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

BACKGROUND: The 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. METHODS: Here, 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). RESULTS: CLSM 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. CONCLUSIONS: To 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.

Unravelling the anthelmintic bioactives from Jasminum grandiflorum L. subsp. Floribundum adopting in vitro biological assessment.

ETHNOPHARMACOLOGICAL RELEVANCE: Jasminum grandiflorum L. is a medicinal plant widely used in the traditional system of Medicine as an anthelmintic in ringworm infections, for treating ulcers, stomatitis, skin diseases, and wounds. AIM OF THE STUDY: The emergence of resistance by different parasites to currently used chemicals has been reported. There are increasing needs for more effective and safer parasiticides. Therefore, the current study was designed to investigate the methanolic extract of the aerial parts of J. grandiflorum subsp. Floribundum (JGTE) to confirm its traditional uses as anthelmintic through a bioassay-guided fractionation and isolation of the active components with anthelmintic activity. MATERIALS AND METHODS: The JGTE was partitioned into dichloromethane (DCM-F) and n-butanol (BuOH-F) fractions. The JGTE, fractions, and the isolated compounds were tested in vitro for their anthelmintic activity using two nematodes; one larval stage of cestode and one arthropod. Four major compounds were isolated from the most active fraction (BuOH-F) including two flavonoids and two secoirridoid glycosides, identified as kaempferol-3-O-neohesperoside (1), rutin (2), oleuropein (3), and ligstroside (4). RESULTS: Among the isolated compounds from most active fraction (BuOH-F), rutin (2) displayed the highest anthelmintic activity in a dose-dependent activity with IC50 of 41.04 µg/mL against H. muscae adult worm, followed by ligstroside (4) with IC50 of 50.56 µg/mL. CONCLUSIONS: These findings could advocate the traditional use of J. grandiflorum L. and provide further insight into the anthelmintic activity of flavonoids.

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

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

Automontage microscopy and SEM: A combined approach for documenting ancient lice.

Human ectoparasites, including lice, have been recovered from a wide range of archaeological materials. The human head louse, Pediculus humanus capitis, has been identified from mummies and sediments for decades. Louse eggs are the body part most commonly encountered and therefore the most frequently quantified. Typically, several types of microscopy are applied for egg documentation. For studies in which quantification of infestation is a goal, counting is done with the naked eye or with the aid of handheld lenses. For determination and stage classification, stereomicroscopy is commonly used. For more detailed examination of microstructure, light microscopy, scanning electron microscopy (SEM), and confocal laser scanning microscopy (CLSM) can be employed. In most reports, researchers use two or more techniques to accomplish interrelated goals. Automontage microscopy is used to document prehistoric arthropods with good success. Herein, we report the results of a combination of SEM and automontage microscopy to document lice and eggs recovered from South American mummies. This combined approach allows for simultaneous examination of internal and external characteristics. Thirty automontage composite images of 2 adult lice and 16 eggs showed that egg internal morphologies were easily examined showing the within-egg anatomy of emergent nymphs. SEM imaging of 9 lice and 129 eggs was completed. In the case of two adults and several eggs, SEM imaging was accomplish after automontage image capture of the same specimens. This one-to-one image comparison of SEM and automontage shows that transmitted light of automontage reveals egg internal structures and details of the adult lice. SEM allows for high magnification examination of egg, nymph and adult microstructures. We conclude that automontage imaging followed by SEM results in efficient graphic documentation of rare louse specimens.

Mouthpart sensory structures of the human head louse Pediculus humanus capitis.

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

Mitochondrial diversity and phylogeographic analysis of Pediculus humanus reveals a new Amazonian clade "F".

Pediculus humanus is an obligate and highly intimate bloodsucking insect parasite of humans that has two ecotypes, head louse and body louse. This study analyzed genetic diversity at three mitochondrial genes (cytochrome b [cytb], cytochrome oxidase subunit 1 [cox1] and 12S ribosomal RNA [12S]) in 98 head lice collected from an isolated Native American population from the Wayampi community in Trois-Sauts, French Guiana. These results are integrated with all prior data of P. humanus (1402 cytb, 743 cox1 and 344 12S) from other parts of the world. The phylogenetic analysis revealed six highly divergent and well-supported monophyletic clades. Five clades corresponded to the previously recognized mitochondrial clades A, D, B, C and E, while the sixth (clade F) was novel, as it exhibited 5.4%, 3.7% and 3.6% divergence at cytb, cox1 and 12S, respectively, from its nearest neighbor clade B. Interestingly, the clade F has only been recovered in a few lice sequences from Mexico and Argentina, while it was the most common lineage in the Amazonian lice, which hints its association with the Native American region. Furthermore, Pediculus mjobergi, a New World monkeys' louse, which is thought to be transmitted to monkeys from the first humans that had reached the American continent thousands of years ago, also belonged to this clade, suggesting that this louse may not be a separate species but an evolutionary lineage of P. humanus. The discovery of new Amazonian clade F with the recovery of additional haplotypes within each of the five clades demonstrates that the levels of genetic diversity in P. humanus are higher than previously thought.

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.

Electron Microscopic Alterations in Pediculus humanus capitis Exposed to Some Pediculicidal Plant Extracts.

Head lice, Pediculus humanus capitis, infestation is an important public health problem in Egypt. Inadequate application of topical pediculicides and the increasing resistance to the commonly used pediculicides made the urgent need for the development of new agents able to induce irreversible changes in the exposed lice leading to their mortality. The aim of the present work is to evaluate pediculicidal efficacy of some natural products such as olive oil, tea tree oil, lemon juice, and ivermectin separately in comparison with tetramethrin-piperonyl butoxide (licid), as a standard pediculicide commonly used in Egypt. The effects of these products were evaluated by direct observation using dissecting and scanning electron microscopes (SEM). Results showed that after 1 hr exposure time in vitro, absolute (100%) mortalities were recorded after exposure to 1% ivermectin and fresh concentrate lemon juice. The mortalities were decreased to 96.7% after exposure to tea tree oil. Very low percentage of mortality (23.3%) was recorded after 1 hr of exposure to extra virgin olive oil. On the other hand, the reference pediculicide (licid) revealed only mortality rate of 93.3%. On the contrary, no mortalities were recorded in the control group exposed to distilled water. By SEM examination, control lice preserved outer smooth architecture, eyes, antenna, respiratory spiracles, sensory hairs, and legs with hook-like claws. In contrast, dead lice which had been exposed to pediculicidal products showed damage of outer smooth architecture, sensory hairs, respiratory spiracles and/or clinching claws according to pediculicidal products used.

PREHISTORICAL Pediculus humanus capitis INFESTATION: QUANTITATIVE DATA AND LOW VACUUM SCANNING MICROSCOPY / Infestação pré-histórica por Pediculus humanus capitis: análise quantitativa e por microscopia de varredura de baixo vácuo

A pre-Columbian Peruvian scalp was examined decades ago by a researcher from the Oswaldo Cruz Foundation. Professor Olympio da Fonseca Filho described nits and adult lice attached to hair shafts and commented about the origin of head lice infestations on mankind. This same scalp was sent to our laboratory and is the subject of the present paper. Analysis showed a massive infestation with nine eggs/cm2 and an impressive number of very well preserved adult lice. The infestation age was roughly estimated as nine months before death based on the distance of nits from the hair root and the medium rate of hair growth. A small traditional textile was associated with the scalp, possibly part of the funerary belongings. Other morphological aspects visualized by low-vacuum scanning electron microscopy are also presented here for adults and nits.

Há décadas um escalpo peruano, datado do período pré-colombiano, foi examinado por um pesquisador da Fundação Oswaldo Cruz. O Professor Olympio da Fonseca Filho descreveu lêndeas e adultos fixos a fios de cabelos e fez comentários sobre a origem da infecção por piolhos na espécie humana. Este mesmo escalpo foi enviado ao nosso laboratório e é objeto deste artigo. Sua análise mostrou maciça infestação, com nove lêndeas/cm2 em impressionante número de adultos muito bem preservados. O tempo de infestação foi estimado em cerca de nove meses antes da morte, baseado na maior distância entre lêndeas e o couro cabeludo, levando em consideração taxa média de crescimento capilar de 1 cm por mês. Um pequeno pedaço de tecido tradicional peruano foi encontrado associado ao escalpo, provavelmente pertencente ao conjunto de peças usado no ritual funerário. Aqui, apresentamos alguns aspectos morfológicos de adultos e lêndeas vizualizados por microscopia eletrônica de varredura de baixo vácuo.

Prehistorical Pediculus humanus capitis infestation: quantitative data and low vacuum scanning microscopy.

A pre-Columbian Peruvian scalp was examined decades ago by a researcher from the Oswaldo Cruz Foundation. Professor Olympio da Fonseca Filho described nits and adult lice attached to hair shafts and commented about the origin of head lice infestations on mankind. This same scalp was sent to our laboratory and is the subject of the present paper. Analysis showed a massive infestation with nine eggs/cm2 and an impressive number of very well preserved adult lice. The infestation age was roughly estimated as nine months before death based on the distance of nits from the hair root and the medium rate of hair growth. A small traditional textile was associated with the scalp, possibly part of the funerary belongings. Other morphological aspects visualized by low-vacuum scanning electron microscopy are also presented here for adults and nits.

Study of archaeological nits/eggs of Pediculus humanus capitis by scanning electron microscopy.

This paper presents and discusses archaeological samples of Pediculus humanus capitis nits/eggs in Arica, northern Chile, dating between 2000 B.C. and A.D. 500. Eight samples of nits/eggs taken directly from seven mummified bodies of both the valley and the coast of Arica, were collected and studied. Samples were analysed with scanning electron microscopy (SEM), uncoated, using low and variable pressure modes. The aim was to study the morphology of the nits/eggs, the different degrees of preservation and their research potential. All samples were in good external condition and due to manipulation before SEM analysis, the oldest ones were fractured allowing the observation in situ of the hatching ad portas of an embryo. This inside view of the egg allowed observation and identification of microstructures of the embryo such as abdominal and thoracic spiracles and claws. In the most recent and best preserved samples, external structures characteristic of the egg such as aeropyles and operculum were observed. SEM can contribute significantly to the study of ectoparasites that affected ancient American populations and in this particular case to illustrate the stages and morphology of Andean archaeological specimens of P. humanus capitis.

Severe head lice infestation in an Andean mummy of Arica, Chile.

Pediculus humanus capitis is an ancient human parasite, probably inherited from pre-hominid times. Infestation appears as a recurrent health problem throughout history, including in pre-Columbian populations. Here, we describe and discuss the occurrence of pre-Columbian pediculosis in the Andean region of the Atacama Desert. Using a light microscope and scanning electron microscopy, we studied a highly infested Maitas Chiribaya mummy from Arica in northern Chile dating to 670-990 calibrated years A.D. The scalp and hair of the mummy were almost completely covered by nits and adult head lice. Low- and high-vacuum scanning electron microscopy revealed a well-preserved morphology of the eggs. In addition, the excellent preservation of the nearly 1,000-yr-old adult head lice allowed us to observe and characterize the head, antennae, thorax, abdomen, and legs. Leg segmentation, abdominal spiracles, and sexual dimorphism also were clearly observed. The preservation of the ectoparasites allowed us to examine the micromorphology using scanning electron microscopy; the opercula, aeropyles, and spiracles were clearly visible. This case study provides strong evidence that head lice were a common nuisance for Andean farmers and herders. Head lice are transmitted by direct head-to-head contact; thus, this ancient farmer and herder was potentially infesting other people. The present study contributes to the body of research focusing on lice in ancient populations.

Scanning electron microscopy of legs of two species of sucking lice (Anoplura: Phthiraptera).

Pretarsal, tarsal and tibial structures of the forelegs, midlegs and hindlegs of Pediculus humanus of humans and of Haematopinus apri Goureau, 1866 (Phthiraptera), a parasite of feral hogs, were studied using light microscopy and scanning electron microscopy. Details of the tibial thumb-like process (tl) with the spine of the thumb (spn), tarsal apophysis (ta) and the coupled finger-like process (cfl) can be observed in the leg photomicrograph of both species. A frontal view of the leg in open position shows the articulation of the claw: the structures of an open-closed system, a tooth row (te), rack-system (rs) and two telescopic columns (tc) which are present near the base of the claw in both species. In H. apri, we observed a pad-like structure, the flap-like tibial lobe (fl) on the ventral surface on the tarsus, the euplantulae, with several sensilla basiconica, which is present in each leg.

The mode of action of dimeticone 4% lotion against head lice, Pediculus capitis.

BACKGROUND: Treatment of head lice using physically acting preparations based on silicones is currently replacing insecticide use due to widespread resistance to neurotoxic agents. It has been postulated that some products act by asphyxiation, although the limited experimental evidence and the anatomy of the louse respiratory system suggest this is unlikely. RESULTS: Observation over several hours of lice treated using 4% high molecular weight dimeticone in a volatile silicone base showed that, although rapidly immobilised initially, the insects still exhibited small movements of extremities and death was delayed. One common effect of treatment is inhibition of the louse's ability to excrete water by transpiration through the spiracles. Inability to excrete water that is ingested as part of the louse blood meal appears to subject the louse gut to osmotic stress resulting in rupture. Scanning electron microscopy coupled with X-ray microanalysis to detect silicon showed dimeticone lotion is deposited in the spiracles and distal region of the tracheae of lice and in some cases blocks the lumen or opening entirely. CONCLUSION: This work raises doubts that lice treated using dimeticone preparations die from anoxia despite blockage of the outer respiratory tract because movements can be observed for hours after exposure. However, the blockage inhibits water excretion, which causes physiological stress that leads to death either through prolonged immobilisation or, in some cases, disruption of internal organs such as the gut.

Lethal effects of treatment with a special dimeticone formula on head lice and house crickets (Orthoptera, Ensifera: Acheta domestica and Anoplura, phthiraptera: Pediculus humanus). Insights into physical mechanisms.

The present study provides the first convincing explanation of the mode of action of the medical device NYDA, a special dimeticone (CAS 9006-65-9) formula containing 92% of two dimeticones with different viscosities specifically designed for the physical treatment of head lice infestations (pediculosis capitis) by suffocation. Both, lice (Pediculus humanus) and house crickets (Acheta domestica) treated with this anti-head lice product are knocked out to the status "of no major vital signs" within less than 1 min that in consequence is accompanied irreversibly with the death of the respective insects. Scanning electron microscopical investigations have revealed that the cuticle is coated by a thin closed layer of the dimeticone formula that also enters the stigmata. In vivo observations and dissections of Acheta domestica have shown that application of the medical device to the thoracic stigmata invariably leads to rapid death; this is strongly correlated with the influx of the special dimeticone formula into the head trachea, whereby the solution effectively blocks the oxygen supply of the central nervous system. Dissections after application of the stained product show that it also enters the finest tracheal branches. Analogous in vivo observations in Pediculus humanus have confirmed the correlation between the disappearance of major vital signs and the displacement of air by the dimeticone formula in the tracheal system of the head. For both insect species, statistical data are provided for the chronological sequence of the filling of the tracheal system in relation to the respective vitality conditions of the Insects. On average, the special dimeticone formula reaches the insect's head tracheae within 0.5 min in house crickets and in less than 1 min in lice with a complete filling of the entire head tracheal system of lice within 3.5 min. In addition, a timed sequence of images illustrates this process for lice. The experiments clearly reveal the exclusive and pure physical mode of action of the tested dimeticone formula.

A simple treatment for head lice: dry-on, suffocation-based pediculicide.

OBJECTIVES: The emergence of drug-resistant lice has created the need for new therapies. This study assesses a new method without neurotoxins, extensive household cleaning, or nit removal. METHODS: One hundred thirty-three subjects participated in 2 open clinical trials. In the first trial, 93 subjects completed treatment using a nontoxic, dry-on, suffocation-based, pediculicide lotion, minimal household cleaning measures, and physical removal of the nits. In the second trial, 40 subjects completed treatment using an identical protocol except that the nits were not removed. Head lice infestation was defined as a wet combing test showing lice. Cure was defined as a wet combing test showing no lice, with an absence of symptoms. Subjects were contacted 6 months later, for assessment of their disease status. RESULTS: Cure was achieved for 97% of the patients in the first trial and 95% in the second trial. Remission at the follow-up assessment was reported for 77 of 82 subjects (94%) in the first trial and 36 of 38 subjects (95%) in the second trial. There was no statistical difference in cure rates or remission rates between the protocols with and without nit removal. The overall cure rate was 96%, with a remission rate of 94%. There were no adverse effects. CONCLUSIONS: Dry-on, suffocation-based, pediculicide lotion effectively treats head lice without neurotoxins, nit removal, or extensive house cleaning. These results are comparable or superior to the results previously reported for treatments with permethrin, pyrethrin, and malathion.

An experimental model of human body louse infection with Rickettsia prowazekii.

Rickettsia prowazekii is transmitted to humans by the body louse. A new experimental model of body louse infection with R. prowazekii is reported here. Eight hundred human lice were infected by feeding on a rabbit that was made bacteremic by injecting 2x106 plaque-forming units of R. prowazekii. The bacterium invaded the stomach cells and was released in feces, in which it was detected 5 days after infection. At day 6 after infection, as a result of the cell burst and the spread of erythrocytes in the hemolymph, the louse became bright red and died within 4 h. The life span of infected lice was shortened by 20-23 days, compared with that of uninfected control lice. Infected lice did not transmit R. prowazekii to their progeny. Through cell culture, rickettsiae were cultivated from fecal samples up to 10 days after their emission. The administration of doxycycline to the rabbit during louse feeding did not cure lice from R. prowazekii infection.