Body Lice Research Articles

SNPs in Entire Mitochondrial Genome Sequences (≈15.4 kb) and cox1 Sequences (≈486 bp) Resolve Body and Head Lice From Doubly Infected People From Ethiopia, China, Nepal, and Iran But Not France.

Some people host lice on the clothing as well as the head. Whether body lice and head lice are distinct species or merely variants of the same species remains contentious. We sought to ascertain the extent to which lice from these different habitats might interbreed on doubly infected people by comparing their entire mitochondrial genome sequences. Toward this end, we analyzed two sets of published genetic data from double-infections of body lice and head lice: 1) entire mitochondrial coding regions (≈15.4 kb) from body lice and head lice from seven doubly infected people from Ethiopia, China, and France; and 2) part of the cox1 gene (≈486 bp) from body lice and head lice from a further nine doubly infected people from China, Nepal, and Iran. These mitochondrial data, from 65 lice, revealed extraordinary variation in the number of single nucleotide polymorphisms between the individual body lice and individual head lice of double-infections: from 1.096 kb of 15.4 kb (7.6%) to 2 bps of 15.4 kb (0.01%). We detected coinfections of lice of Clades A and C on the scalp hair of three of the eight people from Nepal: one person of the two people from Kathmandu and two of the six people from Pokhara. Lice of Clades A and B coinfected the scalp hair of one person from Atherton, Far North Queensland, Australia. These findings argue for additional large-scale studies of the body lice and head lice of double-infected people.

Genome sequence of Candidatus Riesia pediculischaeffi, endosymbiont of chimpanzee lice, and genomic comparison of recently acquired endosymbionts from human and chimpanzee lice.

The obligate-heritable endosymbionts of insects possess some of the smallest known bacterial genomes. This is likely due to loss of genomic material during symbiosis. The mode and rate of this erosion may change over evolutionary time: faster in newly formed associations and slower in long-established ones. The endosymbionts of human and anthropoid primate lice present a unique opportunity to study genome erosion in newly established (or young) symbionts. This is because we have a detailed phylogenetic history of these endosymbionts with divergence dates for closely related species. This allows for genome evolution to be studied in detail and rates of change to be estimated in a phylogenetic framework. Here, we sequenced the genome of the chimpanzee louse endosymbiont (Candidatus Riesia pediculischaeffi) and compared it with the closely related genome of the human body louse endosymbiont. From this comparison, we found evidence for recent genome erosion leading to gene loss in these endosymbionts. Although gene loss was detected, it was not significantly greater than in older endosymbionts from aphids and ants. Additionally, we searched for genes associated with B-vitamin synthesis in the two louse endosymbiont genomes because these endosymbionts are believed to synthesize essential B vitamins absent in the louse’s diet. All of the expected genes were present, except those involved in thiamin synthesis. We failed to find genes encoding for proteins involved in the biosynthesis of thiamin or any complete exogenous means of salvaging thiamin, suggesting there is an undescribed mechanism for the salvage of thiamin. Finally, genes encoding for the pantothenate de novo biosynthesis pathway were located on a plasmid in both taxa along with a heat shock protein. Movement of these genes onto a plasmid may be functionally and evolutionarily significant, potentially increasing production and guarding against the deleterious effects of mutation. These data add to a growing resource of obligate endosymbiont genomes and to our understanding of the rate and mode of genome erosion in obligate animal-associated bacteria. Ultimately sequencing additional louse p-endosymbiont genomes will provide a model system for studying genome evolution in obligate host associated bacteria.

Risk factors for human lice and bartonellosis among the homeless, San Francisco, California, USA.

Homeless persons in San Francisco, California, USA,have been shown to have head and body lice infestations and Bartonella quintana infections. We surveyed a self selected population of homeless persons in San Francisco to assess infestations of head and body lice, risks of having body lice, and presence of B. quintana in lice. A total of 203 persons who reported itching were surveyed during 2008-2010 and 2012: 60 (30%) had body lice, 10 (4.9%)had head lice, and 6 (3.0%) had both. B. quintana was detected in 10 (15.9%) of 63 body lice pools and in 6 (37.5%)of 16 head lice pools. Variables significantly associated(p<0.05) with having body lice in this homeless population included male sex, African-American ethnicity, and sleeping outdoors. Our study findings suggest that specific segments of the homeless population would benefit from information on preventing body lice infestations and louse borne diseases.

Perinatal exposure of mice to the pesticide DDT impairs energy expenditure and metabolism in adult female offspring.

Dichlorodiphenyltrichloroethane (DDT) has been used extensively to control malaria, typhus, body lice and bubonic plague worldwide, until countries began restricting its use in the 1970s. Its use in malaria control continues in some countries according to recommendation by the World Health Organization. Individuals exposed to elevated levels of DDT and its metabolite dichlorodiphenyldichloroethylene (DDE) have an increased prevalence of diabetes and insulin resistance. Here we hypothesize that perinatal exposure to DDT disrupts metabolic programming leading to impaired metabolism in adult offspring. To test this, we administered DDT to C57BL/6J mice from gestational day 11.5 to postnatal day 5 and studied their metabolic phenotype at several ages up to nine months. Perinatal DDT exposure reduced core body temperature, impaired cold tolerance, decreased energy expenditure, and produced a transient early-life increase in body fat in female offspring. When challenged with a high fat diet for 12 weeks in adulthood, female offspring perinatally exposed to DDT developed glucose intolerance, hyperinsulinemia, dyslipidemia, and altered bile acid metabolism. Perinatal DDT exposure combined with high fat feeding in adulthood further impaired thermogenesis as evidenced by reductions in core temperature and in the expression of numerous RNA that promote thermogenesis and substrate utilization in the brown adipose tissue of adult female mice. These observations suggest that perinatal DDT exposure impairs thermogenesis and the metabolism of carbohydrates and lipids which may increase susceptibility to the metabolic syndrome in adult female offspring.

The Sucking Lice (Phthiraptera: Anoplura) of Georgia, USA: Hosts, Geographical Distributions, and Medical/Veterinary Importance

Abstract Twenty-five species of sucking lice (Phthiraptera: Anoplura) are recorded from Georgia, USA. One of these species is currently recognized as 2 distinct subspecies, the body louse (Pediculus humanus humanus L.) and head louse (Pediculus humanus capitis De Geer) of humans. Gray squirrels, southern flying squirrels, humans, and domestic cattle are parasitized by relatively rich faunas of sucking lice in Georgia with 3 characteristic species/subspecies recorded from each of these hosts within the state. Despite some previously published erroneous host-louse records, most species of sucking lice are host specific in Georgia. Sucking lice have been recorded from domestic hogs, cattle, equines, goats, and dogs in Georgia, and some of these lice can cause veterinary problems. The head louse is common in Georgia, especially in school children. The crab/pubic louse [Pthirus pubis (L.)] also appears to be widespread in the state. We report only one verified record of the body louse from Georgia, but we susp...

Identification and comparative analysis of G protein-coupled receptors in Pediculus humanus humanus

The body louse has the smallest genome size among the known genome-sequenced insects. Here, 81 GPCRs were identified in Pediculus humanus humanus, 56, 14, 6 and 5 GPCRs for family-A, -B, -C and -D, respectively. These GPCRs constitute the comparable repertoire of GPCRs with other insects. Moreover, it contains a more complete set of neuropeptide and protein hormone receptors not even than Acyrthosiphon pisum but also Drosophila melanogaster, for example, Sulfakinin, Corazonin, Trissin and PTHRL only presented in P. h. humanus but lost either in A. pisum or D. melanogaster. However, it has less duplication among the sub-families. Meanwhile, ACP, AVPL, HE6 receptors and Boss were also absent from P. h. humanus. These results indicated that the repertoire of GPCRs in P. h. humanus were not affected by its smallest genome size, and further suggested that P. h. humanus has a relatively original and concise GPCR regulation system.

Detection of Bartonella quintana in African body and head lice.

Currently, the body louse is the only recognized vector of Bartonella quintana, an organism that causes trench fever. In this work, we investigated the prevalence of this bacterium in human lice in different African countries. We tested 616 head lice and 424 body lice from nine African countries using real-time polymerase chain reaction targeting intergenic spacer region 2 and specific B. quintana genes. Overall, B. quintana DNA was found in 54% and 2% of body and head lice, respectively. Our results also show that there are more body lice positive for B. quintana in poor countries, which was determined by the gross domestic product, than in wealthy areas (228/403 versus 0/21, P < 0.001). A similar finding was obtained for head lice (8/226 versus 2/390, P = 0.007). Our findings suggest that head lice in Africa may be infected by B. quintana when patients live in poor economic conditions and are also exposed to body lice.

Evaluation of the genotoxicity of the pyrethroid insecticide phenothrin

Phenothrin, a synthetic pyrethroid compound, is widely used to control agricultural and household insects, as well as to eliminate human louse infestation. Toxicity studies on the direct DNA-damaging effect of phenothrin are lacking. We therefore investigated whether phenothrin exposure can lead to increased DNA damage in vitro in human peripheral blood lymphocytes and in human hepatocytes. Genotoxicity was evaluated by means of the comet assay modified with formamidopyrimidine DNA-glycosylase post-treatment for the detection of oxidative base-damage in DNA. We also assessed the cytotoxic potential of this compound by use of combined fluorescence viability staining. Our results show that phenothrin induces statistically significant, dose-dependent DNA damage in the absence of marked cytotoxicity at concentrations higher than 20μM and 50μM in human blood peripheral lymphocytes and hepatocytes, respectively. Oxidative DNA damage could also be detected in the two cell types, although this did not reach statistical significance. These findings provide evidence of the DNA-damaging potential of phenothrin and call for additional studies to reveal the genotoxic properties of this pyrethroid. The observations also point at the importance of using caution when considering the use of phenothrin.

Drought and Epidemic Typhus, Central Mexico, 1655–1918

Epidemic typhus is an infectious disease caused by the bacterium Rickettsia prowazekii and transmitted by body lice (Pediculus humanus corporis). This disease occurs where conditions are crowded and unsanitary. This disease accompanied war, famine, and poverty for centuries. Historical and proxy climate data indicate that drought was a major factor in the development of typhus epidemics in Mexico during 1655–1918. Evidence was found for 22 large typhus epidemics in central Mexico, and tree-ring chronologies were used to reconstruct moisture levels over central Mexico for the past 500 years. Below-average tree growth, reconstructed drought, and low crop yields occurred during 19 of these 22 typhus epidemics. Historical documents describe how drought created large numbers of environmental refugees that fled the famine-stricken countryside for food relief in towns. These refugees often ended up in improvised shelters in which crowding encouraged conditions necessary for spread of typhus.

Effect of Permethrin–Impregnated Underwear on Body Lice in Sheltered Homeless Persons

The control of body lice in homeless persons remains a challenge. To determine whether the use of long-lasting insecticide-treated underwear provides effective long-term protection against body lice in homeless persons. A randomized, double-blind, placebo-controlled trial was conducted in February and December 2011 in 2 homeless shelters (Madrague Ville and Forbin) in Marseille, France. Of the 125 homeless persons screened for eligibility, 73 body lice-infested homeless persons, 18 years or older, were enrolled. Body lice-infested homeless persons were randomly assigned to receive 0.4% permethrin-impregnated underwear or an identical-appearing placebo for 45 days, in a 1:1 ratio, with a permuted block size of 10. Visits were scheduled at days 14 and 45. Data regarding the presence or absence of live body lice were collected. The primary and secondary end points were the proportions of homeless persons free of body lice on days 14 and 45, respectively. Mutations associated with permethrin resistance in the body lice were also identified. Significantly more homeless persons receiving permethrin-impregnated underwear than homeless persons receiving the placebo were free of body lice on day 14 in the intent-to-treat population (28% vs 9%; P = .04), with a between-group difference of 18.4 percentage points (95% CI, 1.4-35.4), and in the per-protocol population (34% vs 11%; P = .03), with a between-group difference of 23.7 percentage points (95% CI, 3.6-43.7). This difference was not sustained on day 45. At baseline, the prevalence of the permethrin-resistant haplotype was 51% in the permethrin group and 44% in the placebo group. On day 45, the permethrin-resistant haplotype was significantly more frequent in the permethrin group than in the placebo group (73% vs 45%, P < .001). Permethrin-impregnated underwear is more efficient than placebo at eliminating body louse infestations by day 14; however, this difference was not sustained on day 45. The use of permethrin may have increased the resistance to permethrin in body lice and thus must be avoided. clinicaltrials.gov Identifier: NCT01287663.

Comparative bioinformatics, temporal and spatial expression analyses of Ixodes scapularis organic anion transporting polypeptides

Organic anion-transporting polypeptides (Oatps) are an integral part of the detoxification mechanism in vertebrates and invertebrates. These cell surface proteins are involved in mediating the sodium-independent uptake and/or distribution of a broad array of organic amphipathic compounds and xenobiotic drugs. This study describes bioinformatics and biological characterization of 9 Oatp sequences in the Ixodes scapularis genome. These sequences have been annotated on the basis of 12 transmembrane domains, consensus motif D-X-RW-(I,V)-GAWW-X-G-(F,L)-L, and 11 conserved cysteine amino acid residues in the large extracellular loop 5 that characterize the Oatp superfamily. Ixodes scapularis Oatps may regulate non-redundant cross-tick species conserved functions in that they did not cluster as a monolithic group on the phylogeny tree and that they have orthologs in other ticks. Phylogeny clustering patterns also suggest that some tick Oatp sequences transport substrates that are similar to those of body louse, mosquito, eye worm, and filarial worm Oatps. Semi-quantitative RT-PCR analysis demonstrated that all 9 I. scapularis Oatp sequences were expressed during tick feeding. Ixodes scapularis Oatp genes potentially regulate functions during early and/or late-stage tick feeding as revealed by normalized mRNA profiles. Normalized transcript abundance indicates that I. scapularis Oatp genes are strongly expressed in unfed ticks during the first 24h of feeding and/or at the end of the tick feeding process. Except for 2 I. scapularis Oatps, which were expressed in the salivary glands and ovaries, all other genes were expressed in all tested organs, suggesting the significance of I. scapularis Oatps in maintaining tick homeostasis. Different I. scapularis Oatp mRNA expression patterns were detected and discussed with reference to different physiological states of unfed and feeding ticks.

A comparison of deterministic and stochastic models for predicting the impacts of different sheep body lice (Bovicola ovis) management practices

A deterministic model for predicting the prevalence of lice in sheep flocks was compared with a stochastic model. The stochastic model was based on data from 100 000 simulated farms and encompassed: a range of lice detection levels at shearing, whether or not treatment was applied where no lice were detected, the efficacy of treatments used, and the adequacy of quarantine measures against entering sheep. The deterministic model generated more extreme estimates of the effects of lice management changes, and was judged unsatisfactory for long-term decision making. Predictions based on the stochastic model were consistent with reported survey values, suggesting the stochastic model could be used to predict benefits and costs associated with changes in louse-control methods. According to the stochastic model, the two factors that could provide the greatest reduction in dollar costs were improvement of quarantine by limiting the incidence of lice entering the flock, and improvement of eradication methods. The deterministic model suggested that there would be large benefits from improvement in detection, but the stochastic model only found small dollar benefits with improved detection in the absence of changes such as more effective treatments. Changing the proportion of flocks that were treated when no lice were detected had little effect on the predicted incidence of lousy flocks.

Differential gene expression in laboratory strains of human head and body lice when challenged with Bartonella quintana, a pathogenic bacterium

Human head and body lice are obligatory hematophagous ectoparasites that belong to a single species, Pediculus humanus. Only body lice, however, are vectors of the infectious Gram-negative bacterium Bartonella quintana. Because of their near identical genomes, yet differential vector competence, head and body lice provide a unique model system to study the gain or loss of vector competence. Using our in vitro louse-rearing system, we infected head and body lice with blood containing B. quintana in order to detect both differences in the proliferation of B. quintana and transcriptional differences of immune-related genes in the lice. B. quintana proliferated rapidly in body lice at 6 days post-infection, but plateaued in head lice at 4 days post-infection. RNAseq and quantitative real-time PCR validation analyses determined gene expression differences. Eight immunoresponse genes were observed to be significantly different with many associated with the Toll pathway: Fibrinogen-like protein, Spaetzle, Defensin 1, Serpin, Scavenger receptor A and Apolipoporhrin 2. Our findings support the hypothesis that body lice, unlike head lice, fight infection from B. quintana only at the later stages of its proliferation.

A genome-wide identification of basic helix-loop-helix motifs in Pediculus humanus corporis (Phthiraptera: Pediculidae).

Basic helix-loop-helix (bHLH) proteins comprise a large superfamily of transcription factors, which are involved in the regulation of various developmental processes. bHLH family members are widely distributed in various eukaryotes including yeast, fruit fly, zebrafish, mouse, and human. In this study, we identified 55 bHLH motifs encoded in genome sequence of the human body louse, Pediculus humanus corporis (Phthiraptera: Pediculidae). Phylogenetic analyses of the identified P. humanus corporis bHLH (PhcbHLH) motifs revealed that there are 23, 11, 9, 1, 10, and 1 member(s) in groups A, B, C, D, E, and F, respectively. Examination to GenBank annotations of the 55 PhcbHLH members indicated that 29 PhcbHLH proteins were annotated in consistence with our analytical result, 8 were annotated different with our analytical result, 12 were merely annotated as hypothetical protein, and the rest 6 were not deposited in GenBank. A comparison on insect bHLH gene composition revealed that human body louse possibly has more hairy and E(spl) genes than other insect species. Because hairy and E(spl) genes have been found to negatively regulate the differentiation of insect preneural cells, it is suggested that the existence of additional hairy and E(spl) genes in human body louse is probably the consequence of its long period adaptation to the relatively dark and stable environment. These data provide good references for further studies on regulatory functions of bHLH proteins in the growth and development of human body louse.

Louse-borne relapsing fever profile at Felegehiwot referral hospital, Bahir Dar city, Ethiopia: a retrospective study.

BackgroundLouse- borne relapsing fever is an acute febrile illness caused by Borrelia recurrentis and is transmitted by body lice, Pediculus humanus corporis. The disease has occurred as epidemic in different parts of the country.Therefore, the aim of this retrospective study was conducted to assess the LBRF profile for the last four years.MethodsA retrospective study was conducted on patients with LBRF admitted from 2009–2012 at Felegehiwot referral hospital. The diagnosis was based on both clinical and laboratory methods. Patients with strong clinical suspicion of LBRF and positive for Borrelia species in their blood was diagnosed as LBRF cases. Data was collected from all patients with LBRF- like symptoms in their registration book. Data was checked for completeness, coded and analysed using SPSS version 16. P < 0.05 was considered significant for comparison.ResultsOf the 4559 patients admitted with LBRF- like symptoms, 4178 (91.6%) were males and 381 (8.4%) were females. Most of the patients (74.2%) were within age groups 11–20 years. The majority of patients (94.4%) were from urban residence. The overall prevalence of LBRF was 225 (4.9%) and the highest prevalence 171 (5.1%) was observed in age groups of 11–20 years. The association between seasonal variation and prevalence of LBRF showed that more patients with positive for Borrelia species were recorded in dry 27 (9.7%) than wet 198 (4.6%) seasons (P < 0.001). Finally, a trend in prevalence of LBRF for the last four years showed that the highest numbers of cases were documented in 2010.ConclusionThe overall prevalence of LBRF was high and the highest prevalence was observed in young age groups. Moreover, most of the patients with LBRF were from urban dwellers. Therefore, health education should be delivered towards LBRF prevention in the city.

Knowledge, Attitude and Practices of High Risk Populations on Louse- Borne Relapsing Fever in Bahir Dar City, North-West Ethiopia

Background: Louse- borne relapsing fever (LBRF) is an acute febrile illness caused by Borrelia recurrentis (B. recurrentis). It is transmitted by body lice, Pediculus humanus corporis (P. humanus corporis). LBRF is more prevalent in high risk populations such as prisoners, street children and yekolotemaries (traditional students of the Ethiopian Orthodox Church with low levels of socio economic status and poor personal hygiene). Thus, this study was conducted to assess the knowledge, attitude and practices (KAPs) among high risk populations towards LBRF prevention in Bahir Dar city. Methods: A cross- sectional survey was conducted on KAPs of high risk populations regarding LBRF from November to December, 2012. Data was collected using a standardized pre- tested closed ended questionnaire by face to face interviews to address socio demographic characteristics, KAPs and sources of information regarding LBRF prevention. The overall KAPs of the study participants were analyzed using the sum score of each outcome based on Bloom’s cut-off point (60-80%). Having a score above the cut-off point was equated with having high levels of knowledge, positive attitude and good practice. Results: Of the 407 study participants, 383 (94.1%) were males with the mean age of 31 years. Among the study participants, 243 (59.7%) had no formal education. The response rate of the participants was 98.2%. Overall, 222 (54.5%) of the study participants had low knowledge, 247(60.7%) had neutral attitude (30-39 scores out of 50 item- questions on LBRF) and 320 (78.6%) had fair practice (20-25 scores out of 32 item-questions). Prisoners had the highest knowledge, attitude and practices followed by street children and yekolotemaries towards LBRF prevention (p < 0.001). Conclusion: The overall KAPs of the high risk populations towards prevention of LBRF were poor. However, prisoners had highest level followed by street children and yekolotemaries. Moreover, the sources of information on LBRF received by the high risk populations have determined their KAP levels towards LBRF prevention. This showed that information on LBRF using television, radio and through their friends is essential to bring knowledge and attitudinal change towards LBRF prevention.

Lice, Life, and Leafhoppers: How Weigl’s vaccine creation influenced my virology research

This paper is dedicated to the memory of my brother Alfred who worked as a physician in the ghetto of Kolomyya. On September 1, 1942 my father was shipped with 8 000 Jews to be gassed in Belzec. Two weeks later my brother was arrested and his dead body returned to the ghetto a few hours later. On October 14 my mother was shipped to the Belzec extermination camp with the remaining 7 000 ghetto inhabitants.My wife and I survived the holocaust in refugee camps in Romania, but 138 closest relatives in Nazi occupied Europe perished in Treblinka, Belzec, and Auschwitz. In 1928, when I was 13 years old, my brother Alfred, who was a medical student in Lviv , told me that his biology professor, Rudolf Weigl, developed during World War I the first vaccine against exanthematic typhus. Weigl, who was a young officer in the Austrian army, got the brilliant idea how to prepare a vaccine to protect people from the deadly disease that killed thousands of soldiers and civilians. Weigl infected healthy body lice individually, giving them enemas containing typhus rickettsiae. The inoculated lice were maintained for 5 days in batches of 140, in cages carried on the bodies ofWeigl’s assistants, because they only fed on human blood. After 5 days the typhus-carrying lice were dissected and from 140 intestines, crushed in a glass micro mortar with a few drops of phenol solution, a single dose of the protective vaccine was produced. I listened fascinated to my brother’s description of Weigl’s procedure and I decided to study medicine, become a researcher, and do similar experiments when I grow up. Twenty years after hearing about Weigl I got the opportunity to follow his steps, not with human lice but with leafhoppers and plant pathogens. Daily contacts with scientists at Cold Spring Harbor, who years later became Wolf Price and Nobel Prize winners greatly influenced me and helped in my own scientific career. Keywords: leafhoppers, virus taxonomy, Weigl conferences, Cold Spring Harbor

Early Thule Winter Houses: An Archaeoentomological Analysis

This paper presents the results of archaeoentomological analyses of soil samples from early Thule (ca. AD 1200–1400) winter-house remains at Cape Grinnell and Qaqaitsut, Northwest Greenland. Excavated over the summers of 2008 and 2009 by the Inglefield Land Archaeological Project (ILAP), four houses yielded 467 ectoparasites, mostly human lice, unevenly distributed across the identified areas of the structures. A recurring pattern of distribution was found in three of the houses and is interpreted as the result of delousing practices. Using historical explorer accounts, Inughuit oral tradition, and archaeoentomological evidence we investigate the potential for studying hygiene practices on Inuit sites.

Geographical Distribution of Pyrethroid Resistance Allele Frequency in Head Lice (Phthiraptera: Pediculidae) From Argentina

The human head louse, Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae), is an obligate ectoparasite that causes pediculosis capitis and has parasitized humans since the beginning of humankind. Head louse infestations are widespread throughout the world and have been increasing since the early 1990s partially because of ineffective pediculicides. In Argentina, the overuse of products containing pyrethroids has led to the development of resistant louse populations. Pyrethroid insecticides act on the nervous system affecting voltage-sensitive sodium channels. Three point mutations at the corresponding amino acid sequence positions M815I, T917I, and L920F in the voltage-gated sodium channel gene are responsible for contributing to knockdown resistance (kdr). The management of pyrethroid resistance requires either early detection or the characterization of the mechanisms involved in head louse populations. In the current study, we estimated the distribution of kdr alleles in 154 head lice from six geographical regions of Argentina. Pyrethroid resistance kdr alleles were found in high frequencies ranging from 67 to 100%. Of these, 131 (85.1%) were homozygous resistant, 13 (8.4%) were homozygous susceptible, and 10 (6.5%) were heterozygous. Exact tests for the Hardy-Weinberg equilibrium for each location showed that genotype frequencies differed significantly from expectation in four of the six sites studied. These results show that pyrethroid resistance is well established reaching an overall frequency of 88%, thus close to fixation. With 30 yr of pyrethroid-based pediculicides use in Argentina, kdr resistance has evolved rapidly among these head louse populations.

保幼激素在昆虫中的分子作用机理

PDF HTML阅读 XML下载 导出引用 引用提醒 保幼激素在昆虫中的分子作用机理 DOI: 10.5846/stxb201306061380 作者: 作者单位: 中国计量学院生命科学学院,中国计量学院生命科学学院 作者简介: 通讯作者: 中图分类号: 基金项目: 国家重点基础研究发展计划（2010CB126200） Molecular mechanisms of the insect juvenile hormone Author: Affiliation: College of Life Sciences,China Jiliang University,Provincial Key Laboratory of Biometrology and Inspection Quarantine,College of Life Sciences,China Jiliang University,Provincial Key Laboratory of Biometrology and Inspection Quarantine Fund Project: 摘要 | 图/表 | 访问统计 | 参考文献 | 相似文献 | 引证文献 | 资源附件 | 文章评论 摘要:随着分子生物学技术的快速发展，对生态环境中各类生物的研究，包括对生物某些特定基因结构和功能的研究等逐步拓展和加深。保幼激素（Juvenile Hormone，JH）是由咽侧体（Corpus Allatum，CA）分泌的，在昆虫发育、变态和生殖过程中起重要作用的激素。目前对JH信号传导途径的作用机理还不十分清楚。现有研究表明，Kruppel homolog-1（Kr-h1）是一种含C2H2锌指结构的转录因子，处于保幼激素信号途径下游，在保幼激素信号通路中起着重要作用。已报道的Kr-h1基因的功能主要包括：调控幼虫生长发育和变态，与蜜蜂的觅食行为密切相关，参与果蝇幼体神经细胞的形成等等。对就近十年来Kr-h1基因的特性和功能研究作一个综述以了解不同昆虫中保幼激素的分子作用机制，为开发生物农药奠定理论基础，也为维护良好的生态环境作出理论贡献。 Abstract:Following the rapid development of molecular biology techniques, many studies have been carried out of specific gene structures and functions, including those in ecological environments. Juvenile hormone (JH) is an important insect hormone that regulates insect larval development, reproduction, and metamorphosis, although the molecular mechanism behind this remains unclear. The transcription factor Kruppel-homolog 1(Kr-h1) acts downstream of the JH receptor and plays a key role in the JH signaling pathway. It has been identified in over 21 insect species, and sequence analysis has shown it to contain 2-8 C2H2-type zinc-finger motifs, which are highly conserved among Kr-h1 proteins. We previously found that zinc-fingers Zn2-Zn7 are more conserved than others in all insect species we compared. Interestingly, we found that the jewel wasp Nasonia vitripennis only contains two zinc-fingers, Zn4 and Zn7, while the body louse Pediculus humanus corporis contains all zinc-fingers except Zn7. As N. vitripennis and P. humanus were the only two parasitoids among the 21 insect species examined, it is possible that zinc fingers might be lost during evolution. Studies in Drosophila melanogester, Bombyx mori, Tribolium castaneum, and Frankliniella occidentalis revealed that Kr-h1 is required for embryonic development and metamorphosis, and that its down-regulation results in development of the precocious phenotype. Knockdown of Kr-h1 by RNAi in the brown planthopper Nilaparvata lugens showed that this gene is required for normal wing and external genitalia development. Kr-h1 is also involved in neuron development, the regulation of photoreceptor maturation, larval growth, insect development and metamorphosis, and the formation of Drosophila melanogaster neurons. In addition, it controls the foraging behavior of honey bees through affecting the expression of the cGMP-mediated activation of protein kinase G. The expression of Kr-h1 is induced by JH and its mimics. The Bombyx mori juvenile hormone response element (bmJHRE), located 141 bp upstream of Kr-h1, includes an E-box with the sequence CACGTG. bmJHRE was found in the genomic sequence of all seven insect species that we previously analyzed, and the E-box was highly conserved in all species (100%). The E-boxes of Tribolium castaneum Kr-h1(TcKr-h1) and Apis mellifera Kr-h1(AmKr-h1) are close to the Kr-h1 promoter, while those of Bombyx mori Kr-h1(BmKr-h1), Acyrthosiphon pisum Kr-h1(ApKr-h1), Drosophila melanogester Kr-h1(DmKr-h1), Nasonia vitripennis Kr-h1(NvKr-h1), and Nilaparvata lugens Kr-h1(NlKr-h1) are not. JH also interacts with the hormone ecdysone (Ecd), and research from D. melanogaster, B. mori, and T. castaneum suggests that Kr-h1 is a key factor in the JH-Ecd interaction. JH mimics methoprene treatment, which increases the expression of Kr-h1 while reducing that of Broad (B), a transcription factor located downstream of Ecd and its receptor that plays an important role in the ecdysone signaling pathway. This indicates that Br expression might be inhibited by Kr-h1. Although much progress has been made in understanding insect hormone signaling pathways, several key questions still remain. For example, what is the role of Kr-h1 in linking the JH and Ecd signaling pathways? How many other genes form a close connection in the JH signaling cascade? This review highlights the characteristics and functions of Kr-h1 that have been elucidated during the past decade. It also summarizes our understanding of the molecular mechanism of JH, establishes a theoretical basis for the development of biological pesticide, and contributes theoretically to the maintenance of a good ecological environment. 参考文献 相似文献 引证文献