Cockroach allergen biology and mitigation in the indoor environment

Behavioral responses of field-collected German cockroaches to pyrethroids and pyrethroid-formulated insecticides

BACKGROUND

Pyrethroids are synthetic insecticides with low mammalian toxicity and broad-spectrum activity across insects. One major challenge with pyrethroids is their perceived repellency. This perception can influence decisions made by pest control operators, especially when insecticides are used to reduce insect entry into or movement within structures. One major indoor pest that has been repeatedly shown to be repelled by some pyrethroids is the German cockroach, Blattella germanica. However, most experiments evaluating pyrethroid repellency in the German cockroach have used end-point assays, which do not provide information on the movement that led to the final position. Therefore, we evaluated the kinetic behavioral response of field-collected German cockroaches to five pyrethroid-based products and their active ingredients (A.I.) in open behavioral arenas using advanced video tracking software. In addition, in an effort to compare our free-moving experiments with end-point assays, we evaluated sheltering behavior using two-choice harborage arrestment assays where German cockroaches were provided a choice between pyrethroid-treated and untreated shelters.

RESULTS

All pyrethroid-formulated products and their respective A.I.'s failed to affect field-collected German cockroach movement behavior in free-moving assays, while positive controls (DEET, corn mint oil) resulted in reduced time spent by German cockroaches in treated areas. However, despite their willingness to move over pyrethroids-treated surfaces, field-collected German cockroaches displayed a reduced propensity to arrest on pyrethroids treated tents.

CONCLUSION

While most pyrethroids/pyrethroid-formulated products affected German cockroach arrestment, pyrethroids and pyrethroid-formulated products failed to change German cockroach movement behavior in free-moving assays. These results indicate the pyrethroids tested act as contact irritants rather than true-spatial repellents on field-collected German cockroaches. This distinction is critical to refining pest management strategies involving pyrethroids. © 2023 Society of Chemical Industry.

Effect of Acetamiprid, a Neonicotinoid Insecticide, on Locomotor Activity of the American Cockroach

Toxicological studies have shown that the American cockroach Periplaneta americana (Linnaeus) is a classical model for studying the mode of action of commonly used insecticides. In a previous study, we demonstrated that thiamethoxam and clothianidin decreased locomotor activity in an open-field-like apparatus. Here, we tested the effect of the neonicotinoid acetamiprid when applied orally, topically, or injected into the haemolymph. We found that acetamiprid was also able to impair locomotor activity in the open-field-like apparatus. When treated with acetamiprid, a strong alteration in locomotor activity was observed 1 h, 24 h, and 48 h after haemolymph and topical applications. Oral application induced an impairment of locomotor activity at 24 h and 48 h. A comparison of the present data with our previously published results showed that neonicotinoids were more active when injected into the haemolymph compared to oral and topical applications. These findings increased our understanding of the effect of neonicotinoid insecticides on insect locomotor activity, and demonstrated that the cyano-substituted neonicotinoid, acetamiprid, was able to alter cockroach locomotor activity.

Plasticity of aggregation pheromones in insects

Pheromone plasticity is widely observed in insects and enhances their survival, adaptation, and reproductive success. Aggregation pheromones, which cause notable individual aggregation and consequently impact agriculture and human life, are renowned for their special function. Here, we present a review of research progress regarding pheromone plasticity in three typical aggregative insects: locusts, bark beetles, and cockroaches. These insects are major pest species with considerable impacts on the social economy and public health. Numerous studies have demonstrated the plasticity of aggregation pheromones in different populations of these insect species. Although pheromone chemicals and compositions vary across the three groups, the plasticity of aggregation pheromones is significantly impacted by population density, location, food resources, and gut symbiotic microorganisms, indicating the complexity of pheromone plasticity regulated by multiple factors. Finally, we discuss the potential application of pheromone plasticity in basic research and pest management.

Indoor Environmental Exposures and Their Relationship to Allergic Diseases

Cockroach, dust mite, cat, dog, mouse, and molds are major indoor allergens that have been associated with the development of allergic diseases and disease morbidity in allergen-sensitized individuals. Physical characteristics, such as allergen particle size, hydrophobicity, and charge, can determine an allergen's propensity to become airborne, location of respiratory tract penetration, and ability to elicit IgE responses in genetically predisposed individuals. Standardization and recent advancements in indoor allergen assessment serve to identify sources and distribution of allergens in a patient's home and public environment, inform public policy, and monitor the efficacy of allergen avoidance and therapeutics. Allergen exposure interventions have yielded mixed results with current US and international asthma guidelines differing on recommendations. A pragmatic, patient-centered approach to allergen avoidance includes: (1) tailoring intervention to the patient's sensitization and exposure status, (2) using a rigorous multifaceted intervention strategy to reduce allergen exposure as much as possible, and (3) beginning the intervention as soon as the patient is diagnosed. Further research into the risks/benefits of early allergen exposure, rapid and affordable in-home allergen assessment, and best practices for environmental control measures for asthma is needed.

The gut microbiota induces melanin deposits that act as substrates for fimA-mediated aggregation of Salmonella Typhimurium and enhance infection of the German cockroach vector

When Salmonella Typhimurium is ingested by German cockroaches, the bacteria replicate in the gut and persist for at least 7 d, enabling transmission in the feces. However, the mechanisms that facilitate survival and persistence in the cockroach gut remain poorly detailed. We previously reported the formation of biofilm-like aggregate populations of S. Typhimurium in the gut of cockroaches upon ingestion. We also reported that deletion of the type-1 fimbrial subunit of S. Typhimurium, fimA, leads to a reduced bacterial load in the cockroach gut. Here, we link these observations and provide further insight into the mechanism and function of S. Typhimurium aggregation in the gut of the cockroach. We show that S. Typhimurium but not Escherichia coli forms aggregated populations in the cockroach gut, and that aggregate formation requires fimA but not the biofilm formation-related genes csgA and csgD. Furthermore, we show that S. Typhimurium aggregates are formed using small granular deposits present in the cockroach gut, which exhibit properties consistent with melanin, as substrates. These melanin deposits are prevalent in the guts of both immature and adult cockroaches from laboratory colonies and are correlated with increased gut bacterial density while being entirely absent in gnotobiotic cockroaches reared without exposure to environmental bacteria, indicating they are induced as a response to the gut microbiota. When cockroaches lacking melanin deposits in the gut are fed S. Typhimurium, they exhibit lower rates of infection than those harboring melanin deposits, demonstrating that microbiota-induced melanin deposits enhance infection of the gut of the vector. IMPORTANCE Cockroaches, including the German cockroach (Blattella germanica), can be both mechanical and biological vectors of pathogenic bacteria. Together, our data reveal a novel mechanism by which S. Typhimurium interacts with the cockroach gut and its microbiota that promotes infection of the vector. These findings exemplify the emerging but underappreciated complexity of the relationship between cockroaches and S. Typhimurium.

Spatial distribution of histamine in bed bug-infested homes

Histamine is a component of the bed bug aggregation pheromone. It was recently identified as an environmental contaminant in homes with active bed bug infestations, posing a potential health risk to humans via skin contact or inhalation. It remains unclear how histamine is distributed in homes and if histamine can become airborne. In the present study, histamine levels in household dust were quantified from multiple locations within bed bug infested and uninfested apartments. Bed bug population levels were quantified using both traps and visual counts. The amount of histamine detected varied significantly with respect to sampling location, with the highest concentration of histamine quantified from bedding material. Infestation severity did not have a significant effect on histamine quantified at any location. Our results indicate that the bedroom should be the primary focus of histamine mitigation efforts, although histamine can be found throughout the home. Histamine quantified from homes without active bed bug infestations suggests that histamine from previous infestations can persist following pest eradication. These findings highlight the importance of histamine as a potential insect allergen and will be important for the development of targeted mitigation strategies of bed bug histamine.

An evolutionary game study of cockroach control strategies in residential households

Cockroach control in Beijing's residential households is supported by the local government previously but now it is paid by the residents themselves. Under the new residential household cockroach control strategy, the evolutionary game theory is applied in this study to construct an evolutionary game model for the choice behaviour of both PCO (Pest Control Operation) enterprises and the local governments under government regulation. The evolutionary stabilization strategies under different situations were suggested and the key factors for the evolutionary game behaviour were analyzed through Matlab simulation. It was found that the benefits and costs of the local governments' promotion for the cockroach eradication activities, the incremental benefits of PCO enterprises through government publicity and the subsidies for the activities, and the additional costs of PCO enterprises to participate in cockroach eradication activities are the key factors. The incremental benefits from the publicity of the activities and the government subsidies can be used to incent the PCO enterprises' activities, which may be failure without the government promotion. This study confirms the decisive role of the strategic choices of PCO enterprises and the government for effective cockroach eradication activities. Therefore, before the campaign is launched, it is necessary to take into account the economic benefits of PCO enterprises and the public interests of the governments so that the game system can evolve out of the "ineffective" and undesirable "locked" state and evolve towards the ideal state, while would be a basis for other anti- pest efforts.

The Arginine Kinase from the Tick Rhipicephalus sanguineus Is an Efficient Biocatalyst

Arginine kinase (AK) is a reversible enzyme that regulates invertebrates’ phosphagen arginine phosphate levels. AK also elicits an immune response in humans, and it is a major food allergen in crustacea and may be a target for novel antiparasitic drugs. Although AK has been primarily described in the shrimp, it is also present in other invertebrates, such as the brown tick Rhipicephalus sanguineus (Rs), the vector for Rocky Mountain Spotted Fever. Here we report the enzymatic activity and the crystal structure of AK from Rhipicephalus sanguineus (RsAK) in an open conformation without substrate or ligands and a theoretical structure of RsAK modeled bound with the substrate/product (Arg-ADP) in a closed conformation. The Michaelis-Menten kinetics confirmed that RsAK is an efficient biocatalyst due to its high kcat/Km parameter. The recombinant enzyme was expressed in bacteria and purified to a 20 mg/L culture yield. AK is an essential enzyme in invertebrates. Future work will be focused on the RsAK enzymatic inhibition that may lead to novel strategies to control this pest, a burden to animal and human health.

Expression profiles of an inactive aspartic protease (Bla g 2 allergen) in different tissues and developmental stages of the German cockroach (Blattella germanica)

Tergal glands are found in many insect species and contain constituents such as pheromones, sugars, proteins, and so forth. Preliminary studies have revealed that tergal gland secretions in the German cockroach (Blattella germanica L.) contain the human allergen Bla g 2 (B. germanica allergen 2), an inactive aspartic protease. Although Bla g 2 protein expression has been detected previously in various German cockroach body parts, including male tergal glands, studies that link protein expression in various life stages and tissues with mRNA and protein abundance have not been conducted. Therefore, the goal of this study was to measure the relative abundances of Bla g 2 protein and mRNA in different tissues and life stages of B. germanica using immunoblotting, quantitative PCR, and liquid chromatography-tandem mass spectrometry (LC-MS/MS)-based quantitative profiling. We found that Bla g 2 protein was detected in every sampled tissue, including the male tergal glands. Protein abundance was relatively high in adult males and their tergal glands in comparison to nymphs and virgin females. Similarly, Bla g 2 mRNA transcript levels were also comparatively higher in male tergal glands and adult males. In conclusion, this study provides new information on the relative abundance and distribution of Bla g 2 allergen, a medically significant protein, in different tissues and developmental stages of the German cockroach and lays the foundation for future studies that aim to determine the function of this protein in B. germanica development.

SARS-CoV-2 Transmission by Arthropod Vectors: A Scoping Review

COVID-19 is a respiratory disease of worldwide importance as it has brought enormous health problems to the world's population. The best-known way of transmission of the virus is through aerosolization. However, research is needed to explore other transmission routes. Researchers hypothesized that arthropods could transmit SARs-CoV-2. This study is aimed at reviewing research on arthropods as possible reservoirs and/or vectors of SARS-CoV-2, the causative agent of COVID-19. Following PRISMA guidelines, we conducted a systematic review using several electronic databases/academic searches with the search terms “arthropods,” “coronavirus,” and “transmission.” A total of 64 unique articles were identified, of which 58 were included in the review. The SARS-CoV-2 virus is tiny and invisible to the naked eye, and its presence in stools, droplets, and surfaces was detected. One doubt is whether insects can transmit the virus from one place to another. Thus, a healthy carrier of the COVID-19 virus can be at the root of the contamination of their community or their family through the transport of the virus by insects from the interior (flies, cockroaches, etc.) from their feces and food surfaces. Hygiene care within communities and families becomes a prime factor. Coronavirus infection is a significant public health problem around the world. The prevention and control of outbreaks remain very important, even with the production of new vaccines. The main option to achieve this is the proper management of the transmission of the virus. The registry of infected people is currently the basis for the transmission of COVID-19. However, questions about the possibility of infection from other sources and its prevention are not receiving adequate attention. Numerous studies have shown the possibility that SARS-COV-2 fragments could have a longer life than shed respiratory droplets. Also, this virus is larger than those of other coronavirus families.

Population Structure of German Cockroaches (Blattodea: Ectobiidae) in an Urban Environment Based on Single Nucleotide Polymorphisms

German cockroaches (Blattella germanica L.) harbor and disperse medically important pathogens and are a source of allergens that impact human health and wellbeing. Management of this pest requires an understanding of their distribution and dispersal. In this study, we collected German cockroaches from three apartment buildings in New Jersey, USA. We identified single-nucleotide polymorphisms (SNPs) from DNA extractions using next generation sequencing. We analyzed the SNPs and characterized cockroach population genetic structure using Fst, principal component, phylogenetic, and STRUCTURE analyses. We found significant differences in German cockroach population structure among the buildings. Within buildings, we found variable population structure that may be evidence for multiple colonization events. This study shows that SNPs derived from next generation sequencing provide a powerful tool for analyzing the genetic population structure of these medically important pests.

Identification and functional characterization of the German cockroach, Blattella germanica, short interspersed nuclear elements

In recent decades, experimental data has accumulated indicating that short interspersed nuclear elements (SINEs) can play a significant functional role in the regulation of gene expression in the host genome. In addition, molecular markers based on SINE insertion polymorphisms have been developed and are widely used for genetic differentiation of populations of eukaryotic organisms. Using routine bioinformatics analysis and publicly available genomic DNA and small RNA-seq data, we first described nine SINEs in the genome of the German cockroach, Blattella germanica. All described SINEs have tRNA promoters, and the start of their transcription begins 11 bp upstream of an “A” box of these promoters. The number of copies of the described SINEs in the B. germanica genome ranges from several copies to more than a thousand copies in a SINE-specific manner. Some of the described SINEs and their degenerate copies can be localized both in the introns of genes and loci known as piRNA clusters. piRNAs originating from piRNA clusters are shown to be mapped to seven of the nine types of SINEs described, including copies of SINEs localized in gene introns. We speculate that SINEs, localized in the introns of certain genes, may regulate the level of expression of these genes by a PIWI-related molecular mechanism.

Potential use of synthetic and natural aromatic mixtures in prevention from Shelfordella lateralis сockroaches

Attractive and repellent properties of many household chemicals may be used to combat synantrophic insects, such as cockroaches. In the natural environment, Shelfordella lateralis (Walker, 1868) (Blattodea, Blattidae) lives in the area spanning Central Asia to North Africa. Furthermore, in many tropical and subtropical countries, it is common in human accomodations. In the laboratory conditions, we determined reaction of cockroaches to aromatic mixtures and medicinal plants often used in households. Attractiveness coefficient was the lowest for cosmetic mixtrures Tutti-fruti and Verbena and Bamboo; other cosmetic aromatizers did not repell this insect (Lilac, Mango) or repelled it poorly (Grapefruit, Amaretto, Pine). Food additives that significantly repelled Sh. lateralis are Apricot, Barberry and Kiwi and lower effects were produced by Biscuit, whereas Vanilla flavouring had no repellent effect. Mixtures for vaping Strawberry pie, Pear, Frozen forest, Irish Cream and Blue Magic exerted strong repellent effects on cockroaches. Low repellent effect on Sh. lateralis were exerted by vaping mixtures Pancakes with Honey, Turkish Tobacco and Grapefruit. No significant effects on the number of cockroaches were exerted by vaping mixtures Vanilla, Club Ice Cream, Blueberry Smoke, Mojito, Chocolate, Apple, Mint and Walnut. Out of the fishing lures, the strongest repellent effects on Sh. lateralis were taken by Blood Worm, Onion and Honey, and weaker effects were exerted by Corn and Vanilla. Imagoes of Sh. lateralis were most significantly repelled by essential oils from jojoba, eucalyptus, daisy, tee tree, Cao Sao Vang balsam, and also fir essential oil. Neither luring nor repellent effects on imagoes of Sh. lateralis were displayed by essential oils from lemon, aloe, peppermint and mandarin. Dry medicinal plants repelled imagoes of Sh. lateralis: inflorescences of Calendula officinalis, leaves of Artemisia absinthium, flowers of Jasminum officinale, leaves of Origanum vulgare, inflorescences of Matricaria chamomilla, inflorescences of Crataegus monogyna, leaves of Mentha x piperita, inflorescences of Achillea millefolium, leaves of Hypericum perforatum, leaves of Aristolochia clematitis and inflorescences of Tanacetum vulgare. No repellent effects on Sh. lateralis were exerted by Chelidonium majus, inflorescences of Tilia cordata and inflorescences of Helichrysum arenarium. Thus, most (40 of 58, or 69.0%) of the tested aromatic substances and medicinal plants repelled synantrophic Turkestan cockroach, while a much smaller share (31.0%) neither significantly lured nor repelled them. No aromatic mixtures attracted Sh. lateralis in our experiment.

Transcriptome Responses to Defined Insecticide Selection Pressures in the German Cockroach (Blattella germanica L.)

Cockroaches are important global urban pests from aesthetic and health perspectives. Insecticides represent the most cost-effective way to control cockroaches and limit their impacts on human health. However, cockroaches readily develop insecticide resistance, which can quickly limit efficacy of even the newest and most effective insecticide products. The goal of this research was to understand whole-body physiological responses in German cockroaches, at the metatranscriptome level, to defined insecticide selection pressures. We used the insecticide indoxacarb as the selecting insecticide, which is an important bait active ingredient for cockroach control. Six generations of selection with indoxacarb bait produced a strain with substantial (>20×) resistance relative to inbred control lines originating from the same parental stock. Metatranscriptome sequencing revealed 1,123 significantly differentially expressed (DE) genes in ≥two of three statistical models (81 upregulated and 1,042 downregulated; FDR P < 0.001; log2FC of ±1). Upregulated DE genes represented many detoxification enzyme families including cytochrome-P450 oxidative enzymes, hydrolases and glutathione-S-transferases. Interestingly, the majority of downregulated DE genes were from microbial and viral origins, indicating that selection for resistance is also associated with elimination of commensal, pathogenic and/or parasitic microbes. These microbial impacts could result from: (i) direct effects of indoxacarb, (ii) indirect effects of antimicrobial preservatives included in the selecting bait matrix, or (iii) selection for general stress response mechanisms that confer both xenobiotic resistance and immunity. These results provide novel physiological insights into insecticide resistance evolution and mechanisms, as well as novel insights into parallel fitness benefits associated with selection for insecticide resistance.

New insight into the relationship between Salmonella Typhimurium and the German cockroach suggests active mechanisms of vector-borne transmission

Diarrheal diseases are among the most common illnesses in the world and the bacterium Salmonella enterica serovar Typhimurium is a leading cause of morbidity and mortality from diarrhea globally. The German cockroach (Blattella germanica) frequently harbors and has been linked to human outbreaks of Salmonella, but the mechanisms of vector-borne transmission are not fully clear. Transmission of S. Typhimurium by cockroaches has been previously described as mechanical. Mechanical transmission is a wholly passive process that involves physical transfer of a pathogen from one location or host to another but lacks bacterial replication in the vector and active bacterial processes that promote vector colonization or transmission. Towards the goal of obtaining novel insight into the mechanisms of S. Typhimurium transmission by cockroaches, here we orally provisioned wild type and mutant strains of the bacteria to adult B. germanica and examined several aspects of colonization and shedding. Our results provide evidence of three previously unappreciated phenomena with significant implications. First, we demonstrate that S. Typhimurium undergoes replication at multiple phases during colonization of the cockroach gut. Second, we show the formation of biofilm-like aggregates by S. Typhimurium in the cockroach foregut. Lastly, we identify two mutant strains of S. Typhimurium that are deficient in colonization and shedding relative to isogenic controls, implicating type III secretion and the formation of fimbriae as two processes that are necessary for interaction with the cockroach vector. Together, our data indicate that transmission of S. Typhimurium by cockroaches is not solely mechanical but may resemble biological transmission by other insect vectors that intake human pathogenic bacteria from infected hosts and are subsequently colonized, enabling active dissemination. Thus, these findings suggest that cockroaches and their control may be more important for infection prevention than is currently appreciated. Additional studies to better understand the cycle and biological mechanisms of vector-borne transmission are warranted.

Evaluation of Reference Genes for Transcriptional Profiling in Two Cockroach Models

The German cockroach, Blattella germanica, and the American cockroach, Periplaneta americana are the most common and synanthropic household pests of interest to public health. While they have increasingly served as model systems in hemimetabolous insects for studying many biological issues, there is still a lack of stable reference gene evaluation for reliable quantitative real-time PCR (qPCR) outputs and functional genomics. Here, we evaluated the expression variation of common insect reference genes, including the historically used actin, across various tissues and developmental stages, and also under experimental treatment conditions in these two species by using three individual algorithms (geNorm, BestKeeper, and NormFinder) and a comprehensive program (RefFinder). RPL32 in B. germanica and EF1α in P. americana showed the overall lowest variation among all examined samples. Based on the stability rankings by RefFinder, the optimal but varied reference genes under specific conditions were selected for qPCR normalization. In addition, the combination of RPL32 and EF1α was recommended for all the tested tissues and stages in B. germanica, whereas the combination of multiple reference genes was unfavorable in P. americana. This study provides a condition-specific resource of reference gene selection for accurate gene expression profiling and facilitating functional genomics in these two important cockroaches.

Effectiveness of Ethyl Formate as a Fumigant of Blattella germanica and Periplaneta americana (Blattodea: Ectobiidae, Blattidae) in Cross-Border Trade Transportation

Simple Summary

Fumigation is one effective cockroach control method. Ethyl formate (EF) has recently been employed as a grain fumigant and has been evaluated as relatively safer than other fumigants. In this experiment, the effects of an ethyl formate fumigant on two species of cockroaches were investigated. Cockroach nymphs and adults had 100% mortality, but the effect on egg hatching inhibition was weak. Therefore, ethyl formate could be used as a fumigant if the control period and its usage should be adjusted considering the developmental stage of the cockroach.

Abstract

Cockroaches cause problems as pests not only locally in residential areas but also internationally, as they can disperse across borders in transport vessels. We investigated the effects of the ethyl formate (EF) fumigant on all developmental stages of Blattella germanica and Periplaneta americana. For B. germanica eggs, the hatching inhibition rate increased directly proportionately with the increasing treatment concentration of EF, but the 100% control was not observed. P. americana eggs did not show any fumigation effect, even after exposure to 60 mg/L of fumigant in a 12 L desiccator. Adults and nymphs of the two species showed various fumigation effects dependent on the concentration in the 12 L desiccator. When EF was applied at the lethal concentration for 99% mortality (LCT₉₉) values of 35 mg/L for 4 h (78.5 mg·h/L) and 60 mg/L for 2 h (70.8 mg·h/L), respectively, adults and nymphs of both species had 100% mortality in a 0.65 m³ fumigation chamber with a 20% loading ratio. However, no significant difference from the control was observed in the egg stage of either species of cockroach. The results of this experiment indicate that EF can be used as a fumigant for cross-border transport vessels if the control period occurs during the cockroach developmental stage and continuous refumigation is performed.

Comparison of Diet Preferences of Laboratory-Reared and Apartment-Collected German Cockroaches

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.

Association of CYP4G19 Expression With Gel Bait Performance in Pyrethroid-Resistant German Cockroaches (Blattodea: Ectobiidae) From Taiwan

Overexpression of a cytochrome P450 gene, CYP4G19, is known to associate with pyrethroid resistance in the German cockroach, Blattella germanica (L.) (Blattodea: Ectobiidae). In this study, we investigated the CYP4G19 expression level in 20 field-collected strains of B. germanica in Taiwan. We also examined the level of adult male susceptibility to imidacloprid, fipronil, indoxacarb, and hydramethylnon using single-diagnostic dose bioassays and their susceptibility to corresponding gel baits to determine how the CYP4G19 expression level influences the cockroach gel bait performance. Results showed that the CYP4G19 gene expression level among the field-collected German cockroach was 1.8- to 9.7-fold higher than that of the susceptible strain. It was negatively correlated (P < 0.05) with the % mortality after treatments with imidacloprid and fipronil diagnostic doses. However, no correlation was found between CYP4G19 gene expression with the % mortality after treatment with indoxacarb and hydramethylnon diagnostic doses. Indoxacarb and hydramethylnon baits showed high efficacy against the field strains with a mean mortality of 97.58 ± 1.35% and 90.95 ±1.65%, respectively. This study provided the first evidence of cross-resistance to imidacloprid and fipronil in pyrethroid-resistant German cockroaches due to overexpression of CYP4G19.

A Review of Alternative Management Tactics Employed for the Control of Various Cockroach Species (Order: Blattodea) in the USA

Simple Summary

Some cockroaches that live within and around human environments are considered pests of public health importance because they can carry and transfer human pathogenic microorganisms to food and food handling surfaces; infestations could result in cockroach allergen-induced allergic sensitization and asthma in sensitized individuals. In addition, cockroaches can cause psychological stress and stigma in people living in infested locations. Historically, cockroach control has been based on the use of insecticide sprays. However, in certain situations, sole dependence on insecticides for cockroach control can lead to issues such as pesticide resistance evolution and raises public concern due to the impact on the environment and human health. To overcome these problems, the use of reduced risk insecticide options (e.g., baits) and their combined use with alternative tactics is recommended. This review aims to examine alternative tactics used for cockroach control, with emphasis on those that are proven to be efficacious, and/or have potential for their incorporation in management programs of important domestic and peridomestic cockroaches in the USA. Remarkable examples of successful cockroach control programs are those that educate the public, promote cleanliness and hygiene, use traps to monitor infestation levels and utilize insecticide baits.

Abstract

Effective control of domestic and peridomestic cockroaches requires integrated approaches that emphasize concurrent use of chemicals with alternative control tactics. An integrated pest management (IPM) approach is particularly justified in environments where satisfactory cockroach control cannot be achieved due to multiple factors including development of insecticide aversion and resistance in some cockroach species, and poor sanitation or structural issues that foster infestations. While a flurry of research effort has been devoted to study alternative tactics for cockroach control, only a few of them have been evaluated in the context of IPM programs. This review focuses on examining studies on alternative tactics that are proven efficacious, economical, and logistically feasible for their inclusion in IPM programs for important domestic and peridomestic cockroaches in the USA. Management programs that educate the public on cockroach biology, behavior, and the importance of sanitation; use of traps to monitor infestation levels; apply targeted low impact insecticides such as baits, have demonstrated a greater success for effective and sustainable control of cockroaches when compared to an insecticide-only approach. Incorporation of other alternative control methods to IPM programs will require more applied research that validates their use in real-world scenarios and demonstrates their cost-effectiveness.

R2 and Non-Site-Specific R2-Like Retrotransposons of the German Cockroach, Blattella germanica

The structural and functional organization of the ribosomal RNA gene cluster and the full-length R2 non-LTR retrotransposon (integrated into a specific site of 28S ribosomal RNA genes) of the German cockroach, Blattella germanica, is described. A partial sequence of the R2 retrotransposon of the cockroach Rhyparobia maderae is also analyzed. The analysis of previously published next-generation sequencing data from the B. germanica genome reveals a new type of retrotransposon closely related to R2 retrotransposons but with a random distribution in the genome. Phylogenetic analysis reveals that these newly described retrotransposons form a separate clade. It is shown that proteins corresponding to the open reading frames of newly described retrotransposons exhibit unequal structural domains. Within these retrotransposons, a recombination event is described. New mechanism of transposition activity is discussed. The essential structural features of R2 retrotransposons are conserved in cockroaches and are typical of previously described R2 retrotransposons. However, the investigation of the number and frequency of 5′-truncated R2 retrotransposon insertion variants in eight B. germanica populations suggests recent mobile element activity. It is shown that the pattern of 5′-truncated R2 retrotransposon copies can be an informative molecular genetic marker for revealing genetic distances between insect populations.

Involvement of integument-rich CYP4G19 in hydrocarbon biosynthesis and cuticular penetration resistance in Blattella germanica (L.)

BACKGROUND

Cuticle penetration plays an important role as a mechanism of insecticide resistance, but the underlying molecular mechanism remains poorly understood. In Blattella germanica, the cytochrome P450 gene, CYP4G19, is overexpressed in a pyrethroid-resistant strain. Here, we investigated whether CYP4G19 is involved in the biosynthesis of hydrocarbons and further contributes to cuticular penetration resistance in B. germanica.

RESULTS

Compared with the susceptible strain, pyrethroid-resistant cockroaches showed lower cuticular permeability with Eosin Y staining. Removal of epicuticular lipids, mainly nonpolar hydrocarbons, with a hexane wash intensified the cuticular permeability and decreased the resistance index of the resistant strain. CYP4G19 was predominately expressed in the abdominal integument and could be upregulated by desiccation stress or short exposure to beta-cypermethrin. Overexpression of CYP4G19 in the resistant strain was positively correlated with a higher level of cuticular hydrocarbons (CHCs). RNAi-mediated knockdown of CYP4G19 significantly decreased its expression and caused a reduction in CHCs. Meanwhile, CYP4G19 suppression resulted in a non-uniform array of the lipid layer, enhanced cuticle permeability, and compromised insecticide tolerance.

CONCLUSION

Our findings confirm that CYP4G19 is involved in hydrocarbon production and appears to contribute to hydrocarbon-based penetration resistance in B. germanica. This study highlights the lipid-based penetration resistance, advancing our understanding of the molecular mechanism underlying P450-mediated cuticular penetration resistance in insects. © 2019 Society of Chemical Industry.

Pervasive Resistance to Pyrethroids in German Cockroaches (Blattodea: Ectobiidae) Related to Lack of Efficacy of Total Release Foggers

Despite limited efficacy data, do-it-yourself (DIY) insecticide products often promise low-cost alternatives to professional pest control. Total release foggers (TRFs, 'bug bombs'), which are prominent DIY products, were recently shown to be ineffective at reducing German cockroach (Blattella germanica L.) infestations, in contrast to highly effective baits. However, the reason(s) for TRF failure remain unknown. Therefore, we investigated insecticide resistance of apartment-collected cockroaches from homes where TRFs failed. In topical (direct) application assays, resistance to cypermethrin (a common active ingredient in TRFs) was 202 ± 33 times that of a laboratory insecticide-susceptible population (based on LD50 ratios), while resistance to fipronil, a common bait active ingredient, was considerably lower at 14 ± 2 times that of the laboratory insecticide-susceptible population. The addition of PBO, a P450 inhibitor that synergizes pyrethroids, enhanced the efficacy of cypermethrin, but only at high doses of cypermethrin. Additionally, >96% of screened cockroaches possessed at least one copy of the L993F mutation in the voltage-gated sodium channel, known to confer resistance to pyrethroids (knockdown resistance, kdr). Because TRF treatments killed insecticide-susceptible sentinel cockroaches but failed to kill apartment-collected cockroaches, these results suggest that pyrethroid resistance is a major factor contributing to the failure of TRFs. Multiple mechanisms of resistance, including metabolic detoxification of the pyrethroids and kdr mutations that confer target-site insensitivity, suggest that TRFs would lack efficacy against German cockroaches in residential settings, where high levels of pyrethroid resistance have been documented globally.

Rapid evolutionary responses to insecticide resistance management interventions by the German cockroach (Blattella germanica L.)

The German cockroach (Blattella germanica L.) is a worldwide pest that lives exclusively in human environments. B. germanica threatens human health by producing asthma-triggering allergens, vectoring pathogenic/antibiotic-resistant microbes, and by contributing to unhealthy indoor environments. While insecticides are essential for reducing cockroach populations and improving health outcomes, insecticide resistance has been a consistent barrier to cockroach control since the 1950s. We conducted seminal field studies to compare three insecticide resistance intervention strategies for cockroaches and evaluated resistance evolution across multiple generations. Using pre-treatment resistance assessment to drive decisions, we found that single active ingredient (AI) treatments can successfully eliminate cockroaches if starting resistance levels are low. We further established that rotation treatments intuitively reduce selection pressure, and are effective when insecticides with no/low resistance are used. We also found that mixture products containing thiamethoxam + λ-cyhalothrin AIs were universally ineffective and highly repellent; and finally, evolution of cross-resistance among AIs is a significant, previously unrealized challenge.

Monomorium ant is a carrier for pathogenic and potentially pathogenic bacteria

Objectives

Household ants are regarded as a major household pest and their close association with microorganisms and people means that they may constitute a disease risk. Our study is the first to provide information on the pathogenicity of Monomorium spp. a common insect in Kuwait by quantifying and identifying the exoskeleton bacterial burden. Samples of Monomorium were collected in June from indoor and outdoor sites of 30 houses located in two residential districts.

Results

The study identified a total of 16 different species of Gram-negative bacteria of which the indoor isolates were 75% greater in species count than the outdoor samples. Indoor isolates identified from both districts were more frequent than the outdoors and similar trends were obtained for a single district. Outdoor ant samples on the other hand carried a high percentage of bacteria but with less diversity in both districts. There was a significant variability in bacterial species in relation to sample sources, indoor and outdoor, and discrete geographical location. The presence of a high percentage of pathogenic and potentially pathogenic bacteria indoor poses a great threat to domestic households, which would be further exacerbated in places with poor standards of hygiene.

A Review on the Insecticide Resistance of Three Species of Cockroaches (Blattodea: Blattidae) in Iran

In Iran, there are four pest domestic species of cockroaches: Periplaneta americana (Linnaeus, Blattodea: Blattidae), Blatta orientalis (Linnaeus, Blattodea: Blattidae), Blattella germanica (Linnaeus, Blattodea: Blattidae), and Supella longipalpa (Fabricius, Blattodea: Blattellidae). The aim of this study was to compile and review studies conducted on insecticide resistance of domestic cockroaches in Iran to assess the current knowledge and gaps. Twenty insecticides were used in susceptibility testing of cockroaches. The bioassay methods varied, and included surface contact (exposure tests), topical applications and feeding studies on baits. Resistance ratio (RR) stated in the reviewed studies showed that B. germanica was resistant (RR > 10) to DDT, permethrin, and cypermethrin, while P. americana and S. longipalpa were categorized as low levels of resistance (RR = 1-2). S. longipalpa is newly reported from houses in some areas of Iran, including Tehran, and there are very few studies on its' biology, ecology and insecticidal resistance. Most studies used adult cockroaches, while the susceptibility status of nymphs was evaluated only in few studies. Use of different test methods and lack of a World Health Organization (WHO) updated procedure, including revised/updated insecticide diagnostic dosages and test kits. The lack of susceptible strains of cockroaches was a major challenge in the assessment of data. A comprehensive national program for monitoring susceptibility of household pests to insecticides in Iran is of great concern and is highly recommended.

Exposure risks and ineffectiveness of total release foggers (TRFs) used for cockroach control in residential settings

Background

The German cockroach, Blattella germanica, is one of the most challenging pests to eradicate from indoor environments. Professional pest control is often prohibitively expensive, prompting low-income residents to turn to over-the-counter consumer products, including total release foggers (TRFs, “bug bombs”). Despite their widespread use, little is known regarding either the associated pesticide exposure risks or the efficacy of TRFs.

Methods

Cockroach-infested homes were recruited into the study. Wipe samples were collected from various surfaces before TRFs were discharged, immediately after, and one month later to determine pesticide exposure risks in 20 homes (divided equally among four different TRF products). Simultaneously, cockroach populations were monitored in all homes to assess the efficacy of TRFs. In parallel, 10 homes were treated with gel baits (divided equally between two bait products), to compare TRFs to a more targeted, low-risk, do-it-yourself intervention strategy.

Results

TRFs failed to reduce cockroach populations, whereas similarly priced gel baits caused significant declines in the cockroach populations. Use of TRFs resulted in significant pesticide deposits throughout the kitchen. Across all products, pesticides, and horizontal kitchen surfaces, pesticide residues following TRF discharge were 603-times (SEM ±184) higher than baseline, with a median increase of 85 times.

Conclusions

The high risks of pesticide exposure associated with TRFs combined with their ineffectiveness in controlling German cockroach infestations call into question their utility in the marketplace, especially because similarly priced and much safer bait products are highly effective in the indoor environment.

Repellency and Laboratory Performance of Selected Insecticides to Field-Collected Insecticide Resistant German Cockroaches (Blattodea: Ectobiidae)

German cockroaches, Blattella germanica (L.) (Blattodea: Ectobiidae), are important indoor insect pests and remain difficult to control because of their ability to develop resistance to insecticides. The toxicity, resistance levels, repellency, and performance index (PI) value of five formulated insecticides (permethrin, chlorpyrifos, propoxur, imidacloprid, and fipronil) were determined for adult males of seven strains of the German cockroach: a laboratory-reared susceptible strain (S) and six field-collected strains (B, D, E, G, H, and I). Propoxur was generally the most toxic insecticide to all strains using continuous exposure methods; however, using Ebeling choice box methods, chlorpyrifos, and fipronil were most toxic. In both continuous exposure and Ebeling choice box tests, the field-collected strains were generally most resistant to permethrin among the five insecticides. The greatest increase in resistance ratios between the two exposure methods was for permethrin and propoxur. Permethrin was the most repellent insecticide against all but two strains (D and H). PI values reached 100 (no repellency and complete mortality) for the susceptible strain against only chlorpyrifos and fipronil. Only fipronil resulted in a PI value of 100 for any of the field-collected strains. Continuous exposure and Ebeling choice box resistance ratios were correlated, and both were correlated with previously reported resistance ratios (based on LD50 values). Choice box repellency, however, was only correlated with LD50 resistance ratios. PIMax was negatively correlated with all measures of resistance ratios.

Overlapping Community Compositions of Gut and Fecal Microbiomes in Lab-Reared and Field-Collected German Cockroaches

German cockroaches, Blattella germanica (Blattodea: Ectobiidae), are human commensals that move freely between food and waste, disseminating bacteria, including potential pathogens, through their feces. However, the relationship between the microbial communities of the cockroach gut and feces is poorly understood. We analyzed the V4 region of the 16S rRNA gene and the V9 region of the 18S rRNA gene by next-generation sequencing (NGS) to compare the bacterial and protist diversities in guts versus feces and males versus females, as well as assess variation across cockroach populations. Cockroaches harbored a diverse array of bacteria, and 80 to 90% of the operational taxonomic units (OTUs) were shared between the feces and gut. Lab-reared and field-collected cockroaches had distinct microbiota, and whereas lab-reared cockroaches had relatively conserved communities, considerable variation was observed in the microbial community composition of cockroaches collected in different apartments. Nonetheless, cockroaches from all locations shared some core bacterial taxa. The eukaryotic community in the feces of field-collected cockroaches was found to be more diverse than that in lab-reared cockroaches. These results demonstrate that cockroaches disseminate their gut microbiome in their feces, and they underscore the important contribution of the cockroach fecal microbiome to the microbial diversity of cockroach-infested homes.IMPORTANCE The German cockroach infests diverse human-built structures, including homes and hospitals. It produces potent allergens that trigger asthma and disseminates opportunistic pathogens in its feces. A comprehensive understanding of gut and fecal microbial communities of cockroaches is essential not only to understand their contribution to the biology of the cockroach, but also for exploring their clinical relevance. In this study, we compare the diversity of bacteria and eukaryotes in the cockroach gut and feces and assess the variation in the gut microbiota across cockroach populations.

Oral edible plant vaccine containing hypoallergen of American cockroach major allergen Per a 2 prevents roach-allergic asthma in a murine model

Background

American cockroaches (Periplaneta americana) are an important indoor allergen source and a major risk factor for exacerbations and poor control of asthma. We previously reported that allergen components from American cockroaches exhibit varying levels of pathogenicity. Sensitization to major American cockroach allergen, Per a 2, correlated with more severe clinical phenotypes among patients with allergic airway diseases.

Materials and methods

In this study, we examined whether oral plant vaccine-encoding full-length Per a 2 clone-996 or its hypoallergenic clone-372 could exert a prophylactic role in Per a 2-sensitized mice. The cDNAs coding Per a 2–996 and Per a 2–372 were inserted into TuMV vector and expressed in Chinese cabbage. Adult female BALB/c mice were fed with the cabbage extracts for 21 days and subsequently underwent two-step sensitization with recombinant Per a 2.

Results

Per a 2-specific IgE measured by in-house ELISA in the sera of Per a 2-372-treated groups were significantly lower than in the control groups after allergen challenge but not the Per a 2-996-treated group. Moreover, Per a 2–372 vaccine markedly decreased airway hyper-responsiveness and infiltration of inflammatory cells into the lungs, as well as reduced mRNA expression of IL-4 and IL-13 in comparison with the control mice.

Conclusion

Our data suggest that oral administration of edible plant vaccine encoding Per a 2 hypo-allergen may be used as a prophylactic strategy against the development of cockroach allergy.

Enormous expansion of the chemosensory gene repertoire in the omnivorous German cockroach Blattella germanica

The acquisition of genome sequences from a wide range of insects and other arthropods has revealed a broad positive correlation between the complexity of their chemical ecology and the size of their chemosensory gene repertoire. The German cockroach Blattella germanica is an extreme omnivore and has the largest chemosensory gene repertoire known for an arthropod, exceeding even the highly polyphagous spider mite Tetranychus urticae. While the Odorant Receptor family is not particularly large, with 123 genes potentially encoding 134 receptors (105 intact), the Gustatory Receptor family is greatly expanded to 431 genes potentially encoding 545 receptors (483 intact), the largest known for insects and second only to the spider mite. The Ionotropic Receptor family of olfactory and gustatory receptors is vastly expanded to at least 897 genes (604 intact), the largest size known in arthropods, far surpassing the 150 known from the dampwood termite Zootermopsis nevadensis. Commensurately, the Odorant Binding Protein family is expanded to the largest known for insects at 109 genes (all intact). Comparison with the far more specialized, but phylogenetically related termite, within the Dictyoptera, reveals considerable gene losses from the termite, and massive species-specific gene expansions in the cockroach. The cockroach has lost function of 11%-41% of these three chemoreceptor gene families to pseudogenization, and most of these are young events, implying rapid turnover of genes along with these major expansions, presumably in response to changes in its chemical ecology.

Histamine as an emergent indoor contaminant: Accumulation and persistence in bed bug infested homes

Histamine is used in bronchial and dermal provocation, but it is rarely considered an environmental risk factor in allergic disease. Because bed bugs defecate large amounts of histamine as a component of their aggregation pheromone, we sought to determine if histamine accumulates in household dust in bed bug infested homes, and the effects of bed bug eradication with spatial heat on histamine levels in dust. We collected dust in homes and analyzed for histamine before, and up to three months after bed bug eradication. Histamine levels in bed bug infested homes were remarkably high (mean = 54.6±18.9 μg/100 mg of sieved household dust) and significantly higher than in control homes not infested with bed bugs (mean < 2.5±1.9 μg/100 mg of sieved household dust). Heat treatments that eradicated the bed bug infestations failed to reduce histamine levels, even three months after treatment. We report a clear association between histamine levels in household dust and bed bug infestations. The high concentrations, persistence, and proximity to humans during sleep suggest that bed bug-produced histamine may represent an emergent contaminant and pose a serious health risk in the indoor environment.

Repellency of zerumbone identified in Cyperus rotundus rhizome and other constituents to Blattella germanica

The compounds 1,8-cineole and zerumbone (ZER) from the Cyperus rotundus rhizome along with another 11 previously identified rhizome essential oil constituents and α-humulene, which lacks the only carbonyl group present in ZER, as well as binary mixtures of ZER and seven active compounds were tested for repellency to male B. germanica. The results were compared to N,N-diethyl-3-methylbenzamide (deet). In filter-paper choice tests, ZER was the most repellent compound, and α-humulene was ineffective, which indicates that the α,β-unsaturated carbonyl group of ZER is a prerequisite component for repellency. At 81.5 μg cm⁻², enhanced repellency was produced by binary mixtures of ZER and 1,8-cineole, (+)-dihydrocarvone or (R)-(+)-limonene (70:30, 50:50 and 30:70 ratios by weight). These mixtures were very effective against male B. germanica within 24 h and were more repellent than a single compound or deet alone. The optimum ZER content was determined to be more than 50%. In Ebeling choice box tests at 652.4 μg cm⁻², these compounds and deet resulted in complete repellency to intact male B. germanica, while they exhibited 35–47% repellency to antennectomized male one. Mixtures formulated from the active constituents of the C. rotundus rhizome could be useful as potential repellents for controlling B. germanica.

Cross-reaction between Formosan termite (Coptotermes formosanus) proteins and cockroach allergens

Cockroach allergens can lead to serious allergy and asthma symptoms. Termites are evolutionarily related to cockroaches, cohabitate in human dwellings, and represent an increasing pest problem in the United States. The Formosan subterranean termite (Coptotermes formosanus) is one of the most common species in the southern United States. Several assays were used to determine if C. formosanus termite proteins cross-react with cockroach allergens. Expressed sequence tag and genomic sequencing results were searched for homology to cockroach allergens using BLAST 2.2.21 software. Whole termite extracts were analyzed by mass-spectrometry, immunoassay with IgG and scFv antibodies to cockroach allergens, and human IgE from serum samples of cockroach allergic patients. Expressed sequence tag and genomic sequencing results indicate greater than 60% similarity between predicted termite proteins and German and American cockroach allergens, including Bla g 2/Per a 2, Bla g 3/Per a 3, Bla g 5, Bla g 6/Per a 6, Bla g 7/Per a 7, Bla g 8, Per a 9, and Per a 10. Peptides from whole termite extract were matched to those of the tropomyosin (Bla g 7), arginine kinase (Per a 9), and myosin (Bla g 8) cockroach allergens by mass-spectrometry. Immunoblot and ELISA testing revealed cross-reaction between several proteins with IgG and IgE antibodies to cockroach allergens. Several termite proteins, including the hemocyanin and tropomyosin orthologs of Blag 3 and Bla g 7, were shown to crossreact with cockroach allergens. This work presents support for the hypothesis that termite proteins may act as allergens and the findings could be applied to future allergen characterization, epitope analysis, and clinical studies.

Insecticide Resistance of Several Field-Collected German Cockroach (Dictyoptera: Blattellidae) Strains

German cockroaches, Blattella germanica (L.), remain one of the most difficult indoor insect species to control because of its ability to develop resistance to insecticides. The toxicity and resistance levels of five technical-grade insecticides (permethrin, chlorpyrifos, propoxur, imidacloprid, and fipronil) were determined for adult males of seven strains of the German cockroach, a laboratory-reared susceptible strain (S) and six field-collected strains (B, D, E, G, H, and I). Using topical application methods, fipronil was the most toxic insecticide to all seven strains. The LD50 values of fipronil in the susceptible strain (S) and the field-collected strains B, D, E, G, H, and I were 1.33, 2.62, 11.53, 5.07, 7.66, 5.15, and 10.15 ng/insect, respectively. The field-collected strains were most resistant to permethrin among the five insecticides, except for strain H. The resistance ratios of strains B, D, E, G, and I to permethrin were 31.8, 37.3, 51.9, 34.9, and 37.5, respectively. With a resistance ratio of 6.4, the field-collected strain H was most resistant to chlorpyrifos. The field-collected strains were not significantly resistant to propoxur. Strains B, H, and I were not significantly resistant to imidacloprid when compared with the susceptible strain. Based on the different resistance ratios for each insecticide, we conclude that there are high rates of insecticide resistance in German cockroaches from Franklin County, NC, and that the field-collected strains most likely had different treatment histories.

Analysis of 10 Environmental Allergen Components of the American Cockroach in Taiwan

BACKGROUND

Cockroaches are important sources of indoor airborne allergens. The American cockroach (Periplaneta americana) is the second leading inhalant allergen causing allergic airway diseases in Taiwan. We previously reported a difference in pathogenicity of different allergen components from American cockroaches.

OBJECTIVE

To analyze the environmental profile of American cockroach allergen components.

METHODS

Polyclonal antibodies were generated to recombinant American cockroach allergens, Per a 1 through Per a 10. The levels of each allergen in (1) whole-body extracts and feces from American cockroaches and in (2) fresh-frozen 6-month-old and 12-month-old dead American cockroaches were evaluated by immunoblotting and quantified. Levels of allergen components from patients' household dust samples were determined by competition enzyme-linked immunosorbent assay.

RESULTS

Per a 1, 2, and 10 proteins were present predominantly in roach feces, whereas other allergen components were found predominantly in roach bodies. There was a time-dependent decrease in total levels of some allergen proteins. Although levels of Per a 4, 5, 6, and 9 significantly decreased to less 20% of the basal level, there was no significant change in levels of Per a 2, 7, and 10 after 1-year decomposition. The most abundant allergen components in 20 dust samples from patients' houses were Per a 9, Per a 10, and Per a 2.

CONCLUSION

The concentration of 10 American cockroach allergen components differed in the environment. Per a 2 and Per a 10 can be used as markers of long-term environmental cockroach control and Per a 9 as current status of control in patients' houses.

Diet quality affects bait performance in German cockroaches (Dictyoptera: Blattellidae)

BACKGROUND

Bait formulations are widely used to control German cockroach (Blattella germanica) populations. To perform optimally, these formulations must compete favorably with non-toxic alternative foods present within the insect's habitat. We hypothesized that the nutritional history of cockroaches and their acceptance or avoidance of glucose would affect their food preference and thus bait efficacy. To test this hypothesis, we conducted a controlled laboratory experiment, first providing glucose-accepting and glucose-averse cockroaches nutritionally defined diets and then offering them identical diets containing the insecticide hydramethylnon as a bait proxy to evaluate the effect of diets of differing macronutrient composition on bait performance.

RESULTS

The interaction between diet composition and bait composition affected the survival of adult males as well as first-instar nymphs exposed to excretions produced by these males. Survival analyses indicated different responses of glucose-averse and glucose-accepting insects, but generally any combination of diet and bait that resulted in high diet intake and low bait intake reduced secondary kill.

CONCLUSIONS

This study represents a comprehensive examination of the effect of alternative foods on bait efficacy. We suggest that disparities between the nutritional quality of baits and the foods that are naturally available could profoundly impact the management of German cockroach infestations. © 2016 Society of Chemical Industry.

Evaluation of sublethal effects of polymer-based essential oils nanoformulation on the german cockroach

The German cockroach, Blattella germanica (L.), is a serious household and public health pest worldwide. The aim of the present study was to evaluate the sublethal activity of polymer-based essential oils (EOs) nanoparticles (NPs) on adults of B. germanica. The LC50 and LC25 for contact toxicity were determined. To evaluate the repellency of EOs and NPs at LC25, a software was specially created in order to track multiple insects on just-recorded videos, and generate statistics using the obtained information. The effects of EOs and NPs at LC25 and LC50 on the nutritional physiology were also evaluated. The results showed that NPs exerted sublethal effects on the German cockroach, since these products enhance the repellent effects of the EOs and negatively affected the nutritional indices and the feeding deterrence index.

INVESTIGATION OF BACTERIOLOGICAL INFECTIONS OF THE AMERICAN COCKROACHES IN PAVEH CITY, KERMANSHAH PROVINCE

Introduction:

American cockroaches, Periplaneta americana, are the most important pests in hospitals and dwelling environments. They are mechanical vectors of some bacterial pathogens.

Goal:

The present investigation was carried out in Ghods hospital and 5 dwelling localities of Paveh city to evaluate bacterial infestations of American cockroaches in this region of Iran.

Methods:

The samples were randomly collected from hospital environments and toilets and kitchens of the dwelling localities from December-March 2012 and July-September 2013. The samples were captured using sterile test tubes and sterile hand gloves.

Results:

Totally, 98 cockroaches were collected from hospital (45.9%) and dwelling (54.1%) environments. Eight groups of bacteria including: Pseudomonas spp., Proteus spp., Klebsiella spp., Staphylococcus spp., Bacillus spp., Serratia spp., Entrobacter spp. and Escherichia coli were extracted.

Conclusions:

The findings of the present study revealed that the American cockroaches are very important in transmission of some bacterial pathogens, so health education and using the effective control methods to elimination and reduction of cockroaches are necessary.

Associations of Early Life Exposures and Environmental Factors With Asthma Among Children in Rural and Urban Areas of Guangdong, China

BACKGROUND

Environmental factors may play important roles in asthma, but findings have been inconsistent.

OBJECTIVE

The goal of this study was to determine the associations between early life exposures, environmental factors, and asthma in urban and rural children in southeast China.

METHODS

A screening questionnaire survey was conducted in 7,164 children from urban Guangzhou and 6,087 from rural Conghua. In the second stage, subsamples of 854 children (419 from Guangzhou, 435 from Conghua) were recruited for a case-control study that included a detailed questionnaire enquiring on family history, early life environmental exposures, dietary habits, and laboratory tests (including histamine airway provocation testing, skin prick tests, and serum antibody analyses). House dust samples from 76 Guangzhou families and 80 Conghua families were obtained to analyze levels of endotoxins, house dust mites, and cockroach allergens.

RESULTS

According to the screening survey, the prevalence of physician-diagnosed asthma was lower in children from Conghua (3.4%) than in those from Guangzhou (6.9%) (P < .001). A lower percentage of asthma was reported in rural subjects compared with urban subjects (2.8% vs. 29.4%; P < .001) in the case-control study. Atopy (OR, 1.91 [95% CI, 1.58-2.29]), parental atopy (OR, 2.49 [95% CI, 1.55-4.01]), hospitalization before 3 years of age (OR, 2.54 [95% CI, 1.37-4.70]), high consumption of milk products (OR, 1.68 [95% CI, 1.03-2.73]), and dust Dermatophagoides farinae group 1 allergen (OR, 1.71 [95% CI, 1.34-2.19]) were positively associated with asthma. Living in a crop-farming family at < 1 year of age (OR, 0.15 [95% CI, 0.08-0.32]) and dust endotoxin levels (OR, 0.69 [95% CI, 0.50-0.95]) were negatively associated with asthma.

CONCLUSIONS

Rural children from an agricultural background exhibited a reduced risk of asthma. Early life exposure to crop farming and high environmental endotoxin levels might protect the children from asthma in southern China.

Gut bacteria mediate aggregation in the German cockroach

Aggregation of the German cockroach, Blattella germanica, is regulated by fecal aggregation agents (pheromones), including volatile carboxylic acids (VCAs). We demonstrate that the gut microbial community contributes to production of these semiochemicals. Chemical analysis of the fecal extract of B. germanica revealed 40 VCAs. Feces from axenic cockroaches (no microorganisms in the alimentary tract) lacked 12 major fecal VCAs, and 24 of the remaining compounds were represented at extremely low amounts. Olfactory and aggregation bioassays demonstrated that nymphs strongly preferred the extract of control feces over the fecal extract of axenic cockroaches. Additionally, nymphs preferred a synthetic blend of 6 fecal VCAs over a solvent control or a previously identified VCA blend. To test whether gut bacteria contribute to the production of fecal aggregation agents, fecal aerobic bacteria were cultured, isolated, and identified. Inoculation of axenic cockroaches with individual bacterial taxa significantly rescued the aggregation response to the fecal extract, and inoculation with a mix of six bacterial isolates was more effective than with single isolates. The results indicate that the commensal gut microbiota contributes to production of VCAs that act as fecal aggregation agents and that cockroaches discriminate among the complex odors that emanate from a diverse microbial community. Our results highlight the pivotal role of gut bacteria in mediating insect-insect communication. Moreover, because the gut microbial community reflects the local environment, local plasticity in fecal aggregation pheromones enables colony-specific odors and fidelity to persistent aggregation sites.

Toxicity of hiba oil constituents and spray formulations to American house dust mites and copra mites

BACKGROUND

Dermatophagoides farinae and Tyrophagus putrescentiae are recognised as an important source of allergens. An assessment was made of the toxicity of hiba, Thujopsis dolabrata var. hondai, oil and 13 organic compounds and the control efficacy of four experimental spray formulations containing the oil (5-30 g L(-1) spray) against both mite species.

RESULTS

In a contact + fumigant mortality bioassay, (-)-thujopsene was the most toxic constituent against D. farinae and T. putrescentiae (24 h LC50 9.82 and 10.92 µg cm(-2)), and the toxicity of the compound was nearly identical to that of benzyl benzoate (9.33 and 10.14 µg cm(-2)). The toxicity was more pronounced in carvacrol, (+)-terpinen-4-ol, β-thujaplicin, (-)-terpinen-4-ol, cedrol and α-terpineol (LC50 12.05-15.20 and 12.74-16.48 µg cm(-2)) than in N,N-diethyl-3-methylbenzamide (LC50 35.53 and 38.42 µg cm(-2)) against both mite species. The hiba oil 30 g L(-1) spray and commercial permethrin (cis:trans 25:75) 2.5 g L(-1) spray treatment resulted in 100 and 11% mortality against the two mite species respectively. In vapour-phase mortality tests, the two compounds were consistently more toxic in closed versus open containers, indicating that toxicity was achieved mainly through the action of vapour.

CONCLUSION

Reasonable mite control in indoor environments can be achieved by a spray formulation containing the 30 g L(-1) hiba oil as a potential contact-action fumigant.