Louse Pediculus Humanus Research Articles

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

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

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

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

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

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

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

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

Yersinia pestis can infect the Pawlowsky glands of human body lice and be transmitted by louse bite.

Yersinia pestis, the causative agent of plague, is a highly lethal vector-borne pathogen responsible for killing large portions of Europe's population during the Black Death of the Middle Ages. In the wild, Y. pestis cycles between fleas and rodents; occasionally spilling over into humans bitten by infectious fleas. For this reason, fleas and the rats harboring them have been considered the main epidemiological drivers of previous plague pandemics. Human ectoparasites, such as the body louse (Pediculus humanus humanus), have largely been discounted due to their reputation as inefficient vectors of plague bacilli. Using a membrane-feeder adapted strain of body lice, we show that the digestive tract of some body lice become chronically infected with Y. pestis at bacteremia as low as 1 × 105 CFU/ml, and these lice routinely defecate Y. pestis. At higher bacteremia (≥1 × 107 CFU/ml), a subset of the lice develop an infection within the Pawlowsky glands (PGs), a pair of putative accessory salivary glands in the louse head. Lice that developed PG infection transmitted Y. pestis more consistently than those with bacteria only in the digestive tract. These glands are thought to secrete lubricant onto the mouthparts, and we hypothesize that when infected, their secretions contaminate the mouthparts prior to feeding, resulting in bite-based transmission of Y. pestis. The body louse's high level of susceptibility to infection by gram-negative bacteria and their potential to transmit plague bacilli by multiple mechanisms supports the hypothesis that they may have played a role in previous human plague pandemics and local outbreaks.

Highly Resolved Genomes of Two Closely Related Lineages of the Rodent Louse Polyplax serrata with Different Host Specificities.

Sucking lice of the parvorder Anoplura are permanent ectoparasites with specific lifestyle and highly derived features. Currently, genomic data are only available for a single species, the human louse Pediculus humanus. Here, we present genomes of two distinct lineages, with different host spectra, of a rodent louse Polyplax serrata. Genomes of these ecologically different lineages are closely similar in gene content and display a conserved order of genes, with the exception of a single translocation. Compared with P. humanus, the P. serrata genomes are noticeably larger (139 vs. 111 Mbp) and encode a higher number of genes. Similar to P. humanus, they are reduced in sensory-related categories such as vision and olfaction. Utilizing genome-wide data, we perform phylogenetic reconstruction and evolutionary dating of the P. serrata lineages. Obtained estimates reveal their relatively deep divergence (∼6.5 Mya), comparable with the split between the human and chimpanzee lice P. humanus and Pediculus schaeffi. This supports the view that the P. serrata lineages are likely to represent two cryptic species with different host spectra. Historical demographies show glaciation-related population size (Ne) reduction, but recent restoration of Ne was seen only in the less host-specific lineage. Together with the louse genomes, we analyze genomes of their bacterial symbiont Legionella polyplacis and evaluate their potential complementarity in synthesis of amino acids and B vitamins. We show that both systems, Polyplax/Legionella and Pediculus/Riesia, display almost identical patterns, with symbionts involved in synthesis of B vitamins but not amino acids.

Local Solutions against Head Lice: A Comparative Study in Nepalese Schools

Background: Infestation by the human head louse Pediculus humanus var capitis is one of the most common parasitic conditions among children worldwide. Availabiliy of commercial products against head lice is often limited in low‐ and middle‐income countries. Different versions of homemade anti-lice solutions were assessed and compared. In addition, differences in results between using a metal louse comb and a plastic one were also evaluated. Method: In five schools of the Kathmandu Valley, 1,323 schoolchildren were screened for this study, designed as a comparative satisfaction survey. Theatre was used as a tool encourage an open dialogue on this much-stigmatized topic. Results: Out of 351 children affected by lice, 208 were included in the final analysis. In the group receiving the solution containing 5% of salt, vinegar, and a wetting agent, the proportion getting rid of head lice (parasite elimination-adults and nits) was 71,1% as compared to 56,8% with mustard oil (difference 14.4%, p-value=0,032). Among the two saline solutions tested, the one using 1% vinegar instead of 10% appeared just as effective, at less cost. Locally available plastic louse combs also appeared to be just as effective as the standard metal louse comb in eliminating head lice. Conclusions: This research programme showed that a product made with natural ingredients can satisfactorily combat head lice. At the same time theatre as a tool to neutralize the stigma accompanying head lice infestation may have helped in implementing the anti-lice program.

Effects of selected blood-derived factors on innate immunity in the human body louse.

The human body louse (Pediculus humanus humanus) is a host-specific hematophagous ectoparasite that frequently infests populations experiencing a breakdown of hygienic conditions. Body lice are also vectors for several bacterial human pathogens, including Bartonella quintana, the agent of trench fever. However, the factors that influence immunity and infection in body lice are poorly understood. Human infection with B. quintana is associated with alcoholism and homelessness and can coincide with elevated circulating levels of the cytokine IL-10 and the inflammatory marker neopterin. Hematophagous arthropods are capable of responding physiologically and immunologically to a variety of biomolecules present in the blood of their hosts. Therefore, we sought to investigate whether ingestion of alcohol, its metabolic product acetaldehyde, IL-10 or neopterin could affect innate immunity and infection in the body louse. Groups of lice were provisioned multiple blood meals containing physiological concentrations of alcohol, acetaldehyde, IL-10 or neopterin, and expression of six previously identified immunity-related genes (Defensin 1, Defensin 2, Prophenoloxidase, Hemocytin, Noduler and Dual Oxidase) was examined by qRT-PCR. Alcohol, acetaldehyde and IL-10 had no significant effects on gene expression relative to blood-fed controls while ingestion of neopterin significantly downregulated expression of Defensin 1 and Defensin 2. Nonetheless, ingestion of neopterin concurrent with B. quintana had no significant effect on the load of infection, indicating that neopterin-induced repression of Defensin expression is insufficient to reduce resistance to the pathogen. Our findings demonstrate that the immune system of body lice can be affected by factors present in the blood of their human hosts and suggest potential conservation of the function of some immune molecules from human host to ectoparasite. Further, the discord between the effects of neopterin on immunity-related gene expression and B. quintana load highlights the complexity of the regulation of pathogen infection in the louse vector.

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

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

Draft genome assemblies of the avian louse Brueelia nebulosa and its associates using long-read sequencing from an individual specimen.

Sequencing high molecular weight (HMW) DNA with long-read and linked-read technologies has promoted a major increase in more complete genome sequences for nonmodel organisms. Sequencing approaches that rely on HMW DNA have been limited to larger organisms or pools of multiple individuals, but recent advances have allowed for sequencing from individuals of small-bodied organisms. Here, we use HMW DNA sequencing with PacBio long reads and TELL-Seq linked reads to assemble and annotate the genome from a single individual feather louse (Brueelia nebulosa) from a European Starling (Sturnus vulgaris). We assembled a genome with a relatively high scaffold N50 (637 kb) and with BUSCO scores (96.1%) comparable to louse genomes assembled from pooled individuals. We annotated a number of genes (10,938) similar to the human louse (Pediculus humanus) genome. Additionally, calling phased variants revealed that the Brueelia genome is more heterozygous (∼1%) then expected for a highly obligate and dispersal-limited parasite. We also assembled and annotated the mitochondrial genome and primary endosymbiont (Sodalis) genome from the individual louse, which showed evidence for heteroplasmy in the mitogenome and a reduced genome size in the endosymbiont compared to its free-living relative. Our study is a valuable demonstration of the capability to obtain high-quality genomes from individual small, nonmodel organisms. Applying this approach to other organisms could greatly increase our understanding of the diversity and evolution of individual genomes.

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

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

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

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

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

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

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

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

Head lice dispose of blood meal fluid through breathing tubules

The moment when you realize that your itchy child has an infestation of headlice can be an instant of pure horror suffused with relief. Horror at the thought of the hideous creatures dining on your child's blood, and relief that they can usually be cleared. It's a rite of passage. Most insects that feast on fluids pee large volumes as they process their liquid lunches. But not lice. In fact, they don't urinate at all, for fear of alerting their host to their presence. Yet they lose fluid and dehydrate rapidly if separated from their succulent host, desiccating within 24 h when unable to feed regularly. So how do these pernicious pests dispose of the large volumes of fluid they ingest each day? Headlouse expert Ian Burgess (Insect Research & Development Ltd, UK) decided to find out.Fortunately, Burgess had access to a ready supply of fresh head lice: the school children of Cambridgeshire, UK. ‘Some of our regulars just give us a call when the kids next get lice’, says Burgess, who has been working with local schools and parents for 25 years, helping them to vanquish tenacious infestations. Fortunately, the larger and more robust human clothing louse (Pediculus humanus humanus) survives more easily in the lab, so Burgess was able to keep a colony content by simply offering them a rabbit to feed on once a day.Monitoring the insects’ masses before and after dining, Burgess recorded that the smaller head lice (P. h. capitis ∼0.68 mg) consumed ∼0.11 mg of blood, losing 75% of the mass they gained within 3 h. In contrast, the larger clothing lice (∼1.87 mg) downed more than 50% of their body mass in blood (∼0.98 mg), losing the mass more slowly. ‘Most head lice returned to their pre-feeding mass by approximately 4 h after feeding, compared with 17–24 h for clothing lice’, says Burgess, explaining that head lice dine little and often.However, when Burgess checked how fast the insects lost mass after feeding in air at different humidities, there was no difference in the rate of mass loss, even at 100% humidity. ‘If humidity affected the rate of water loss, then the lice exposed to a saturated atmosphere would have some difficulty eliminating water… through cuticular evaporation’, says Burgess. In other words, the lice must be actively pumping water out of their bodies instead of simply allowing it to evaporate like sweat. But which orifices were the insects losing water from?As insects breathe through a network of tubules (tracheae) that open at structures – spiracles – at the surface of the body, Burgess recorded the mass change of clothing lice as they excreted water after dining and found that the creatures lost 15% of their blood meal mass over the next 40 min. Then, after feeding the lice, he smeared Vaseline (petroleum jelly) over their spiracles and the thoracic spiracles turned out to be particularly critical: blocking them reduced the insects’ water loss by ∼50%. In addition, when Burgess blocked the spiracles by immersing the insects in water – which should allow them to lose water but without breathing air – the lice also failed to lose mass; they could no longer inhale oxygen to power water excretion through their spiracles.Most intriguingly, when Burgess coated the insects’ abdomens in Vaseline, that supercharged their ability to lose water. The partially smothered insects disposed of more than 25% of their blood meal through the remaining spiracles. Burgess suspects that blocking the abdominal spiracles stimulates a feedback mechanism that triggers each louse to work harder to excrete water, ‘with the result that it “overdoes” it’, he says.

Phylogenetic relationship between the endosymbiont \u201cCandidatus Riesia pediculicola\u201d and its human louse host

BackgroundThe human louse (Pediculus humanus) is a haematophagous ectoparasite that is intimately related to its host. It has been of great public health concern throughout human history. This louse has been classified into six divergent mitochondrial clades (A, D, B, F, C and E). As with all haematophagous lice, P. humanus directly depends on the presence of a bacterial symbiont, known as “Candidatus Riesia pediculicola”, to complement their unbalanced diet. In this study, we evaluated the codivergence of human lice around the world and their endosymbiotic bacteria. Using molecular approaches, we targeted lice mitochondrial genes from the six diverged clades and Candidatus Riesia pediculicola housekeeping genes.MethodsThe mitochondrial cytochrome b gene (cytb) of lice was selected for molecular analysis, with the aim to identify louse clade. In parallel, we developed four PCR primer pairs targeting three housekeeping genes of Candidatus Riesia pediculicola: ftsZ, groEL and two regions of the rpoB gene (rpoB-1 and rpoB-2).ResultsThe endosymbiont phylogeny perfectly mirrored the host insect phylogeny using the ftsZ and rpoB-2 genes, in addition to showing a significant co-phylogenetic congruence, suggesting a strict vertical transmission and a host–symbiont co-speciation following the evolutionary course of the human louse.ConclusionOur results unequivocally indicate that louse endosymbionts have experienced a similar co-evolutionary history and that the human louse clade can be determined by their endosymbiotic bacteria.Graphical

Light sheet fluorescence microscopy for the investigation of blood-sucking arthropods dyed via artificial membrane feeding

Physical methods to control pest arthropods are increasing in importance, but detailed knowledge of the effects of some of these methods on the target organisms is lacking. The aim of this study was to use light sheet fluorescence microscopy (LSFM) in anatomical studies of blood-sucking arthropods in vivo to assess the suitability of this method to investigate the morphological structures of arthropods and changes in these structures over time, using the human louse Pediculus humanus (Phthiraptera: Pediculidae) as sample organism. Plasma treatment was used as an example of a procedure employed to control arthropods. The lice were prepared using an artificial membrane feeding method involving the ingestion of human blood alone and human blood with an added fluorescent dye in vitro. It was shown that such staining leads to a notable enhancement of the imaging contrast with respect to unstained whole lice and internal organs that can normally not be viewed by transmission microscopy but which become visible by this approach. Some lice were subjected to plasma treatment to inflict damage to the organisms, which were then compared to untreated lice. Using LSFM, a change in morphology due to plasma treatment was observed.These results demonstrate that fluorescence staining coupled with LSFM represents a powerful and straightforward method enabling the investigation of the morphology—including anatomy—of blood-sucking lice and other arthropods.Graphical

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

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

Borreliae Part 2: Borrelia Relapsing Fever Group and Unclassified Borrelia.

Simple SummaryFollowing Borreliae Part 1, this second review describes Borreliae of the relapsing fever group (RFG) and unclassified Borreliae. The RFG is further divided according to vector transmission and geographical distribution in other subgroups, namely the soft-tick-borne relapsing fever (STBRF) group, the hard-tick-borne relapsing fever (HTBRF) one, the louse-borne relapsing fever (LBRF) group, and the Avian relapsing fever group. Where possible, according to the literature description, each sub-group of the RFG Borreliae is organized here in sections explaining the geographical distribution, the vectors, the hosts, the epidemiology, and the microbiology. In case of human infectiveness, clinical aspects are also discussed. Isolation and sequencing of Borrelia species is ongoing, and in addition to the groups mentioned in these reviews, there are Borreliae that at present cannot be cultivated, but according to sequencing data they share some characteristics with one specific group. Nevertheless, they still cannot be classified in one of them. This is the case of Borreliae with not-yet-identified pathogenicity for humans or animals, which are here named “unclassified Borreliae” and described separately, recalling the similarities with Borreliae already classified. In the future, we expect that those Borreliae are going to be characterized, including them in one of the previous groups.Borreliae of the relapsing fever group (RFG) are heterogenous and can be divided mainly into three groups according to vectors, namely the soft-tick-borne relapsing fever (STBRF) Borreliae, the hard-tick-borne relapsing fever (HTBRF) Borreliae, the louse-borne relapsing fever (LBRF) Borreliae, and the avian relapsing fever ones. With respect to the geographical distribution, the STBRF Borreliae are further subdivided into Old World and New World strains. Except for the Avian relapsing fever group Borreliae, which cause avian spirochetosis, all the others share infectivity in humans. They are indeed the etiological agent of both endemic and epidemic forms of relapsing fever, causing high spirochaetemia and fever. Vectors are primarily soft ticks of Ornithodoros spp. in the STBRF group; hard ticks, notably Ixodes sp., Amblyomma sp., Dermacentor sp., and Rhipicephalus sp., in the HTBRF group; and the louse pediculus humanus humanus in the TBRF one. A recent hypothesis was supported for a common ancestor of RFG Borreliae, transmitted at the beginning by hard-body ticks. Accordingly, STBRF Borreliae switched to use soft-bodied ticks as a vector, which was followed by the use of lice by Borrelia recurrentis. There are also new candidate species of Borreliae, at present unclassified, which are also described in this review.

Louse-borne relapsing fever-A systematic review and analysis of the literature: Part 1-Epidemiology and diagnostic aspects.

Louse-borne relapsing fever (LBRF) is a classical epidemic disease, which in the past was associated with war, famine, poverty, forced migration, and crowding under poor hygienic conditions around the world. The disease’s causative pathogen, the spirochete bacterium Borrelia recurrentis, is confined to humans and transmitted by a single vector, the human body louse Pediculus humanus. Since the disease has had its heyday before the days of modern medicine, many of its aspects have never been formally studied and to date, remain incompletely understood. In order to shed light on some of these aspects, we have systematically reviewed the accessible literature on LBRF, since the recognition of its mode of transmission in 1907, and summarized the existing data on epidemiology and diagnostic aspects of the disease. Publications were identified by using a predefined search strategy on electronic databases and a subsequent review of the reference lists of the obtained publications. All publications reporting patients with a confirmed diagnosis of LBRF published in English, French, German, and Spanish since 1907 were included. Data extraction followed a predefined protocol and included a grading system to judge the certainty of the diagnosis of reported cases. Historically, Ethiopia is considered a stronghold of LBRF. The recognition of LBRF among East African migrants (originating from Somalia, Eritrea, and Ethiopia) arriving to Europe in the course of the recent migration flow from this region suggests that this epidemiological focus ostensibly persists. Currently, there is neither evidence to support or refute active transmission foci of LBRF elsewhere on the African continent, in Latin America, or in Asia. Microscopy remains the most commonly used method to diagnose LBRF. Data are lacking on sensitivity and specificity of most diagnostic methods.