. Oxidative stress was assessed by examining brain malondialdehyde (MDA) and reduced glutathione (GSH) levels and catalase (CAT) activity. A significant reduction in SDL and prolongation of TL and spatial navigation test was found for the propoxur (10 mg/kg/d; p.o.) treated group at weeks 6 and 7 as compared with control. One-week treatment with 4CD (0.5 mg/kg/d; i.p.) antagonized the effect of propoxur on SDL, spatial navigation test as well as TL; whereas, PROG failed to modulate this effect at a dose of 15 mg/kg/d, i.p. Propoxur produced a statistically significant increase in the brain MDA levels and decrease in the brain GSH levels and CAT activity. Treatment with 4CD at the above dose attenuated the effect of propoxur on oxidative stress whereas PROG (15 mg/kg/d; i.p.) failed to influence the same. The results of the present study thus show that 4-CD has the potential to attenuate cognitive dysfunction and oxidative stress induced by toxicants like propoxur in the brain.

Ultrasound-assisted emulsification-microextraction coupled to HPLC was applied to the determination of propoxur in environmental and beverage samples. Carbon tetrachloride (the extraction solvent) is added to the aqueous sample, and the liquids are sonificated at 60 °C, upon which an emulsion is formed. This is followed by centrifugation the lower phase being analyzed by HPLC. The extraction solvent, its volume, extraction time, temperature and salt concentration were optimized. Linear range (0.01–10 µg mL-1), correlation coefficient (0.9965), detection limit (1 ng mL-1 at a SNR of 3), and precision (4.5% RSD, n = 5) were determined. The technique was applied to the determination of propoxur in environmental and beverage samples and no target analyte was found in these samples. Therefore, samples were spiked and recoveries of 93–106% and RSDs of 1.5–6.2% were obtained.

Studies were carried out to determine the toxicity of some selected pesticides on fresh water fish in a tropical environment. The uptake of the pesticides lindane, pentachlorophenol (PCP), and propoxur, which are frequently used on farms, and in industries as well as by loggers and timber men on wood were studied in concrete ponds at the University of Cape Coast, in Ghana. The fish used for the study were Oreochromis niloticus, Clarias gariepinus, and Chrysicthys nigrodigitatus. They were obtained from cultured ponds in the Cape Coast and Mankessim districts in the Central Region and Weija Dam, in the Greater Accra region of Ghana. Single high lethal concentration (SD) or acute treatment and cumulative/chronic (or multiple minor) lethal concentration (CD) treatment were employed in administering the pesticides to the fish via water. Gas chromatograph electron capture detector analysis was done on the dead fish to see the extent of ingestion. The LC(50 )values obtained for lindane on the three fish samples were as follows: Chrysicthys - 0.38 mg L(-1); Oreochromis - 0.42 mg L(-1), and Clarias - 1.2 mg L(-1). Mortalities occurred in fish within 3-5 days of application. For the PCP on Chrysicthys, Oreochromis, and Clarias species the LC(50) values were 0.42, 0.32 and 0.64 mg L(-1), respectively, for over a 2- to 3-day period. For a three-time influx period of propoxur the LC(50) for Chrysicthys, Oreochromis, and Clarias, were 22.0, 30.40, and 45.04 (all in mg L(-1)), respectively. The results obtained indicated that the pesticides had adverse effects on the general growth and reproduction of fish as shown by gonadosomatic indices.

Determination of carbamate pesticides such as carbaryl, carbofuran, propoxur and bendiocarb was demonstrated on a microchip with newly designed microchannels developed for efficient solvent extraction. The pesticides were hydrolyzed to corresponding naphthols, coupled with p-nitrobenzenediazonium fluoroborate reagent, and then extracted into 1-butanol as colored azo derivatives and detected with a thermal lens microscope. Optimum flow rates for the aqueous and organic phases were evaluated in the continuous-flow chemical process established in the microchip. The calibration lines showed good linearity in the range of concentrations of 0.03 - 3 ppm (10(-7) - 10(-5) M) and a mass detection limit down to a nanogram level was achieved that is at least two orders of magnitude lower than the LODs for conventional spectrophotometric methods. Azo derivatives of the pesticides were successfully separated and identified by micellar electrokinetic chromatography (MEKC) using a sample prepared on a bulk scale.

Several classes of pesticides were extracted from maternal hair by solid-liquid extraction. Analysis of their selected metabolites involved a methanolic/hydrochloric acid methyl ester derivatization and liquid-liquid extraction. Gas chromatography electron impact mass spectrometry was used to detect and quantify the pesticides and metabolites. Recovery of parent compounds and metabolites from the analysis of spiked hair ranged from 87 to 112% with coefficients of variation less than 11%. Limits of detection ranged from 0.031 to 5.88 μg g(-1). Analysis of hair samples from pregnant women in the Philippines showed maternal exposure during pregnancy to bioallethrin, propoxur, chlorpyrifos, pretilachlor and malathion.

In order to investigate a role of paraoxonase 1 (PON1) polymorphism in organophosphorus (OP)-induced 8-hydroxydeoxyguanosine (8-OHdG) levels, urinary metabolites of OP, PON1 genotypes, and 8-OHdG levels in leukocyte and urine were measured in OP indoor insecticide sprayers and controls in summer and winter. The study population contained 18 male sprayers and age-matched 18 male controls. Sprayers were primarily exposed to OP insecticides (mainly fenitrothion, dichlorvos, chlorpyrifos, and diazinon), and partially to pyrethroids (mainly permethrin) and carbamates (mainly propoxur). Urinary metabolites of OP were measured by gas chromatography-mass spectrometry. 8-OHdG levels in leukocyte and urine were measured by ELISA kit. PON1 genotype was identified using allele-specific fluorogenic TaqMan probes. The mean concentrations of urinary dimethyl phosphate (DMP) and total dialkyl phosphates (DAP) in summer and those of 8-OHdG in summer and winter were significantly higher in OP sprayers than controls. This resulted in a significant positive correlation between 8-OHdG levels and urinary DMP or DAP, suggesting a correlation between OP metabolites and production of oxidative stress. Of PON1 genotypes, incidences of Q/Q, Q/R, and R/R types were 17, 39, and 44% in OP sprayers and controls, respectively. Although PON1 polymorphism did not contribute to the leukocyte and urinary 8-OHdG levels, the urinary OP metabolite concentrations in summer showed a significant decrease as the number Q allele decreased. These results indicate that an increase in OP metabolites is associated with a high level of oxidative stress in OP sprayers, although the contribution of the PON1 polymorphism to the metabolism of OP is still unclear.

A simple spectrophotometric method for the determination of propoxur, a widely used insecticide, in various environmental samples and pesticide formulations is described. The method is based on the coupling of the hydrolysis product of propoxur with diazotized 3-aminopyridine in an alkaline medium, to form an azo-dye which has a maximum absorbance at 463 nm. Beer's law is obeyed over the concentration range of 0.05 to 1.2 microg ml(-1) of propoxur. The molar absorptivity and Sandell's sensitivity are found to be 3.10 x 10(4) l mol(-1) cm(-1) and 0.007 microg cm(-2), respectively. The important analytical parameters and optimum reaction conditions were evaluated. The method is free from the interference of other commonly used pesticides and inorganic metal ions.

Carbamates belonged to an older insecticide group, with propoxur being representative of this group. However, today carbamates with hormonal effects on insects, like fenoxycarb, or with fungicide properties, like propamocarb, are also used. The goal was a comparison of three structurally and functional different carbamates with a possibly common toxicological mechanism. Primary neuronal cell cultures of the rat are a well established model to identify neurotoxic compounds like n-hexane or acrylamide. In this cell culture model endpoints such as viability, energy supply, glucose consumption, glutathione (GSH) levels and cytoskeleton elements were determined. Added to cultured rat cortical neurons for 1 week, fenoxycarb, propamocarb and propoxur considerably decreased ATP levels, mitochondrial membrane potential and glucose consumption. Besides this, fenoxycarb and propamocarb had an impact on neurofilaments. After recovery for 1 week, propoxur also showed effects on neurofilaments, whereas with the other carbamates no tendency for a recovery was seen. These effects were prevented completely by pyruvate for propoxur and propamocarb, and partly so for fenoxycarb. In contrast to the main experimental design, GSH was determined after 1-h treatment with the test substances. Surprisingly, the compounds had only slight or no effect on the GSH level within this time. Further mechanistic studies indicated that carbamates primarily interacted with SH-groups, most likely by interfering with glycolysis and the construction of fibrillary proteins like neurofilaments. The prevention by pyruvate and acetylcysteine pointed to these biochemical endpoints.

Rapid and sensitive detection of resistance to insecticides in arthropods is needed. In the cattle tick, Boophilus microplus, resistance to a variety of acaricides is widespread. The most commonly used assay for resistance, the larval packet test, takes at least two, but generally six weeks for a one-host tick like B. microplus to complete and may take up to three months to complete for three-host ticks. Here we describe a test for resistance to organophosphate acaricides that can be used on larvae and adult ticks which takes less than 24 hours. The test measures the difference in acetylcholinesterase (AChE) activity in homogenates of ticks in the presence and absence of propoxur, a carbamate acaricide. We found clear discrimination of organophosphate-susceptible and organophosphate-resistant adults with 100 μM propoxur. AChE from susceptible ticks had almost no activity at this concentration of propoxur whereas AChE from resistant ticks had 67% of its potential activity. AChE from heterozygote ticks could also be distinguished from AChE from homozygous-susceptible and homozygous-resistant ticks. This is the first biochemical test for resistance to an acaricide. Rapid, sensitive tests like ours will allow resistance to organophosphates to be detected soon after it develops in the field, thus, the spread of resistance might be slowed and the useful life of acaricides extended.

Die Untersuchung eines Todesfalls nach oraler Aufnahme einer groseren Menge eines Kombinationsinsektizids bestehend aus Propoxur und Tetramethrin sowie den Losungsmitteln Isopropanol und Benzylalkohol ergab als wesentlichen morphologischen Befund eine koagulationsnekrotische Verhartung der Speiserohre und der Magenwand. Die in Venenblut, Leber, Niere, Glaskorperflussigkeit und Liquor durch HPLC bzw. GC/MS bestimmten Konzentrationen lagen fur Propoxur (< 0,3– 18 μg/g) im komatos-lateralen Bereich, wahrend Tetramethrin (bis 0,1 μg/g) nahezu vollstandig abgebaut war. Weiterhin wurden als Propoxurabbauprodukt o-Isopropoxyphenol (2,8–56 μg/g), Benzylalkohol (18–58 μg/g) sowie dessen Abbauprodukt Benzoesaure (85–140 μg/g), Isopropanol (0,45–1,1 mg/g) und Aceton (0,01–0,03 mg/g) gefunden. Die Werte im Herzblut und in der Lunge waren hingegen bis zu 30-fach hoher. Als Ursache fur diese immensen Konzentrationsunterschiede wird eine agonale Aspiration des erbrochenen, bis zu drei Grosenordnungen hoher konzentrierten Mageninhaltes diskutiert. Der hauptsachlich postmortal angenommene Abbau von Propoxur zu o-Isopropoxyphenol und von Benzylalkohol zu Benzoesaure ist in der Leber nahezu vollstanding und in den ubrigen Probenmaterialien sehr unterschiedlich ausgepragt. Als Todesursache ergibt sich eine Intoxikation durch den Acetylcholinesterasehemmer Propoxur in Kombination mit der neurotoxischen Wirkung des Tetramethrins.

Three acaricides, permethrin, propoxur and diazinon, were tested against Argas persicus ticks in a test of susceptibility and in a multiple choice test in bioassay. A mixture of guanine hydrochloride and diatomaceous earth in saline was used as an attractant in bioassays, causing 53.1–95.7% assembly. The attractant was mixed with acaricides to reduce their repellency and enhance their efficiency in bioassays. Permethrin was the most toxic (LC95 at day 7=0.5–1.4mg m−2 depending on the developmental stage) and most repellent acaricide. The mortality of males in the bioassay was significantly higher (76.7–94.3%, p

A method for the supercritical fluid extraction of carbamate pesticides (propoxur, aminocarb, carbaryl and methiocarb) from soil and cereal samples using CO2 is proposed. Extractions were at 378 bar and 54 °C. Analytes were determined in the extracts by HPLC with fluorescence detection after post-column derivatization. Recoveries from spiked soil ranged between 39.6 and 91.7%, depending on analyte and soil components. Lowest recoveries were from sandy soils. Aminocarb could not be recovered from any soil using CO2. Recovery of aminocarb from diatomaceous earth was improved by adding methanol to the extraction cell prior to SFE, but the effect was not observed in soil samples. Recoveries for propoxur and aminocarb from spiked wheat were about 75%, and only between 30–50% for aminocarb from corn and oats, and carbaryl from wheat. Fat was coextracted using CO2 and retained in the trap together with the analytes, however, appropriate rinsing solvent allowed on-line clean-up of the extract.

Background Two concomitant dengue 3 (DEN-3) epidemics occurred in Cape Verde Archipelago and Senegal between September and October 2009. Aedes aegypti was identified as the vector of these epidemics as several DEN-3 virus strains were isolated from this species in both countries. The susceptibility to pyrethroids, organochlorine, organophosphates and carbamate was investigated in two field strains of Aedes aegypti from both countries using WHO diagnostic bioassay kits in order to monitor their the current status of insecticide susceptibility. Findings The two tested strains were highly resistant to DDT. The Cape Verde strain was found to be susceptible to all others tested insecticides except for propoxur 0.1%, which needs further investigation. The Dakar strain was susceptible to fenitrothion 1% and permethrin 0.75%, but displayed reduced susceptibility to deltamethrin, lambda-cyhalothrin and propoxur. Conclusions As base-line results, our observations stress a careful management of insecticide use for the control of Ae. aegypti. Indeed, they indicate that DDT is no longer efficient for the control of Ae. aegypti populations in Cape Verde and Dakar and further suggest a thorough follow-up of propoxur susceptibility status in both sites and that of deltamethrin and lambda-cyhalothrin in Ae. aegypti populations in Dakar. Thus, regular monitoring of susceptibility is greatly needed as well as the knowing if this observed resistance/susceptibility is focal or not and for observed resistance, the use of biochemical methods is needed with detailed comparison of resistance levels over a large geographic area. Keywords Aedes aegypti, Insecticides, Susceptibility, Cape Verde, Senegal

Background The insecticide dichloro-diphenyl-trichloroethane (DDT) is widely used in indoor residual spraying (IRS) for malaria control owing to its longer residual efficacy in the field compared to other World Health Organization (WHO) alternatives. Suitable stabilization to render these alternative insecticides longer lasting could provide a less controversial and more acceptable and effective alternative insecticide formulations than DDT. Methods This study sought to investigate the reasons behind the often reported longer lasting behaviour of DDT by exposing all the WHO approved insecticides to high temperature, high humidity and ultra-violet light. Interactions between the insecticides and some mineral powders in the presence of an aqueous medium were also tested. Simple insecticidal paints were made using slurries of these mineral powders whilst some insecticides were dispersed into a conventional acrylic paint binder. These formulations were then spray painted on neat and manure coated mud plaques, representative of the material typically used in rural mud houses, at twice the upper limit of the WHO recommended dosage range. DDT was applied directly onto mud plaques at four times the WHO recommended concentration and on manure plaques at twice WHO recommended concentration. All plaques were subjected to accelerated ageing conditions of 40°C and a relative humidity of 90%. Results The pyrethroids insecticides outperformed the carbamates and DDT in the accelerated ageing tests. Thus UV exposure, high temperature oxidation and high humidity per se were ruled out as the main causes of failure of the alternative insecticides. Gas chromatography (GC) spectrograms showed that phosphogypsum stabilised the insecticides the most against alkaline degradation (i.e., hydrolysis). Bioassay testing showed that the period of efficacy of some of these formulations was comparable to that of DDT when sprayed on mud surfaces or cattle manure coated surfaces. Conclusions Bioassay experiments indicated that incorporating insecticides into a conventional paint binder or adsorbing them onto phosphogypsum can provide for extended effective life spans that compare favourably with DDT's performance under accelerated ageing conditions. Best results were obtained with propoxur in standard acrylic emulsion paint. Similarly, insecticides adsorbed on phosphogypsum and sprayed on cattle manure coated surfaces provided superior lifespans compared with DDT sprayed directly on a similar surface.

Background The spread of pyrethroid resistance in Anopheles gambiae s.s. is a critical issue for malaria vector control based on the use of insecticide-treated nets. Carbamates and organophosphates insecticides are regarded as alternatives or supplements to pyrethroids used in nets treatment. It is, therefore, essential to investigate on the susceptibility of pyrethroid resistant populations of An. gambiae s.s. to these alternative products. Methods In September 2004, a cross sectional survey was conducted in six localities in Côte d'Ivoire: Toumbokro, Yamoussoukro, Toumodi in the Southern Guinea savannah, Tiassalé in semi-deciduous forest, then Nieky and Abidjan in evergreen forest area. An. gambiae populations from these localities were previously reported to be highly resistant to pyrethroids insecticides. Anopheline larvae were collected from the field and reared to adults. Resistance/susceptibility to carbamates (0.4% carbosulfan, 0.1% propoxur) and organophosphates (0.4% chlorpyrifos-methyl, 1% fenitrothion) was assessed using WHO bioassay test kits for adult mosquitoes. Then, PCR assays were run to determine the molecular forms (M) and (S), as well as phenotypes for insensitive acetylcholinesterase (AChE1) due to G119S mutation. Results Bioassays showed carbamates (carbosulfan and propoxur) resistance in all tested populations of An. gambiae s.s. In addition, two out of the six tested populations (Toumodi and Tiassalé) were also resistant to organophosphates (mortality rates ranged from 29.5% to 93.3%). The M-form was predominant in tested samples (91.8%). M and S molecular forms were sympatric at two localities but no M/S hybrids were detected. The highest proportion of S-form (7.9% of An. gambiae identified) was in sample from Toumbokro, in the southern Guinea savannah. The G119S mutation was found in both M and S molecular forms with frequency from 30.9 to 35.2%. Conclusion This study revealed a wide distribution of insensitive acetylcholinesterase due to the G119S mutation in both M and S molecular forms of the populations of An. gambiae s.s. tested. The low cross-resistance between carbamates and organophosphates highly suggests involvement of other resistance mechanisms such as metabolic detoxification or F290V mutation.

In order to examine the photostability of the insecticide propoxur (2-isopropoxyphenyl-N-methylcarbamate) in the field model experiments with organic solvents were performed. Photodegradation (λ>280 nm) of propoxur was found to be more efficient in isopropanol solution than in the presence of cyclohexane or cyclohexene. Photolysis in isopropanol and cyclohexane mainly resulted in formation of isopropylphenyl ether. As a trace component 2-isopropoxyphenol was detected. In the presence of cyclohexene on the other hand photomineralisation was found to be the main degradation pathway.

An integrated flow injection (FI)/HPLC system for the total and individual determination of carbamate pesticides (propoxur, carbofuran and carbaryl) is proposed. The determination is based on the alkaline hydrolysis of the analytes and subsequent coupling with diazotized sulphanilic acid to yield the monitored dyes with or without a prior separation step by HPLC in a C18 column. The calibration curves obtained are linear in the μg/ml range and r.s.d. values are between 0.5 and 3.7% in all instances. Injection of the sample into the FI manifold allows the total pesticide content in the sample to be screened. The manifold thus acts as a post-column reactor/detector of the chromatograph for samples with high overall carbamate content, which are also injected into the HPLC instrument. The performance was checked with contaminated water samples.

A bacterium capable of degrading propoxur (2-isopropoxyphenyl-N-methylcarbamate) was isolated from soil by enrichment cultures and was identified as a Pseudomonas species. The organism grew on propoxur at 2 g/l as sole source of carbon and nitrogen, and accumulated 2-isopropoxyphenol as metabolite in the culture medium. The cell free extract of Pseudomonas sp. grown on propoxur contained the activity of propoxur hydrolase. The results suggest that the organism degraded propoxur by hydrolysis to yield 2-isopropoxyphenol and methylamine, which was further utilized as carbon source.

Natural pyrethrins from insecticidal pyrethrum extract and pyrethroids (e.g. allethrin, tetramethrin, permethrin, cyphenothrin, cypermethrin, cyfluthrin) are active ingredients in insecticidal formulations such as powder, sprays, impregnated paper for electro-evaporators, mosquito coils, and solutions for wood treatment, all mainly intended for indoor use. Some commercial preparations contain also non-pyrethroid insecticides, such as dichlorovos, propoxur, or phoxim, and piperonyl butoxid as synergist. High-resolution gas-chromatography with oncolumn injection and FID and ECD detection is employed for the analysis of these insecticides in commercial formulations, in air during and after indoor application, and as residues on surfaces. The total input of pyrethroids into a large room amounts to 1 to 30 mg. The concentrations of the pyrethrins and pyrethroids in air (2 to 300 μg/m3) and their deposition on surfaces (up to 1000 μg/m2) reveal possible exposure of humans by inhalation (e.g. 30 μg allethrin or 60 μg tetramethrin) or by skin resorption (e.g. 200 μg allethrin and up to 1000 μg tetramethrin). The insecticides deposited on surfaces and some readily formed transformation products persist for 60 h or longer.

Propoxur with a non-toxic dose (5 mg/kg) administered intraperitoneally (ip) in tetraisopropylpyrophosphoramide (iso-OMPA, 1 mg/kg) pretreated rats subcutaneously, sc) produced severe intoxication of anticholinesterase nature. The observed severity was comparable to that caused by an acute sublethal dose of propoxur (15 mg/kg) suggesting at least threefold potentiation of toxicity. Either drug given alone produced neither signs of toxicity nor alterations in acetylcholinesterase (AChE) activity, while carboxylesterase (CarbE) activity was markedly reduced indicating tremendous nonspecific binding. The administration of iso-OMPA followed by propoxur elicited inhibition of AChE to a critical level and produced severe intoxication. These results suggested that iso-OMPA induced potentiation of propoxur toxicity stemmed through irreversible inhibition of CarbE.

Background To manage the kdr pyrethroid-resistance in Anopheline malaria vectors, new compounds or new strategies are urgently needed. Recently, mixing repellents (DEET) and a non-pyrethroid insecticide (propoxur) was shown to be as effective as deltamethrin, a standard pyrethroid, under laboratory conditions, because of a strong synergy between the two compounds. In the present study, the interactions between two repellents (DEET and KBR 3023) and a non-pyrethroid insecticide (pyrimiphos methyl or PM) on netting were investigated. The residual efficacy and the inhibition of blood feeding conferred by these mixtures were assessed against Anopheles gambiae mosquitoes. Methods DEET and KBR 3023 were mixed with pyrimiphos methyl (PM), a organophosphate (OP) insecticide. The performance of mono- and bi-impregnated nets against adult mosquitoes was assessed using a miniaturized, experimental hut system (laboratory tunnel tests) that allows expression of behavioural responses to insecticide, particularly the mortality and blood feeding effects. Results Both mixtures (PM+DEET and PM+KBR3023) induced 95% mortality for more than two months compared with less than one week for each compound used alone, then reflecting a strong synergy between the repellents and PM. A similar trend was observed with the blood feeding rates, which were significantly lower for the mixtures than for each component alone. Conclusion Synergistic interactions between organophosphates and repellents may be of great interest for vector control as they may contribute to increase the residual life of impregnated materials and improve the control of pyrethroid-resistance mosquitoes. These results prompt the need to evaluate the efficacy of repellent/non-pyrethroid insecticide mixtures against field populations of An. gambiae showing high level of resistance to Ops and pyrethroids.

Following the report of deaths in a few flocks of domestic pigeons in the Mazandaran province, Northern Iran, we conducted an investigation on the live and dead pigeons. We found reddish larvae on the skin of the pigeons and after close analysis of the mouthparts and spiracles; they were identified as second instar larvae of Protocalliphora sp. These blow fly larvae are obligate haematophagous parasites, highly pathogenic and cause high mortality in birds. Mortality in the infected flocks was approximately 25% and mainly among nestlings and young birds. Infected birds were treated with propoxur powder which was very effective, following which no additional mortalities or larvae were found. This is the first report of this myiasis agent in Iran.

Pyrethroids are the insecticides of choice for the treatment of bednets for malaria control. Pyrethroid resistance in Anopheles spp. vectors may adversely impact malaria control measures, and therefore it is important to know the initial level of pyrethroid resistance before pyrethroid-treated bednets are introduced. Furthermore, a search for replacement insecticides is necessary to manage any eventual high-resistance levels to pyrethroid insecticides that may affect the effectiveness of treated bednets. This study reports on the susceptibility of Anopheles gambiae s.s. exposed for 1 h to the pyrethroid insecticide permethrin and the carbamate insecticide propoxur, at eight localities in the Greater Accra region of Ghana. The observed mortality rates ranged between 21-92% and 92-100% to permethrin and propoxur, respectively. The results also showed a reduction in the knockdown time (KD50 and KD95) in propoxur (mean KD50 = 20 min and mean KD95 = 31 min) when compared with permethrin (mean KD50 = 47 min and mean KD95 = 87min). The results suggest that permethrin may not be effective in all areas. Where pyrethroid resistance is a problem, propoxur could be an alternative for indoor residual spraying and for insecticide-treated materials such as curtains and eave screens.

Organophosphates (OPs) and carbamates exhibit their toxicity by inhibiting acethylcholinesterase (AChE, EC 3.1.1.7) due to phosphorylation, or carbamylation in case of carbamate poisoning. OP poisoning is treated by atropine (muscarinic cholinergic receptor antagonist) and cholinesterase reactivators - oximes (PAM-2Cl, TMB-4, and HI-6). In contrast to the irreversible inhibition of AChE by OPs, carbamylated enzyme reactivates rapidly and antidotal treatment is limited to atropine. The objective of this study was to evaluate the efficiency of thienyl phencyclidine (tenocyclidine, TCP) and its new synthesized adamantyl derivatives containing piperidine (TAPIP), pyrolidine (TAPIR) and morpholine (TAMORF) group in mice poisoned with OPs and carbamates. These new compounds were characterized by m.p. determination, elemental analysis, and spectroscopic methods (IR, 1H-NMR, 13C-NMR, MS). They showed low acute toxicity (LD50), and their LD50 values varied from 106.00 mg kg -1 b.m. (TCP) to >504.00 mg kg -1 b.m. (TAMORF). TCP and its adamantyl derivatives were administered intraperitoneally (2.5 mg kg-1 b.m.) together with atropine (10.0 mg kg-1 b.m.) and with or without 1/4 LD50 of HI-6. Each compound administered with atropine had a therapeutic effect in the poisoning with carbamates propoxur, aldicarb, and Ro 02-0683 (therapeutic dose was from 3.18 LD50 of aldicarb to 16.00 LD50 for propoxur). However, the efficiency of those compounds in combination with atropine was lower in poisoning with OP insecticide dichlorvos (DDVP) and warfare agents soman and tabun. In soman-poisoned mice the best therapeutic effects were obtained with the combination of HI-6 plus atropine and tested compounds, which ensured the survival of all treated animals with 4.00-6.40 LD50 of soman. The results suggest that TCP and adamantyl tenocyclidines could be used in combination with atropine as antidotes in carbamate poisoning and as adjuvant therapy to HI-6 and atropine in soman poisoning.

Etude de la dissipation dans l'air du DDVP et du Propoxur et evaluation du risque de rentrer dans la piece avec fumigation de celle-ci selon les instructions portees sur l'etiquette

Simple, direct, and sensitive low temperature phosphorimetric methods for the determination of Chlorpropham, Propham, Propoxur, and Terbucarb in EPA solvent are described. The minimum detectable amounts are 0.01 p. p. m. for Chlorpropham and Propham and 0.02 and 0.3 p. p. m. for Propoxur and Terbucarb respectively. The ranges of linearity of the analytical calibration graphs are 0.05-7.5, 0.05–10, 0.5–50, and 1–50 p. p. m. for Chlorpropham, Propham, Propoxur, and Terbucarb respectively. The procedure for Chlorpropham has been applied to the analysis of a solid commercial formulation.

Propoxur /2-tsopropoxyphe nyl N-methylcarbamate/ is widely used in protecting crops and in the hygienic sector against e number of household pests. For this reason there is often a necessity to determine trace amounts of propoxur and its main metaboXite 2-is~ropoxyphenoX in different bloXoglcaX materials, There ere many methods to determine propoxur; actually gaschromatographic methods ere preferred. However, there are some difficulties unless propoxur and lts metabo11re are determined ,sparer,lye as during the derlvatleatlon step propoxur le hydrollsed to 2-1sopropoxyphenoZ. The methods usually recommended to separate carbametes from phenols /HAGALLONA 1975/: partitioning operations wlth dllute sXka11, coXumn chromatography wlth ssXectlve elutlon or oxidation wlth cerlum suXfate gave for propoxur and 2-1sopropoxyphsnol unsatisfactory results. Therefore a procedure is presented in whlch propoxur is separated from 2-1e.~ropoxyphanol by thinlayer chromatography end both substances are separately determined by gas chromatography uslng basically the methods published Dy COHEN et el. /1970/. Simultaneously wlth the separation a cZeanup of extract occurs on the chromatoplates

The effects of two carbamate insecticides, Baygon and Temik, on microbial processes in soil were investigated. Total plate counts revealed that Baygon and Temik at field rate applications (5 ppm) did not greatly influence the microbial populations in the soil. At a concentration of 500 ppm the fungal and actinomycete populations showed a marked increase in response to Temik and Baygon. Nitrification was severely inhibited by the granular (formulated) Baygon and Temik at 500 ppm, but was much less inhibited with the technical grade (technical) insecticides. The discrepancy appeared due to metabolism of the corn cob grits carrier, the resulting immobilization of nitrogen causing an apparent ‘inhibition’ of nitrification. At the approximate field rate applications of 5 ppm, only slight inhibition was observed with formulated Baygon or Temik. An accumulation of nitrite was noted, especially with technical Baygon at 500 ppm. Populations of the autotrophic nitrifying bacteria were depressed for 2–3 weeks by application of either Baygon or Temik to the soil at 500 ppm. Pure culture studies on Nitrobacter agilis and Nitrosomonas europaea indicated that Baygon and Temik were toxic to both organisms, but particularly the latter. The toxicity to Nitrosomonas was more severe in pure cultures than in soil. Oxygen uptake studies showed that formulated Baygon (but not Temik) added to soil at 500 ppm resulted in high respiratory activity, mostly due to metabolism of the carrier. The technical insecticides had little effect on respiration as measured by carbon dioxide evolution, although there were indications that Temik was being metabolized during the interval from 16 to 30 days. Baygon was found to be quite resistant to degradation in the test soil. Temik residues decreased by about 50% during the 30-days test period.