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Could ectoparasites act as vectors for prion diseases?

Prion diseases are rare neurodegenerative diseases of humans and animals with a lethal evolution. Several cell types found on the human skin, including keratinocytes, fibroblasts and lymphocytes, are susceptible to the abnormal infective isoform of the prion protein, which transforms the skin to produce a potential target for prion infection. Iatrogenic transmission of Creutzfeldt-Jakob disease was also recognized after corneal transplants in humans, and scrapie was successfully transmitted to mice after ocular instillation of infected brain tissue, confirming that these new routes, as well as cerebral inoculation and oral ingestion, could be important in prion infections. Animal prion infections, such as scrapie (sheep) and "mad cow disease" (cattle), have shown a pattern of horizontal transmission in farm conditions and several ectoparasites have been shown to harbor prion rods in laboratory experiments. Fly larvae and mites were exposed to brain-infected material and were readily able to transmit scrapie to hamsters. New lines of evidence have confirmed that adult flies are also able to express prion proteins. Because ocular and cerebral myiases and mite infestation are not rare worldwide, and most cases are caused by fly larvae or hay mites that usually affect sheep and cattle, it is important to discuss the possibility that these ectoparasites could eventually act as reservoirs and/or vectors for prion diseases.

Animals↗

Simulation analysis of the population dynamics of the mite, Psoroptes ovis, infesting sheep.

The pattern of population growth of the ectoparasitic mite, Psoroptes ovis (Acari: Psoroptidae), on its ovine host is considered through the development of a Leslie matrix-based, simulation model. The model is parameterised using experimental data in conjunction with reanalysis of published data. The model shows that on sheep P. ovis populations grow at a rate of approximately 11% per day and the population doubles every 6.3 days. Additional rates of adult mortality, in excess of 50% per day, need to be imposed to prevent population growth. The predictions of the model are tested by comparison of the expected numbers of mites with the numbers recorded in lesions either on naturally infested sheep where the date of infestation can be estimated or on one artificially infested animal, where the initial number of mites and date of infestation are known precisely. In both cases the observed number of mites in lesions relate closely to the numbers expected from the simulations. The model simulations do not support the concept of a 'lag' phase as distinct from the 'growth' phase in the changing pattern of mite abundance on an infested sheep and suggests that the observed pattern of growth is a natural function of an exponential increase in numbers. The development of such models and their use in explaining the demographic processes which drive mite population dynamics are discussed.

Animals↗

An experimental field approach to parasitism and immune defence in voles.

The fox tapeworm Echinococcus multilocularis is typically perpetuated in a cycle with red foxes as definitive hosts and various rodent species as intermediate hosts. In this study, foxes were baited with a highly efficient drug against cestodes (praziquantel) in 5 blocks of 1 km2. Voles, Arvicola terrestris, the most abundant intermediate host species, were trapped in the 5 baited blocks and in 5 non-baited control blocks. Baiting the foxes reduced the prevalence of E. multilocularis in fox faecal samples in the baited blocks, but voles trapped in the two blocks did not differ in their infection rates. However, voles from the baited blocks had significantly smaller spleen masses and were more likely to be infested with mites than those from the control blocks, possibly reflecting different immunological activities. Our study suggests that the environmental contamination with E. multilocularis eggs, and perhaps those of other tapeworms, influences the immune system of the intermediate host species A. terrestris in the wild.

Animals↗

Zoonotic skin diseases of dogs and cats.

Although there are over 250 zoonotic diseases, only 30-40 of them involve dogs and cats. Transmission of zoonotic infections occurs via bites, scratches or touch; exposure to saliva, urine or feces; inhalation of particles or infectious aerosols; contact with a transport or intermediate host (e.g. ticks, fleas); or exposure to contaminated water, soil or vegetation. This paper summarizes the most important common zoonotic dermatological diseases of dogs and cats. The most common dermatological zoonoses are flea and tick infestations and the diseases they transmit; dermatophytosis; and mite infestations (Sarcoptes and Cheyletiella). Prevention of zoonotic infestations or infections can be accomplished easily by the use of routine flea and tick control, screening of new pets for dermatophytosis, and routine hand-washing.

Animals↗

Human infestation by Ophionyssus natricis snake mite.

A family presented with a papular vesiculo-bullous eruption of the skin, found to be caused by the snake mite, Ophionyssus natricis (Cervais, 1844). A pet python was the primary host. Treatment of the animal and its environment led to clearance of the human skin lesions.

Adult↗

[Indoor climate and allergy. The prevalence of allergens in Norwegian primary schools].

We have investigated the prevalence of allergens from cat, dog, house dust mite, pollen, mould and food in dust samples from schools and homes in Norway. Occurrence of cat and dog allergens in schools was surprisingly high, especially in classrooms with carpeted floors. Cat and dog-derived allergens are brought into schools through the pupils' outside contact with pets. Children who are in contact with pets at home or in their surroundings carry animal hair and dander into the classrooms on their clothes, shoes and bags. The schools seemed to be a protective environment against mite infestation, as verified by very low content of mites in both carpeted and smooth floors. Furthermore, while cat and dog allergens were more prevalent in schools than in homes without pets, mite and food allergens were more dominant in homes. Frequent cleaning is important in schools, to prevent accumulation of animal hair and dander in the classrooms. We emphasize the obvious advantages of linoleum floors over carpets in decreasing the pupils' level of exposure to indoor allergens and dust.

Air Pollution, Indoor↗

Dust mite allergens in the office environment.

The objective of this study was to evaluate the extent of dust mite infestation and its contribution to the health complaints in office settings. The methodology recommended for residential dwellings was evaluated for use in the work environment. Der p I allergen-specific ELISA was chosen as a primary method. A liquid chromatography method for guanine is suggested as a backup method to cover a few cases where other mite species may be encountered. The levels of dust mite allergens were measured in 14 offices in response to numerous health complaints. Approximately one-half of the offices investigated were identified as having a dust mite population. Four offices showed levels of Der p I in the dust greater than 1 microgram/g. In two offices, the dust mite allergens were the source of the health complaints. In the other two offices, dust mite allergens were one of the contaminants in the office environment. In all cases, the infestation of dust mites in the offices was localized to a few specific work areas. Office chairs were the primary location where dust mites thrived. The remedial measures included regular cleanup of all fabric-covered office furnishings. Steam cleaning was recommended to eliminate dust mite populations.

Air Pollution, Indoor↗

An abattoir survey of diseases of feral goats.

Caseous lymphadenitis was the most frequently encountered pathological condition in 3,720 feral goats examined during routine meat inspection procedures. Among 9 separate consignments of animals, the prevalence of infection averaged 7.4% (range 0.3% to 18.8%). The majority of lesions were seen in lymph nodes draining superficial body areas although many also occurred in internal nodes and organs. Corynebacterium ovis was isolated from 25 of 32 lesions submitted for bacteriological examination. Other conditions regularly encountered included pneumonia, cysticercosis, sarcosporidiosis and lice infestation, while myonecrosis, pleurisy, pericarditis, nephritis, hepatitis, cirrhosis and mite infestation were only occasionally found. A total of 171 serum samples were collected and tested against 17 antigens. Samples from 57.9% and 51.5% of goats showed positive serological reactions to the antigens for sarcosporidiosis and Q fever respectively.

Abattoirs↗

Mite and mite allergen removal during machine washing of laundry.

BACKGROUND: Few studies have investigated live house dust mite and mite allergen removal from clothing and bedding by washing machines. No studies have investigated the transfer of mites from infested to uninfested clothing and bedding during washing. OBJECTIVE: The purpose of this study was to wash different types of clothing and bedding in residential washing machines to determine the live Dermatophagoides farinae mite and allergen removal and the mite transfer from mite-infested items to mite-free items. METHODS: Clothing and bedding items were machine washed in 6- and 8-lb loads in warm (36 degrees C-38 degrees C) or cold (22 degrees C-27 degrees C) water with and without recommended concentrations of laundry detergent and sodium hypochlorite bleach. Live mites and allergen present in washed versus unwashed and washed mite-infested versus washed mite-free items were compared. RESULTS: Washing clothing and bedding in water alone, detergent, or detergent plus bleach removed 60% to 83% of the live mites. Washing removed more mites from some items than from others. When mite-infested items were washed with identical sets of mite-free items, many live mites were transferred to the previously mite-free items. Overall, 84% of Der f 1 was removed from items washed in water alone or in detergent and 98% from items washed in detergent plus bleach. CONCLUSIONS: Washing clothing and bedding in cold or warm water with detergent or detergent plus bleach removed most allergen and a significant (P <.05) portion of live mites. Repeated washing is required to further reduce mite levels. Live mites were transferred from mite-infested to mite-free items during washing.

Air Pollution, Indoor↗

Jasmonic acid is a key regulator of spider mite-induced volatile terpenoid and methyl salicylate emission in tomato.

The tomato (Lycopersicon esculentum) mutant def-1, which is deficient in induced jasmonic acid (JA) accumulation upon wounding or herbivory, was used to study the role of JA in the direct and indirect defense responses to phytophagous mites (Tetranychus urticae). In contrast to earlier reports, spider mites laid as many eggs and caused as much damage on def-1 as on wild-type plants, even though def-1 lacked induction of proteinase inhibitor activity. However, the hatching-rate of eggs on def-1 was significantly higher, suggesting that JA-dependent direct defenses enhanced egg mortality or increased the time needed for embryonic development. As to gene expression, def-1 had lower levels of JA-related transcripts but higher levels of salicylic acid (SA) related transcripts after 1 d of spider mite infestation. Furthermore, the indirect defense response was absent in def-1, since the five typical spider mite-induced tomato-volatiles (methyl salicylate [MeSA], 4,8,12-trimethyltrideca-1,3,7,11-tetraene [TMTT], linalool, trans-nerolidol, and trans-beta-ocimene) were not induced and the predatory mite Phytoseiulus persimilis did not discriminate between infested and uninfested def-1 tomatoes as it did with wild-type tomatoes. Similarly, the expression of the MeSA biosynthetic gene salicylic acid methyltransferase (SAMT) was induced by spider mites in wild type but not in def-1. Exogenous application of JA to def-1 induced the accumulation of SAMT and putative geranylgeranyl diphosphate synthase transcripts and restored MeSA- and TMTT-emission upon herbivory. JA is therefore necessary to induce the enzymatic conversion of SA into MeSA. We conclude that JA is essential for establishing the spider mite-induced indirect defense response in tomato.

Animals↗