The origin and distribution of human lice in the world

Pediculosis capitis risk factors in schoolchildren: hair thickness and hair length

The human head lice is a cosmopolitan ectoparasite that causes pediculosis. The main way of spreading lice is through direct head-to-head contact. It is popular knowledge that some individuals are more susceptible to contracting head lice than others. Reports of individuals who have never been affected by the disease are common, even living in the same environment and under the same conditions as people who regularly have lice infestations. Previous research has been carried out on the risk of this infection associated with different human factors like gender or age. However, studies on the influence of the individual hair characteristics are scarce. The objective of the study was to analyze the pediculosis risk using geographical location, gender, age and individual hair characteristics as variables. Pediculosis was diagnosed through the detection of living lice in the hair. This cross-sectional school-based epidemiological study was conducted in 310 schoolchildren aged 1 to 13 years of schools in 4 municipalities situated in the State of Paraná, Brazil. The prevalence of head louse infection in primary school students was 49.35 %. The Odds Ratio of presence of pediculosis (OR) was estimated using multivariate logistic regression analysis. The results obtained indicate that hair length and thickness increase the risk of infection. Furthermore, the inclusion of hair color, hair shape, kind of hair-scale as covariates increases the risk of pediculosis, indicating that these variables partly explain this susceptibility and that pediculosis is independent of gender. A smaller hair diameter may favor insect fixation to the hair in the nymphal phases. These results may explain why girls are a greater risk as they let their hair grow for cultural reasons, i.e., being of female gender is an agglutinating variable. The conclusions drawn may explain the discrepancies obtained in previous analyses.

POPULATION STRUCTURE AND BARTONELLA QUINTANA IN HEAD AND BODY LICE IN POKHARA, NEPAL (ANOPLURA: PEDICULIDAE)

This study examined the population structure of head and body lice infesting a random sample of people in Pokhara, Nepal during 2003, 2004, and 2005. A total of 106 participants (6 to 72 yr old, median = 12) volunteered to have lice collected from their heads and clothing. Most participants (70%) harbored only head lice, some (15%) had only body lice, and some (15%) had concurrent infestations of head and body lice (dual infestations). A total of 1,472 lice was collected. Significantly more nymphs were collected than adult lice. Louse populations were generally small (geometric mean = 8.8 lice per person) but a few participants harbored larger louse populations (maximum = 65 lice). People with dual infestations harbored significantly more lice than people with single infestations; however, there was no difference in the infestation intensities between people infested with head lice only vs. those infested with body lice only. Male participants harbored significantly more lice than did females. There were no significant differences in infestation intensity due to participant age or their socioeconomic level. The sex ratio of adult lice was increasingly female biased with increasing adult louse density. Infection of lice with Bartonella quintana was low (ca. 1.5%). Pediculosis is a common problem in urban Nepal.

Nuclear genetic diversity of head lice sheds light on human dispersal around the world

The human louse, Pediculus humanus, is an obligate blood-sucking ectoparasite that has coevolved with humans for millennia. Given the intimate relationship between this parasite and the human host, the study of human lice has the potential to shed light on aspects of human evolution that are difficult to interpret using other biological evidence. In this study, we analyzed the genetic variation in 274 human lice from 25 geographic sites around the world by using nuclear microsatellite loci and female-inherited mitochondrial DNA sequences. Nuclear genetic diversity analysis revealed the presence of two distinct genetic clusters I and II, which are subdivided into subclusters: Ia-Ib and IIa-IIb, respectively. Among these samples, we observed the presence of the two most common louse mitochondrial haplogroups: A and B that were found in both nuclear Clusters I and II. Evidence of nuclear admixture was uncommon (12%) and was predominate in the New World potentially mirroring the history of colonization in the Americas. These findings were supported by novel DIYABC simulations that were built using both host and parasite data to define parameters and models suggesting that admixture between cI and cII was very recent. This pattern could also be the result of a reproductive barrier between these two nuclear genetic clusters. In addition to providing new evolutionary knowledge about this human parasite, our study could guide the development of new analyses in other host-parasite systems.

Evidence for Bartonella quintana in Lice Collected from the Clothes of Ethiopian Homeless Individuals

Human lice, Pediculus humanus, can transmit various pathogens, including Bartonella quintana, Borrelia recurrentis, and Rickettsia prowazekii. Xenosurveillance is an epidemiological approach to assessing human infection risks performed by screening vectors of infectious disease agents. In the proof-of-principle study reported herein, the DNA of 23 human lice was collected from the clothes of 30 homeless Ethiopian individuals. These samples were assessed using 16S rRNA gene-specific pan-eubacterial PCR for screening, followed by Bartonella genus 16S-23S internal transcribed spacer (ITS) sequence-specific PCR, Bartonella genus gltA gene-specific PCR, and 16S rRNA gene PCR with specificity for relapsing-fever-associated Borrelia spp. with subsequent sequencing of the amplicons. In one sample, the pan-eubacterial 16S rRNA gene-specific screening PCR, the Bartonella genus 16S-23S ITS sequence-specific PCR, and the Bartonella genus gltA gene-specific PCR allowed for the sequencing of B. quintana-specific amplicons. In two additional samples, Bartonella genus gltA gene-specific PCR also provided sequences showing 100% sequence identity with B. quintana. In total, 3/23 (13.0%) of the assessed lice were found to be positive for B. quintana. Correlating clinical data were not available; however, the assessment confirmed the presence of B. quintana in the local louse population and thus an associated infection pressure. Larger-sized cross-sectional studies seem advisable to more reliably quantify the infection risk of lice-infested local individuals. The need for prevention by providing opportunities to maintain standard hygiene for Ethiopian homeless individuals is stressed by the reported findings, especially in light of the ongoing migration of refugees.

Infectious diseases may have arrested the southward advance of microblades in Upper Palaeolithic East Asia

An unsolved archaeological puzzle of the East Asian Upper Palaeolithic is why the southward expansion of an innovative lithic technology represented by microblades stalled at the Qinling-Huaihe Line. It has been suggested that the southward migration of foragers with microblades stopped there, which is consistent with ancient DNA studies showing that populations to the north and south of this line had differentiated genetically by 19 000 years ago. Many infectious pathogens are believed to have been associated with hominins since the Palaeolithic, and zoonotic pathogens in particular are prevalent at lower latitudes, which may have produced a disease barrier. We propose a mathematical model to argue that mortality due to infectious diseases may have arrested the wave-of-advance of the technologically advantaged foragers from the north.

Comparative efficacy of chemical and botanical pediculicides in Thailand and 4% dimeticone against head louse, Pediculus humanus capitis

Head louse infestations remain a global public-health concern due to increased resistance of lice to artificial pediculicides. In Thailand, there is a lack of comparative data on the current efficacy of pediculicides for treating head lice. In this study, we explored the status of botanical and toxic synthetic pediculicides with that of 4% dimeticone liquid gel for treating head lice in Thailand. The ex-vivo pediculicidal activity of various pediculicidal shampoos available at drugstores in Thailand was assessed and compared with that of 4% dimeticone liquid gel. The shampoos chosen were based on active ingredients toxic to lice (1% permethrin, 0.6% carbaryl, 0.15% Stemona root crude extract, or mixed plant extracts), whereas dimeticone acts physically on lice. We found that exposure to 4% dimeticone liquid gel following the manufacturer's instructions completely killed 100% of head lice in 15 min, whereas other pediculicide products failed to kill the great majority of head lice, whether treatment was for 10 min (resulting in 0% to 50.0% mortality) or 30 min (resulting in 17.0% to 60.0% mortality). We also extended a clinical assessment to confirm the efficacy of 1% permethrin for treating head lice in infested schoolchildren. In this clinical assessment, none of the 26 children treated with 1% permethrin shampoo achieved a cure after two applications. These results highlight that 4% dimeticone demonstrated a higher ex-vivo pediculicidal efficacy compared to both chemical and botanical pediculicides in Thailand. Conversely, 1% permethrin showed low efficacy in both laboratory and clinical assessments. Given its physical mode of action, 4% dimeticone merits consideration as an alternative treatment option for lice in Thailand, particularly in cases where treatment with toxic pediculicides has proven ineffective.

Lice and lice-borne diseases in humans in Africa: a narrative review

Lice are host-specific insects. Human lice include Pediculus humanus humanus (body lice) which are known to be vectors of serious human bacterial infectious diseases including epidemic typhus, relapsing fever, trench fever and plague; Pediculus humanus capitis (head lice) that frequently affect children; and Pthirus pubis, commonly known as crab lice. In Africa, human infections transmitted by lice remained poorly known and therefore, underestimated, perhaps due to the lack of diagnostic tools and professional knowledge. In this paper we review current knowledge of the microorganisms identified in human lice in the continent of Africa, in order to alert health professionals to the importance of recognising the risk of lice-related diseases.

Human pediculosis, a global public health problem

BACKGROUND

Human pediculosis is caused by hematophagous lice, which are transmitted between individuals via direct and/or indirect contact. Despite the public health importance of louse infestation, information concerning the global burden of pediculosis and the epidemiological landscape of louse-borne diseases is limited. The aim of this review was to summarize the biology, epidemiology, diagnosis, and control of lice infestation in humans. We also discussed the latest advances in molecular taxonomy and molecular genetics of lice.

METHODS

We searched five electronic bibliographic databases (PubMed, ScienceDirect, CNKI, VIP Chinese Journal Database, and Wanfang Data) and followed a standard approach for conducting scoping reviews to identify studies on various aspects of human lice. Relevant information reported in the identified studies were collated, categorized, and summarized.

RESULTS

A total of 282 studies were eligible for the final review. Human pediculosis remains a public health issue affecting millions of people worldwide. Emerging evidence suggests that head lice and body lice should be considered conspecific, with different genotypes and ecotypes. Phylogenetic analysis based on mitochondrial (mt) cytb gene sequences identified six distinct clades of lice worldwide. In addition to the direct effect on human health, lice can serve as vectors of disease-causing pathogens. The use of insecticides plays a crucial role in the treatment and prevention of louse infestation. Genome sequencing has advanced our knowledge of the genetic structure and evolutionary biology of human lice.

CONCLUSIONS

Human pediculosis is a public health problem affecting millions of people worldwide, particularly in developing countries. More progress can be made if emphasis is placed on the use of emerging omics technologies to elucidate the mechanisms that underpin the physiological, ecological, and evolutionary aspects of lice.

Serologic study of Bartonella sp. infection among human population of Southern Spain

INTRODUCTION

The purpose of this study was to determine the prevalence of IgG antibodies against Bartonella sp. in a randomly selected sample from the population of the patients of North Sanitary District of Jaén.

METHODS

We used a commercially available immunofluorescent test (Focus-Technology IFA Bartonella quintana and B. henselae test).

RESULTS

Six hundred five healthy individuals were divided by sex into three age groups. We detected that 13.55% and 11.07% subjects were IgG seropositive to B. henselae and B. quintana, respectively.

CONCLUSIONS

Our data show that the prevalence of both Bartonella species in Andalusia (Southern Spain) is relatively high. No statistical difference in the seropositivity was observed among these groups. In both cases, the IgG antibody titers ranged from 1/128 to 1/512.

Head Lice Infestation in Schoolchildren, in Poland-Is There a Chance for Change?

Pediculosis capitis is a current and neglected health issue worldwide. The lack of screening programs contributes to the marginalization of the problem and delays therapeutic measures. Our study aimed to analyze the occurrence of this parasitosis in primary schools in Poland and to determine factors contributing to the persistence of its foci. The research tools were two questionnaires: one for primary school children and the other for school managers. While children answered questions about the epidemiology of pediculosis capitis and expressed their opinion on the hygienic condition of infested persons, the school directors were asked about the occurrence of head lice in schools, preventive measures, and institutions supporting schools in combating the infestation. The survey covered the period 2014–2018. Pediculosis capitis was reported in 87.5% of the schools. The greatest number of cases was reported in the group of 6–9 year-olds (68%). Among 4970 children, 16.7% had no knowledge of head lice; however, 57.1% wanted to increase their awareness of the problem. Campaigns on lice were conducted mainly as a result of emerging pediculosis capitis cases, and most schools could not rely on institutional support. Screening programs and preventive educational campaigns should be part of pediculosis capitis control in Poland.

Frequency of pyrethroid resistance in human head louse treatment: systematic review and meta-analysis

Head lice (Pediculus humanus capitis) are one of the most common insects causing infestations in humans worldwide, and infestation is associated with adverse socio-economic and public health effects. The development of genetic insensitivity (e.g., target site insensitivity = knockdown resistance or kdr) to topical insecticides has impaired effective treatment. Therefore, this study was undertaken to review and meta-analyze the frequency of pyrethroid resistance in treated head louse populations from the beginning of 2000 to the end of June 2021 worldwide. In order to accomplish this, all English language articles published over this period were extracted and reviewed. Statistical analyses of data were performed using fixed and random effect model tests in meta-analysis, Cochrane, meta-regression and I2 index. A total of 24 articles from an initial sample size of 5033 were accepted into this systematic review. The mean frequency of pyrethroid resistance was estimated to be 76.9%. In collected resistant lice, 64.4% were homozygote and 30.3% were heterozygote resistant. Globally, four countries (Australia, England, Israel, and Turkey) have 100% kdr gene frequencies, likely resulting in the ineffectiveness of pyrethrin- and pyrethroid-based pediculicides. The highest resistance recorded in these studies was against permethrin. This study shows that pyrethroid resistance is found at relatively high frequencies in many countries. As a result, treatment with current insecticides may not be effective and is likely the cause of increased levels of infestations. It is recommended that resistance status be evaluated prior to insecticide treatment, to increase efficacy.

Human Ectoparasites Are Highly Prevalent in the Rural Communities of Northwest Ethiopia: A Community-Based Cross-Sectional Study

BACKGROUND

Ectoparasites are organisms which inhabit the skin or outgrowths of the skin of another organism (the host). Many ectoparasites are known to be vectors of pathogens, which the parasites typically transmit to hosts. Though, ectoparasites are common in the vulnerable groups and economically disadvantaged communities, there is limited evidence on its magnitude in Ethiopia. This community-based cross-sectional study was, therefore, conducted to assess the prevalence and associated factors of ectoparasites in the rural communities of northwest Ethiopia.

METHODS

A community-based cross-sectional study design with structured observation was conducted among 1191 randomly selected rural households in northwest Ethiopia in May 2016. Data were collected using structured interviewer administered interview questionnaire and structured observation checklist. Prevalence of human ectoparasites in the rural communities was defined as the presence of one or more lice, fleas, bed bugs, mites, and ticks and the presence of these ectoparasites were observed by trained environmental health experts. Multivariable binary logistic regression analysis was used to identify variables associated with prevalence of ectoparasites on the basis of adjusted odds ratio (AOR) with 95% confidence interval (CI) and P values <.05.

RESULTS

Of a total of 1191 rural households, human or hair lice were observed in one or more of the family members in 186 (15.6%) rural households. Similarly, fleas were observed in more than half, 609 (51.1%) of rural households and bed bugs were observed in 441 (37%) rural households. Furthermore, mites and ticks were reported in 113 (9.5%) and 130 (10.9%) of the households respectively. Accordingly, one or more ectoparasites were observed in 865 of 1191 rural households. The presence of one or more ectoparasites was, therefore, found to be 72.6% (95% CI = 70%-75.1%). The prevalence of ectoparasites was statistically associated with educational status of the female head being not educated (AOR = 1.476, 95% CI = 1.001, 2.177) and absence close supervision by health extension workers (AOR = 2.151, 95% CI = 1.205, 3.843).

CONCLUSION

The prevalence of one or more ectoparasites was high in the rural communities of northwest Ethiopia. The high prevalence was associated with education status of the female head and close supervision of households by health extension workers. Disseminating health information about intervention strategies of ectoparasites and closely supervising the rural households need to be considered.

Promiscuous specialists: Host specificity patterns among generalist louse flies

Ectoparasites such as louse flies (Diptera: Hippoboscidae) have tendency for host specialization, which is driven by adaptation to host biology as well as competition avoidance between parasites of the same host. However, some louse fly species, especially in genera attacking birds, show wide range of suitable hosts. In the presented study, we have surveyed the current status of bird specific louse flies in Finland to provide comprehensive host association data to analyse the ecological requirements of the generalist species. A thorough sampling of 9342 birds, representing 134 species, recovered 576 specimens of louse flies, belonging to six species: Crataerina hirundinis, C. pallida, Ornithomya avicularia, O. chloropus, O. fringillina and Ornithophila metallica. Despite some overlapping hosts, the three Ornithomya species showed a notable pattern in their host preference, which was influenced not only by the host size but also by the habitat and host breeding strategy. We also provide DNA barcodes for ten Finnish species of Hippoboscidae, which can be used as a resource for species identification as well as metabarcoding studies in the future.

The Diadenylate Cyclase CdaA Is Critical for Borrelia turicatae Virulence and Physiology

Relapsing fever (RF), caused by spirochetes of the genus Borrelia, is a globally distributed, vector-borne disease with high prevalence in developing countries. To date, signaling pathways required for infection and virulence of RF Borrelia spirochetes are unknown. Cyclic di-AMP (c-di-AMP), synthesized by diadenylate cyclases (DACs), is a second messenger predominantly found in Gram-positive organisms that is linked to virulence and essential physiological processes. Although Borrelia is Gram-negative, it encodes one DAC (CdaA), and its importance remains undefined. To investigate the contribution of c-di-AMP signaling in the RF bacterium Borrelia turicatae, a cdaA mutant was generated. The mutant was significantly attenuated during murine infection, and genetic complementation reversed this phenotype. Because c-di-AMP is essential for viability in many bacteria, whole-genome sequencing was performed on cdaA mutants, and single-nucleotide polymorphisms identified potential suppressor mutations. Additionally, conditional mutation of cdaA confirmed that CdaA is important for normal growth and physiology. Interestingly, mutation of cdaA did not affect expression of homologs of virulence regulators whose levels are impacted by c-di-AMP signaling in the Lyme disease bacterium Borrelia burgdorferi Finally, the cdaA mutant had a significant growth defect when grown with salts, at decreased osmolarity, and without pyruvate. While the salt treatment phenotype was not reversed by genetic complementation, possibly due to suppressor mutations, growth defects at decreased osmolarity and in media lacking pyruvate could be attributed directly to cdaA inactivation. Overall, these results indicate CdaA is critical for B. turicatae pathogenesis and link c-di-AMP to osmoregulation and central metabolism in RF spirochetes.

Phylogeography and demographic history of Thai Pediculus humanus capitis (Phthiraptera: Pediculidae) revealed by mitochondrial DNA sequences

Pediculus humanus (human louse) is a hematophagous insect that feeds on human blood. It is distributed worldwide. Understanding phylogeography and population-genetic structure of the human louse will illuminate the evolution of this insect and the dynamics of how resistance alleles might spread in the landscape. In this work, we used mitochondrial (cox1 and cytb genes) sequences of the human louse to investigate genetic diversity, population-genetic structure and demographic history of the louse in Thailand. Human lice in Thailand belonged to mitochondrial clades A and C. Most genetic variation was attributed to intra-region 65.71% within provinces for clade A and 68.92% for clade C, while inter-region level was 34.40% among provinces within regions for clade A and 20.09% for clade C. Neutrality and other indices suggested that louse populations from clades A and C in Thailand have experienced a population expansion. But head lice from Khon Kaen Province in clade C demonstrated a significant recent population bottleneck or natural selective pressure with constant population size. Head lice in Thailand showed varying degrees of low to high genetic differentiation at the level of province with many populations being genetically distinct from each other among regions and within the same region. Knowledge of the clades present in Thailand and that gene flow occurs between regions will assist in developing appropriate strategies for management of head lice at the local level in the country.

Molecular identification of Campanulotes bidentatus Scopoli, 1763 (Phthiraptera, Philopteridae) infecting the domestic pigeon Columba livia from Saudi Arabia

The taxonomy of the order Phthiraptera is unstable and still problematic to researchers. Most of the current taxon classifications are mainly based on morphological features. Campanulotes bidentatus belongs to the chewing lice of the Philopteridae family that mostly parasitic on birds. There is a lack of sequence data and phylogenetic analyses on the family Philopteridae. In the current study, C. bidentatus was collected from the domestic pigeon Columba livia and identified morphologically and molecularly based on the mitochondrial cytochrome c oxidase subunit 1 gene (COI). The infection rate of the Campanulotes genus was approximately 58.82% in this study. Phylogenetic analysis based on the mt COI gene was informative for members of Philopteridae and the group taxon genera formed distinct clades. Future studies were recommended using the 16s rRNA to enhance the tree topology and obtain clear differentiation between genera.

The molecular targets of ivermectin and lotilaner in the human louse Pediculus humanus humanus: New prospects for the treatment of pediculosis

Control of infestation by cosmopolitan lice (Pediculus humanus) is increasingly difficult due to the transmission of parasites resistant to pediculicides. However, since the targets for pediculicides have no been identified in human lice so far, their mechanisms of action remain largely unknown. The macrocyclic lactone ivermectin is active against a broad range of insects including human lice. Isoxazolines are a new chemical class exhibiting a strong insecticidal potential. They preferentially act on the γ-aminobutyric acid (GABA) receptor made of the resistant to dieldrin (RDL) subunit and, to a lesser extent on glutamate-gated chloride channels (GluCls) in some species. Here, we addressed the pediculicidal potential of isoxazolines and deciphered the molecular targets of ivermectin and the ectoparasiticide lotilaner in the human body louse species Pediculus humanus humanus. Using toxicity bioassays, we showed that fipronil, ivermectin and lotilaner are efficient pediculicides on adult lice. The RDL (Phh-RDL) and GluCl (Phh-GluCl) subunits were cloned and characterized by two-electrode voltage clamp electrophysiology in Xenopus laevis oocytes. Phh-RDL and Phh-GluCl formed functional homomeric receptors respectively gated by GABA and L-glutamate with EC₅₀ values of 16.0 μM and 9.3 μM. Importantly, ivermectin displayed a super agonist action on Phh-GluCl, whereas Phh-RDL receptors were weakly affected. Reversally, lotilaner strongly inhibited the GABA-evoked currents in Phh-RDL with an IC₅₀ value of 40.7 nM, whereas it had no effect on Phh-GluCl. We report here for the first time the insecticidal activity of isoxazolines on human ectoparasites and reveal the mode of action of ivermectin and lotilaner on GluCl and RDL channels from human lice. These results emphasize an expected extension of the use of the isoxazoline drug class as new pediculicidal agents to tackle resistant-louse infestations in humans.

Human cosmopolitan lice are responsible for pediculosis, which represent a significant public health concern. Resistant lice against insecticides and lack of safety of the treatments for human and environment is a growing issue worldwide. Here we investigated the efficacy on lice of the classical macrocyclic lactone drug, ivermectin, and of the isoxazoline drug, lotilaner. This study was done to decipher their mode of action at the molecular and functional levels in order to propose new strategies to control lice infestation. Our bioassay results indicate that ivermectin and lotilaner were potent at killing human adult lice, with lotilaner showing a higher efficacy than ivermectin. Furthermore, we identified and pharmacologically characterized the first glutamate- and GABA-gated chloride channels ever described in human lice yet. Mechanistically, our molecular biology and electrophysiology findings demonstrate that ivermectin acted preferentially at glutamate channels, while lotilaner specifically targeted GABA channels. These results provide new insights in the understanding of the insecticide mode of action and highlight the potential of isoxazolines as a new alternative for the treatment of human lice.

Study on Efficacy of 1% Permethrin Shampoo and Some Traditional Physical Treatment for Head Lice Infestation

Background:

There is an increase in the prevalence of head lice among urban communities with high density in recent years. This study was aimed to determine the efficacy of 1% permethrin shampoo and some traditional physical treatment for head lice infestation in Qom Province, central Iran.

Methods:

This analytical cross-sectional study was carried out on all 11,223 cases in six categories that were referred to Qom health care system from 2016 to March of 2017. The infested people were treated with 1% permethrin shampoo, twice at a 1-week interval and other recommended therapeutic categories, such as the use of physical treatments such as wooden fine-toothed combs impregnated with a mixture of water and white vinegar on infested hair for 30 min and secondly, carrier oils such as olive oil, bitter almond on infested hair over a therapeutic period. After completing the course of treatment, treatment success was checked by questionnaires.

Results:

A total of 11,223 cases with head lice infestation were confirmed and were enrolled for study. Out of six categories, three therapeutic categories were utilized as follows: (a) 1% permethrin shampoo and the use of physical treatments; (b) 1% permethrin shampoo and the use of carrier oils; (c) the above-mentioned therapeutic categories combined had high treatment success. It was estimated to be 82.00%, 87.31%, and 94.33%, respectively.

Conclusions:

According to the findings, in addition to the application of 1% permethrin shampoo, the use of physical treatments and carrier oils such as olive oil, bitter almond can increase the treatment success of head lice infestation.

Yersinia pestis: the Natural History of Plague

The Gram-negative bacterium Yersinia pestis is responsible for deadly plague, a zoonotic disease established in stable foci in the Americas, Africa, and Eurasia. Its persistence in the environment relies on the subtle balance between Y. pestis-contaminated soils, burrowing and nonburrowing mammals exhibiting variable degrees of plague susceptibility, and their associated fleas. Transmission from one host to another relies mainly on infected flea bites, inducing typical painful, enlarged lymph nodes referred to as buboes, followed by septicemic dissemination of the pathogen. In contrast, droplet inhalation after close contact with infected mammals induces primary pneumonic plague. Finally, the rarely reported consumption of contaminated raw meat causes pharyngeal and gastrointestinal plague. Point-of-care diagnosis, early antibiotic treatment, and confinement measures contribute to outbreak control despite residual mortality. Mandatory primary prevention relies on the active surveillance of established plague foci and ectoparasite control. Plague is acknowledged to have infected human populations for at least 5,000 years in Eurasia. Y. pestis genomes recovered from affected archaeological sites have suggested clonal evolution from a common ancestor shared with the closely related enteric pathogen Yersinia pseudotuberculosis and have indicated that ymt gene acquisition during the Bronze Age conferred Y. pestis with ectoparasite transmissibility while maintaining its enteric transmissibility. Three historic pandemics, starting in 541 AD and continuing until today, have been described. At present, the third pandemic has become largely quiescent, with hundreds of human cases being reported mainly in a few impoverished African countries, where zoonotic plague is mostly transmitted to people by rodent-associated flea bites.

Serologic study of Bartonella sp. infection among human population of Southern Spain

INTRODUCTION

The purpose of this study was to determine the prevalence of IgG antibodies against Bartonella sp. in a randomly selected sample from the population of the patients of North Sanitary District of Jaén.

METHODS

We used a commercially available immunofluorescent test (Focus-Technology IFA Bartonella quintana and B. henselae test).

RESULTS

Six hundred five healthy individuals were divided by sex into three age groups. We detected that 13.55% and 11.07% subjects were IgG seropositive to B. henselae and B. quintana, respectively.

CONCLUSIONS

Our data show that the prevalence of both Bartonella species in Andalusia (Southern Spain) is relatively high. No statistical difference in the seropositivity was observed among these groups. In both cases, the IgG antibody titers ranged from 1/128 to 1/512.

Detection of permethrin resistance and phylogenetic clustering of turkish head lice (Pediculus humanus capitis; De Geer, 1767 populations

Head lice infestation caused by Pediculus humanus capitis De Geer, 1767 is one of the most common public health problems. The relationship between humans and head lice dates back millions of years ago that differentiated into different phylogenetic clades. Treatment of head lice infestation usually based on insecticide-based products, which promotes the resistance in the head lice populations. In the present study, we aimed to screen the presence of permethrin resistance among collected P. h. capitis specimens in Turkey. Three mutation sites (T917I, L920F, and M815I) were screened using real-time PCR and resistance was identified by melt analysis. Of the studied specimens, resistance allele frequency (RAF) was found 0.98 for T917I, 0.99 for L920F, and 1.00 for M815I. The phylogenetic study revealed that Clade A and Clade B are present and overlap in Turkey. The present study is first to screen the resistance among Turkish head lice specimens. To not stimulate the pyrethroids resistance in head lice populations, early detection of resistance is crucial and will help the health professionals to choose suitable formula in the treatment. We suggest that the resistance status needs to be screened in randomly selected populations before any treatment application is given.

Forecasting head lice (Pediculidae: Pediculus humanus capitis) infestation incidence hotspots based on spatial correlation analysis in Northwest Iran

Background and Aim

Pediculus humanus capitis has been prevalent throughout the world, especially in developing countries among elementary students and societies with a weak socio-economic status. This study aimed to forecast head lice (Pediculidae: P. capitis) infestation incidence hotspots based on spatial correlation analysis in Ardabil Province, Northwest Iran.

Materials and Methods

In this retrospective analytical study, all cases of head lice infestations who were confirmed by Centers for Disease Control office have been studied from 2016 to 2018. Head lice infestation incidence hotspots in the province should be detected based on general G statistics in ArcMap GIS10.4.1. Furthermore, MaxEnt.3.3.3 model was used for modeling the high-risk areas.

Results

The prevalence rate of pediculosis was 14.90/100,000 populations. The general G statistics revealed that the head lice infestation in this study area has a high cluster pattern. The analysis showed that the Parsabad and Germi counties were identified as a head lice infestation incidence hotspots. Statistical and spatial analyses of head lice infestation incidence showed a significant positive correlation with head lice infestation incidence hotspots and the altitudes (15-500 m), annual temperature range (14-16.5°C), and slope and average diurnal temperature (12-18°C).

Conclusion

The results of this study showed that the most ecologically suitable areas of head lice occurrence were identified in two hotspots (Parsabad and Germi) in the Northern areas of Ardabil Province (Parsabad and Germi counties); in the borderline of Iran and the Republic of Azerbaijan.

A simplified protocol for in vitro rearing of human body lice

Human body lice (Pediculus humanus) are neglected ectoparasites and pathogen vectors. Difficulties in raising and maintaining colonies of body lice in a laboratory setting remain a barrier to fundamental studies of physiology and vector-pathogen interactions in these insects. Several in vivo and in vitro rearing systems have been previously described and used by multiple research groups. However, these methods suffer from drawbacks that still complicate the rearing of body lice relative to many other commonly studied hematophagous insects. Here, a simplified protocol for raising and maintaining body lice in vitro using the commercially available Hemotek apparatus is described. This protocol draws from published methods for rearing body lice as well as other hematophagous insect species to further reduce labor, time, costs, and regulatory requirements typically associated with keeping human body lice in the laboratory. Using this protocol, the insects consistently fed on commercially available rabbit blood with little mortality, reached adulthood at a high rate, and produced a significant number of viable eggs, resulting in a 4.8-fold increase in population over a period of 40 days. The data suggest that the process described here can propagate modest populations for ongoing laboratory experiments and is a useful alternative to existing methods. The use and further optimization of in vitro rearing systems may facilitate dynamic studies of body lice by a wider range of investigators, enabling new progress in combating lice infestations, and louse-borne infections.

Where Are We With Human Lice? A Review of the Current State of Knowledge

Pediculus humanus is an obligate bloodsucking ectoparasite of human that includes two ecotypes, head louse and body louse, which differ slightly in morphology and biology, but have distinct ecologies. Phylogenetically, they are classified on six mitochondrial clades (A, B, C, D, E, and F), head louse encompasses the full genetic diversity of clades, while body louse belongs to clades A and D. Recent studies suggested that not only body louse, but also head louse can transmit disease, which warrants greater attention as a serious public health problem. The recent sequencing of body louse genome confirmed that P. humanus has the smallest genome of any hemimetabolous insect reported to date, and also revealed numerous interesting characteristics in the nuclear and mitochondrial genomes. The transcriptome analyses showed that body and head lice were almost genetically identical. Indeed, the phenotypic flexibility associated with the emergence of body lice, is probably a result of regulatory changes, perhaps epigenetic in origin, triggered by environmental signals. Current lice control strategies have proven unsuccessful. For instance, ivermectin represents a relatively new and very promising pediculicide. However, ivermectin resistance in the field has begun to be reported. Therefore, novel opportunities for pest control strategies are needed. Our objective here is to review the current state of knowledge on the biology, epidemiology, phylogeny, disease-vector and control of this fascinating and very intimate human parasite.

Body lice and bed bug co-infestation in an emergency department patient, Ohio, USA

Body lice and bed bugs are hematophagous insects that parasitize humans. Body lice are established vectors of several bacterial pathogens (e.g. Bartonella quintana, Borrelia recurrentis). Bed bugs are biologically competent vectors of some of the same agents, but their vectorial capacity for these in nature is unclear. In particular, a lack of exposure to louse-borne pathogens in bed bugs in the field could be a factor that limits their contribution to transmission. Here, we describe a case of a patient seen in an urban emergency department who was suffering from infestation with both body lice and bed bugs. Insects were collected from the patient and tested for the presence of louse-borne bacterial pathogens using 16S rRNA gene amplicon sequencing. Although no Bartonella, Borrelia, or Rickettsia were detected, this case provides evidence of ecological overlap between body lice and bed bugs and highlights several potential risk factors for co-infestation. The ecological relationships between bed bugs, body lice, and louse-borne bacteria should be further investigated in the field to determine the frequency of co-infestations and identify possible instances of pathogen infection in bed bugs.

Climate factors driven typhus group rickettsiosis incidence dynamics in Xishuangbanna Dai autonomous prefecture of Yunnan province in China, 2005-2017

BACKGROUND

Typhus group rickettsiosis (TGR), which is a neglected vector-borne infectious disease, including epidemic typhus and endemic typhus. We explored the lag effects and nonlinear association between meteorological factors and TGR incidence in Xishuangbanna Dai autonomous prefecture from 2005 to 2017, China.

METHODS

A Poisson regression with a distributed lag nonlinear model (DLNM) was utilized to analyze TGR cases data and the contemporaneous meteorological data.

RESULTS

A J-shaped nonlinear association between weekly mean temperature and TGR incidence was found. The cumulative exposure to weekly mean temperature indicated that the RR increased with the increment of temperature. Taking the median value as the reference, lower temperatures could decrease the risk of TGR incidence, while higher temperatures could increase the risk of TGR incidence and last for 21 weeks. We also found a reversed U-shaped nonlinear association between weekly mean precipitation and TGR incidence. Precipitation between 5 mm and 13 mm could increase the risk of TGR incidence. Taking the median value as the reference, no precipitation and lower precipitation could decrease the risk of TGR incidence, while higher precipitation could increase the risk of TGR incidence and last for 18 weeks.

CONCLUSIONS

The prevention and control measures of TGR should be implemented according to climatic conditions by the local government and health departments in order to improve the efficiency.

Deterministic approaches for head lice infestations and treatments

Pediculus humanus capitis are human ectoparasites which cause infestations, mostly in children, worldwide. Understanding the life cycle of head lice is an important step in knowing how to treat lice infestations, as the parasite behavior depends considerably on its age and gender. In this work we propose a mathematical model for head lice population dynamics in hosts who could be or not quarantined and treated. Considering a lice population structured by age and gender we formulate the model as a system of hyperbolic PDEs, which can be reduced to compartmental systems of delay or ordinary differential equations. Besides studying fundamental properties of the model, such as existence, uniqueness and nonnegativity of solutions, we show the existence of (in certain cases multiple) equilibria at which the infestation persists on the host’s head. Aiming to assess the performance of treatments against head lice infestations, by mean of computer experiments and numerical simulations we investigate four possible treatment strategies. Our main results can be summarized as follows: (i) early detection is crucial for quick and efficient eradication of lice infestations; (ii) dimeticone-based products applied every 4 days effectively remove lice in at most three applications even in case of severe infestations and (iii) minimization of the reinfection risk, e.g. by mean of synchronized treatments in families/classrooms is recommended.

Medical and Social Factors of Pediculosis

Pediculosis is a global problem in public health. An important factor in the efficient eradication of lice is ensuring adequate recognition and treatment of the disease by the population. In the present study, awareness of the population about the physiological properties of head lice, the ways of infestation with head lice, and the methods of treatment and prevention were studied. Perception of the disease by the people who had had head pediculosis and other people around them was identified.

Prevalence of pediculosis capitis and associated factors among schoolchildren in Woreta town, northwest Ethiopia

Objectives

The aim of the study was to determine the associated risk factors and prevalence of pediculosis capitis among school-aged children in Woreta town, northwest Ethiopia. An institution-based cross-sectional study was carried out on 402 schoolchildren in Woreta town public schools from grades 1 to 4 students conducted from April to June 2018. After selection by simple random sampling, face to face interview and observations were performed using a semi-structured pre-tested questionnaire. Data were entered into EPI Info 7 and exported to SPSS 21 for further analysis. Descriptive results were presented by simple frequency, percentage, and mean. Binary logistic regression was used to identify associated factors. Those variables with a p-value ≤ 0.05 in the multivariable logistic regression were declared as significantly associated with pediculosis capitis infestation.

Result

The prevalence of pediculosis capitis was 65.7% [95% CI 60.01–70.3%]. Sex of child, age of the child, maternal education, sharing hair comb, knowledge, and attitude towards pediculosis capitis infestation and hygiene practice were significantly associated with pediculosis (a p-value ≤ 0.05). Pediculosis infestation is found to be a major public health problem which demands special attention of the community and the government at large particularly the health sector to reduce the problem.

Genetic diversity of human head lice and molecular detection of associated bacterial pathogens in Democratic Republic of Congo

BACKGROUND

Head louse, Pediculus humanus capitis, is an obligatory blood-sucking ectoparasite, distributed worldwide. Phylogenetically, it occurs in five divergent mitochondrial clades (A-E); each exhibiting a particular geographical distribution. Recent studies suggest that, as in the case of body louse, head louse could be a disease vector. We aimed to study the genetic diversity of head lice collected in the Democratic Republic of the Congo (DR Congo) and to screen for louse-borne pathogens in these lice.

METHODS

A total of 181 head lice were collected from 27 individuals at the Monkole Hospital Center located in Kinshasa. All head lice were genotyped and screened for the presence of louse-borne bacteria using molecular methods. We searched for Bartonella quintana, Borrelia recurrentis, Rickettsia prowazekii, Anaplasma spp., Yersinia pestis, Coxiella burnetii and Acinetobacter spp.

RESULTS

Among these head lice, 67.4% (122/181) belonged to clade A and 24.3% (44/181) belonged to clade D. Additionally, for the first time in this area, we found clade E in 8.3% (15/181) of tested lice, from two infested individuals. Dual infestation with clades A and D was observed for 44.4% individuals. Thirty-three of the 181 head lice were infected only by different bacterial species of the genus Acinetobacter. Overall, 16 out of 27 individuals were infested (59.3%). Six Acinetobacter species were detected including Acinetobacter baumannii (8.3%), Acinetobacter johnsonii (1.7%), Acinetobacter soli (1.7%), Acinetobacter pittii (1.7%), Acinetobacter guillouiae (1.1%), as well as a new potential species named "Candidatus Acinetobacter pediculi".

CONCLUSIONS

To our knowledge, this study reports for the first time, the presence of clade E head lice in DR Congo. This study is also the first to report the presence of Acinetobacter species DNAs in human head lice in DR Congo.

Ectoparasite defence in humans: relationships to pathogen avoidance and clinical implications

Currently, disgust is regarded as the main adaptation for defence against pathogens and parasites in humans. Disgust's motivational and behavioural features, including withdrawal, nausea, appetite suppression and the urge to vomit, defend effectively against ingesting or touching sources of pathogens. However, ectoparasites do not attack their hosts via ingestion, but rather actively attach themselves to the body surface. Accordingly, by itself, disgust offers limited defence against ectoparasites. We propose that, like non-human animals, humans have a distinct ectoparasite defence system that includes cutaneous sensory mechanisms, itch-generation mechanisms and grooming behaviours. The existence of adaptations for ectoparasite defence is supported by abundant evidence from non-human animals, as well as more recent evidence concerning human responses to ectoparasite cues. Several clinical disorders may be dysfunctions of the ectoparasite defence system, including some that are pathologies of grooming, such as skin picking and trichotillomania, and others, such as delusory parasitosis and trypophobia, which are pathologies of ectoparasite detection. We conclude that future research should explore both distinctions between, and overlap across, ectoparasite defence systems and pathogen avoidance systems, as doing so will not only illuminate proximate motivational systems, including disgust, but may also reveal important clinical and social consequences.This article is part of the Theo Murphy meeting issue 'Evolution of pathogen and parasite avoidance behaviours'.

Insects and the Transmission of Bacterial Agents

Arthropods are small invertebrate animals, among which some species are hematophagous. It is during their blood meal that they can transmit pathogenic microorganisms that they may be harboring to the vertebrate host that they parasitize, which in turn will potentially develop a vector-borne disease. The transmission may occur directly through their bite, but also through contaminated feces. Zoonotic diseases, diseases that can naturally be transmitted between humans and animals, are a considerable part of emerging diseases worldwide, and a major part of them are vector-borne. Research and public attention has long been focused on malaria and mosquito-borne arboviruses, and bacterial vector-borne diseases remains today a neglected field of medical entomology. Despite the emphasis on Lyme disease in recent decades, and despite the major outbreaks caused by bacteria in the last few centuries, this field has in fact been poorly explored and is therefore relatively poorly known, other than the most famous examples such as the plague and epidemic typhus outbreaks. Here we propose to review the state of knowledge of bacterial agents transmitted by arthropod vectors.

Clinical studies evaluating abametapir lotion, 0.74%, for the treatment of head louse infestation

BACKGROUND

There is a need for better control of head louse infestations. Abametapir is an inhibitor of metalloproteinases critical for louse survival and egg development. The efficacy of abametapir lotion, 0.74%, was assessed for its ability to clear head louse infestations after a single application.

METHODS

Two randomized, double-blind, multicenter, vehicle-controlled studies were conducted in subjects aged 6 months and older to compare the effectiveness of abametapir lotion versus vehicle control for eliminating head louse infestations without nit combing. Abametapir lotion was applied to dry hair for 10 minutes on day 0 and then rinsed with water. The primary endpoint was the proportion of index subjects (youngest household member with ≥ 3 live lice at screening) in the intent-to-treat population who were louse free at all follow-up visits through day 14. Older household members with one or more live lice at screening were designated as nonindex subjects and treated as per the index subject within their household.

RESULTS

In the intent-to-treat population (index subjects, N = 216), 81.5% of subjects treated with abametapir lotion were louse free through day 14 after a single treatment, versus 49.1% with vehicle (P < 0.001). For the combined index and nonindex population (N = 704), 85.9% were louse free through day 14 in the abametapir group, versus 61.3% in the vehicle group (P < 0.001). The most frequently reported adverse events were erythema (4.0%), rash (3.2%), and skin burning sensation (2.6%).

CONCLUSION

Abametapir lotion, 0.74%, was effective at clearing active head louse infestations through day 14 in subjects aged 6 months and older. All adverse events (including one serious but unrelated to study drug) resolved uneventfully.

Detection of bacterial pathogens in clade E head lice collected from Niger's refugees in Algeria

Background

Head lice, Pediculus humanus capitis, are obligate blood-sucking parasites. Phylogenetically, they occur in five divergent mitochondrial clades (A, D, B, C and E), each having a particular geographical distribution. Recent studies have revealed that head lice, as is the case of body lice, can act as a vector for louse-borne diseases. Here, we aimed to study the genetic diversity of head lice collected from Niger’s refugees (migrant population) arriving in Algeria, northern Africa, and to look for louse-borne pathogens. Comparative head lice samples collected from indigenous population of schoolchildren (non-immigrant) were also analyzed to frame the study.

Results

In this study, 37 head lice samples were collected from 31 Nigerien refugees, as well as 45 head lice from 27 schoolchildren. The collection was established in three localities of eastern Algiers, north Algeria. Quantitative real-time PCR screening of pathogens bacteria and the genetic characterisation of the head lice satut were performed. Through amplification and sequencing of the cytb gene, results showed that all head lice of Nigerien refugees 37/82 (45.12%) belonged to clade E with the presence of four new haplotypes, while, of the 45 head lice of schoolchildren, 34/82 lice (41.46%) belonged to clade A and 11/82 (13.41%) belonged to clade B. Our study is the first to report the existence of clade E haplogroup in Nigerien head lice. DNA of Coxiella burnetii was detected in 3/37 (8.10%) of the head lice collected from 3 of the 31 (9.67%) migrant population. We also revealed the presence of Acinetobacter DNA in 20/37 (54.05%) of head lice collected from 25/31 (80.64%) of the Nigerien refugees, and in 25/45 (55.55%) head lice collected from 15/27 (55.55%) schoolchildren. All positive Nigerien-head lice for Acinetobacter spp. were identified as A. baumannii, while positive schoolchildren-head lice were identified as A. johnsonii 15/25 (60%), A. variabilis 8/25 (32%) and A. baumannii 2/25 (8%).

Conclusions

Based on these findings from head lice collected on migrant and non-migrant population, our results show, for the first time, that head lice from Niger belong to haplogroup E, and confirm that the clade E had a west African distribution. We also detected, for the first time, the presence of C. burnetii and A. baumannii in these Nigerien head lice. Nevertheless, further studies are needed to determine whether the head lice can transmit these pathogenic bacteria from one person to another.

Body lice of homeless people reveal the presence of several emerging bacterial pathogens in northern Algeria

BACKGROUND

Human lice, Pediculus humanus, are obligate blood-sucking parasites. Body lice, Pediculus h. humanus, occur in two divergent mitochondrial clades (A and D) each exhibiting a particular geographic distribution. Currently, the body louse is recognized as the only vector for louse-borne diseases. In this study, we aimed to study the genetic diversity of body lice collected from homeless populations in three localities of northern Algeria, and to investigate louse-borne pathogens in these lice.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, 524 body lice specimens were collected from 44 homeless people in three localities: Algiers, Tizi Ouzou and Boumerdès located in northern Algeria. Duplex clade specific real-time PCRs (qPCR) and Cytochrome b (cytb) mitochondrial DNA (mtDNA) analysis were performed in order to identify the mitochondrial clade. Screening of louse-borne pathogens bacteria was based on targeting specific genes for each pathogen using qPCR supplemented by sequencing. All body lice belong to clade A. Through amplification and sequencing of the cytb gene we confirmed the presence of three haplotypes: A5, A9 and A63, which is novel. The molecular investigation of the 524 body lice samples revealed the presence of four human pathogens: Bartonella quintana (13.35%), Coxiella burnetii (10.52%), Anaplasma phagocytophilum (0.76%) and Acinetobacter species (A. baumannii, A. johnsonii, A. berezeniae, A. nosocomialis and A. variabilis, in total 46.94%).

CONCLUSIONS/SIGNIFICANCE

To the best of our knowledge, our study is the first to show the genetic diversity and presence of several emerging pathogenic bacteria in homeless' body lice from Algeria. We also report for the first time, the presence of several species of Acinetobacter in human body lice. Our results highlight the fact that body lice may be suspected as being a much broader vector of several pathogenic agents than previously thought. Nevertheless, other studies are needed to encourage epidemiological investigations and surveys of louse-associated infections.

The epidemic typhus and trench fever are risk for public health due to increased migration in southeast of Turkey

Pediculus humanus capitis is a small ectoparasitic insect that has lived and feds on human beings for thousands of years. Molecular techniques have been used for Pediculus species identification and evolutionary, phylogenic, and ecological studies. A total of 23 adults of P. h. capitis were collected in Gaziantep, located in southeast Turkey, and DNA was isolated from all P. h. capitis using DNA extraction kit. All DNA samples were screened for investigate of Ricettsia prowazekii, Bartonella quintana and Borrelia recurrentis with real-time polymerase chain reaction. In addition, we investigated genetic variation in DNA samples of Pediculus humanus capitis using the cytochrome oxidase I genetic DNA sequence. We found 4 (17.4%) Ricettsia prowazekii and 3 (13.1%) Bartonella quintana in DNA samples of Pediculus humanus capitis, while we did not find any Bartonella recurrentis in any of the DNA samples. We demonstrated 1.8% genetic variations in DNA samples of Pediculus humanus capitis with Bartonella quintana. The phylogenetic tree based on the cytochrome oxidase I gene revealed that P. h. capitis in southeast Turkey are classified into two clades (clade A, clade B) and Bartonella quintana was found in only clade B. However, we did not find any genetic variations in other DNA samples in this region. The genetic variations may be related to P. h.capitis vector of Bartonella quintana has found in this study. In addition, this study was shown that P. h. capitis do transmit Rickettsia prowazekii and Bartonella quintana to people, epidemic typhus and trench fever may emergence in Gaziantep southeast of Turkey in the future.

Prevalence of Pediculus capitis in schoolchildren in Battambang, Cambodia

BACKGROUND/PURPOSE

Pediculus capitis is the most common human ectoparasite. When it feeds on the blood through the scalp of its host, the anticoagulant in its saliva causes scalp inflammation and itching, and consequent scratching by the host causes further inflammation from bacterial infection. P. capitis infestation is currently a common parasitic dermatosis and a critical public health concern in underdeveloped countries.

METHODS

Through naked eye inspection of P. capitis on or in the hair from 323 school children in Cambodia.

RESULTS

A total of 143 children (44.3%) were found to have P. capitis infestation. Univariate analysis revealed that girls had a significantly higher infection rate than boys. Overall, young aged schoolchildren (10 yrs old ≤) showed significantly higher infection rate than old aged schoolchildren (>10 yrs old). Groups stratified by time revealed that schoolchildren studied at the afternoon classes than morning classes in Tuol Prum Muoy Primary School had a significantly higher risk in acquisition of P. capitis infestation. Multivariate analysis results indicated that relative to the boys, the girls were at a significantly higher risk of contracting P. capitis infection. When stratified by inspection time with the Tuol Prum Muoy Primary School morning classes as the reference, the Tuol Prum Muoy Primary School afternoon classes exhibited a significantly higher risk of P. capitis infection.

CONCLUSION

Primary school children in Cambodia have a high P. capitis infection rate and thus require effective treatment and prevention measures to treat symptoms and lower the infection rate.

Identification of Novel Voltage-Gated Sodium Channel Mutations in Human Head and Body Lice (Phthiraptera: Pediculidae)

In recent years, the increase of head louse infestation in Iran (7.4%) and especially in West-Azerbaijan Province (248%) has raised the hypothesis of insecticide resistance development. There are different mechanisms of resistance to various groups of insecticides, and knockdown resistance (kdr) is a prominent mechanism of resistance to pyrethroids, an insecticide group which is used conventionally for pediculosis control. For detection of kdr-type well-known amino acid substitutions (M815I-T917I-L920F) and additional sodium channel mutations potentially associated with kdr resistance in head and body lice, louse populations were collected from West-Azerbaijan and Zanjan Provinces of Iran. Six novel mutations were found to be located in the IIS1-2 extracellular loop (H813P) and IIS5 (I927F, L928A, R929V, L930M, and L932M) of the α-subunit. Genotyping results showed that all specimens (100%) have at least one of these or the well-known mutations. Therefore, the presence of kdr-related and novel mutations in the sodium channel is likely to be the reason for the frequent use of pyrethroid insecticides due to treatment failure against lice. Further studies are now required to evaluate the prevalence of the kdr-like mutant allele for monitoring of insecticide resistance and the management of head and body lice in other provinces of the country.

Human Lice in Paleoentomology and Paleomicrobiology

Lice are a classic example of cospeciation. Human lice confirm this cospeciation with lice specialized in hominids which differ from those of gorillas and chimpanzees. Head lice and body lice seem to belong to closely related species with different ecotypes and a different geographical distribution which may reflect population movements. Paleo-entomology allows us in some cases to trace the migrations of archaic human populations. The analysis of lice found on mummies in Egypt and South America has clarified a certain number of these migrations, also the study of lice and the diseases they transmit has shed a new light on the epidemics of the past.

Human head lice and pubic lice reveal the presence of several Acinetobacter species in Algiers, Algeria

There are two majorspecies of medically important lice that parasitize humans: Phthirus pubis, found in pubic hair, and Pediculus humanus. Pediculus humanus consists of two eco types that live in specific niches on the human host: body lice (Pediculus humanus humanus), found on the human body and clothing, and head lice (Pediculus humanus capitis), found on the scalp. To date, only body lice are known to be vectors of human disease; however, it has recently been reported that the DNA of several bacterial agents has been detected in head lice, raising questions about their role in the transmission of pathogens. This issue caught our attention, in addition to the fact that the pathogenic bacteria associated with P. pubis and P. humanus capitis have never been investigated in Algeria. To investigate this,molecular techniques (real-time PCR) were used to screen for the presence of Acinetobacter spp., Bartonella spp., Borrelia spp. and Rickettsia prowazekii DNA from P. humanus capitis (64 lice) collected from schoolchildren,and P. pubis (4 lice),collected from one adultman living in Algiers. Positive samples for Acinetobacter spp.were identified by sequencing therpoBgene. Conventional PCR targeting the partial Cytb gene was used to determine the phylogenetic clade of the collected lice. Of the 64 samples collected, Acinetobacter spp. DNA was detected in 17/64 (27%) of head lice, identified as: A. baumannii (14%), A. johnsonii (11%) and A. variabilis (2%). Of the four P. pubissamples, 2(50%) were positive for A. johnsonii. The phylogenetic tree based on the Cytb gene revealed that P. humanus capitis were grouped into clades A and B. In this study, we report andidentify for the first time Acinetobacter spp.in Algerian P. pubis and P. humanus capitis. The detection of the genus Acinetobacter in lice should not be underestimated, especially in P. humanus capitis, which is distributed worldwide. However, additional epidemiological data are required to determine if human lice may act as an environmental reservoir and are actively involved in the propagation of these bacteria to humans.

Migrating microbes: what pathogens can tell us about population movements and human evolution

BACKGROUND

The biology of human migration can be observed from the co-evolutionary relationship with infectious diseases. While many pathogens are brief, unpleasant visitors to human bodies, others have the ability to become life-long human passengers. The story of a pathogen's genetic code may, therefore, provide insight into the history of its human host. The evolution and distribution of disease in Africa is of particular interest, because of the deep history of human evolution in Africa, the presence of a variety of non-human primates, and tropical reservoirs of emerging infectious diseases.

METHODS

This study explores which pathogens leave traces in the archaeological record, and whether there are realistic prospects that these pathogens can be recovered from sub-Saharan African archaeological contexts.

RESULTS

Three stories are then presented of germs on a journey. The first is the story of HIV's spread on the back of colonialism and the railway networks over the last 150 years. The second involves the spread of Schistosoma mansoni, a parasite which shares its history with the trans-Atlantic slave trade and the origins of fresh-water fishing. Finally, we discuss the tantalising hints of hominin migration and interaction found in the genome of human herpes simplex virus 2.

CONCLUSIONS

Evidence from modern African pathogen genomes can provide data on human behaviour and migration in deep time and contribute to the improvement of human quality-of-life and longevity.

Comparative study of the claws of Pediculus humanus capitis between archaeological and modern specimens

Metric data of the claws of archaeological specimens of Pediculus humanus capitis (dating between 1500 B.C. and A.D. 1500) and modern lice specimens coming from school children were analyzed and compared. Both sets of samples come from Arica in northern Chile. The overall sample is comprised of 14 archaeological specimens (6 females and 8 males) of Pediculus humanus capitis and 22 modern specimens (13 females and 9 males). All specimens were studied with scanning electron microscopy (SEM), uncoated, using variable pressure mode. The objective of this study was to metrically analyze the first couple of clutches of ancient and modern adult lice specimens (width and length of the tibio-tarsal claw and tarsus length) to test if morphological changes have taken place throughout time in these anatomical elements. We found that archaeological male and female specimens presented significant differences in the tibio-tarsal width (right and left). When comparing data between archaeological and modern male specimens, statistically significant differences were found in almost all the parameters studied, except for the right tarsal length. On the other hand, archaeological and modern female specimens showed no statistically significant change in the variables studied. In brief, our data suggest that modern male specimens have undergone a process of claw reduction, but females have maintained the same dimensions.

Flammability testing of 22 conventional European pediculicides

Lice have been parasitizing humans for at least 10,000 years. Since then, humans have tried to rid themselves of these unpleasant and potentially disease-carrying insects. Despite various plant extracts and chemical compounds being used to combat recurring infestations to this date, several lice populations have developed resistance to some of the abundantly used compounds. This resulted in the development of anti-louse products that physically kill the different lice stages. Today, a widely used group of delousing agents are dimethicones (polydimethylsiloxane PDMS) which function by suffocating the lice. However, many dimethicones and related products are highly flammable which makes them potentially dangerous for treatment. In the present study, we tested the flammability of 22 delousing agents in order to shed some light onto this currently unresolved problem in the product design of pediculicides. Thirteen products were easily ignitable, some even by distant contact with a sparkler.

High Ancient Genetic Diversity of Human Lice, Pediculus humanus, from Israel Reveals New Insights into the Origin of Clade B Lice

The human head louse, Pediculus humanus capitis, is subdivided into several significantly divergent mitochondrial haplogroups, each with particular geographical distributions. Historically, they are among the oldest human parasites, representing an excellent marker for tracking older events in human evolutionary history. In this study, ancient DNA analysis using real-time polymerase chain reaction (qPCR), combined with conventional PCR, was applied to the remains of twenty-four ancient head lice and their eggs from the Roman period which were recovered from Israel. The lice and eggs were found in three combs, one of which was recovered from archaeological excavations in the Hatzeva area of the Judean desert, and two of which found in Moa, in the Arava region, close to the Dead Sea. Results show that the head lice remains dating approximately to 2,000 years old have a cytb haplogroup A, which is worldwide in distribution, and haplogroup B, which has thus far only been found in contemporary lice from America, Europe, Australia and, most recently, Africa. More specifically, this haplogroup B has a B36 haplotype, the most common among B haplogroups, and has been present in America for at least 4,000 years. The present findings confirm that clade B lice existed, at least in the Middle East, prior to contacts between Native Americans and Europeans. These results support a Middle Eastern origin for clade B followed by its introduction into the New World with the early peoples. Lastly, the presence of Acinetobacter baumannii DNA was demonstrated by qPCR and sequencing in four head lice remains belonging to clade A.

Neanderthal genomics suggests a pleistocene time frame for the first epidemiologic transition

High quality Altai Neanderthal and Denisovan genomes are revealing which regions of archaic hominin DNA have persisted in the modern human genome. A number of these regions are associated with response to infection and immunity, with a suggestion that derived Neanderthal alleles found in modern Europeans and East Asians may be associated with autoimmunity. As such Neanderthal genomes are an independent line of evidence of which infectious diseases Neanderthals were genetically adapted to. Sympathetically, human genome adaptive introgression is an independent line of evidence of which infectious diseases were important for AMH coming in to Eurasia and interacting with Neanderthals. The Neanderthals and Denisovans present interesting cases of hominin hunter-gatherers adapted to a Eurasian rather than African infectious disease package. Independent sources of DNA-based evidence allow a re-evaluation of the first epidemiologic transition and how infectious disease affected Pleistocene hominins. By combining skeletal, archaeological and genetic evidence from modern humans and extinct Eurasian hominins, we question whether the first epidemiologic transition in Eurasia featured a new package of infectious diseases or a change in the impact of existing pathogens. Coupled with pathogen genomics, this approach supports the view that many infectious diseases are pre-Neolithic, and the list continues to expand. The transfer of pathogens between hominin populations, including the expansion of pathogens from Africa, may also have played a role in the extinction of the Neanderthals and offers an important mechanism to understand hominin-hominin interactions well back beyond the current limits for aDNA extraction from fossils alone. Am J Phys Anthropol 160:379-388, 2016. © 2016 Wiley Periodicals, Inc.