Humanus Capitis Research Articles

A severe head louse (Pediculus humanus capitis) infestation: Timeline, pathogen detection, kdr-gene screening and morphological anomalies of lice.

Lice are assuming an increasing importance in forensic investigations, given their capacity to provide information about an individual's care. Head louse pediculosis is a frequent condition in school-age children and can be properly controlled using topical treatments combined with good personal hygiene. Prolonged and chronic infestations may result in more serious outcomes including severe iron deficiency anaemia. We conducted entomological and laboratory investigations of a head louse infestation in a 12-year-old girl who experienced severe anaemia and subsequent death. Numerous lice were found postmortem on the head, face and neck of the patient, as well as on bedding and clothing. Analysis of nits on individual hairs determined that the louse infestation had been present for at least 166 days. The lice had some morphological traits characteristic of body lice: the third antennal segment in some specimens was distinctly longer than wide, and the apices of some paratergal plates did not extend into intersegmental membranes, while other morphological features were characteristic of head or body lice. All lice were heterozygous for the T917I kdr genotype, a marker of permethrin resistance. Nineteen (79.2%, 95%CI 59.5%-90.8%) louse DNA samples tested TaqMan positive for Acinetobacter (Moraxellales; Moraxellaceae) sp. Available information and laboratory findings are further discussed regarding their possible contribution to the negative outcome of this case. We stress the impact head louse pediculosis can have on children with limited parental attention, and how severe head louse infestation may serve as warning sign of neglect, and other high-risk situations.

Prevalence of pediculosis among primary school children in Tunisia

Background: Pediculus humanus capitis (head lice) infestation is a global health concern, yet no study has examined its occurrence among primary school children in Tunisia. Aim: To assess the prevalence of Pediculus capitis and its epidemiological characteristics among primary school children living in rural and urban areas of Monastir, Tunisia. Methods: We used 2-step stratified cluster sampling to randomly select 2396 children from 14 primary schools in Monastir during the 2022/2023 academic year. Head lice infestation was assessed through visual inspection of the hair, and data on the socio-demographic characteristics, lifestyle and pediculosis history of the children were collected. We used SPSS version 20 to analyse the data and used descriptive statistics to rate the frequencies. Multivariate logistic regression was used to examine the association between pediculosis and the predictor variables. Results: Overall infestation rate was 17.5% (95% CI 16.0–19.1%); infestation was 5 times higher among girls (29.1%) than boys (6.3%). Schoolchildren living in crowded family households, those in the third and fourth grades and whose parents had low education level were more exposed to infestation. Combing frequency, comb sharing and history of previous infestation had significant impact (P < 0.05) on the prevalence of pediculosis. Multivariate logistic regression showed gender and treatment outcome as the main potentiating factors. Conclusion: These findings highlight the need for pediculosis prevention and integrated health promotion programmes among primary school children and their parents, teachers and nurses in Monastir and other parts of Tunisia.

Crimean-Congo haemorrhagic fever in Iraq

Background: Pediculus humanus capitis (head lice) infestation is a global health concern, yet no study has examined its occurrence among primary school children in Tunisia. Aim: To assess the prevalence of Pediculus capitis and its epidemiological characteristics among primary school children living in rural and urban areas of Monastir, Tunisia. Methods: We used 2-step stratified cluster sampling to randomly select 2396 children from 14 primary schools in Monastir during the 2022/2023 academic year. Head lice infestation was assessed through visual inspection of the hair, and data on the socio-demographic characteristics, lifestyle and pediculosis history of the children were collected. We used SPSS version 20 to analyse the data and used descriptive statistics to rate the frequencies. Multivariate logistic regression was used to examine the association between pediculosis and the predictor variables. Results: Overall infestation rate was 17.5% (95% CI 16.0–19.1%); infestation was 5 times higher among girls (29.1%) than boys (6.3%). Schoolchildren living in crowded family households, those in the third and fourth grades and whose parents had low education level were more exposed to infestation. Combing frequency, comb sharing and history of previous infestation had significant impact (P < 0.05) on the prevalence of pediculosis. Multivariate logistic regression showed gender and treatment outcome as the main potentiating factors. Conclusion: These findings highlight the need for pediculosis prevention and integrated health promotion programmes among primary school children and their parents, teachers and nurses in Monastir and other parts of Tunisia.

Quantitative structure-insecticidal activity of essential oils on the human head louse (Pediculus humanus capitis)

ABSTRACT In the search for natural and non-toxic products alternatives to synthetic pesticides, the fumigant and repellent activities of 35 essential oils are predicted in the human head louse (Pediculus humanus capitis) through the Quantitative Structure-Activity Relationships (QSAR) theory. The number of constituents of essential oils with weight percentage composition greater than 1% varies from 1 to 15, encompassing up to 213 structurally diverse compounds in the entire dataset. The 27,976 structural descriptors used to characterizing these complex mixtures are calculated as linear combinations of non-conformational descriptors for the components. This approach is considered simple enough to evaluate the effects that changes in the composition of each component could have on the studied bioactivities. The best linear regression models found, obtained through the Replacement Method variable subset selection method, are applied to predict 13 essential oils from a previous study with unknown property data. The results show that the simple methodology applied here could be useful for predicting properties of interest in complex mixtures such as essential oils.

Presence of the knockdown resistance (kdr) mutations in the head lice (Pediculus humanus capitis) population in the North of Iran

Presence of the knockdown resistance (kdr) mutations in the head lice (Pediculus humanus capitis) population in the North of Iran

Toxicity of 6-gingerol and Cymbopogon citratus against Pediculus humanus capitis De Geer (Phthiraptera: Pediculidae): Mortality, detoxifying enzymes, and morphological ultrastructure alterations in lice

Pediculus humanus capitis (head louse), which causes pediculosis capitis, remains a global health concern. Plant products are efficient alternative pediculicides for treating the human ectoparasite P. h. capitis which is resistant to permethrin. The study evaluates the toxicity and mechanisms of 6-gingerol and Cymbopogon citratus leaf extract on P. h. capitis. Pediculus humanus capitis adult stages were exposed to three different dosages of 6-gingerol and C. citratus crude leaf extract on filter sheets for 5, 10, and 30 min, respectively. The biochemical approach was used to assess the activity of detoxifying enzymes including acetylcholinesterase (AChE), glutathione S-transferase (GST), and oxidase. Scanning electron microscope (SEM) was used to investigate the ultrastructure of the morphological body of lice. After 30 min, 6-gingerol and C. citratus leaf extract killed P. h. capitis completely. Bioassay periods significantly affected lice mortality (P < 0.05). The LC50 values for 6-gingerol and C. citratus extract were 1.79 μg/cm2 and 25.0 μg/cm2, respectively. 6-Gingerol and C. citratus leaf extract significantly lower AChE and GST activity (P < 0.05). Cymbopogon citratus also caused morphological ultrastructure changes in P. h. capitis, including an irregularly formed head, thorax, abdominal respiratory spiracles, and belly. 6-Gingerol and C. citratus leaf extracts could be used as an alternate pediculicide to decrease P. h. capitis populations.

Measuring local genetic variation in permethrin-resistant head lice (Phthiraptera: Pediculidae) from Buenos Aires, Argentina.

The cosmopolitan ectoparasite human head louse, Pediculus humanus capitis (De Geer)(Phthiraptera:Pediculidae), affects mostly school-aged children, with infestations reported every year mainly due to louse resistance to pyrethroids. One of the main resistance mechanisms of pyrethroids is the target site insensitivity (kdr), which is caused by single-nucleotide point mutations (SNPs) located in the voltage-sensitive sodium channel gene. In this study, we analyzed individual head lice toxicologically via the description of their susceptibility profile to permethrin and genetically through the genotypification of their kdr alleles as well as nuclear microsatellite loci. Lice were collected from 4 schools in the city of Buenos Aires, Argentina. The resistance ratios varied from 33.3% to 71.4%, with a frequency of the T917I kdr mutation of 87.31% and with 83.6% of the head lice being homozygous resistant to pyrethroids. Microsatellite data indicated that all the louse school populations had genotype proportions that deviated from Hardy-Weinberg expectations, with FIS > 0 reflecting a deficit of heterozygotes. Bottleneck analysis suggested that all louse school populations underwent a recent reduction in population sizes, while 3 of the 4 schools had gene flow values around 1, indicating ongoing gene flow among those schools. Our study suggests that school louse populations in the city of Buenos Aires may form a metapopulation, where each school represents a small population that undergoes extinction and recolonization processes under strong permethrin selection. This is the first multilevel analysis integrating toxicological, kdr-genotyping, and microsatellite data in human louse populations.

Knowledge and Practice of Primary School Teachers Regarding Pediculosis Capitis in Baghdad, Iraq

Abstract Background: Pediculosis is a disease which is caused by the ectoparasite Pediculus humanus capitis. There is an estimated 19% global prevalence of head lice infestation among schoolchildren. Health education programs have a beneficial impact on the prevention and control of the disease. Increasing knowledge, changing attitudes and behaviors, and improving personal hygiene practices reduce the morbidity and prevalence of pediculosis capitis. Aim of Study: The aim of the study was to assess the knowledge and practice of primary school teachers about pediculosis capitis and to find the association of studied variables with knowledge and practice scores. Patients and Methods: A cross-sectional study was conducted in 20 primary schools in Baghdad, Iraq, from November 1, 2022, to January 31, 2023. It included 351 primary school teachers who had worked for at least 1 year. A questionnaire was distributed to teachers at selected schools for assessment of knowledge and practice. Results: In this study, 20.5% of studied cases had poor knowledge, 58% had fair and 21.5% had good knowledge. Regarding practice level, 43% of studied cases had poor, 37% had fair and 20% had good practice about pediculosis capitis. Poor knowledge and poor practice are significantly higher among participants with an institute level of education and lower duration of work, among singles, those who did not have children who had arts or sports specialties, and those who did not have pediculosis capitis cases. A strong positive correlation was noticed between knowledge and practice scores. Conclusion: The knowledge scores were fair, while the practice scores were poor. Multiple sources are considered a major source of information. There is no association between the gender of the participant and the level of knowledge and practice parameters.

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.

High mitochondrial gene diversity of Pediculus humanus capitis among children in northern Iran.

The head louse, Pediculus humanus capitis, is an obligate ectoparasite and its infestation remains a major public health issue worldwide. Determining the genetic characteristics of the existing clades is essential to identify the population structure and to develop head lice-control programs. Hence, we aimed to investigate the genetic diversity of head lice among infested individuals in northern Iran. Adult head lice were collected from 100 infested individuals referring to the health centers throughout five geographical regions in Mazandaran Province, Iran. Partial fragments of the mitochondrial cytb gene were amplified by PCR, then consequently sequenced. The results of the phylogenetic tree of collected head lice confirmed the existence of two clades, A and B, in the studied areas. Thirteen haplotypes were detected in the studied populations, of which 11 were novel haplotypes. Clade A was the dominant form and accounted for 75% of samples, while clade B included the rest. Haplotype and nucleotide diversity were 0.999 and 0.0411, respectively. Clade A and B of Pediculus humanus capitis exist among the human populations of northern Iran. We observed high genotypic diversity of this head lice.

OPTIMAL COMBINATION OF TOLUENE AND CLOVE OIL (Syizigium aromaticum) IN THE PROCESS OF CLEARING THE PERMANENT PREPARATION PEDICULUS HUMANUS CAPITIS

Clearing is a vital process in microscopy, aimed at enhancing the transparency of tissue preparations for clearer observation of insect structures. Despite its effectiveness, Toluene poses safety concerns due to its explosive nature. Therefore, clove oil (Syzygium aromaticum) has been explored as a safer alternative. This study evaluates the quality of permanent preparations of Pediculus humanus capitis using both toluene and clove oil. Comparative tests were conducted, treating adult head lice specimens with each solvent for three repetitions. Permanent preparations were assessed for clarity, color quality, and morphological integrity. Results indicate a significant difference in quality between the two methods. Toluene yielded mainly poor-quality preparations, while clove oil resulted in a higher proportion of preparations of good quality. The Mann-Whitney test confirmed the significance of this difference (p = 0.002). This study highlights the efficacy of clove oil as a safer alternative to toluene in the clearing process, contributing to entomological practices and chemical safety.

Study of prevalence of Head Lice (Pediculus Humanus Capitis) Among Schoolchildren in the Zawiya Region, Libya

Head lice are external parasitic insects, obligatory parasitism on humans, and their presence is widespread in all countries of the world. It affects children and adults, and children are more affected, and girls are more affected than boys. The sample size was about 3795 male and female students, with an average of 292 male and female students in each school. The percentage of boys was 52%, compared to 48% of girls. The number of people infected with the head lice parasite reached 232 male and female patients, representing a rate of 6.1%. While the number of male students infected with the head lice parasite reached 86 boys, out of the total number of boys, numbering 2,115 students, and their percentage was 4%, while the number of girls infected with the head lice parasite reached 146, out of the total number of girls, numbering 1,448 girls, and their percentage was 10% girls infected with head lice. Head. The highest infection rate in one of the schools was 32%, while the percentages in the rest of the schools ranged from 1% to 9%. The infection rate in the first semester was 9%, while in the second semester the percentage was 6.4%, while in the third semester the infection rate was 6.3%, while in the fourth semester the percentage was 6.2%, while the percentage of infected students in the fifth semester was 5.3%, in the semester Sixth, the percentage was 2.4%, which is considered the lowest percentage. The value of Sig = 0.000, which is less than 0.05, showed that the difference between the percentage of injuries in the years of study is a significant difference between the average of injuries and the years of study.

The Use of Rabbits Used to Propagate Human Lice for Research.

The globally important human diseases of trench fever, epidemic typhus, and relapsing fever are vectored by the human louse Pediculus humanus humanus. Although these conditions are epidemically quiescent at present, they persist in socially dysfunctional situations of war, deprivation, and crowding. The taxonomically closely related head louse, Pediculus humanus capitis, does not respect economic or social status and is quite common in most countries. The 2 types of lice are now recognized as conspecific ecotypes of a single species. While the body louse has been adapted for propagation in the laboratory by feeding in vivo on live rabbits, a similar animal model has not been developed for the host-specific head louse. Accordingly, research for treatment and control of the head louse has largely been performed by using laboratory-reared body lice. This review describes methods for the propagation of body lice in the laboratory and outlines at least 4 areas of research that require sufficient numbers of aged body louse cohorts produced in rabbits for use in controlled studies: 1) pediculicide development and resistance, 2) immunity and vaccine potential, 3) endosymbiotic bacteria needed by lice for nutrition, and 4) lice as vectors of human disease. The review concludes with a discussion of several ethical issues involved with the standard method of using unsedated rabbits and recommends consideration of providing sedating anesthetics for rabbits used in louse feeding procedures.

Optimizing Fixation Duration for Enhanced Clarity in Pediculus humanus capitis Whole Mount Preparations Using 10% KOH at 70°C

This study evaluates the optimal fixation duration using 10% potassium hydroxide (KOH) at 70°C for whole mount preparations of Pediculus humanus capitis (head lice). Accurate head lice identification is crucial for effective public health management. Specimens were fixed for 20, 25, 30, 35, and 40 minutes at 70°C, then processed through rinsing, acetic acid treatment, dehydration, and clearing before mounting for microscopic examination. Results showed that 25 minutes of fixation provided the clearest and most detailed preparations. This duration effectively achieved tissue dehydration and clarification without significant damage. Fixation for 20 minutes was insufficient, resulting in opaque specimens due to incomplete KOH diffusion. Conversely, 40 minutes of fixation caused over-fixation, leading to tissue damage and poorer color quality. The study underscores the importance of finding the right fixation duration. While shorter times are inadequate, longer durations can degrade specimen quality. A 25-minute fixation at 70°C is optimal for balancing clarity and structural preservation, improving head lice identification. This method enhances the quality of whole mount preparations and provides practical guidance for accurate and reliable ectoparasite examination in clinical and research settings.

The Association between Gender, Personal Hygiene Indicators, and Occupancy Density with the Incidence of Pediculosis Capitis at Madrasah Tsanawiyah Pondok Pesantren (Ponpes) Nurus Sunnah Semarang

Background: Pediculosis capitis is one of the neglected tropical diseases (NTDs) caused by Pediculus humanus capitis, an obligate ectoparasite that lives parasitically on human skin. This disease is most common in women, in people with poor personal hygiene, and in densely populated areas. Boarding schools are densely populated and pose a risk for transmission of pediculosis capitis due to the many interactions among residents. Purpose: This study aims to investigate the association between gender, personal hygiene indicators, and occupancy density with the incidence of pediculosis capitis at Madrasah Tsanawiyah Pondok Pesantren Nurus Sunnah Semarang. Methods: In this cross-sectional observational study, all the junior high school students at Ponpes Nurus Sunnah were included in a total of 49 subjects. The data were collected by filling out questionnaires, doing a direct examination of the hair, and counting the measurements of the room area. Data analysis was performed using SPSS 23.0 for Windows. Result: Pediculosis capitis infestation was found among 13 (26.5%) students, with a higher incidence in females (46.4%) than males (0%), in respondents with the habit of combing hair using a personal comb (37.1%), and in non-densely populated areas (58.8%). There was an association between gender (p=0.000), the habit of combing hair using a personal comb (p=0.006), and occupancy density (p=0.000) and the incidence of pediculosis capitis. Conclusion: Gender, the habit of combing hair using a personal comb, and occupancy density are associated with the incidence of pediculosis capitis...

Increasing the Knowledge of High School Biology Teachers on the Preservation of Pediculus humanus capitis in Preparat Glass

Pediculus humanus capitis (head lice) is an obligate ectoparasite. Preparation of specimens is a procedure carried out to accurately preserve, identify, and analyze head lice. The Palangka Raya Biology Teachers Forum (MGMP) has collaborated with the Community Service Team of the Biology Study Program. This activity aims to improve high school Biology teachers' skills in preserving Pediculus humanus capitis (morphological observation and identification). This provides a solution to make school laboratory practicals more attractive, as preserved specimens can be stored and used long-term. The activity was offline at the PPIIG Building Laboratory, Palangka Raya University, in August 2023. The activity included lectures, discussions, training, and pre-test and post-test evaluation. The evaluation results show an increase in scores after the training, with an average pre-test score of 50.00 increasing to 80.33 in the post-test. It can be concluded that participants' knowledge increased after attending this training.

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.

Growing Eucalypt Outside its Native Range: A Review on Suitability and Beneficial Role

Eucalypt is an industrial short rotation fast growing tree species (SRFGTs), having wide range regarding climatic and edaphic requirements in Indian subcontinent. Eucalyptus camaeldulensis, E. globulus, E. grandis, E. tereticornis and E. citriodora are the widely planted eucalyptus species for different purposes in the country. Oil extracted from E. globulus has medicinal value and used to inhibit the avian influenza virus H11N9, and has wide scope in cosmetics, perfume, food, beverages, phytotherapy and aromatherapy. Oil contain p-coumaric, gallic, gentisic, p-hydroxybenzoic, syringic and vanillic acids and catechol are the responsible for retarding seed germination growth and survival of Parthenium, Solanum lycopersicum, Lactuca sativa and Agrostis stolonifera. Burning of eucalypt leaves used as mosquito repellent and compound 1, 8 cineole of eucalypt oil damage and kills Pediculus humanus capitis and lice. Aqueous solutions extracted from different parts of eucalypt showed nematocidal properties. Maize, wheat, mustard, berseem, potato, lentil are agricultural crops widely grown under eucalypt based agroforestry systems. Wider spacing of eucalypt in block plantations or boundary plantation mostly adopted in the agroforestry systems. Eucalypt sequester carbon 6 – 43 Mg C ha-1 yr-1 under plantations and agroforestry systems. The species has potential to reclaim waterlogged sites and escalate soil health through improving soil physical, chemical and biological properties. In case of economic returns from eucalypt based agroforestry systems, it gives nearly 1.5 B:C ratio.

Essential Oil of Eucalyptus: A Natural Solution for Treating Pediculosis

Objective: Pediculosis is a condition caused by the infestation of Pediculus Humanus Capitis. The pesticides used in current formulations exhibit toxicity and carcinogenic effects on consumers. This study aimed to investigate the pediculicidal activity of the essential oil from Eucalyptus Globulus leaves, with the intention of adding it as an active ingredient in pediculicidal formulations to replace harmful chemicals.&#x0D; Design/methodology/approach: In vivo tests were conducted to assess the repellency and mortality of the essential oil obtained through hydrodistillation. The major components were determined through gas chromatography-mass spectrometry analysis. Additionally, proximate, and chemical composition analyses were performed on the eucalyptus leaves using ASTM E871, ASTM E872, ASTM D1104, TAPPI T264, TAPPI T207, ASTM D1106, and ASTM D1104 methods.&#x0D; Results: A repellency of 66.66% and 100% mortality within 2.26 minutes were obtained in the in vivo tests. The yield of hydrodistilled essential oil was 4 mL/kg, primarily composed of 71.04% 1,8-cineole, 18.94% 4-Ethyl-m-xylene, 2.72% γ-Terpinene, and 1.23% L-α-Pinene. Furthermore, the composition of eucalyptus leaves was determined as 61.25% moisture, 30.32% volatile matter, 6% ash, 2.40% fixed carbon, 11.22% acetone extractives, 33.03% water extractives, 31.49% lignin, 69.33% holocellulose, 62.09% cellulose, and 7.24% hemicellulose.&#x0D; Limitations on study/implications: The pediculicidal activity study was conducted solely on the essential oil, and further testing on the formulation of the finished product is necessary.&#x0D; Findings/conclusions: The pediculicidal activity study was conducted solely on the essential oil, and further testing on the formulation of the finished product is necessary.

A Clutching Claw: Unexpected Coexistence of Pediculosis Capitis and Tinea Capitis

Introduction: Pediculosis capitis and tinea capitis are very common superficial infections/infestations, primarily affecting school-aged children. The overall pediculosis capitis infestation rate exceeds 25% in some studies, and the occurrence rate for tinea capitis may be as high as 45%. They are more prevalent, but not exclusively, in crowded conditions and environments with low socioeconomic status. Scaly scalp is a common presentation of tinea that may be, at first glance, confused with pediculosis nits. Case Presentation: Here, we describe a case report showing the coexistence of both tinea capitis and pediculosis capitis in a young girl, supplemented with an interesting photograph of a nymph of Pediculus humanus capitis attached by its claws to a hair, with dystrophic endothrix hairs in the background. We also describe further fungal culture performed, with the result and the treatment the patient received. Conclusions: Tinea and pediculosis should always be excluded first in case of a scaly scalp in children. Whether their coexistence is attributed to a causal relation and not simply a poor environment is still to be investigated. This is especially important because body louse is a proven vector for a number of pathogens; however, this is still a matter of debate for head louse.