Genetic analysis of lice supports direct contact between modern and archaic humans

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.

Genomic Diversity in the Endosymbiotic Bacteria of Human Head Lice

Insects have repeatedly forged symbioses with heritable microbes, gaining novel traits. For the microbe, the transition to symbioses can lead to the degeneration of the symbiont's genome through transmission bottlenecks, isolation, and the loss of DNA repair enzymes. However, some insect-microbial symbioses have persisted for millions of years, suggesting that natural selection slows genetic drift and maintains functional consistency between symbiont populations. By sampling in multiple countries, we examine genomic diversity within a symbiont species, a heritable symbiotic bacterium found only in human head lice. We find that human head louse symbionts contain genetic diversity that appears to have arisen contemporaneously with the appearance of anatomically modern humans within Africa and/or during the colonization of Eurasia by humans. We predict that the observed genetic diversity underlies functional differences in extant symbiont lineages, through the inactivation of genes involved in symbiont membrane construction. Furthermore, we find evidence of additional gene losses prior to the appearance of modern humans, also impacting the symbiont membrane. From this, we conclude that symbiont genome degeneration is proceeding, via gene inactivation and subsequent loss, in human head louse symbionts, while genomic diversity is maintained. Collectively, our results provide a look into the genomic diversity within a single symbiont species and highlight the shared evolutionary history of humans, lice, and bacteria.

Mitochondrial genome sequence comparisons indicate that the elephant louse Haematomyzus elephantis (Piaget, 1869) contains cryptic species

The parvorder Rhynchopthirina contains three currently recognised species of lice that parasitize elephants (both African savanna elephant Loxodonta africana and Asian elephant Elephas maximus), desert warthogs (Phacochoerus aethiopicus) and Red River hogs (Potamochoerus porcus), respectively. The Asian elephant lice and the African savanna elephant lice are currently treated as the same species, Haematomyzus elephantis (Piaget, 1869), based on morphology despite the fact that their hosts diverged 8.4 million years ago. In the current study, we sequenced 23 mitochondrial (mt) genes of African savanna elephant lice collected in South Africa and analysed the sequence divergence between African savanna elephant lice and previously sequenced Asian elephant lice. Sequence comparisons revealed >23% divergence for the 23 mt genes as a whole and ~17% divergence for cox1 gene between African savanna and Asian elephant lice, which were far higher than the divergence expected within a species. Furthermore, the mt gene sequence divergences between these lice are 3.76-4.6 times higher than that between their hosts, the African savanna and Asian elephants, which are expected for the co-divergence and co-evolution between lice and their elephant hosts. We conclude that (1) H. elephantis (Piaget, 1869) contains cryptic species and (2) African savanna and Asian elephant lice are different species genetically that may have co-diverged and co-evolved with their hosts.

Molecular detection of Bartonella quintana, Acinetobacter baumannii and Acinetobacter haemolyticus in Pediculus humanus lice in Nigeria, West Africa

The human lice Pediculus humanus is distributed worldwide but, it thrives and flourishes under conflict situations where people are forced to live in crowded unhygienic conditions. Molecular methods were used to identify and screen human lice for the DNA of pathogens of public health importance in an area that has been under insurgency related to religious and political conflicts with tens of thousands of internally displaced people (IDP). DNA of Bartonella quintana, Acinetobacter baumannii and Acinetobacter haemolyticus was detected in 18.3%, 40.0% and 1.7%, respectively, of human lice collected from children in Maiduguri, Nigeria. More body lice than head lice were positive for pathogen's DNA (64.3% vs. 44.4%; χ2  = 1.3, p = 0.33), but the difference was not significant. Two lice samples were found to harbour mixed DNA of B. quintana and A. baumannii. Phylogenetic analysis of the cytochrome b (cytb) gene sequences of the positive lice specimens placed them into clades A and E. This is the first report on the molecular identification of human lice and the detection of the DNA of pathogens of public health importance in lice in Nigeria, West Africa. The findings of this study will assist policy makers and medical practitioners in formulating a holistic healthcare delivery to IDPs.

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.

Phylogenetic and network analysis of Pediculus humanus in Nigeria reveal the presences of clade E body lice and novel haplotypes

An investigation was conducted for the first time to determine the prevalence and genetic diversity of human lice, for the first time in Nigeria, using conventional PCR and sequencing methods. Three mitochondrial genes, cytochrome oxidase subunit 1 (cox1), cytochrome b (cytb), and 12S rRNA of Nigerian human lice, were amplified, sequenced, and analyzed. Overall, high prevalence (72.5%; 103/142) of lice infestation was recorded among the examined volunteers. Head lice infestation was more common 63 (61.2%) than body lice infestation 34 (33.0%). Co-infestation with both head and body lice was recorded in six humans (5.8%). The Nigerian human lice specimens were placed mostly into clade A with few in clade E, including body lice for the first time. Six, three, and eight haplotypes of Nigerian human lice were obtained for the cytb, cox1, and 12S rRNA genes, respectively. Additionally, one (E51), three (A31, A32, and E5), and six (A20, A21, A23, A24, A30, and E1) novel haplotypes were recorded for cox1, cytb, and 12S rRNA, respectively, from the Nigerian specimens which were corroborated by the ML phylogenetic trees and MJ network analyses. Genetic diversity indices indicate minimal variation in the parameters analyzed among the clades of the three genes. However, a statistically significant Snn test, negative Tajima's D test for clade A (cox1 and 12S rRNA genes), and negative Fu and Li's D test in clade A for cox1 gene indicate a geographical structure and the signature of population expansion of the Nigerian human lice. The findings from this study provide additional data on the human lice structure in Africa.

Infectious disease in the Pleistocene: Old friends or old foes?

The impact of endemic and epidemic disease on humans has traditionally been seen as a comparatively recent historical phenomenon associated with the Neolithisation of human groups, an increase in population size led by sedentarism, and increasing contact with domesticated animals as well as species occupying opportunistic symbiotic and ectosymbiotic relationships with humans. The orthodox approach is that Neolithisation created the conditions for increasing population size able to support a reservoir of infectious disease sufficient to act as selective pressure. This orthodoxy is the result of an overly simplistic reliance on skeletal data assuming that no skeletal lesions equated to a healthy individual, underpinned by the assumption that hunter-gatherer groups were inherently healthy while agricultural groups acted as infectious disease reservoirs. The work of van Blerkom, Am. J. Phys. Anthropol., vol. suppl 37 (2003), Wolfe et al., Nature, vol. 447 (2007) and Houldcroft and Underdown, Am. J. Phys. Anthropol., vol. 160, (2016) has changed this landscape by arguing that humans and pathogens have long been fellow travelers. The package of infectious diseases experienced by our ancient ancestors may not be as dissimilar to modern infectious diseases as was once believed. The importance of DNA, from ancient and modern sources, to the study of the antiquity of infectious disease, and its role as a selective pressure cannot be overstated. Here we consider evidence of ancient epidemic and endemic infectious diseases with inferences from modern and ancient human and hominin DNA, and from circulating and extinct pathogen genomes. We argue that the pandemics of the past are a vital tool to unlock the weapons needed to fight pandemics of the future.

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.

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.

Putative native South Amerindian origin of head lice clade F: evidence from head lice nits infesting human shrunken heads

The head louse, Pediculus humanus capitis, is a strictly obligate human ectoparasite with a long history of association with humans. Here, 17 ancient head lice nits were recovered from six shrunken human heads (known as tsantsas) of individuals from the Shuar/Jivaro tribe, a native Amazonian population from Ecuador, South America. Cytochrome b DNA analysis revealed the presence of three known mitochondrial clades. Clade A was the most frequent (52.94%), followed by F (35.29%), and B (11.76%). Eleven haplotypes were found in 17 samples, and nine of the haplotypes were novel, indicating an unusually high genetic diversity. In conclusion, we confirmed the presence of clades A, B and F in South Amerindian population. Moreover, the description of clade F, together with its previous reports in another Amerindian population from French Guiana, strongly support the hypothesis of a native South American origin for this clade, and probably derived from clade B which was carried to America by an ancestral Eurasian Beringian population. Further support to our conclusion and new insights might come from the analysis of a larger collection of modern and ancient native American lice.

A Theory of City Biogeography and the Origin of Urban Species

Many of the choices humans make with regard to infrastructure, urban planning and other phenomena have impacts that will last thousands of years. This can readily be seen in modern cities in which contemporary streets run along street grids that were laid out thousands of years prior or even in which ancient viaducts still play a role. However, rarely do evolutionary biologists explicitly consider the future of life likely to be associated with the decisions we are making today. Here, we consider the evolutionary future of species in cities with a focus on the origin of lineages and species. We do so by adjusting evolutionary predictions from the theory of island biogeography so as to correspond to the unique features of cities as islands. Specifically, the species endemic to cities tend to be associated with the gray habitats in cities. Those habitats tend to be dominated by human bodies, pet bodies and stored food. It is among such species where the origin of new lineages is most likely, although most research on evolution in cities has focused on green habitats. We conclude by considering a range of scenarios for the far future and their implications for the origin of lineages and species.

Long-distance dispersal of pigeons and doves generated new ecological opportunities for host-switching and adaptive radiation by their parasites

Adaptive radiation is an important mechanism of organismal diversification and can be triggered by new ecological opportunities. Although poorly studied in this regard, parasites are an ideal group in which to study adaptive radiations because of their close associations with host species. Both experimental and comparative studies suggest that the ectoparasitic wing lice of pigeons and doves have adaptively radiated, leading to differences in body size and overall coloration. Here, we show that long-distance dispersal by dove hosts was central to parasite diversification because it provided new ecological opportunities for parasites to speciate after host-switching. We further show that among extant parasite lineages host-switching decreased over time, with cospeciation becoming the more dominant mode of parasite speciation. Taken together, our results suggest that host dispersal, followed by host-switching, provided novel ecological opportunities that facilitated adaptive radiation by parasites.

Phylogenetic relationship between the endosymbiont "Candidatus Riesia pediculicola" and its human louse host

Background

The 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.

Methods

The 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).

Results

The 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.

Conclusion

Our 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 Abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05203-z.

High Genetic Diversity and Rickettsia felis in Pediculus humanus Lice Infesting Mbuti (pygmy people), -Democratic Republic of Congo

Pediculus humanus is an obligate bloodsucking parasite of humans that has two ecotypes, the head louse and the body louse, which share an intimate history of coevolution with their human host. In the present work, we obtained and analysed head and body lice collected from Mbuti pygmies living in the Orientale province of the Democratic Republic of the Congo. Cytochrome b DNA analysis was performed in order to type the six known lice clades (A, D, B, F, C and E). The results revealed the presence of two mitochondrial clades. Clade D was the most frequent (61.7% of 47), followed by clade A (38.3% of 47). Sixteen haplotypes were found in 47 samples, of which thirteen were novel haplotypes, indicating an unusually high genetic diversity that closely mirrors the diversity of their hosts. Moreover, we report for the first time the presence of the DNA of R. felis in three (6.4% of 47) head and body lice belonging to both clades A and D. Additional studies are needed to clarify whether the Pediculus lice can indeed transmit this emerging zoonotic bacterium to their human hosts.

Ancient human genomes and environmental DNA from the cement attaching 2,000 year-old head lice nits

Over the past few decades, there has been a growing demand for genome analysis of ancient human remains. Destructive sampling is increasingly difficult to obtain for ethical reasons, and standard methods of breaking the skull to access the petrous bone or sampling remaining teeth are often forbidden for curatorial reasons. However, most ancient humans carried head lice and their eggs abound in historical hair specimens. Here we show that host DNA is protected by the cement that glues head lice nits to the hair of ancient Argentinian mummies, 1,500–2,000 years old. The genetic affinities deciphered from genome-wide analyses of this DNA inform that this population migrated from north-west Amazonia to the Andes of central-west Argentina; a result confirmed using the mitochondria of the host lice. The cement preserves ancient environmental DNA of the skin, including the earliest recorded case of Merkel cell polyomavirus. We found that the percentage of human DNA obtained from nit cement equals human DNA obtained from the tooth, yield 2-fold compared with a petrous bone, and 4-fold to a bloodmeal of adult lice a millennium younger. In metric studies of sheaths, the length of the cement negatively correlates with the age of the specimens, whereas hair linear distance between nit and scalp informs about the environmental conditions at the time before death. Ectoparasitic lice sheaths can offer an alternative, nondestructive source of high-quality ancient DNA from a variety of host taxa where bones and teeth are not available and reveal complementary details of their history.

Molecular analysis of mitochrondrial cytb of Pediculus humanus capitis in Thailand revealed potential historical connection with South Asia

Background

Pediculus humanus capitis or head louse is an obligate ectoparasite and its infestation remains a major public health issue worldwide. Molecular analysis divides head lice into six clades and intra-clade genetic differences have been identified. Several hypotheses have been formulated to elucidate the discrepancies of the variety of head lice among different regions of the world. It is currently concluded that head lice distribution might be associated with human migration history. This study aims to investigate genetic data of human head lice in Thailand. We believe that the analysis could help establish the correlation between local and global head lice populations.

Method

We investigated mitochondrial cytochrome b (cytb) gene of the collected 214 head lice to evaluate genetic diversity from 15 provinces among 6 regions of Thailand. The head lice genes were added to the global pool for the phylogenetic tree, Bayesian tree, Skyline plot, and median joining network construction. The biodiversity, neutrality tests, and population genetic differentiation among the 6 Thailand geographic regions were analyzed by DNAsp version 6.

Results

The phylogenetic tree analysis of 214 collected head lice are of clade A and clade C accounting for roughly 65% and 35% respectively. The Bayesian tree revealed a correlation of clade diversification and ancient human dispersal timeline. In Thailand, clade A is widespread in the country. Clade C is confined to only the Central, Southern, and Northeastern regions. We identified 50 novel haplotypes. Statistical analysis showed congruent results between genetic differentiation and population migration especially with South Asia.

Conclusions

Pediculosis remains problematic among children in the rural areas in Thailand. Cytb gene analysis of human head lice illustrated clade distribution and intra-clade diversity of different areas. Our study reported novel haplotypes of head lice in Thailand. Moreover, the statistic calculation provided a better understanding of their relationship with human, as an obligate human parasite and might help provide a better insight into the history of human population migration. Determination of the correlation between phylogenetic data and pediculicide resistance gene as well as residing bacteria are of interest for future studies.

Between a rock and a cold place: Neanderthal biocultural cold adaptations

A large body of work focuses on the unique aspects of Neanderthal anatomy, inferred physiology, and behavior to test the assumption that Neanderthals were hyper-adapted to living in cold environments. This research has expanded over the years to include previously unexplored and potentially adaptive features such as brown adipose tissue and fire-usage. Here we review the current state of knowledge of Neanderthal cold adaptations along morphological, physiological, and behavioral lines. While highlighting foundational as well as recent work, we also emphasize key areas for future research. Despite thriving in a variety of climates, it is well-accepted that Neanderthals appear to be the most cold-adapted of known fossil hominin groups; however, there are still many unknowns. There is a great deal yet to be uncovered about the nature and manifestation of Neanderthal adaptation and how the synergy of biology and culture helped buffer them against extreme and variable environments.

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 Characterization and Genetic Diversity of Haplogroup E Human Lice in Guinea, West Africa

Pediculus humanus capitis, the head louse, is an obligate blood-sucking ectoparasite that occurs in six divergent mitochondrial clades (A, D, B, F, C and E). Several studies reported the presence of different pathogenic agents in head lice specimens collected worldwide. These findings suggest that head louse could be a dangerous vector and a serious public health problem. Herein, we aimed to study the mitochondrial genetic diversity, the PHUM540560 gene polymorphisms profile of head lice collected in Guinea, as well as to screen for their associated pathogens. In 2018, a total of 155 head lice were collected from 49 individuals at the Medicals Centers of rural (Maférinyah village) and urban (Kindia city) areas, in Guinea. Specimens were subjected to a genetic analysis and pathogens screening using molecular tools. Results showed that all head lice belonged to eight haplotypes in the E haplogroup, with six newly identified for the first time. The study of the PHUM540560 gene polymorphisms of our clade E-head lice revealed that 82.5% exhibited the same polymorphism profile as the previously reported clade A-body lice. Screening for targeted pathogens revealed the presence of Acinetobacter spp., while sequencing highlighted the presence of several species, including Acinetobacter baumannii, Acinetobacter nosocomialis, Acinetobacter variabilis, Acinetobacter towneri and for the first time Acinetobacter haemolyticus. Our study is the first to report the existence of the Guinean haplogroup E, the PHUM540560 gene polymorphism profile as well as the presence of Acinetobacter species in head lice collected from Guinea.

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

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

Diversity of mitochondrial genes and predominance of Clade B in different head lice populations in the northwest of Iran

BACKGROUND

The head louse, Pediculus humanus capitis, is the most important ectoparasite causing many health problems. Several linkages are presented for this parasite, each representing a particular geographical distribution, prevalence rate, vector competence, susceptibility to pediculicides, and infestation rate. Determining the genetic nature of these linkages is necessary to identify the population structure and also to develop and monitor control programmes against head lice. This study was designed to analyse cox1 and cytb genes and determine the mitochondrial clades in head lice populations in the northwest of Iran.

METHODS

Adult head lice were collected from infested females of Ardabil, East and West Azerbaijan, and Zanjan Provinces from 2016 to 2018. Partial fragments of the mitochondrial genes cox1 and cytb were amplified by PCR and some of the amplicons were sequenced. All confirmed sequences were analysed, and the frequency of each mitochondrial clade was determined in the studied areas.

RESULTS

A total of 6410 females were clinically examined, and 897 adult head lice were collected from 562 infested cases. Genomic DNA was extracted from 417 samples, and fragments of cox1 and cytb genes were amplified in 348 individuals. Analysis of the 116 sequences showed the 632-bp and 495-bp fragments for cox1 and cytb genes, respectively. The nucleotide and haplotype diversities of cytb and cox1 genes were 0.02261 and 0.589 and 0.01443 and 0.424, respectively. Sequence analysis indicated 6 haplotypes clustered in two clades, A and B. The relative prevalence of clade B was 73% for cytb and 82% for cox1 gene. Haplotypes of clade B were found in all the studied areas, while those of clade A were observed only in rural and suburban areas.

CONCLUSIONS

To our knowledge, this is the first study investigated deeply the field populations of Pediculus and documented two clades in the Middle East. The considerable prevalence of pediculosis in the studied areas requires authorities' attention to establish effective control and preventive measures. Given the role of cytb in monitoring population groups, application of this marker is suggested for future epigenetic studies to evaluate the factors affecting the abundance of these clades.

Fragmented mitochondrial genomes evolved in opposite directions between closely related macaque louse Pedicinus obtusus and colobus louse Pedicinus badii

We report for the first time the fragmented mitochondrial (mt) genomes of two Pedicinus species: Pedicinus obtusus and Pedicinus badii, and compared them with the lice of humans and chimpanzees. Despite being congeneric, the two monkey lice are distinct from each other in mt karyotype. The variation in mt karyotype between the two Pedicinus lice is the most pronounced among the congeneric species of sucking lice observed to date and is attributable to the opposite directions between them in mt karyotype evolution. Two of the inferred ancestral mt minichromosomes of the higher primate lice merged as one in the macaque louse whereas one of the ancestral minichromosomes split into two in the colobus louse after these two species diverged from their most recent common ancestor. Our results showed that mt genome fragmentation was a two-way process in the higher primate lice, and minichromosome merger was more common than previously thought.

Molecular identification of head lice collected in Franceville (Gabon) and their associated bacteria

BACKGROUND

Pediculus humanus, which includes two ecotypes (body and head lice), is an obligate bloodsucking parasite that co-evolved with their human hosts over thousands of years, thus providing a valuable source of information to reconstruct the human migration. Pediculosis due to head lice occurred each year throughout the world and several pathogenic bacteria, which are usually associated with body lice, are increasingly detected in them. In Gabon, where this pediculosis is still widespread, there is a lack of data on genetic diversity of head lice and their associated bacteria.

METHODS

This study aimed to investigate the phylogeny of head lice collected in Gabon and their associated bacteria, using molecular tools. Between 26 March and 11 April 2018, 691 head lice were collected from 86 women in Franceville. We studied the genetic diversity of these lice based on the cytochrome b gene, then we screened them for DNA of Bartonella quintana, Borrelia spp., Acinetobacter spp., Yersinia pestis, Rickettsia spp., R. prowazekii, Anaplasma spp. and C. burnetii, using real time or standard PCR and sequencing.

RESULTS

Overall 74.6% of studied lice belonged to Clade A, 25.3% to Clade C and 0.1% to Clade E. The phylogenetic analysis of 344 head lice yielded 45 variable positions defining 13 different haplotypes from which 8 were novel. Bacterial screening revealed the presence of Borrelia spp. DNA in 3 (0.4%) of 691 head lice belonging to Clade A and infesting one individual. This Borrelia is close to B. theileri (GenBank: MN621894). Acinetobacter spp. DNA has been detected in 39 (25%) of the 156 screened lice; of these 13 (8.3%) corresponded to A. baumannii. Acinetobacter nosocomialis (n = 2) and A. pittii (n = 1) were also recorded.

CONCLUSIONS

To of our knowledge, this study is the first to investigate the genetic diversity of head lice from Gabon. It appears that Clade C is the second most important clade in Gabon, after Clade A which is known to have a global distribution. The detection of Borrelia spp. DNA in these lice highlight the potential circulation of these bacteria in Gabon.

Molecular investigation and genetic diversity of Pediculus and Pthirus lice in France

BACKGROUND

Humans are parasitized by three types of lice: body, head and pubic lice. As their common names imply, each type colonizes a specific region of the body. The body louse is the only recognized disease vector. However, an increasing awareness of head lice as a vector has emerged recently whereas the status of pubic lice as a vector is not known since it has received little attention.

METHODS

Here, we assessed the occurrence of bacterial pathogens in 107 body lice, 33 head lice and 63 pubic lice from Marseille and Bobigny (France) using molecular methods.

RESULTS

Results show that all body lice samples belonged to the cytb Clade A whereas head lice samples belonged to Clades A and B. DNA of Bartonella quintana was detected in 7.5% of body lice samples and, for the first time to our knowledge, in 3.1% of pubic lice samples. Coxiella burnetii, which is not usually associated with transmission by louse, was detected in 3.7% of body lice samples and 3% of head lice samples. To the best of our knowledge, this is the first report of C. burnetii in Pediculus lice infesting humans in France. Acinetobacter DNA was detected in 21.5% of body lice samples, 6% of head lice samples and 9.5% of pubic lice samples. Five species were identified with A. baumannii being the most prevalent.

CONCLUSIONS

Our study is the first to report the presence of B. quintana in pubic lice. This is also the first report of the presence of DNA of C. burnetii in body lice and head lice in France. Further efforts on the vectorial role of human lice are needed, most importantly the role of pubic lice as a disease vector should be further investigated.

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.

Rapid host expansion of an introduced parasite, the spiny rat louse Polyplax spinulosa (Psocodea: Phthiraptera: Polyplacidae), among endemic rodents in Australia

BACKGROUND

Historical European exploration and colonization resulted in the introduction of four species of rodents to the Australian continent from Eurasia: the brown rat, Rattus norvegicus, the black rat, R. rattus, the Pacific rat, R. exulans, and the house mouse, Mus musculus. The spread of these rodents created opportunities for their co-introduced sucking lice to parasitize and adapt to endemic rodents in Australia.

METHODS

We collected sucking lice from rodent specimens in seven museums across Australia. We identified the spiny rat louse, Polyplax spinulosa, based on morphology. We sequenced the mitochondrial cox1 and rrnL genes of P. spinulosa specimens and constructed a phylogenetic tree with rrnL sequences.

RESULTS

We examined 989 rodent specimens of 54 species and collected 2111 adult sucking lice and 1064 nymphal sucking lice. We found that P. spinulosa had nearly doubled its host range by parasitizing at least six endemic rodent species in Australia. The other two introduced lice, P. serrata and Hoplopleura pacifica, however, have apparently failed to expand to any endemic rodents in Australia. Our analysis of mitochondrial rrnL gene sequences divided P. spinulosa into two genotypes (European vs Southeast Asian), which differ by 7.5%; both genotypes were introduced into Australia and then expanded their host ranges to include endemic rodents.

CONCLUSIONS

The earliest record of a European ship landing in Australia was in 1606, followed by British settlement in 1788. The expansion of P. spinulosa to at least six endemic rodent species in Australia has therefore occurred in the time frame of 200 to 400 years, which is extremely rapid relative to its host expansion to eight native rat species in Eurasia in ~ 16 million years since it diverged from P. serrata. The host expansion of P. spinulosa is remarkable for a blood-sucking louse and is in stark contrast to the absence of host expansion by P. serrata and H. pacifica. Comparison among these three introduced sucking lice indicated that both louse-specific factors and host-specific factors can contribute to the success or failure of host expansion.

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.

Evolution, Prehistory and Vitamin D

Aspects of human evolutionary biology and prehistory are discussed in relation to vitamin D. The evolution of hairlessness, combined with the need for efficient eccrine sweat production for cooling, provided evolutionary pressure to protect the skin from ultraviolet damage by developing cutaneous pigmentation. There was a subsequent loss of pigmentation as humans journeyed to northern latitudes. Their increasing mastery of technology outstripped evolution's finite pace as further dispersal occurred around the globe. A timeline for the development of clothing to provide warmth, and the consequent shielding from ultraviolet light, which diminished vitamin D synthesis, can be inferred by an examination of mutations in the human louse.

Disease transmission and introgression can explain the long-lasting contact zone of modern humans and Neanderthals

Neanderthals and modern humans both occupied the Levant for tens of thousands of years prior to the spread of modern humans into the rest of Eurasia and their replacement of the Neanderthals. That the inter-species boundary remained geographically localized for so long is a puzzle, particularly in light of the rapidity of its subsequent movement. Here, we propose that infectious-disease dynamics can explain the localization and persistence of the inter-species boundary. We further propose, and support with dynamical-systems models, that introgression-based transmission of alleles related to the immune system would have gradually diminished this barrier to pervasive inter-species interaction, leading to the eventual release of the inter-species boundary from its geographic localization. Asymmetries between the species in the characteristics of their associated ‘pathogen packages’ could have generated feedback that allowed modern humans to overcome disease burden earlier than Neanderthals, giving them an advantage in their subsequent spread into Eurasia.

Modern humans and Neanderthals coexisted in the Levant for tens of thousands of years before modern humans spread and replaced Neanderthals. Here, Greenbaum et al. develop a model showing that transmission of disease and genes can explain the maintenance and then collapse of this contact zone.

New Genus and Two New Species of Chewing Lice from Southeast Asian Trogons (Aves: Trogoniformes), with a Revised Key to the Philopterus-complex

PURPOSE

To describe a new genus and two new species of chewing lice from Southeast Asian trogons (Trogoniformes). These lice belong in the Philopterus-complex.

METHODS

Slide-mounted lice were examined in a light microscope, illustrated by means of a drawing tube, and described using standard procedures.

RESULTS

The new genus and species were successfully described.

CONCLUSIONS

The genus Vinceopterus n. gen. is described from two species of Southeast Asian trogons (Trogoniformes: Harpactes). It presently comprises two species: Vinceopterus erythrocephali n. sp. from three subspecies of the Red-headed Trogon Harpactes erythrocephalus (Gould, 1834), and Vinceopterus mindanensis n. sp. from two subspecies of the Philippine Trogon Harpactes ardens (Temminck, 1826). Vinceopterus belongs to the Philopterus-complex, and thus likely constitutes a genus of head lice. Vinceopterus is the second new genus of chewing lice discovered on Southeast Asian trogons in recent years, the first genus of presumed head lice on trogons worldwide, and the fifth genus of chewing lice known from trogons globally. A translated and revised key to the Philopterus-complex is provided, as well as notes on the various chewing lice genera known from trogons.

Using human head lice to unravel neglect and cause of death

Despite the common association of human lice with abandoned or neglected people, no procedure to assess pediculosis, aimed to detect signs of neglect, exists. Investigating the two most common forms of head louse infestation, regular and severe, we define lice-markers of neglect and develop a protocol and survey form to record and assess pediculosis. The study of head lice from a deceased victim of neglect helped unravel time-length since death, frequency of exposure to neglect and the cause and circumstances related to the death. Nit-clusters are markers of neglect, indicating length and frequency of neglect episodes. In the case study used here that culminated in the death of the victim, sustained abandonment started circa 2 years before discovery. The lice suggested that death was caused by overconsumption of a powerful calcium channel blocker, an antihypertensive, an excess of which in lice food supply (blood) stops oogenesis. Despite hosting thousands of adult females on the hair, lice reproduction stopped and nits were no longer developed or deposited on the hairs at the root end. This short distance of the shaft with no nits provided a time estimation of overdosing of almost 2 months before death.

The ectoparasites of hybrid ducks in New Zealand (Mallard x Grey Duck)

We studied the population genetics of one population sample of hybrid Mallard x Grey Ducks and their lice in New Zealand. We aimed to document the relationship between ectoparasite load and host phenotype, and test for an association between the mtDNA diversity of the lice and their hosts, which is predicted based on maternal care. We found three feather lice species previously described for these hosts: Anaticola crassicornis (wing louse), Anatoecus dentatus (head louse), and Trinoton querquedulae (body louse). No new or rare lice species were uncovered. Most ducks in our sample were more Mallard-like than Grey Duck-like hybrids for the five colour and plumage traits examined. We confirm that based solely on phenotypic characters it is difficult to distinguish between Mallards, hybrids and Grey Ducks. We detected no association between the number of lice and host phenotype for two of the three louse species (while controlling for bird size). However, the Grey Duck-like hybrids had fewer head lice (A. dentatus) than their Mallard-like counterparts. Only three of the 40 hosts had mtDNA haplotypes that characterise Grey Ducks. We present the first genetic data of Anaticola crassicornis, Anatoecus dentatus and Trinoton querquedulae from New Zealand waterfowl. We found that the lice mtDNA had greater sequence diversity than the homologous gene for the ducks. A mitochondrial phylogeny for A. crassicornis collected from hosts worldwide has been previously published, and we added our novel data to infer evolutionary relationships among worldwide populations of this louse. None of the three lice species showed a close association of parasite and host mtDNA lineage despite lack of paternal care in these duck species.

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We studied population genetics of hybrid Mallard x Grey Ducks and their lice in New Zealand.

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We found three feather lice species previously described for these hosts.

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Most ducks were more Mallard-like than Grey Duck-like hybrids for the traits examined.

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Only three of the forty hosts had mtDNA haplotypes that characterise Grey Ducks.

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We present the first genetic data for the three lice species from New Zealand.

Signatures of human-commensalism in the house sparrow genome

House sparrows (Passer domesticus) are a hugely successful anthrodependent species; occurring on nearly every continent. Yet, despite their ubiquity and familiarity to humans, surprisingly little is known about their origins. We sought to investigate the evolutionary history of the house sparrow and identify the processes involved in its transition to a human-commensal niche. We used a whole genome resequencing dataset of 120 individuals from three Eurasian species, including three populations of Bactrianus sparrows, a non-commensal, divergent house sparrow lineage occurring in the Near East. Coalescent modelling supports a split between house and Bactrianus sparrow 11 Kya and an expansion in the house sparrow at 6 Kya, consistent with the spread of agriculture following the Neolithic revolution. Commensal house sparrows therefore likely moved into Europe with the spread of agriculture following this period. Using the Bactrianus sparrow as a proxy for a pre-commensal, ancestral house population, we performed a comparative genome scan to identify genes potentially involved with adaptation to an anthropogenic niche. We identified potential signatures of recent, positive selection in the genome of the commensal house sparrow that are absent in Bactrianus populations. The strongest selected region encompasses two major candidate genes; COL11A-which regulates craniofacial and skull development and AMY2A, part of the amylase gene family which has previously been linked to adaptation to high-starch diets in humans and dogs. Our work examines human-commensalism in an evolutionary framework, identifies genomic regions likely involved in rapid adaptation to this new niche and ties the evolution of this species to the development of modern human civilization.

The Role of aDNA in Understanding the Coevolutionary Patterns of Human Sexually Transmitted Infections

Analysis of pathogen genome data sequenced from clinical and historical samples has made it possible to perform phylogenetic analyses of sexually transmitted infections on a global scale, and to estimate the diversity, distribution, and coevolutionary host relationships of these pathogens, providing insights into pathogen emergence and disease prevention. Deep-sequenced pathogen genomes from clinical studies and ancient samples yield estimates of within-host and between-host evolutionary rates and provide data on changes in pathogen genomic stability and evolutionary responses. Here we examine three groups of pathogens transmitted mainly through sexual contact between modern humans to provide insight into ancient human behavior and history with their pathogens. Exploring ancient pathogen genomic divergence and the ancient viral-host parallel evolutionary histories will help us to reconstruct the origin of present-day geographical distribution and diversity of clinical pathogen infections, and will hopefully allow us to foresee possible environmentally induced pathogen evolutionary responses. Lastly, we emphasize that ancient pathogen DNA research should be combined with modern clinical pathogen data, and be equitable and provide advantages for all researchers worldwide, e.g., through shared data.

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.

High-capacity optical long data memory based on enhanced Young's modulus in nanoplasmonic hybrid glass composites

Emerging as an inevitable outcome of the big data era, long data are the massive amount of data that captures changes in the real world over a long period of time. In this context, recording and reading the data of a few terabytes in a single storage device repeatedly with a century-long unchanged baseline is in high demand. Here, we demonstrate the concept of optical long data memory with nanoplasmonic hybrid glass composites. Through the sintering-free incorporation of nanorods into the earth abundant hybrid glass composite, Young’s modulus is enhanced by one to two orders of magnitude. This discovery, enabling reshaping control of plasmonic nanoparticles of multiple-length allows for continuous multi-level recording and reading with a capacity over 10 terabytes with no appreciable change of the baseline over 600 years, which opens new opportunities for long data memory that affects the past and future.

Storing and reading data for long periods of time is of huge interest. Here, the authors demonstrate long optical data memory with nanoplasmonic hybrid glass composites. They show continuous multi-level recording and reading with a capacity over 10 terabytes with no change of the baseline over 600 years.

Craniomandibular form and body size variation of first generation mouse hybrids: A model for hominin hybridization

Hybridization occurs in a number of mammalian lineages, including among primate taxa. Analyses of ancient genomes have shown that hybridization between our lineage and other archaic hominins in Eurasia occurred numerous times in the past. However, we still have limited empirical data on what a hybrid skeleton looks like, or how to spot patterns of hybridization among fossils for which there are no genetic data. Here we use experimental mouse models to supplement previous studies of primates. We characterize size and shape variation in the cranium and mandible of three wild-derived inbred mouse strains and their first generation (F1) hybrids. The three parent taxa in our analysis represent lineages that diverged over approximately the same period as the human/Neanderthal/Denisovan lineages and their hybrids are variably successful in the wild. Comparisons of body size, as quantified by long bone measurements, are also presented to determine whether the identified phenotypic effects of hybridization are localized to the cranium or represent overall body size changes. The results indicate that hybrid cranial and mandibular sizes, as well as limb length, exceed that of the parent taxa in all cases. All three F1 hybrid crosses display similar patterns of size and form variation. These results are generally consistent with earlier studies on primates and other mammals, suggesting that the effects of hybridization may be similar across very different scenarios of hybridization, including different levels of hybrid fitness. This paper serves to supplement previous studies aimed at identifying F1 hybrids in the fossil record and to introduce further research that will explore hybrid morphologies using mice as a proxy for better understanding hybridization in the hominin fossil record.

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.

Ancient oncogenesis, infection and human evolution

The recent discovery that malignant neoplastic lesions date back nearly 2 million years ago not only highlights the antiquity of cancer in the human lineage, but also provides remarkable insight into ancestral hominin disease pathology. Using these Early Pleistocene examples as a point of departure, we emphasize the prominent role of viral and bacterial pathogens in oncogenesis and evaluate the impact of pathogens on human evolutionary processes in Africa. In the Shakespearean vernacular "what's past is prologue," we highlight the significance of novel information derived from ancient pathogenic DNA. In particular, and given the temporal depth of human occupation in sub-Saharan Africa, it is emphasized that the region is ideally positioned to play a strategic role in the discovery of ancient pathogenic drivers of not only human mortality, but also human evolution. Ancient African pathogen genome data can provide novel revelations concerning human-pathogen coevolutionary processes, and such knowledge is essential for forecasting the ways in which emerging zoonotic and increasingly transmissible diseases might influence human demography and longevity in the future.

Primates, Lice and Bacteria: Speciation and Genome Evolution in the Symbionts of Hominid Lice

Insects with restricted diets rely on symbiotic bacteria to provide essential metabolites missing in their diet. The blood-sucking lice are obligate, host-specific parasites of mammals and are themselves host to symbiotic bacteria. In human lice, these bacterial symbionts supply the lice with B-vitamins. Here, we sequenced the genomes of symbiotic and heritable bacterial of human, chimpanzee, gorilla, and monkey lice and used phylogenomics to investigate their evolutionary relationships. We find that these symbionts have a phylogenetic history reflecting the louse phylogeny, a finding contrary to previous reports of symbiont replacement. Examination of the highly reduced symbiont genomes (0.53–0.57 Mb) reveals much of the genomes are dedicated to vitamin synthesis. This is unchanged in the smallest symbiont genome and one that appears to have been reorganized. Specifically, symbionts from human lice, chimpanzee lice, and gorilla lice carry a small plasmid that encodes synthesis of vitamin B5, a vitamin critical to the bacteria-louse symbiosis. This plasmid is absent in an old world monkey louse symbiont, where this pathway is on its primary chromosome. This suggests the unique genomic configuration brought about by the plasmid is not essential for symbiosis, but once obtained, it has persisted for up to 25 My. We also find evidence that human, chimpanzee, and gorilla louse endosymbionts have lost a pathway for synthesis of vitamin B1, whereas the monkey louse symbiont has retained this pathway. It is unclear whether these changes are adaptive, but they may point to evolutionary responses of louse symbionts to shifts in primate biology.

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.

Detection of bacterial pathogens including potential new species in human head lice from Mali

In poor African countries, where no medical and biological facilities are available, the identification of potential emerging pathogens of concern at an early stage is challenging. Head lice, Pediculus humanus capitis, have a short life, feed only on human blood and do not transmit pathogens to their progeny. They are, therefore, a perfect tool for the xenodiagnosis of current or recent human infection. This study assessed the occurrence of bacterial pathogens from head lice collected in two rural villages from Mali, where a high frequency of head lice infestation had previously been reported, using molecular methods. Results show that all 600 head lice, collected from 117 individuals, belonged to clade E, specific to West Africa. Bartonella quintana, the causative agent of trench fever, was identified in three of the 600 (0.5%) head lice studied. Our study also shows, for the first time, the presence of the DNA of two pathogenic bacteria, namely Coxiella burnetii (5.1%) and Rickettsia aeschlimannii (0.6%), detected in human head lice, as well as the DNA of potential new species from the Anaplasma and Ehrlichia genera of unknown pathogenicity. The finding of several Malian head lice infected with B. quintana, C. burnetii, R. aeschlimannii, Anaplasma and Ehrlichia is alarming and highlights the need for active survey programs to define the public health consequences of the detection of these emerging bacterial pathogens in human head lice.

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.

Network analysis of the hominin origin of Herpes Simplex virus 2 from fossil data

Herpes simplex virus 2 (HSV2) is a human herpesvirus found worldwide that causes genital lesions and more rarely causes encephalitis. This pathogen is most common in Africa, and particularly in central and east Africa, an area of particular significance for the evolution of modern humans. Unlike HSV1, HSV2 has not simply co-speciated with humans from their last common ancestor with primates. HSV2 jumped the species barrier between 1.4 and 3 MYA, most likely through intermediate but unknown hominin species. In this article, we use probability-based network analysis to determine the most probable transmission path between intermediate hosts of HSV2, from the ancestors of chimpanzees to the ancestors of modern humans, using paleo-environmental data on the distribution of African tropical rainforest over the last 3 million years and data on the age and distribution of fossil species of hominin present in Africa between 1.4 and 3 MYA. Our model identifies Paranthropus boisei as the most likely intermediate host of HSV2, while Homo habilis may also have played a role in the initial transmission of HSV2 from the ancestors of chimpanzees to P.boisei.

Arrestant Effect of Human Scalp Components on Head Louse (Phthiraptera: Pediculidae) Behavior

Relevant evidence has shown that parasites process host-related information using chemical, visual, tactile, or auditory cues. However, the cues that are involved in the host-parasite interaction between Pediculus humanus capitis (De Geer 1767) and humans have not been identified yet. In this work, we studied the effect of human scalp components on the behavior of adult head lice. Filter paper segments were rubbed on volunteers' scalps and then placed in the experimental arena, where adult head lice were individually tested. The movement of the insects was recorded for each arena using the software EthoVision. Average movement parameters were calculated for the treatments in the bioassays such as total distance, velocity, number of times a head louse crossed between zones of the arena, and time in each zone of the arena. We found that scalp components induced head lice to decrease average locomotor activity and to remain arrested on the treated paper. The effect of the ageing of human scalp samples in the response of head lice was not statistically significant (i.e., human scalp samples of 4, 18, 40, and 60 h of ageing did not elicit a significant change in head louse behavior). When we analyzed the effect of the sex in the response of head lice to human scalp samples, males demonstrated significant differences. Our results showed for the first time the effect of host components conditioning head lice behavior. We discuss the role of these components in the dynamic of head lice infestation.

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.

Transmission between Archaic and Modern Human Ancestors during the Evolution of the Oncogenic Human Papillomavirus 16

Every human suffers through life a number of papillomaviruses (PVs) infections, most of them asymptomatic. A notable exception are persistent infections by Human papillomavirus 16 (HPV16), the most oncogenic infectious agent for humans and responsible for most infection-driven anogenital cancers. Oncogenic potential is not homogeneous among HPV16 lineages, and genetic variation within HPV16 exhibits some geographic structure. However, an in-depth analysis of the HPV16 evolutionary history was still wanting. We have analyzed extant HPV16 diversity and compared the evolutionary and phylogeographical patterns of humans and of HPV16. We show that codivergence with modern humans explains at most 30% of the present viral geographical distribution. The most explanatory scenario suggests that ancestral HPV16 already infected ancestral human populations and that viral lineages co-diverged with the hosts in parallel with the split between archaic Neanderthal-Denisovans and ancestral modern human populations, generating the ancestral HPV16A and HPV16BCD viral lineages, respectively. We propose that after out-of-Africa migration of modern human ancestors, sexual transmission between human populations introduced HPV16A into modern human ancestor populations. We hypothesize that differential coevolution of HPV16 lineages with different but closely related ancestral human populations and subsequent host-switch events in parallel with introgression of archaic alleles into the genomes of modern human ancestors may be largely responsible for the present-day differential prevalence and association with cancers for HPV16 variants.