Head Lice Pediculus Humanus Capitis Research Articles

Identification and Spatiotemporal Expression of a Putative New GABA Receptor Subunit in the Human Body Louse Pediculus humanus humanus.

The human louse (Pediculus humanus) is an obligatory blood feeding ectoparasite with two ecotypes: the human body louse (Pediculus humanus humanus), a competent vector of several bacterial pathogens, and the human head louse (Pediculus humanus capitis), responsible for pediculosis and affecting millions of people around the globe. GABA (γ-aminobutyric acid) receptors, members of the cys-loop ligand gated ion channel superfamily, are among the main pharmacological targets for insecticides. In insects, there are four subunits of GABA receptors: resistant-to-dieldrin (RDL), glycin-like receptor of drosophila (GRD), ligand-gated chloride channel homologue3 (LCCH3), and 8916 are well described and form distinct phylogenetic clades revealing orthologous relationships. Our previous studies in the human body louse confirmed that subunits Phh-RDL, Phh-GRD, and Phh-LCCH3 are well clustered in their corresponding clades. In the present work, we cloned and characterized a putative new GABA receptor subunit in the human body louse that we named HoCas, for Homologous to Cys-loop α like subunit. Extending our analysis to arthropods, HoCas was found to be conserved and clustered in a new (fifth) phylogenetic clade. Interestingly, the gene encoding this subunit is ancestral and has been lost in some insect orders. Compared to the other studied GABA receptor subunits, HoCas exhibited a relatively higher expression level in all development stages and in different tissues of human body louse. These findings improved our understanding of the complex nature of GABA receptors in Pediculus humanus and more generally in arthropods.

Cuticular extracts induce aggregation in head lice.

The human head lice Pediculus humanus capitis (De Geer) (Phthiraptera: Pediculidae) are strict, obligate human ectoparasites that spends their entire life cycle in the host and cause skin irritation and derived infections. Despite the health-related importance, few studies have evaluated the chemical communication among these insects. Here, we evaluate the response of lice of both sexes to cuticular extracts using two solvents of different polarity (hexane and methanol). Cuticular extracts that elicited an attraction response towards head lice were analysed by gas chromatography-mass spectrometry (GC-MS) to determine the cuticular lipid profile. Both lice sexes were attracted to the hexane extracts but not the methanol extracts, suggesting the non-polarity of the compounds present in the cuticle. Chemical analyses of hexane extracts from males and females showed high similarity in major compounds. This study provides the first evidence that lice respond to cuticle extracts, which may be important to understand aggregation behaviour.

Anti-lice activity of Citrullus colocynthis fruits against Pediculus humanus capitis in vitro

The increasing resistance of head lice Pediculus humanus capitis to many drugs has highlighted the need for new alternatives to control head lice in adults. The effect of two types of extracts (aqueous and alcoholic) of Citrullus colocynthis fruit on adult lice was tested in vitro. The results showed that the alcoholic extract with a concentration of 20% showed similar efficacy in killing adult lice to that of Natroba 9% w/w, with values ranging between 87% to 98% within 18 minutes, followed by a 20% aqueous extract with a 44% to 79% death rate. A 10% concentration of both types of extracts had moderate lethality for lice, while a 5% concentration did not show strong lethality for adult lice. These results revealed significant differences between the control group and those treated with alcoholic and aqueous extract concentrations of C. colocynthis fruits at the probability level p ≤ 0.05.

Embryonic Development of Pediculus humanus capitis: Morphological Update and Proposal of New External Markers for the Differentiation Between Early, Medium, and Late Eggs

Background and ObjectivesThe head louse Pediculus humanus capitis is a cosmopolitan ectoparasite that causes pediculosis. In the study of human lice, little research focuses on embryonic development. Currently, external markers of embryonic development represent a new approach in the evaluation of ovicidal drugs. The objective of this work was to update the morphology of embryonic development and propose novel external markers to differentiate between early, medium, or late P. h. capitis eggs.MethodsUsing stereoscopic light microscopy, we describe the morphological characteristics of P. h. capitis eggs with a special focus on embryonic development.ResultsThe morphological analysis of the eggs revealed the presence of an operculum with ten aeropyles, although no micropyles were observed. For the first time, the presence of defective eggs that were non-viable due to the apparent absence of yolk granules was documented. The early eggs presented yolk granules and developing germ bands, while the medium eggs presented an embryonic rudiment and the outlines of the eyes and limbs. In late eggs, the head with eyes and antennae, the thorax with three pairs of legs, and the abdomen with six pairs of spiracles were observed as formed structures. At the end of this stage, the embryos acquired the morphology of the nymph I stage.ConclusionWe propose novel biomarkers (e.g., the presence of spiracles and antennae, the proportion of the egg occupied by the embryo) to facilitate the differentiation between the developmental stages. The updated morphological characteristics of P. h. capitis eggs facilitate the standardization of toxicological tests in the quest for ovicidal drugs.

First report of classical knockdown resistance (kdr) mutation, L1014F, in human head louse Pediculus humanus capitis (Phthiraptera: Anoplura).

There are at least three known knockdown resistance (kdr) mutations reported globally in the human head louse Pediculus humanus capitis De Geer (Phthiraptera: Anoplura) that are associated with reduced sensitivity to pyrethroids. However, the prevalence of kdr mutation in head lice is not known in the Indian subcontinent. To identify kdr mutations in the Indian head lice population, the genomic region of the voltage-gated sodium channel gene encompassing IIS1-2 linker to IIS6 segments was PCR-amplified and sequenced from P. humanus capitis samples collected from different geographic localities of India. DNA sequencing revealed the presence of four kdr mutations: M827I, T929I, L932F and L1014F. The presence of a classical kdr mutation L1014F, the most widely reported mutation across insect-taxa associated with the kdr-trait, is being reported for the first time in P. humanus capitis.

Don't Be a Nit Wit; Know Your Lousy Companions!

Lice have been a burden on humans since antiquity. The species implicated in human infestations, the head louse (Pediculus humanus capitis), body louse (Pediculus humanus humanus), and pubic louse (Pthirus pubis), are very well adapted to the human host and are readily transmissible between and among individuals. In addition to dermal reactions and social stigmas associated with louse infestations, the body lice are of additional medical and public health concern in the spreading of bacterial agents associated with louse-borne relapsing fever, epidemic typhus, and trench fever. In the United States, pthiriasis, caused by P. pubis, is classified as a sexually transmitted infection. In this review, we provide an update on the taxonomy, epidemiology, biology, evolution, clinical importance, treatment and control, diagnosis, and reporting of parasitic human lice.

The Potential of Natural Ingredients as Anti Pediculosis capitis: A Narrative Review

Head louse (Pediculus humanus capitis) is a small parasite that feeds itself by sucking human blood, which causes infection of the scalp so that it becomes inflamed. The most common way to kill fleas is through the use of pharmaceutical insecticides. Some insecticide products contain permethrin, lindane, and DDT which are toxic to the body and are not easily biodegradable in the environment. Uncontrolled use of insecticides can make ticks resistant to these insecticides. Lemon, kirinyuh leaves, pandan wangi, Srikaya leaves, garlic, jarak pagar, citronella leaves, papaya, and lime have potential as anti-parasitic head lice.

The Attractivity of the Head Louse, Pediculus humanus capitis (Pediculidae: Anoplura) to Isolated Compounds and Blends of Human Skin.

Human head lice Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae) are ectoparasites that cause pediculosis, a global scale disease mainly found in school-age children. Previous works from our laboratory found nonanal, sulcatone, and geranylacetone as the main human scalp volatile components, and individually evaluated their attraction to head lice using an olfactometer. In this work, we compared how their blends at different concentrations attract head lice, and how their blended effect compares to the effect of isolated compounds. At the concentrations evaluated, individual components did not show attraction towards head lice, but a ternary mixture of them was attractive. Moreover, a solvent extract from the human head scalp was analyzed by GC-MS, finding that tetradecanoic acid, palmitic acid, oleic acid, palmitoleic acid, and squalene are the most abundant components. Attraction to these individual compounds at natural concentrations was tested by bioassays in a circular experimental arena. No attraction was observed when the components were tested individually, but when they were evaluated as a blend they attracted head lice. This work presents new information about how chemical signals are attractive at certain concentrations and proportions. This information could be used to better understand communication mechanisms in head lice and for the development of louse repellents.

Epidemiology Study of the Head Lice Pediculus humanus capitis Isolated among Primary School Students in Erbil city, Kurdistan Region, Iraq

Background: The association between man and the head lice is one of the oldest relationship and its history return to 10000 years ago. Blood sucking head lice belong to Kingdom Animalia, Class: Insecta, Order: Phiroptera, Family: Pediculidae, Genus: Pediculus, Species: humanus and Subspecies: capitis that’s obligate parasite on human this highly specialized to suck blood and close association with their host where completed its entire life cycle. Objective: To determine the rate of infestation by the head lice, Pediculus humanus capitis and its associated factors among primary school children in Erbil City. Patients and Methods: A case control study was conducted on the twenty two (22) randomly selected primary school in the center of Erbil city. For this purpose, a total of 1082 students (430 boys and 652 girls) were examined from first to sixth stage (age ≥6 years old) during 1st October 2020 to 31th May 2021. Personal requested information was recorded by student parents in a questionnaire form. Results: An overall prevalence of infestation of 25.5% (276/1082) was recorded in the present study. Study reveals the existence of a significant relationship age [6 and < 9 years old , 178/759 (23.5%), and ≥ 9 years old, 98/323 (30.3%), P = 0.0174], gender [girls, 215/652 (33%) and boys, 61/430 (14.2%), P < 0.001], education level of parent (educated family, 146/694 (21%) and none educated family, 130/388 (33.5%), P < 0.001], longevity of hair [ long hair, 157/473 (33.2%) and short hair 119/609 (19.5%), P < 0.001] hair washing frequency [daily washing, 243/587 (41.4%), and weekly washing 33/495 (6.7%), P < 0.001], hair combing condition [common comb user,165/499 (33%) and special comb user, 111/583 (19%), P < 0.001] and sleeping habitat [ sleeping together 222/693 (32%) and sleeping habitat alone, 54/389 (13.9%), P < 0.001]. There’s no significant existence related to density of students in classroom [ one student per table, 114/486 (23.5%) and sitting in pair, 162/596 (27.2%), P = 0.1621], hair type, smooth and wrinkle [smooth hair, 183/741 (24.7%), 93/341 (27.3), P = 0.366] and head lice infestation. Conclusion: We concluded that head lice infestation rate was varied depending on the several physio and socioeconomic factors including, age, gender, type of hair, education level of parents, frequency of hair washing, sleeping habitat and condition of hair combing. Among variables, only density of pupils in classroom, smooth and wrinkled hair show no any significant relationship with pediculosis capitis (P- value = 0.1621 and P –value = 0.366 respectively). Keywords:Pediculus humanus capitis; Pediculosis; Head lice; Epidemiology; Erbil

Pediculus humanus capitis: a study of the male genitalia using a combined stereoscopic, confocal laser scanning, and scanning electron microscopy approach

BackgroundThe male genital structures of arthropods are key features in the taxonomic and phylogenetic study of these organisms. The male genitalia of the head louse Pediculus humanus capitis are complex organs which are partly composed of structures that dynamically extrude during copulation.MethodsHere, we describe the morphology of the genitalia of P. humanus capitis at the copulation stage, and at rest, by using stereoscopic microscopy, confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM).ResultsCLSM and SEM images revealed that the vesica is composed of two distinct anatomical parts, the proximal lobe and the distal lobe. Both lobes have short and narrow spines, as well as long and wide scales with either sharp or rounded tips. The rounded scales vary in size and have a wavy base and rounded tips, and thus resemble a tongue in appearance. We identified a gland-like area on the penis with 11 shallow circular depressions, and a flat area with 14–16 exit orifices. The apical end of the penis has a foliaceous trifurcation and serves to expel the contents of the ejaculatory duct. These characteristics were recorded for all the specimens analyzed, indicating that these structures are highly conserved; to our knowledge, they have not been previously reported for any suborder of lice.ConclusionsTo the best of our knowledge, our results reveal for the first time the morphological details, and complexity, of the male genitalia of the head louse P. humanus capitis at different stages of copulation. The new approach described here provided information that should be taken into consideration in future research on the genitalia of lice. Application of this approach will also impact the taxonomic and phylogenetic study of other insect taxa.Graphical

Mouthpart sensory structures of the human head louse Pediculus humanus capitis

Head lice are exclusive human parasitic blood-sucking insects. Distributed worldwide among school-age children, this parasitosis generates scalp irritation and sometimes social prejudice. Understanding how head lice detect and perceive their human hosts is crucial to control transmission. Here, we describe the sensory structures present on the mouthparts of Pediculus humanus capitis and their possible contribution to the feeding decision-making process. On the anterior zone of the clypeus around the haustellum two morphological types of sensilla, invariable in location and number, were identified: fourteen short clypeus bristles (SCB) and six long clypeus bristles (LCB). During feeding these structures contact the host skin but not its blood. Located antero-dorsally on the everted haustellum and between the epipharyngeal teeth, a third sensillar type was identified: about four short peg epipharyngeal (SPE) sensilla. These structures are bathed with the incoming blood, when head lice feed, so may have a gustatory role. In behavioural experiments antennectomy of lice did not interfere with feeding behaviour, suggesting that the sensory structures on the mouthparts could be involved in host assessment.

Essential Oils as a Potential Treatment Option for Pediculosis.

Pediculosis is a prevalent ectoparasite infestation caused by lice. The head louse (Pediculus humanus capitis) and body louse (Pediculus humanus humanus) are obligatory parasites whose only known hosts are humans. Pediculosis is probably the most common ectoparasitic infestation, affecting up to 80% of the population in several countries, and particularly prevalent in the infant population worldwide. Several treatment options, including shampoos and creams containing insecticides, have been introduced for the treatment of pediculosis. Recently, the use of synthetic chemicals to control human lice has raised concerns pertaining to human health and the environment. Therefore, increasing efforts have been undertaken to develop effective pediculicides with low environmental toxicity and minimal environmental residual activity. In this study, we focus on the essential oils derived from 22plant genera, their constituents, and the major factors that play important roles in the effectiveness of these oils in the treatment of pediculosis. Furthermore, we discuss the advantages and limitations of the mentioned essential oils, and ultimately suggest those demonstrating the most effective in vitro pediculicidal activities. The genera such as Aloysia, Cinnamomum, Eucalyptus, Eugenia, Lavandula, Melaleuca, Mentha, Myrcianthes, Origanum, Pimpinella, and Thymus appear to be more efficient against lice. These genera are rich in anethole, 1,8-cineole, cinnamaldehyde, p-cymene, eugenol, linalool, limonene, pulegone, terpinen-4-ol, and thymol compounds.

Comparison of prevalence of head lice Pediculus humanus capitis among male and female students of some primary schools in Tikrit City

A study was conducted to evaluate the prevalence of pediculus humanus capitis (De Geer, 1767) among male and female students of five primary schools in Tikrit (Abu Musa Al-Ash'ari for Boys and Fara'a schools for girls in Al-Shuhada neighborhood, and Hawa for girls ’school in Al-Qadisiyah / Al-Duibbat neighborhood, and a school Sincerely, first born for boys in Al-Asri neighborhood, and Madar mixed school in Shishen district).
 The results showed prevalence of infection with parasite among the five school students, with a total injury rate of 21.9%, of which 13.8% for males and 80.11% for females. Consequently, the prevalence of parasite among students in 6-7 age group was higher than in rest of age groups, reaching 23.23% and lowest in 10-year age group and over, which reached 16.03%.
 The study showed length and nature of hair (tribe or curly) in percentage of infection with parasite, as percentage of infection in females with short hair reached 12.14%, while weakness in females with long hair reached 23.12%, and percentage of injury among students of lower hair was 36.32% for those with Curly hair and 11.81% for tribute hair.

Head Louse Feces: Chemical Analysis and Behavioral Activity.

Human head lice Pediculus humanus capitis (De Geer) (Phthiraptera: Pediculidae) are insect parasites closely associated with humans, feeding on the blood of their hosts and causing them skin irritation and probable secondary infections. Despite being a severe nuisance, very few studies have reported on intraspecific chemical communication in head lice. Here, we evaluated the attractive response of head lice to the volatile compounds and solvent extracts from their feces. We also chemically analyzed the main volatile components of these feces and those of the feces' extracts. Head lice were attracted to the methanol extract of their feces but not to the hexane or dichloromethane extracts, suggesting the polar nature of bioactive chemicals present in head louse feces. Follow-up chemical identifications, in fact, showed the presence of hypoxanthine, uric acid, and another purine tentatively identified as either guanine or iso-guanine. Additionally, head lice were significantly attracted by volatiles emitted from samples containing feces. The volatiles emanated from feces alone contained 19 identified substances: 2-pentanone, hexanal, heptanal, 3-methyl-3-buten-1-ol, octanal, sulcatone, nonanal, acetic acid, 2-ethyl-1-hexanol, decanal, 1-octanol, butyric acid, 1-nonanol, hexanoic acid, octanoic acid, 2,6-dimethyl-7-octen-2-ol, 2-undecanone, geranylacetone, and hexadecane. The major compounds found were decanal, nonanal, hexanal, and acetic acid, together representing approximately 60% of the identified compounds. This work represents the first chemical evidence of intraspecies communication among head lice. The results support the existence of active substances present in the feces of P. humanus capitis that may be involved in its aggregation behavior.

The Sensory Machinery of the Head Louse Pediculus humanus capitis: From the Antennae to the Brain.

Insect antennae are sophisticated sensory organs, usually covered with sensory structures responsible for the detection of relevant signals of different modalities coming from the environment. Despite the relevance of the head louse Pediculus humanus capitis as a human parasite, the role of its antennal sensory system in the highly dependent relation established with their hosts has been barely studied. In this work, we present a functional description of the antennae of these hematophagous insects by applying different approaches, including scanning electron microscopy (SEM), anterograde antennal fluorescent backfills, and behavioral experiments with intact or differentially antennectomized lice. Results constitute a first approach to identify and describe the head louse antennal sensilla and to determine the role of the antenna in host recognition. SEM images allowed us to identify a total of 35–40 sensilla belonging to seven different morphological types that according to their external architecture are candidates to bear mechano-, thermo-, hygro-, or chemo-receptor functions. The anterograde backfills revealed a direct neural pathway to the ipsilateral antennal lobe, which includes 8–10 glomerular-like diffuse structures. In the two-choice behavioral experiments, intact lice chose scalp chemicals and warm surfaces (i.e., 32°C) and avoided wet substrates. Behavioral preferences disappeared after ablation of the different flagellomeres of their antenna, allowing us to discuss about the location and function of the different identified sensilla. This is the first study that integrates morphological and behavioral aspects of the sensory machinery of head lice involved in host perception.

EFEKTIFITAS EKSTRAK KULIT DUKU (Lansium domesticum corr) TERHADAP MORTALITAS PEDIKULUS HUMANUS CAPITIS SEBAGAI PENYEBAB PEDIKULOSIS PADA ANAK

Head lice (Pediculus humanus capitis) is an insect that carries a disease that makes the loss of confidence. Efforts of control and pembutuasan head lice is the use of natural insecticides, one of the plants that have the potential as a natural insecticide is duku skin extract (Lansium domesticum Corr.). The purpose of this study was to determine mortality of head lice (Pediculus humanus capitis) and to know the compounds contained in duku skin extract. The research used laboratory experimental method with design research design post only control group. Based on the result of the research, the most effective rate of death of head louse (Pediculus humanus capitis) is 15% concentration with 4 head of head louse (80%), while at concentration 10% is 2 tail (40%) and at concentration 5% there is a dead head louse 0 (0%). The results of this study can be concluded that duku leaf extract (Lansium domesticum Corr.) Serves as a natural insecticide due to the presence of secondary metabolite compounds that are active in killing head lice (Pediculus humanus capitis).

Prevalence and Risk Factors Associated with Head Louse (Pediculus humanus capitis) among Primary School Girls in Qom Province, Central Iran

Background: Head louse infestation is highly common in collective centers such as schools, garrisons and campuses. This study was done to determine the prevalence and risk factors associated with Pediculus humanus capitis in primary school girls in Qom Provincecentral Iran. Materials and Methods: This descriptive –analytic study was conducted among 1,725 feminine primary students from 89 schools of Qom province, Central Iran were randomly selected during 2015 to 2017. Data collection was done using standard check list that was provided by the Iran Centres for Disease Control and Prevention (CDC), and physical exams of the hairby visual scalp examination. Head examinations were performed by medical entomologist experts. Analysis of data was done using SPSS version 20.0 software. Results: The prevalence rate of infestation was 13.28%. The rate of head lice infestation was 13.73% in the urban areas and 10.22% in the villages. According to the multivariable logistic regression analysis, a significant relationship was observed between Pediculus capitis and each of these factors: family size, water source, family income (per month for each family, in US dollars), father occupation, parental education, access to primary health care services, having previous history of Pediculus capitis infestation, number of comb uses per day (p<0.05). Conclusion: The head lice infestation is a significant public health issue in primary school girls of Qom province. Risk factors associated with head louse among primary school girls were some demographic and socioeconomic factors. Improvement of these status and designing and implementing appropriate educational and preventive programs can be helpful for surveillance of infestation among primary school girls.

Risk Factors Associated with Head lice (Pediculosis) Infestation among Elementary School Students in Meshkinshahr County, North West of Iran

Background: Head louse (Pediculus humanus capitis) is one of the common health problems of the children in elementary schools. The aim of this study was to determine risk factors associated with head lice (Pediculosis) infestation among elementary school students in Meshkinshahr County, Northwestern Iran. Materials and Methods: This descriptive-analytic study is done over 1,950 students (1,055 girls and 895 boys) in Meshkinshahr County, North West of Iran that were selected two-stage cluster. Data collection was conducted using researcher-made questionnaire. In addition, the suspected cases were confirmed via physical examination for the presence of adult lice, and eggs. Head examinations were done by general physicians and medical entomologist experts. For data analysis, Chi-square and Regression Logistics tests were used. Results: In total, out of 1,950 students of primary schools, 200 students (10.25%) were infested with pediculosis. A total of 131 (12.42%) of girls, and 69 (7.71%) of boys were head lice infested. Most of head lice infested students 145 (72.5%) were in the classrooms with capacity of more than 20 students. Also, one hundred sixty-one (80.5%) of the cases were in the schools with capacity of more than 100 students. This study revealed significant differences among student’s family size, students and their parents' history of infestation, type of bathrooms, history of use shared hygiene items and head lice infestation (P < 0.05). Conclusion: The prevalence of head lice infestation in Meshkinshahr County was relatively high in comparison to other studied areas of Iran. It seems family size, students and their parents' history of infestation, type of bathrooms, and history of use shared hygiene items were probably risk factors associated with head lice infestation among students of primary schools.

Response of Pediculus humanus capitis (Phthiraptera: Pediculidae) to Volatiles of Whole and Individual Components of the Human Scalp.

The head louse Pediculus humanus capitis (De Geer) (Phthiraptera: Pediculidae) is a cosmopolitan human ectoparasite causing pediculosis, one of the most common arthropod parasitic conditions of humans. The mechanisms and/or chemicals involved in host environment recognition by head lice are still unknown. In this study, we evaluated the response of head lice to volatiles that emanate from the human scalp. In addition, we identified the volatile components of the odor and evaluated the attractive or repellent activity of their pure main components. The volatiles were collected by means of Solid Phase microextraction and the extract obtained was chemically analyzed by gas chromatograph-mass spectrometer. Twenty-four volatile were identified in the human scalp odor, with the main compounds being the following: nonanal, sulcatone, geranylacetone, and palmitic acid. Head lice were highly attracted by the blend human scalp volatiles, as well as by the individual major components. A significant finding of our study was to demonstrate that nonanal activity depends on the mass of the compound as it is repellent at high concentrations and an attractant at low concentrations. The results of this study indicate that head lice may use chemical signals in addition to other mechanisms to remain on the host.

Do drowning and anoxia kill head lice?

Chemical, physical, and mechanical methods are used to control human lice. Attempts have been made to eradicate head lice Pediculus humanus capitis by hot air, soaking in various fluids or asphyxiation using occlusive treatments. In this study, we assessed the maximum time that head lice can survive anoxia (oxygen deprivation) and their ability to survive prolonged water immersion. We also observed the ingress of fluids across louse tracheae and spiracle characteristics contrasting with those described in the literature. We showed that 100% of lice can withstand 8 h of anoxia and 12.2% survived 14 h of anoxia; survival was 48.9% in the untreated control group at 14 h. However, all lice had died following 16 h of anoxia. In contrast, the survival rate of water-immersed lice was significantly higher when compared with non-immersed lice after 6 h (100% vs. 76.6%, p = 0.0037), and 24 h (50.9% vs. 15.9%, p = 0.0003). Although water-immersed lice did not close their spiracles, water did not penetrate into the respiratory system. In contrast, immersion in colored dimeticone/cyclomethicone or colored ethanol resulted in penetration through the spiracles and spreading to the entire respiratory system within 30 min, leading to death in 100% of the lice.