Explore the vast range of titles available.

Background: The German cockroach (Blattella germanica) is a pest with a global distribution that has adapted to live in human environments. Blattella germanica threatens human health by producing asthma-inducing allergens, carrying pathogenic/antibiotic-resistant microbes, and contributing to unhealthy indoor environments. Effective application of insecticides can play an important role in cockroach control programs. The purpose of this research was to develop and optimize a nanoparticle-based imidacloprid insecticide and evaluate its effectiveness against the German cockroach. Methods: A bioassay was conducted to determine the LC50 and LC90 of imidacloprid technical against adult German cockroaches. The appropriate initial concentration of 3mg/m2 was then utilized in the synthesis of nanoencapsulated imidacloprid via the ionic gelation method. The average particle size was determined using Dynamic Light Scattering (DLS) and the dried nanoparticles were analyzed using a Scanning Electron Microscope (SEM). The LC50 and LC90 values of Nano-imidacloprid were then compared with the technical grade of the insecticide. Results: A comparison of the bioassay results for nanoencapsulated and imidacloprid technical revealed a superior in­secticidal effect of the nanoencapsulated imidacloprid against the German cockroach. The LC50 value for the nanoen­capsulated imidacloprid decreased from 4.656 to 3.081 mg/m2 and the LC90 value decreased from 8.381 to 4.486 mg/m2 when compared to imidacloprid technical. Conclusion: The use of nanotechnology in insecticides can lead to increased efficacy and reduced consumption. This is because the smaller particle size of nanomaterials allows for better penetration and targeted delivery to pest organisms, reducing the overall amount needed for control.

Background: Cytochrome P450-dependent monooxygenases are a very important metabolic system involve in insecti­cide resistance. This study was conducted to find the association between the expression level of cytochrome P450 (CYP450) and permethrin-resistance level among four strains of the German cockroach Blattella germanica (L) (Blat­todea: Ectobiidae). Methods: Three field strains of German cockroach with different frequency of exposure to pesticides, and a laboratory susceptible strain were used in the present study. Insecticide susceptibility bioassays were carried out to detect re­sistance to permethrin. The concentration of CYP450 in each strain was determined using ion-exchange HPLC chroma­tography. Biochemical assays was performed to analyse CYP450 activities. Results: The resistance ratios (RR) to permethrin among three field strains were 3.29, 4.10 and 6.17-fold comping with the susceptible stain. The CYP450 activity of three field strains was 1.6, 2.4 and 2.7 times higher than in the sus­ceptible stain. The amount of CYP450 per mg of protein was significantly different between the susceptible and the three re­sistant strains. The resistant cockroaches showed a relatively high expression of CYP450 enzymes. A strong corre­la­tion was found between permethrin resistance level and total concentration of CYP450 enzymes. Conclusion: The results of current study show that more frequent usage of a pyrethroid insecticide cause the metabolic insecticide resistance to rise in German cockroach. Therefore, there is a ratio correlation between resistance level and monooxygenases activities in insect. Thus, the control program must be managed according to history of pesticide us­age.  

Background: Lectin molecules have crucial biological role in insects’ immune system. The aim of present study was to find the agglutinin activities in haemolymph of German cockroach, Belatella germanica with appropriate screening and purification. Methods: The heamolymph of cockroach was collected and agglutinin test performed against different animal and human red blood cells (RBC). Then sugar inhibition assay was carried out to find carbohydrate specific binding lectin. The proteins of haemolymph was purified using ion-exchange chromatography (HPLC) and each fraction was tested for agglutinin activity. Finally the molecular weight of the agglutinin protein was determined using SDS-page. Results: The most agglutinin activity of haemolymph was found against RBC of mouse at titer 1/128ml/L dilution and sugar inhibition assay showed that fucos, N-acetyglucoseamine and galactose reduced titer of agglutinin to ½ml/L. Only one fraction of heamolymph at rotation time of 36 minute showed agglutinin activity. The molecular weight of this lectin was measured as 120Kds. Conclusion: The range of agglutinin activities against different RBC indicates that the isolated lectin is not specific for a particular carbohydrate. In addition, the isolated lectin at low concentration present in heamolymph should be an innate lactin not secreted, because we found it without any trigger immunity of the insect.

Blattella germanica is considered to be a pest insect that is difficult to control and which tends to be controlled by the use of chemical products. As such, the indiscriminate use of insecticides can result in cockroach resistance and environmental contamination. Aiming to promote a more conscientious and effective control method, formulations of toxic gel baits were developed. These baits result in less environmental contamination and can be applied in areas where the use of conventional insecticides is not possible. This study aimed to evaluate which toxic bait presented the most efficient control of B. germanica, taking into consideration characteristics such as attractiveness, feeding stimulation and mortality rate. For the bioassay, four compositions of toxic gel baits were used in a test arena, where, in the presence of the baits, (1) the time until consumption, (2) the bait consumed, (3) the time taken for feeding stimulation and (4) the time until death were evaluated. Toxic baits were compared using paired T-tests. We verified that the Fipronil toxic bait did not present attractiveness nor consumption and the Indoxacarb toxic bait presented the greatest attractiveness. There was no statistical difference between the baits when evaluating feeding stimulation and mortality, indicating, in this case, that both baits acted in a similar manner. The Imidacloprid and Indoxacarb toxic baits were recommended for the control of B. germanica, as they caused mortalities during a period of less than 24h. However, Indoxacarb presented a greater rate of attractiveness when compared to the Imidacloprid gel baits.

The activity of the serine protease in the German cockroach allergen is important to the development of allergic disease. The protease-activated receptor (PAR)-2, which is expressed in numerous cell types in lung tissue, is known to mediate the cellular events caused by inhaled serine protease. Alveolar macrophages express PAR-2 and produce considerable amounts of tumor necrosis factor (TNF)-[alpha]. We determined whether the serine protease in German cockroach extract (GCE) enhances TNF-[alpha] production by alveolar macrophages through the PAR-2 pathway and whether the TNF-[alpha] production affects GCE-induced pulmonary inflammation. Effects of GCE on alveolar macrophages and TNF-[alpha] production were evaluated using in vitro MH-S and RAW264.6 cells and in vivo GCE-induced asthma models of BALB/c mice. GCE contained a large amount of serine protease. In the MH-S and RAW264.7 cells, GCE activated PAR-2 and thereby produced TNF-[alpha]. In the GCE-induced asthma model, intranasal administration of GCE increased airway hyperresponsiveness (AHR), inflammatory cell infiltration, productions of serum immunoglobulin E, interleukin (IL)-5, IL-13 and TNF-[alpha] production in alveolar macrophages. Blockade of serine proteases prevented the development of GCE induced allergic pathologies. TNF-[alpha] blockade also prevented the development of such asthma-like lesions. Depletion of alveolar macrophages reduced AHR and intracellular TNF-[alpha] level in pulmonary cell populations in the GCE-induced asthma model. These results suggest that serine protease from GCE affects asthma through an alveolar macrophage and TNF-[alpha] dependent manner, reflecting the close relation of innate and adaptive immune response in allergic asthma model.

The German cockroach Blattella germanica is commonly infected with the pinworm Blatticola blattae . To determine the effect of pinworm infection on cockroach survival, we artificially altered the pinworm infection status of cockroaches and determined the number of survival days under no-feeding conditions, with and without opportunities for fecal feeding. Four lines of the German cockroach (Wn, Wp, Nn, and Np groups) were used in the experiment. Wp and Np were pinworm-infected lines. Wn and Nn were pinworm-free lines. The 50% survival days of cockroaches in the absence of opportunities for fecal feeding were not significantly different in Wp (3.45 days) vs Wn (3.27), and in Np (4.60) vs Nn (4.48). In contrast, in the presence of fecal feeding, the 50% survival times for the pinworm-infected Wp (4.04) and Np (6.65) were significantly longer than those for the pinworm-free Wn (2.77) and Nn (5.46). The number of survival days without feeding was significantly higher in the pinworm-infected group given the opportunity to eat feces than in the non-infected group. These results suggest that pinworm infection of cockroaches during starvation, in association with fecal feeding, may be associated with longer survival.

We propose a mathematical model, namely a reaction–diffusion system, to describe social behaviour of cockroaches. An essential new aspect in our model is that the dispersion behaviour due to overcrowding effect is taken into account as a counterpart to commonly studied aggregation. This consideration leads to an intriguing new phenomenon which has not been observed in the literature. Namely, due to the competition between aggregation towards areas of higher concentration of pheromone and dispersion avoiding overcrowded areas, the cockroaches aggregate more at the transition area of pheromone. Moreover, we also consider the fast reaction limit where the switching rate between active and inactive subpopulations tends to infinity. By utilising improved duality and energy methods, together with the regularisation of heat operator, we prove that the weak solution of the reaction–diffusion system converges to that of a reaction-cross-diffusion system.

Background Insects exhibit remarkable resilience and maintain high levels of reproduction despite frequently encountering nutritional restriction. However, the mechanisms governing their adaptive reproductive strategies under nutrition-restricted conditions remain poorly understood. The German cockroach Blattella germanica , a widespread urban pest, exhibits remarkable reproductive capabilities even in domestic environments where food resources are frequently limited. Results In this study, we demonstrate that the ovary plays a crucial role in promoting vitellogenin biosynthesis and oocyte development under nutrition-restricted conditions through hemiovariectomy. Employing transcriptome analysis, RNAi screening, and fluorescence in situ hybridization, we identified an ovarian-enriched insulin-like peptide gene ( BgILP2 ) that is dramatically upregulated during low nutrition conditions. Repression of BgILP2 impairs vitellogenesis in the fat body through downregulation of p-AKT and p-ERK levels while simultaneously disrupting juvenile hormone synthesis, ultimately leading to delayed oocyte development under nutrient restriction. Furthermore, under low-nutrient conditions, repression of BgILP2 led to elevated circulating sugar levels, reduced lipid and glycogen storage, and a modest increase in the lifespan of female cockroaches. Conclusions The ovarian-enriched BgILP2 responds to nutritional stress and activates the insulin signaling pathway to sustain oocyte development under nutrient-restricted conditions. Furthermore, BgILP2 mediates energy allocation and prioritizes reproductive investment potentially at the expense of longevity, which reflects a tradeoff between reproduction and somatic maintenance under nutrient restriction. These findings provide novel insights into the molecular mechanisms and adaptive strategies that enable cockroaches to maintain reproductive success in food-limited environments. Graphical Abstract

The German cockroach, Blattella germanica (L.) (Blattodea: Ectobiidae), is a common pest of human-built structures worldwide. German cockroaches are generalist omnivores able to survive on a wide variety of foods. A number of studies have concluded that laboratory-reared B. germanica self-select diets with an approximate 1P:3C (protein-to-carbohydrate) ratio. We predicted that field-collected insects would exhibit more variable dietary preferences, related to the wide-ranging quality, quantity, and patchiness of foods available to them. We compared diet self-selection of B. germanica within apartments and in the laboratory by offering them a choice of two complementary diets with 1P:1C and 1P:11C ratios. We observed high variation in the population-level self-selection of these diets among individual apartment sites as well as among various life stages tested in laboratory-based assays. Significant differences between populations in various apartments as well as between populations maintained in the laboratory suggested that factors beyond temporary food scarcity influence diet choice. Nevertheless, we found significant correlations between the amounts of diets ingested by cockroaches in apartments and cockroaches from the same populations assayed in the laboratory, as well as between males, females, and nymphs from these populations. These findings suggest that females, males, and nymphs within apartments adapt to the local conditions and convergently prefer similar amounts of food of similar dietary protein content.

Populations of Blattella germanica (L.) (German cockroach) have been documented worldwide to be resistant to a wide variety of insecticides with multiple modes of action. The phenylpyrazole insecticide fipronil has been used extensively to control German cockroach populations, exclusively in baits, yet the highest reported fipronil resistance is 38-fold in a single population. We evaluated five populations of German cockroaches, collected in 2018–2019 in apartments in North Carolina and assayed in 2019, to determine the status of fipronil resistance in the state. Resistance ratios in field-collected strains ranged from 22.4 to 37.2, indicating little change in fipronil resistance over the past 20 yr. In contrast, resistance to pyrethroids continues to escalate. We also assessed the roles of detoxification enzymes in fipronil resistance with four synergists previously shown to diminish metabolic resistance to various insecticides in German cockroaches—piperonyl butoxide, S,S,S-tributyl phosphorotrithioate, diethyl maleate, and triphenyl phosphate. These enzymes appear to play a variable role in fipronil resistance. We also sequenced a fragment of the Rdl (resistant to dieldrin) gene that encodes a subunit of the GABA receptor. Our findings showed that all field-collected strains are homozygous for a mutation that substitutes serine for an alanine (A302S) in Rdl, and confers low resistance to fipronil. Understanding why cockroaches rapidly evolve high levels of resistance to some insecticides and not others, despite intensive selection pressure, will contribute to more efficacious pest management.