Monitoring pyrethroid resistance in field collected Blattella germanica Linn. (Dictyoptera: Blattellidae) in Indonesia

The German cockroach, Blattella germanica , is a major and the most common pest in public areas in Indonesia. Although intensive control measures have been carried out to control the populations of this pest, results have been far from successful, which is believed to be because of its resistance to insecticides. A standard World Health Organization (WHO) glass jar test was carried out to determine the resistance level of this insect to pyrethroid insecticides, the most commonly used insecticides for cockroach control in Indonesia. A susceptible S1 strain collected from Tembagapura Papua was compared with four strains collected from Bandung, West Java: strain S2, from a local restaurant; strain S3, from the Bandung train station; and strains S4 and S5, from two different hotels. All strains showed low resistance to the pyrethroid, except the S5 strain, which had a Resistance Ratio (RR)₅₀ of 95 for permethrin. The addition of piperonyl butoxide (PBO) suggests that the detoxifying enzyme mixed function oxidases (MFO) played an important role in the development of resistance to permethrin in the S5 strain, suggested by the high Synergist Ratio (SR) of 70.4. However, the low level of resistance to cypermethrin was not affected by PBO, suggesting that other mechanisms of pyrethroid resistance are involved. Our study is the first report of German cockroach resistance to permethrin in Indonesia, and the findings can be used in formulating potential strategies for cockroach resistance management.     

Effect of the synergist, piperonyl butoxide, on the development of deltamethrin resistance in yellow fever mosquito, Aedes aegypti L. (Diptera: Culicidae)

The larvae and adults of Aedes aegypti were tested for the potential to develop resistance to the synthetic pyrethroid, deltamethrin, alone or a combination of deltamethrin with the synergist, piperonyl butoxide (PBO). Although continuous larval selection for 40 generations resulted in 703-fold resistance, the resistance ratio in the adults was only 1.3. Similarly, adult selections with deltamethrin showed a resistance ratio of less than four after 40 generations, indicating differential response to deltamethrin selection in the two developmental stages of the insect. When the susceptible larvae were subjected to selection pressure of deltamethrin and PBO in the ratio of 1:5 for 20 generations, the speed of selection for deltamethrin resistance slowed down by 60%. The F24 larvae obtained from the strain selected with deltamethrin alone were further subjected to selection pressure with synergized deltamethrin, which resulted in 89% reversal in deltamethrin resistance in just one generation. However, long-term selection with the insecticide-synergist combination returned resistance close to original levels in 15 generations. The data indicate the involvement of cytochrome P450-dependent detoxification as the primary mechanism of development of resistance to deltamethrin in the larvae. Implications of the results on the management of larval and adult stages of Ae. aegypti are discussed.     

Mechanisms of resistance to DDT and pyrethroids in Patagonian populations of Simulium blackflies

Mixed populations of the pest blackflies Simulium bonaerense Coscarón & Wygodzinsky, S. wolffhuegeli (Enderlein) and S. nigristrigatum Wygodzinsky & Coscarón (Diptera: Simuliidae) are highly resistant to DDT and pyrethroids in the Neuquén Valley, a fruit-growing area of northern Patagonia, Argentina. As these insecticides have not been used for blackfly control, resistance is attributed to exposure to agricultural insecticides. Pre-treatment with the synergist piperonyl butoxide (PBO) reduced both DDT and fenvalerate resistance, indicating that resistance was partly due to monooxygenase inhibition. Pre-treatment with the synergist tribufos to inhibit esterases slightly increased fenvalerate toxicity in the resistant population. Even so, biochemical studies indicated almost three-fold higher esterase activity in the resistant population, compared to the susceptible. Starch gel electrophoresis confirmed higher frequency and staining intensity of esterase electromorphs in the resistant population. Incomplete synergism against metabolic resistance indicates additional involvement of a non-metabolic resistance mechanism, such as target site insensitivity, assumed to be kdr-like in this case. Glutathione S-transferase activities were low and inconsistent, indicating no role in Simulium resistance. Knowing these spectra of insecticide activity and resistance mechanisms facilitates the choice of more effective products for Simulium control and permits better coordination with agrochemical operations.     

An independent occurrence of the chimeric P450 enzyme CYP337B3 of Helicoverpa armigera confers cypermethrin resistance in Pakistan

The increasing resistance level of insect pest species is a major concern to agriculture worldwide. The cotton bollworm, Helicoverpa armigera, is one of the most important pest species due to being highly polyphagous, geographically widespread, and resistant towards many chemical classes of insecticides. We previously described the mechanism of fenvalerate resistance in Australian populations conferred by the chimeric cytochrome P450 monooxygenase CYP337B3, which arose by unequal crossing-over between CYP337B1 and CYP337B2. Here, we show that this mechanism is also present in the cypermethrin-resistant FSD strain from Pakistan. The Pakistani and the Australian CYP337B3 alleles differ by 18 synonymous and three nonsynonymous SNPs and additionally in the length and sequence of the intron. Nevertheless, the activity of both CYP337B3 proteins is comparable. We demonstrate that CYP337B3 is capable of metabolizing cypermethrin (trans- and especially cis-isomers) to the main metabolite 4'-hydroxycypermethrin, which exhibits no intrinsic toxicity towards susceptible larvae. In a bioassay, CYP337B3 confers a 7-fold resistance towards cypermethrin in FSD larvae compared to susceptible larvae from the Australian TWB strain lacking CYP337B3. Linkage analysis shows that presence of CYP337B3 accounts for most of the cypermethrin resistance in the FSD strain; up-regulation of other P450s in FSD plays no detectable role in resistance. The presence or absence of CYP337B3 can be easily detected by a simple PCR screen, providing a powerful tool to rapidly distinguish resistant from susceptible individuals in the field and to determine the geographical distribution of this resistance gene. Our results suggest that CYP337B3 evolved twice independently by unequal crossing-over between CYP337B2 and two different CYP337B1 alleles.     

Chemiluminescence in the autoxidation of the pyruvic acid analogues of a thyroid hormone and related molecules

Since the hydroperoxide formed from 4-hydroxy-3,5-diiodopheyl-pyruvic acid and oxygen, a likely precursor of thyroxine, is also known to undergo cleavage to 4-hydroxy-3,5-diiodobenzaldehyde and oxalic acid, that is, to products expected from a dioxetane intermediate, we have investigated the chemiluminescence of aerated solutions of 4-hydroxy-3,5-diiodophenylpyruvic acid. Light was emitted in dimethyl-sulfoxide solution containing potassium t-butoxide. The emitting species is the excited singlet aldehyde. Other pyruvic acid analogues, including that of the hormone 3,5,3′-triiodothyronine, chemiluminesce in similar conditions. Extremely weak emission occurs in aqueous solution.     

增效醚(PBO)对棉铃虫细胞色素P450的抑制 作用及对拟除虫菊酯的增效作用

在增效醚（PBO）对棉铃虫Helicoverpa armigera 3龄幼虫处理后的不同时段,细胞色素P450的含量受到不同程度的抑制:在处理后1 h,细胞色素P450的含量仅为对照的43.9%,至处理后12 h,细胞色素P450的含量下降到最低点,仅为对照的23.4%;而处理后18～24 h,细胞色素P450被抑制的程度有所减弱,其含量分别为对照的85.8%和70.0%。生物测定结果表明,PBO对所测定的7种拟除虫菊酯均有不同程度的增效作用,对氰戊菊酯的增效比最高(119.3),对氯菊酯的增效比最低(2.1)。由于细胞色素P450是拟除虫菊酯的重要解毒酶系,PBO的处理可使棉铃虫细胞色素P450的含量大幅度下降,使其对杀虫剂的解毒能力减弱,从而对杀虫剂产生增效作用。     

Evaluation of the efficacy of Olyset® Plus in a village‐based cohort study in the Cukurova Plain,Turkey, in an area of hyperendemic cutaneous leishmaniasis

The aim of this study was to measure the protective efficacy of Olyset® Plus, a new long‐lasting factory‐treated insecticidal net (LLIN) incorporated with 2% permethrin and 1% of the synergist piperonyl butoxide (PBO), against cutaneous leishmaniasis (CL) transmission under field conditions. A village‐scale trial, promoting the use of LLIN by the local inhabitants of the study area was conducted as a pilot study in a new hyperendemic focus of CL caused by a Leishmania infantum/L. donovani hybrid parasite transmitted by proven vector species Phlebotomus tobbi in Cukurova Plain, Adana, Turkey, between May, 2013 and May, 2014. The study area comprised eight villages; two of them were selected as an intervention village with Olyset® Plus net (Kizillar) and a control village without net application (Malihidirli). Six villages with surrounding allopatric barriers were utilized as a buffer zone cluster between intervention and control villages. Monthly entomological surveys were performed in the intervention and control villages and Damyeri, representing the other six villages, to collect adults of Phlebotomus tobbi. Results showed a significant reduction in cutaneous leishmaniasis incidence in the intervention village from 4.78% to 0.37%. The protective efficacy rate of LLIN was 92.2%. In contrast, incidence rates increased in the control village from 3.67% to 4.69%. We also evaluated residual insecticide levels of used nets after six and 12 months of usage. It was determined that the nets had retained full insecticidal strength. These results highlight the value of real‐world data on bed net effectiveness and longevity to guide decisions regarding sand fly control strategies. To the best of our knowledge, this is the first field study to evaluate Olyset® Plus efficacy in a hyperendemic cutaneous leishmaniasis area.     

Insecticide resistance of Culex pipiens (L.) populations (Diptera: Culicidae) from Riyadh city,Saudi Arabia: Status and overcome

Three field populations of Cx. pipiens (L.) mosquitoes were collected from three different localities in Riyadh city. They were tested for developing resistance against commonly used insecticides to control mosquitoes in Riyadh. Two populations from Wadi Namar (WN1 and WN2) were highly resistant to deltamethrin (187.1- and 161.4-folds respectively). The field population from AL-Wadi district (AL-W) showed low resistance to lambda-cyhalothrin (3.8-folds) and moderate resistance to beta-cyfluthrin and bifenthrin (14- and 38.4-folds respectively). No resistance to fenitrothion was observed in WN1 population. Fenitrothion concentrations required to inhibit 50% of Acetylcholinesterase (AChE) activity in both WN1 population and the laboratory susceptible strain (S-LAB) were 0.073 and 0.078 ppm respectively. Piperonyl butoxide suppressed resistance to pyrethroid insecticides (>90%) in field populations indicating that oxidases and/or esterases play an important role in the reduction of pyrethroids toxicity. These results should be considered in the current mosquitoes control programs in Riyadh.     

Effects of Maternal Exposure to Piperonyl Butoxide (PBO) on Behavioral Development in F1‐Generation Mice

Female mice were exposed maternally to piperonyl butoxide (PBO) through diet to provide dietary levels of 0% (control), 0.01%, 0.03%, and 0.09% during gestation and lactation periods, and selected reproductive and neurobehavioral parameters were measured in the F₁ generation. There was no adverse effect of PBO on litter size, litter weight, or sex ratio at birth. The average body weights of male offspring decreased significantly in dose‐related manners on postnatal days (PNDs) 0, 4, 7, and 14 (p = 0.0019, 0.0096, 0.033, and 0.038, respectively) during the lactation period. In female offspring, the average body weights decreased in dose‐related manners on PNDs 0, 4, 7, and 14 (p = 0.0027, 0.0104, 0.0193, and 0.0062, respectively). The survival of dams slightly decreased (p = 0.0209) in the high‐dose group during the lactation period. With respect to behavioral developmental parameters, surface righting on PND 7 of male and female offspring was delayed significantly in a dose‐related manner (p < 0.001 in each). Swimming direction on PND 7 of male offspring was delayed significantly in a dose‐related manner (p < 0.01), and for female offspring it was delayed significantly in the high‐dose group (p < 0.05). Swimming head angle on PND 7 of male offspring was delayed significantly in a dose‐related manner (p < 0.05). Spontaneous behavior examination in males indicated that rearing increased in the high‐dose group in the F₁ generation. The dose levels of PBO in the present study produced some adverse effects in neurobehavioral parameters in mice     

Characterization of oxidase(s) associated with the sex pheromone gland in Manduca sexta (L.) females

An oxidase that converts primary aliphatic alcohols into aldehydes was discovered in the cuticle of the sex pheromone gland and in the papillae anales on the tip of the abdomen of Manduca sexta females. Oxidase activity was not found in the epidermal cells of the pheromone gland where fatty acid precursors of the pheromonal aldehydes are found. This oxidase requires oxygen and water to function and appears to have a rather broad substrate specificity. The activity of the oxidase is reduced by the application of piperonyl butoxide, which also interferes with the PBAN induced production of the natural pheromone aldehydes. However, endogenous alcohols cannot be found in the pheromone gland. Thus, it is not yet clear whether or not the oxidase is involved in the terminal step of biosynthesis of the pheromone aldehydes in M. sexta females. © Wiley-Liss, Inc.

1 This article is a U.S. Government work and, a such, is in the public domain in the United States of America.