The parasitism of the itch mite Sarcoptes scabiei (Acariformes: Sarcoptidae)]

The life cycle of the itch mite Sarcoptes scabiei (L.), an intracutaneous parasite of man and animals, has been studied. The paper concerns morphological adaptations, embryonal and postembryonal development, life cycle pattern, scabious passage as a reproductive formation, invasive stages, feeding, reproduction and topical relationships with the host, distribution and survival in the environment.     

Pruritus and behavior of pigs infested by itch mites, Sarcoptes scabiei (Acari: Sarcoptidae)

Effects of infestation by Sarcoptes scabiei (De Geer) on pruritus and other behaviors of pigs for 9-13 wks after weaning were evaluated. Regardless of the dose of mites inoculated, pigs fed ad lib. spent approximately 60% of their time at rest. Within their average day, pigs spent more time eating in morning and evening, were more active and pruritic at midday, and rested more and spent the least time drinking water at night. Mite infestations increased total activity and time spent scratching and rubbing. Infested pigs sprayed with water rubbed and scratched 4-10 times more frequently than those left undisturbed or disturbed by other means. Pigs receiving inoculating doses of 1,000 mites became more pruritic than pigs receiving 100 mites, and both groups developed more pruritus than non-infested control pigs.     

Genetic epidemiology of Sarcoptes scabiei (Acari: Sarcoptidae) in northern Australia

Utilising three hypervariable microsatellite markers we have previously shown that scabies mites on people are genetically distinct from those on dogs in sympatric populations in northern Australia. This had important ramifications on the formulation of public health control policies. In contrast phylogenetic analyses using mitochondrial markers on scabies mites infecting multiple animal hosts elsewhere in the world could not differentiate any genetic variation between mite haplotype and host species. Here we further analyse the intra-specific relationship of Sarcoptes scabiei var. hominis with S. scabiei var. canis by using both mitochondrial DNA and an expanded nuclear microsatellite marker system. Phylogenetic studies using sequences from the mitochondrial genes coding for 16S rRNA and Cytochrome Oxidase subunit I demonstrated significant relationships between S. scabiei MtDNA haplotypes, host species and geographical location. Multi-locus genotyping using 15 microsatellite markers substantiated previous data that gene flow between scabies mite populations on human and dog hosts is extremely rare in northern Australia. These data clearly support our previous contention that control programs for human scabies in endemic areas with sympatric S. scabiei var. hominis and var. canis populations must focus on human-to-human transmission. The genetic division of dog and human derived scabies mites also has important implications in vaccine and diagnostic test development as well as the emergence and monitoring of drug resistance in S. scabiei in northern Australia.     

Development of the larvae inside the body of the itch mites Sarcoptes scabiei (L.) (Sarcoptidae) and the ontogenetic level of eclosion in mites of the order Acariformes]

Several larvae-containing females of Sarcoptes have been found in skin biopsy of heavily infected Rangifer tarandas L. A. viviparity hypothesis is disproved. The larvae in the body of egg-containing dead females of the human Sarcoptes were obtained by incubation in the suspended water drop. Embryogenesis types as well as eclosion stage in Acariformes are discussed. The term "postmortal pregnancy" is proposed.     

Macropodicoptes mironovi n. g., n. sp. (Acariformes: Sarcoptidae), a new mange mite from Wallabia bicolor (Desmarest) (Diprotodonia: Macropodidae)

A new mange mite species, Macropodicoptes mironovi n. g., n. sp. (Acariformes: Sarcoptidae), is described from Wallabia bicolor (Desmarest) (Diprotodontia: Macropodidae) from the Taronga Western Plains Zoo at Dubbo, NSW, Australia. This is the fourth species and third genus allocated to the sarcoptid subfamily Diabolicoptinae, whose representatives exclusively parasitise marsupials. The new genus differs from Diabolicoptes Fain & Domrow, 1974, in both sexes, by the proportions of the gnathosoma, the shape of many hysterosomal setae and the absence of setae e1, pRII-II, sRIII and solenidion ω3I; and, in males, by the lack of fusion of coxal apodemes I.     

Molecular analyses suggest monospecificity of the genus Sarcoptes (Acari: Sarcoptidae).

To clarify the taxonomic status of mites of the genus Sarcoptes, the second internal transcribed spacer (ITS-2) of the rRNA gene, as well as phenotypic characters, were investigated in 23 isolates from nine host species in four continents. Phenotypic differences among isolates were observed, but the range of variation within each isolate precluded the differentiation of individual mites. Genotypically, there was no delimitation between distinct genotypic groups and no correlation with host species or geographic origin was evident. These results support the conspecificity of the mites investigated and confirm the view that the genus Sarcoptes consists of a single, heterogenous species.     

Preliminary Molecular Characterizations of Sarcoptes scaibiei (Acari: Sarcoptidae) from Farm Animals in Egypt

Little is known about the genetic diversity of Sarcoptes scabiei mites in farm animals in Egypt. In this study, we characterized S. scabiei in 25 skin scrapes from water buffalo, cattle, sheep, and rabbits at the nuclear marker ITS2 and mitochondrial markers COX1 and 16S rRNA. Sequences of the ITS2 showed no host segregation or geographical isolation, whereas those of the mitochondrial COX1 and 16S rRNA genes indicated the presence of both host-adapted and geographically segregated populations of S. scabiei. Host adaptation may limit inter-species transmission of. S. scabiei, thus restrict gene flow among S. scabiei from different hosts. This is the first report on the molecular characterization of sarcoptic mites in Egypt. Further genetic studies involving larger numbers of specimens, especially those from humans and companion animals, are needed to understand the molecular epidemiology of sarcoptic mange in Egypt.     

Sarcoptes mange (Sarcoptes scabiei) increases diurnal activity of bare-nosed wombats (Vombatus ursinus) in an agricultural riparian environment

Sarcoptes mange is an important disease that affects the health, mobility and longevity of bare-nosed wombats (Vombatus ursinus) in Australia. We measured the activity patterns of wombats infected with varying levels of mange in an agricultural riparian environment using motion-sensing cameras. Over a 10 month period we observed a greater increase in nocturnal activity of mange-free wombats than those with mange on six or more body sections. The percentage of mange-infected wombats was greater during the day, but in the 6 h after midnight, wombats were detected with fewer mange-infected segments. Air temperature at the time of wombat detections was generally higher for individuals with mange than those without mange. Our results show that diurnal activity of wombats is likely to increase with higher levels of infection by sarcoptes mange. Increased diurnal activity is likely to present serious problems for the persistence of sustainable populations of wild wombats.     

Sarcoptes scabiei: The Mange Mite with Mighty Effects on the Common Wombat (Vombatus ursinus)

Parasitism has both direct and indirect effects on hosts. Indirect effects (such as behavioural changes) may be common, although are often poorly described. This study examined sarcoptic mange (caused by the mite Sarcoptes scabiei) in the common wombat (Vombatus ursinus), a species that shows severe symptoms of infection and often causes mortality. Wombats showed alterations to above ground behaviours associated with mange. Infected wombats were shown to be active outside of the burrow for longer than healthy individuals. Additionally, they spent more time scratching and drinking, and less time walking as a proportion of time spent above ground when compared with healthy individuals. They did not spend a higher proportion of time feeding, but did have a slower feeding rate and were in poorer body condition. Thermal images showed that wombats with mange lost considerably more heat to the environment due to a diminished insulation layer. Infection status did not have an effect on burrow emergence time, although this was strongly dependent on maximum daily temperature. This study, through the most detailed behavioural observations of wombats to date, contributes to a broader understanding of how mange affects wombat health and abundance, and also to our understanding of the evolution of host responses to this parasite. Despite being globally dispersed and impacting over 100 species with diverse intrinsic host traits, the effects of mange on hosts are relatively poorly understood, and it is possible that similar effects of this disease are conserved in other host species. The indirect effects that we observed may extend to other pathogen types.     

Fatal Sarcoptes scabiei infection of blue sheep (Pseudois nayaur) in Pakistan

Sarcoptes scabiei was detected for the first time in skin scrapings, hair pluckings, and histologic sections from a blue sheep (Pseudois nayaur) from the Shimshali Pamir in the Karakorum range of the western Himalaya in Pakistan (36 degrees 28'N, 75 degrees 36'E). Local reports suggest many hundred animals have been affected by a severe skin disease over a 10-yr period, but the shy nature of this species and the extreme climate that they inhabit meant only a single affected animal was available for detailed evaluation. The severe skin lesions were confined to the forelegs and brisket, and many Sarcoptes scabiei mites were present in all the samples examined. Histologic preparations of the skin showed hyperkeratotic and parakeratotic hyperkeratosis of the epidermis with a severe exudative dermatosis with many polymorphonuclear neutrophils and gram-positive cocci, yet no eosinophils. These findings might suggest the lack of an appropriate immune response to the parasite or other coping strategies because there has been no abatement of the clinical signs in affected animals over several years. Treatment options are limited due to the behavior of the species and its habitat. The blue sheep is a primary source of prey for the endangered snow leopard (Panthera uncia) and continued depletion could have serious consequences for the survival of the latter.     

The ultrastructure and possible functions of nephrocytes in the trombiculid mite Hirsutiella zachvatkini (Acariformes: Trombiculidae)

The ultrastructure of nephrocytes during the post-larval development of the trombiculid mite Hirsutiella zachvatkini (Schluger) was investigated by means of transmission electron microscopy. Nephrocytes are situated either individually or in groups inside the haemocoelic space and are always ensheathed by a basal membrane. They contain numerous tubular elements, electron-dense inclusions and sometimes electron-lucent vacuoles. Invaginations of the plasma membrane, often in the form of labyrinthine channels, with coated pits of plasma membrane and characteristic slit diaphragms linking adjacent pedicels, typically occupy the peripheral parts of the cells. However, no distinct zonation of organelles in the nephrocytes of trombiculids was observed. The number of nephrocytes in the haemocoel and the intensity of development of their tubular elements and in particular of labyrinthine channels vary significantly during the ontogenesis of mites. The possible functions of nephrocytes and their structure and differentiation in comparison with other arachnids are discussed.     

Endoplasmic reticulum (a review of the literature)]

Recent data on the structural and molecular organisation of the endoplasmic reticulum (ER) are reviewed. A special attention is paid to the mechanism of soluble and integral membrane protein translocation across the ER bilayer. A model of phospholipid-coupled polypeptide translocation is introduced served to overcome hydrophobic and (or) conformational constraints during the passage of polar amino acid residues within a polar environment of the ER membrane. In addition the mechanisms of diverse covalent and noncovalent post-translocational polypeptide modifications are considered, together with the process of the sorting events among ER-resident polypeptides and those destined to leave the ER domain for the Golgi apparatus.