Henk Braig

ABSTRACT Wolbachia are maternally inherited alpha-proteobacteria that induce feminization of genetic males in most terrestrial crustacean isopods. Two clusters of vir genes for a type IV secretion machinery have been identified at two separate loci and characterized for the first time in a feminizing Wolbachia. Furthermore, we demonstrated that these operons are transcriptionally active in ovaries and in all other tissues tested, suggesting that T4SS has a significant role in Wolbachia biology. These observations and the identification of homologous vir genes in Wolbachia strains infecting insects or nematodes show that vir genes are conserved among Wolbachia strains whatever the phenotype induced by the bacteria.

A continuous cell line, Aa23, was established from eggs of a strain of the Asian tiger mosquito, Aedes albopictus , naturally infected with the intracellular symbiont Wolbachia pipientis . The resulting cell line was shown to be persistently infected with the bacterial endosymbiont. Treatment with antibiotics cured the cells of the infection. In the course of establishing this cell line it was noticed that RFLPs in the PCR products of two Wolbachia genes from the parental mosquitoes were fixed in the infected cell line. This indicates that the mosquito host was naturally superinfected with different Wolbachia strains, whereas the infected cell line derived from these mosquitoes only contained one of the original Wolbachia strains. The development of an in vitro culture system for this fastidious microorganism should facilitate molecular analysis of the reproduction distorting phenotypes it induces in natural arthropod hosts.

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After an intraperitoneal infection of hamsters with scrapie agent, early low and constant titres of about 100 LD50/brain between days 10 to 50 were followed by a dramatic increase to maximum levels of 3 X 10(9) LD50/brain within about 15 days. The plateau of maximum infectivity remained unchanged from day 70 to the time of the first and final signs of disease at 95 and 123 days post-infection, respectively. Scrapie-associated fibrils (SAF) as measured by immunoblotting of SAF protein could not be detected before 79 days post-infection even when a total brain was used for analysis. Subsequently, the concentration of SAF increased gradually by about 100,000-fold until the time of clinical disease. The kinetics suggest a virus-induced amyloidosis of the brain as the cause of disease.

ABSTRACT The Acari is the most numerous and diverse group of the subphylum Chelicerata. With approximately 55 000 described species (and estimates of up to 1 million extant species), their adaptations for parasitism, phytophagy, mycophagy, saprophagy and predation rival other arthropods and challenge us with a wide variety of biological interactions. While a few studies have unravelled the nature of some endosymbiotic associations between mites or ticks and prokaryotes, almost nothing has been done yet regarding acarine eukaryotic ectosymbionts. Microbial ectosymbionts can benefit their hosts by providing nutrients, by aiding digestion, by enhancing communication, by assisting in mating and/or fertilization, by protecting their host against pathogenic microorganisms, against predation and so on. In this sketch, we introduce a number of described cases of fungal and protist ectosymbionts and discuss the role they might play in the life of their acarine hosts.

Following intracerebral infection of hamsters with scrapie agent replication started with or without a very short lag phase. Infectivity titres increased exponentially within 35 to 40 days post-infection to a maximum level of 3 x 10(9) LD50 per brain and then remained constant until death. Minimal detectable amounts of scrapie-associated fibrils (SAF) appeared at 42 days and reached high levels 56 days after inoculation. The first clinical symptoms were diagnosed at about 65 days and animals died after 85 to 95 days. These data confirm earlier results in which peripheral infection first revealed agent replication, then SAF formation and finally clinical disease. Unconventional virus diseases, therefore, can best be described as virus-induced, organ-specific amyloidoses.

A review of mites associated to carcasses and corpses is done. Host-insect species and their phoretic mites are studied, as well as the importance of phoretic mites as markers of time of death. Since 2006, and thanks to funding from the Leverhulme Trust, a group of researchers at UK Universities undertook a revival and expansion of the pioneering efforts of Mégnin. New research, plus evidence from crime cases, is demonstrating that mites can be as relevant as the insects that carry them to a corpse or to/from a crime scene.

The human head louse (Pediculus humanus capitis) is an obligate ectoparasite of humans and has the potential to uncover aspects of human history that cannot be directly inferred from genetic data derived from humans. Previous studies have shown that global louse populations exhibit restricted patterns of genetic variation. However, these studies were restricted both genetically and lacked a global sampling. With the aim of capturing the genetic diversity of head louse populations from around the world, we generated whole genome sequences of human head lice from 43 countries, spanning five continents and Oceania, to determine if louse nuclear diversity mirrors its mitochondrial haplotypes or if population genetic structure, genetic diversity, and population connectivity are associated with geographical regions or host behavior. Here we show that there are five nuclear genetic clusters that are associated with large geographical regions, either at continental or intercontinental levels. High genetic variation was found between African and non-African individuals and the highest genetic diversity was found in samples from sub-Saharan Africa, similar to that of humans. Unlike the mitochondrial clades examined in previous studies, nuclear genetic clusters of lice examined here are highly structured based on geography (continentally and major regions within continents). Results from our genome analyses revealed that host-mediated global dispersal as the likely primary process in shaping diversity and maintaining genetic population boundaries within the nuclear genome of the human head louse.

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...

Metamorphosis is a key innovation allowing the same species to inhabit different environments and accomplish different functions, leading to evolutionary success in many animal groups. Astigmata is a megadiverse lineage of mites that expanded into a great number of habitats via associations with invertebrate and vertebrate hosts (human associates include stored food mites, house dust mites, and scabies). The evolutionary success of Astigmata is linked to phoresy-related metamorphosis, namely the origin of the heteromorphic deutonymph, which is highly specialized for phoresy (dispersal on hosts). The origin of this instar is enigmatic since it is morphologically divergent and no intermediate forms are known. Here we describe the heteromorphic deutonymph of Levantoglyphus sidorchukae n. gen. and sp. (Levantoglyphidae fam. n.) from early Cretaceous amber of Lebanon (129 Ma), which displays a transitional morphology. It is similar to extant phoretic deutonymphs in its modifications for ...

The biology of macrochelid mites might offer new venues for the interpretation of the environmental conditions surrounding human death and decomposition. Three human corpses, one from Sweden and two from Spain, have been analysed for the occurrence of Macrochelidae species. Macrocheles muscaedomesticae (Scopoli) females were associated with a corpse that was found in a popular beach area of southeast Spain. Their arrival coincides with the occurrence of one of their major carrier species, the filth fly Fannia scalaris, the activity of which peaks during midsummer. Macrocheles glaber (Müller) specimens were collected from a corpse in a shallow grave in a forest in Sweden at the end of summer, concurrent with the arrival of beetles attracted by odours from the corpse. Macrocheles perglaber Filipponi and Pegazzano adults were sampled from a corpse found indoors in the rural surroundings of Granada city, south Spain. The phoretic behaviour of this species is similar to that of M. glaber, but it is more specific to Scarabaeidae and Geotrupidae dung beetles, most of which favour human faeces. Macrocheles muscaedomesticae is known from urban and rural areas and poultry farms, M. glaber from outdoors, particularly the countryside, whereas M. perglaber is known from outdoor, rural, and remote, potentially mountainous locations. Macrocheles muscaedomesticae and M. perglaber are reported for the first time from the Iberian Peninsula. This is the first record of M. perglaber from human remains.

Introduction
Stored-Products Forensics of Mites
Medico-Legal Forensics of Mites
Mites on Human Skin
Mites and Estimating Time of Colonization of Corpses
Mites and Corpses 
Mites on Fabrics and Human Clothing
Mites and Location: Soil Mites, Domestic Mites, and House Dust
Mites and Relocated, Missing or Destroyed Corpses Mites and Sniffer Dogs
Mites and Delusional Infestation/Parasitosis
Mites, Hosts, and Host DNA
Acknowledgements
References

Metamorphosis is a key innovation allowing the same species to inhabit different environments and accomplish different functions, leading to evolutionary success in many animal groups. Astigmata is a megadiverse lineage of mites that expanded into a great number of habitats via associations with invertebrate and vertebrate hosts (human associates include stored food mites, house dust mites, and scabies). The evolutionary success of Astigmata is linked to phoresy-related metamorphosis, namely the origin of the heteromorphic deutonymph, which is highly specialized for phoresy (dispersal on hosts). The origin of this instar is enigmatic since it is morphologically divergent and no intermediate forms are known. Here we describe the heteromorphic deutonymph of Levantoglyphus sidorchukae n. gen. and sp. (Levantoglyphidae fam. n.) from early Cretaceous amber of Lebanon (129 Ma), which displays a transitional morphology. It is similar to extant phoretic deutonymphs in its modifications for phoresy but has the masticatory system and other parts of the gnathosoma welldeveloped. These aspects point to a gradual evolution of the astigmatid heteromorphic morphology and metamorphosis. The presence of well-developed presumably host-seeking sensory elements on the gnathosoma suggests that the deutonymph was not feeding either during phoretic or pre-or postphoretic periods.

We carry them in our skin pores through our entire life, from birth to death. We offer them shelter and in return, they tidy-up our pores. We go on with our busy day life and they sleep. They wake up when we go to sleep and while we are deeply dreaming, they move around, visit other pores and mates, and reproduce. Despite being our ‘very own’ life companions, until recently, we knew very little about their struggle.
Their miniaturised Bauplan is perfectly fit for life inside the pores of hair follicles and sebaceous glands. Perception of light is achieved by one of the smallest ‘eyes’ (photoreceptors) known to date, and movement and dispersal is accomplished by minute legs powered by just three unicellular-uninucleate muscle segments. With a unique arrangement of Hox genes, their reproductive organs allow them to mate and to deliver offspring inside the limited space offered by the pores.
Unless they soon find a way out, genome erosion, on an evolutionary time scale, is leading them to a dead end, to extinction. They outbreed less and less: each of us has a unique population, started by a few colonisers, legacy of our moms when we were babies. This resulted in a mite species that presents the lowest number of protein genes. Yet, they manage to successfully carry on with their lives by synchronising with our lifestyles, and we hope they will keep doing it for the foreseeable future!
Demodex folliculorum (Prostigmata, Demodecidae) has adapted to the life in the human pores and the circadian rhythm of their host (Smith et al., 2022). The difference between an ectosymbiont and a pathogen lies in the numbers. The amount of Demodex mites on healthy human faces is controlled by several factors.
First, the physical size of the pores. The older a person gets, the wider the pores become and the more mites a pore can accommodate (Zeytun, 2017; El Bassiouni et al., 2005). Pore size also increases with inflammation and with it Demodex (Casas et al., 2012; karabay and Çerman, 2020; Forton and De Maertelaer, 2021).
Second, the physiology, the feeding of the mites. The mites feed on sebum produced inside the pores. Sebum production is the highest in the age range of 20 to 30 years (Foley et al., 2021).
The immune system of a healthy person seems to control the density of Demodex. This becomes evident in various ways.
Suppression of cellular immunity by cancers might lead to increase in Demodex numbers or to abnormal antiparasitic attacks of the immune system on Demodex (Seyhan et al., 2004; Bakacak et al., 2020; Ziaja‐Sołtys et al., 2021). Immunosuppressive viruses such as HIV I can lead to an increase of Demodex (Yamaoka et al., 2014; grigoryan et al., 2018; Trama et al., 2018). Iatrogenic induced immunosuppression for the treatment of autoimmune diseases, essential thrombocytosis, Crohn’s disease, psoriasis, Cushing’s syndrome and neoplasms, and for the support of organ transplantation support demodicosis/demodicidosis (Amitay-Laish et al., 2022). Autoimmune diseases themselves in the form of failure of the thyroid in humans and dogs or in rheumatoid arthritis can lead to breakdown of the host’s regulation of Demodex density (Pinsenschaum et al., 2019; Yazisiz et al., 2020; Dursun et al., 2022). From alcoholism to heart failure, if homeostasis is compromised, Demodex increases (kokaçya et al., 2016; Yüksel and Yüksel, 2020; Pormann et al., 2021). This are all cases of secondary demodicosis.
The older clinical literature on demodicosis in humans and dogs argues that Demodex suppresses the host immune system and therefore leads to the clinical manifestations. These reports fail to explain why or how Demodex persists in healthy humans and dogs.
Bit by bit, mechanisms of immune dysregulation are being discovered that lead to pathological levels of Demodex. Paediatric demodicosis, chronic demodicosis, and demodicosis as part of rosacea in humans is caused by a Signal transducer and activator of transcription (STAT) 1 heterozygous gain-of-function (gOF) mutations eventually leading to excessive interferon γ response and compromised T helper cell 17 differentiation (Second et al., 2017; Molho-Pessach et al., 2020; Saez-de-Ocariz et al., 2020; Baghad et al., 2021; Martinot et al., 2021; Shamriz et al., 2021; Zhang et al., 2021).
Demodex is controlled by its host through innate type 2 immunity (Ricardo-gonzalez et al., 2022). This raises the question whether primary demodicosis in humans exists at all.

The Acari are one of the most ubiquitous arthropod inhabitants and associates of human and animal remains. Over 150 years ago, Jean Pierre Mégnin proposed that mites arrive at corpses at two particular stages of the decomposition process, that is within the first and the sixth waves of arthropod arrival or colonisation event (Mégnin, 1895). Now we know that mites actually arrive at each stage of the decomposition process of corpses, in a continuum (Rai et al., 2021). Interestingly, the mite fauna of cadavers is very diverse, and mite species composition varies as decomposition progresses and according to the environment where decomposition occurs (Baker, 2009; Braig & Perotti, 2009). In fact, specific stages of decomposition can be characterised by the associated mite species (Kamaruzaman et al., 2018; Leclercq & Verstraeten, 1988; Mašán et al., 2013; Mégnin, 1895).
In terms of the environment where a corpse decomposes, if on a soil surface, outdoors, it will attract epigeal and hypogeal mites and a variety of carrion insects, which will bring their own phoretic mites (Fig. 1-A). Mites travelling on insects or small rodents are the most common and ubiquitous arthropods arriving on remains (Perotti & Braig, 2009; Perotti et al., 2010). Some carrion insects, like beetles, are able to transport several species and a great number of individuals, up to the hundreds or thousands. For example, silphid beetles are able to bring species of Parasitidae, Macrochelidae, Melicharidae, Uropodidae, Histiostomatidae, Acaridae at the same time—just to name some of the most common families of phoretic mites brought to a corpse (Perotti & Braig, 2009).
Opportunistic insects visiting or colonising, somehow taking advantage of the corpse (Byrd & Castner, 2009), for example, a queen bumblebee using part of it to build its nest, will bring too its diverse phoretic mites (Klimov et al., 2016). Ticks, although opportunistic, are also assiduous visitors of the decomposition environment (McNemee et al., 2003). They need to be nearby, ready to jump on the next host approaching the decomposed body, likely a scavenger or a forensic investigator. This is becoming so frequent that in Europe, the widespread species Ixodes ricinus utilises carrion and coprophagous beetles moving to and from carcasses to secure availability of hosts (Salona-Bordas et al., 2015).

Most humans carry mites in the hair follicles of their skin for their entire lives. Follicular mites are the only metazoans that continuously live on humans. We propose that Demodex folliculorum (Acari) represents a transitional stage from a host-injuring obligate parasite to an obligate symbiont. Here, we describe the profound impact of this transition on the genome and physiology of the mite. Genome sequencing revealed that the permanent host association of D. folliculorum led to an extensive genome reduction through relaxed selection and genetic drift, resulting in the smallest number of protein-coding genes yet identified among panarthropods. Confocal microscopy revealed that this gene loss coincided with an extreme reduction in the number of cells. Single uninucleate muscle cells are sufficient to operate each of the three segments that form each walking leg. While it has been assumed that the reduction of the cell number in parasites starts early in development, we identified ...