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

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.

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.

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.

HEAD LOUSE PALEOEPIDEMIOLOGY IN THE OSMORE RIVER VALLEY, SOUTHERN PERU.

Recent studies of louse ectoparasites from mummies have developed robust data sets that allow a true epidemiological approach to the prehistory of louse parasitism. One epidemiological principle is that the binomial of overdispersion is normally negative, meaning that in a host population, parasites are aggregated in a few individuals. We demonstrate the overdispersion of lice in 3 different prehistoric communities that differ along 3 axes or variables: environmental setting, socioeconomic status, and cultural affiliation. Distinct cultural practices could have been involved in different patterns of louse infestation. Prevalence, intensity, and abundance of infestations exhibit statistically significant differences between the communities. We also find differences in prevalence between subadults and adults that contrasted by cultural affiliation and suggest conditions different from those seen today. We show that overall prevalence was affected primarily by ecological setting, not socioeconomic status nor cultural affiliation. These findings demonstrate that statistical analysis of archaeological data can reveal the states of infestation in past populations with lifestyles not seen in modern people. Our approach paves the way for future comparisons of subpopulations within archaeological communities.

Pediculosis knowledge among schoolchildren parents and its relation with head lice prevalence.

Pediculosis mainly affects school-age children worldwide. The aim of this study was to identify and analyze the knowledge of the parents and guardians of children in elementary schools in Niterói, Brazil, regarding pediculosis. Questionnaires were applied to 237 guardians of children at five 1-5 grade municipal schools. The responses were analyzed and correlated with positivity to louse infestation, detected by scalp aspiration. 73.8% of the respondents reported that their child had already been infested with lice. 32.9% presented correct responses about transmission. Incorrect responses were attributed to the air/wind, blood type and the fact that lice jump and fly. 40.1% of the respondents erroneously correlated control over the parasitosis with hygiene. A majority of the participants (58.6%) responded that pediculosis is harmful to health, while a small proportion (20.7%) considered it to be a disease. The prevalence of pediculosis was 19.8% among schoolchildren. Female sex, pruritus on the head and indifference regarding infestation were shown to be risk factors for pediculosis. The lack of perception of pediculosis as a disease may lead to naturalization of this parasitosis. Incorrect responses may add difficulty to implementation of preventive and curative approaches, which highlights the importance of dissemination of correct information about pediculosis.

Determination of Knockdown Resistance (kdr) Allele Frequencies (T929I mutation) in Head Louse Populations from Mexico, Canada, and Peru.

The head louse Pediculus humanus capitis (De Geer) is a hematophagous ectoparasite that inhabits the human scalp. The infestations are asymptomatic; however, skin irritation from scratching occasionally may cause secondary bacterial infections. The present study determined the presence and frequency of the knockdown resistance (kdr) mutation T929I in 245 head lice collected from Mexico, Peru, and Canada. Head lice were collected manually using a comb in the private head lice control clinic. Allele mutation at T9291 was present in 100% of the total sampled populations (245 lice) examined. In addition, 4.89% of the lice were homozygous susceptible, whereas 6.93% heterozygous and 88.16% homozygous were resistant, respectively. This represents the second report in Mexico and Quebec and fist in Lima.

First exploratory study of bacterial pathogens and endosymbionts in head lice from a Mayan community in southern Mexico.

Lice represent one of the most neglected group of vectors worldwide, particularly in Latin America. Records of bacterial agents related to head lice are non-existent in this region of the continent. Many of these communities often do not have adequate access to public services and/or health protection. The normalization of this condition prevents them from manifesting discomfort, such as bites and itching, which further aggravates the situation, as they can be vectors of important diseases. For this reason, the aim of this work was to identify the richness of bacterial pathogens (Acinetobacter, Bartonella, and Rickettsia) and endosymbionts (Wolbachia) in head lice of paediatric patients from the indigenous municipality of Hoctun, Yucatan, Mexico. DNA extraction was performed using the QIAamp DNA Mini Kit. For the detection of bacterial pathogens, fragments of the gltA, rpoB, and 16S rDNA genes were amplified. For the detection of Wolbachia, the wsp gene was amplified. Of the 28 lice analysed, the presence of two genera of bacterial pathogens was detected Acinetobacter (42.9% = 12/28) and Bartonella (7.14% = 2/28). We also detected the endosymbiont Wolbachia (71.42% = 20/28). Our results showed that DNA from three bacteria species (Acinetobacter baumannii, Bartonella quintana, and Wolbachia pipientis) was present with frequencies ranging from 3.57% to 71.42%. This work represents the first exploratory study of the diversity of agents associated with head lice (Pediculus humanus capitis) in Mexico and Latin America. Due to the findings generated in the present study, it is important to perform surveillance of head lice populations to identify the degree of spread of these pathogens and their impact on populations in the region.

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.

Head lice were also affected by COVID-19: a decrease on Pediculosis infestation during lockdown in Buenos Aires.

Pediculosis is a worldwide disease affecting school-aged children produced by the presence of the head louse, Pediculus humanus capitis De Geer, an obligate ectoparasite on the human scalp feeding exclusively on blood. Transmission occurs primarily through direct physical head-to-head contact. In March 2020, the World Health Organization (WHO) declared the COVID-19 outbreak as a pandemic. COVID-19 is caused by SARS-CoV-2, a variant of the coronavirus. Therefore, on March 18, 2020, the Argentinean government established mandatory isolation for an indefinite period. This obligatory isolation interrupted regular classes avoiding direct contact between children, thus affecting the dispersal route of individuals and the evolution of head louse populations. In this study, we evaluated through an online survey how confinement affected the prevalence of lice during lockdown compared to the situation prior to confinement. The survey allowed to discriminate the different control strategies, the number of treatments, and the amount of insects recorded by parents. Data of 1118 children obtained from 627 surveys were analyzed. As the main result, it was observed that prevalence of lice decreased significantly from before (69.6%) to during (43.9%) COVID-19 lockdown. Moreover, head lice infestation was more effectively controlled in households with up to 2 children in comparison to households with 3 or more children. This is the first study that analyzed the prevalence of head lice during COVID-19 pandemic. In addition, this work demonstrated the impact of social distance in the population dynamics of head lice and how it could affect the control strategies in the future.

Pediculosis Affects Mexican Children from Different Socioeconomic Status Equally: A Cross-Sectional Study.

The prevalence of pediculosis in Mexican children was studied in San Nicolas and Tapachula, Mexico. A cross-sectional study included 888 students between six and 12 years old from two urban communities with an unequal socioeconomic status between September 2015 and March 2016. A Pearson χ2 and multivariate logistic analysis were carried out to associate risk factors to pediculosis. The overall prevalence of pediculosis from both localities was 23.9%. The female gender; long and medium hair; living with someone infested; previously infested by head lice and curling hair were variables linked to a significantly higher prevalence of pediculosis (p < 0.01). Nevertheless, no significant differences were observed in the age groups, localities and socioeconomic status for human lice infection. Socioeconomic variables such as numbers of inhabitants, floors of house, beds and rooms; and parents' qualification did not show a significative association for pediculosis. Health education in schools is needed for pediculosis prevention and remove the stigmatization of this disease related to poverty.

Sensory features of the human louse antenna: new contributions and comparisons between ecotypes.

Body and head lice are known to be exclusive ectoparasites of human hosts. Current genomic and transcriptomic data suggest that both louse types represent ecotypes of the same species. They exhibit morphological and physiological differences that probably arose from living in different biotopes. Sensory traits represent suitable candidates to be affected by environmental heterogeneity. Therefore, through scanning electron microscope studies, this study analysed and compared the sensory structures of both ecotypes' antennae. Seven types of sensory structures were identified in both ecotypes: bristles, tuft organs, pore organs, single pore and three morphotypes of sensilla basiconica. Notably, the single pore and the morphotypes of sensilla basiconica were described for the first time in the body louse antenna. This study's comparative analysis mainly revealed size differences across the sensory structures of the ecotypes. Bristles of the flagellomere 2 of the body louse antenna were longer than the head louse bristles. In addition, the pore organs of the head louse antenna presented a higher diameter than those of the body louse. The possible relevance of size differences regarding the biotopes exploited by the body louse and the head louse is discussed. Yet, physiological studies may help to fully understand the phenotypical differences of both ecotypes.

Island and Riverine populations of Alouatta belzebul from the Brazilian Amazon parasitized by Pediculus mjobergi.

Mammalian lice are obligate hematophagous ectoparasites that remain on the host throughout the life cycle. This study showed an endangered wild howler species (Alouatta belzebul) parasitized by Pediculus mjobergi. Twenty-seven primates were rescued during wildlife rescue activities in the process of vegetation suppression at the Belo Monte Hydroelectric Power Plant (UHE), located on the lower Xingu River, in the Brazilian Amazon basin. Among the 27 primates examined from two vegetal formations (alluvial rainforest and liana-infested forest) areas, 13 (48.15%) were parasitized by lice with all positive primates being from alluvial rainforest. Optical and scanning electron microscopy allowed the visualization of the structures and the diagnostic characters of the lice species in greater detail expanding the current description. These results highlight the importance of considering ecological and regional features to provide a better understanding of the factors that promote parasitism.

Pediculosis capitis among school-age students worldwide as an emerging public health concern: a systematic review and meta-analysis of past five decades.

Pediculosis by Pediculus humanus capitis is still an important health issue in school-age students worldwide. Although pediculicidal agents effectively kill head lice, the re-infestation rate is still high. This study was conducted to provide a summary of evidence about the prevalence of pediculosis capitis among school-age students worldwide. Different databases including MEDLINE/PubMed, Scopus, and Web of Science were searched for publications related to pediculosis capitis in school-age students from 1977 to 2020. All peer-reviewed original research articles describing pediculosis capitis among school-age students were included. Statistical heterogeneity of the different years among studies was assessed using the standard chi squared and I2 tests. Due to the significant heterogeneity, a random effect model was adopted to estimate the pooled, continent, and gender-specific prevalence of pediculosis. Two hundred and one papers met the inclusion criteria of this review and entered into the meta-analysis including 1,218,351 individuals. Through a random effect model, the prevalence of pediculosis capitis among school students was estimated as 19% (CI 95% = 0.18-0.20%, I2 = 99.89%). The prevalence of pediculosis capitis among boys was 7% (CI 95% = 0.05-0.10) compared to 19% (CI 95% = 0.15-0.24) in girls. The highest prevalence was in Central and South America (33%, CI 95% = 0.22-0.44, I2 = 99.81%) and the lowest was in Europe (5%, CI 95% = 4-6, I2 = 99.28%). Relatively high pediculosis capitis prevalence among school-age students observed in this study emphasizes the need for implementing screening and prophylaxis tailored to the local context.

First evidence of the mutations associated with pyrethroid resistance in head lice (Phthiraptera: Pediculidae) from Honduras.

BACKGROUND: The human head louse, Pediculus humanus capitis, is a cosmopolitan blood-sucking ectoparasite affecting mostly schoolchildren in both developed and developing countries. In Honduras, chemical pediculicides are the first line of treatment, with permethrin as their main active ingredient. Despite the extended use of these products, there is currently no research investigating insecticide resistance in Honduran head lice. In head lice, the most common mechanism is knockdown resistance (kdr), which is the result of two point mutations and the associated amino acid substitutions, T917I and L920F, within the voltage-sensitive sodium channel (VSSC). METHODS: Genomic DNA was extracted from 83 head lice collected in the localities of San Buenaventura and La Hicaca, Honduras. Polymerase chain reaction (PCR) was used to amplify a 332-bp fragment of the VSSC gene that contains a site affected by C/T mutation which results in a T917I amino acid substitution on each human head louse genomic DNA fragments. RESULTS: The C/T non-synonymous mutation which results in the T917I kdr amino acid substitution was detected in both head lice populations at frequencies ranging between 0.45-0.5. Globally, the frequency of this substitution was 0.47. Of these, 5 (6.1%) were homozygous susceptible and 78 (93.9%) were heterozygotes. The kdr-resistant homozygote (RR) was not detected in the studied populations. Thus, 93.9% of the head lice collected in Honduras harbored only one T917I allele. Exact test for the Hardy-Weinberg equilibrium for both localities showed that genotype frequencies differed significantly from expectation. In addition, San Buenaventura and La Hicaca populations had an inbreeding coefficient (Fis) < 0, suggesting an excess of heterozygotes. CONCLUSIONS: To our knowledge, this is the first study showing the presence of the C/T mutation responsible of the T917I kdr allele associated with pyrethroid resistance in P. h. capitis from Honduras. The PCR-restriction fragment length polymorphism (RFLP) employed here has demonstrated to be a reliable, economic, and reproducible assay that can be used to accurately genotype individual head lice for the mutation encoding the resistance-conferring T917I amino acid substitution. This highlights the necessity of proactive resistance management programmes designed to detect pyrethroid mutations before they become established within populations of head lice.

Vaccuuming method as a successful strategy in the diagnosis of active infestation by Pediculus humanus capitis.

Most human epidemiological and clinical studies use visual inspection of the hair and scalp to diagnose Pediculus humanus capitis , however this method has low sensitivity to diagnose active infestations (presence of nymphs and adult lice). Vacuuming the hair and scalp has been used as a diagnostic method, but there are no previous data comparing its effectiveness with visual inspection. The aim of this study was to determine the prevalence of overall infestation (nits and trophic stages), of active infestation by Pediculus humanus capitis , and to evaluate the effectiveness of vacuuming in comparison with the visual inspection. Visual inspection was performed by three examiners and vacuuming of the scalp by one investigator, with an adapted vacuum cleaner. A total of 166 children aged 4 to 10 years old were randomly selected from public schools in Southern Brazil. Considering the positive results obtained by both methods, the prevalence of overall infestation was 63.3%, whereas active infestation was 18.7%. The visual inspection was more effective on diagnosing overall infestation, however, its effectiveness to detect active infestation was lower, ranging from 0.6% (RR=3%, p<0.001) to 6.6% (RR=35%, p=0.001), depending on the number of examiners. The effectiveness of vacuuming to diagnose active infestation was higher than the one of visual inspection, with a prevalence rate of 16.3% (RR=87%, p=0.332). As presented in our study, the vacuuming method was 2.74 to 7.87 times most likely to detect active infestation, thus it could be adopted as a more accurate method to diagnose active pediculosis.

Severe pediculosis capitis in a nursery school girl / Pediculosis capitis grave en una niña inscrita en una guardería

Pediculosis capitis is the most frequent ectoparasitosis around the world. The infestation is caused by Pediculus humanus capitis (head louse), which affects hair, scalp, and skin. It rarely presents with more symptoms and in the majority of the cases, it shows a benign course if treated properly. We present the case of a nursery school girl with head lice infestation for 18 months. She did not improve after the shampoo treatment. This case was associated with furunculosis, skin lesions, multiple adenopathies, and anemia. Initially, the presence of boils, alopecia, and lymphadenopathy was evident. The persistence of pediculosis capitis and intense scratching induced changes on skin integrity, facilitating opportunistic bacterial superinfection that led to impetiginization, furunculosis, excoriations, hematic scabs, anemia, alopecia, and lymphadenopathies. Pediculosis capitis affected the patient triggering psychological, economic, social, and other health problems. The patient presented uncommon symptoms (furunculosis, anemia, fever, alopecia, and adenopathies) resulting from the persistence of risk factors and the absence of head inspection and mechanical removal of insects. The education about the risk factors, as well as sanitary controls, are essential to contain the infestation.

La pediculosis capitis es la ectoparasitosis más frecuente a nivel mundial. La infestación es causada por Pediculus humanus capitis (piojo de la cabeza) y afecta el cabello, el cuero cabelludo y la piel. Rara vez se manifiesta con otro tipo de sintomatología y, por lo general, su curso es benigno si se trata adecuadamente. Se presenta el caso de una menor con pediculosis capitis de 18 meses de evolución, asociada con forúnculos, lesiones cutáneas, múltiples adenopatías y anemia, que no mejoró tras la aplicación del champú. Inicialmente, llamó la atención la presencia de forúnculos, alopecia y adenopatías. La persistencia de la pediculosis capitis y el rascado intenso alteraron la integridad de la epidermis y facilitaron las infecciones secundarias por bacterias patógenas y oportunistas que produjeron impétigo, forunculosis, excoriaciones, costras hemáticas, anemia, alopecia y linfadenopatías. La pediculosis capitis afectó notoriamente a la paciente al causarle problemas psicológicos y de salud, agudizados por su condición económica y social. La paciente presentó manifestaciones clínicas poco frecuentes (forunculosis, anemia, fiebre, alopecia y adenopatías), lo cual se vio facilitado por la persistencia de los factores de riesgo y el hecho de que no se le inspeccionaba la cabeza ni se removían los insectos. La educación sobre los factores de riesgo y el control sanitario es indispensable para controlar la infestación.

Pediculosis capitis grave en una niña inscrita en una guardería / Severe pediculosis capitis in a nursery school girl

La pediculosis capitis es la ectoparasitosis más frecuente a nivel mundial. La infestación es causada por Pediculus humanus capitis (piojo de la cabeza) y afecta el cabello, el cuero cabelludo y la piel. Rara vez se manifiesta con otro tipo de sintomatología y, por lo general, su curso es benigno si se trata adecuadamente. Se presenta el caso de una menor con pediculosis capitis de 18 meses de evolución, asociada con forúnculos, lesiones cutáneas, múltiples adenopatías y anemia, que no mejoró tras la aplicación del champú. Inicialmente, llamó la atención la presencia de forúnculos, alopecia y adenopatías. La persistencia de la pediculosis capitis y el rascado intenso alteraron la integridad de la epidermis y facilitaron las infecciones secundarias por bacterias patógenas y oportunistas que produjeron impétigo, forunculosis, excoriaciones, costras hemáticas, anemia, alopecia y linfadenopatías. La pediculosis capitis afectó notoriamente a la paciente al causarle problemas psicológicos y de salud, agudizados por su condición económica y social. La paciente presentó manifestaciones clínicas poco frecuentes (forunculosis, anemia, fiebre, alopecia y adenopatías), lo cual se vio facilitado por la persistencia de los factores de riesgo y el hecho de que no se le inspeccionaba la cabeza ni se removían los insectos. La educación sobre los factores de riesgo y el control sanitario es indispensable para controlar la infestación.

Pediculosis capitis is the most frequent ectoparasitosis around the world. The infestation is caused by Pediculus humanus capitis (head louse), which affects hair, scalp, and skin. It rarely presents with more symptoms and in the majority of the cases, it shows a benign course if treated properly. We present the case of a nursery school girl with head lice infestation for 18 months. She did not improve after the shampoo treatment. This case was associated with furunculosis, skin lesions, multiple adenopathies, and anemia. Initially, the presence of boils, alopecia, and lymphadenopathy was evident. The persistence of pediculosis capitis and intense scratching induced changes on skin integrity, facilitating opportunistic bacterial superinfection that led to impetiginization, furunculosis, excoriations, hematic scabs, anemia, alopecia, and lymphadenopathies. Pediculosis capitis affected the patient triggering psychological, economic, social, and other health problems. The patient presented uncommon symptoms (furunculosis, anemia, fever, alopecia, and adenopathies) resulting from the persistence of risk factors and the absence of head inspection and mechanical removal of insects. The education about the risk factors, as well as sanitary controls, are essential to contain the infestation.

Lifestyle Recommendations for Management of Pediculosis from the Viewpoint of Persian Medicine

Introduction: Pediculosis Capitis (head lice infestation) is the most common disease of the bloodsucking insect which affects approximately six to twenty million cases and results considerable economic burden annually. In this study we aim to investigate some medieval Persian views on the role of non-pharmacological treatment strategies for prevention and control of pediculosis and compare their prescriptions with current findings. Materials and methods: In this qualitative study, we reviewed some well-known Persian medicine (PM) textbooks based on the selected keywords (Shepesh, Reshk, Ghamal and Seyban) to collect the viewpoint of PM scholars for pediculosis and its treatments. Also, we searched in the databases such as PubMed, Science direct and Scopus about the topic. Results: Persian medicine scientists believed that there are six essential health principles (SetteZaroorieh), which can affect human health and prevent diseases including air, nutrition, exercise, sleep and wakefulness, exertion of unnecessary materials from the body and finally psychological concepts. Proper management of these essential factors can improve lifestyle of people affected with pediculosis and also play a key role in prevention of head lice infestation. Conclusion: There are several suitable recommendations for prevention and control of pediculosis according to essential health principles in PM which can consider beside current drug treatments and the individual health recommendations for complete control of the disease