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Mites have been recognized as the most important allergen in the house dust. This review deals with morphology, ecology and biology of house dust mites including factors affecting the distribution, abundance and seasonality of the species. Clinical, diagnostic and therapeutical aspects of the allergy to domestic mites are also reviewed. Finally, preventive and control measures against house dust mites are suggested.
Ear canals of 284 domestic goats from Florida were examined via swabbing for the presence of ear mites; 57% were infested with Psoroptes cuniculi. Raillietia caprae was recovered from 2 goats in one herd. Breeds examined were Nubian, Alpine, Saanen, Toggenburg, La Mancha, Spanish/Woods and Pygmy. Goats with dependent ear types were infested more commonly than those with erect ears; no goats with vestigial ears were found to harbor mites. Goats less than 1 year old had a significantly higher mite prevalence than did goats over 1 year of age. Gross lesions were noted in the ear canals of only three individuals.
Pyemotes mites, of which the grain itch mite is the most important for human medicine, are ectoparasites of many insect species. Human infestation occurs only accidentally and temporally. The source materials are most often grain, straw and plant-based foods. Bites produce an intensely itching urticarial wheal capped by pin-point vesicles, which often are destroyed by scratching. Pyemotes dermatitis favours the back, the abdomen and the flexor side of the forearms. The mites are barely visible to the naked eye and reside only briefly on humans and thus are not found by physicians during clinical examination. When itching starts, the parasites have usually left their hosts. Therefore it is important to investigate the patient's environment and to identify the infested materials. We describe an outbreak of Pyemotes dermatitis in at least 16 persons, most of them warehouse workers in a hobby mail-order house. Infested decorative wheat was the source of the problem. Successful eradication was achieved by fumigation of the storage facilities with the insecticide methylbromide. Our cases demonstrate the importance of examination of environmental specimens for ectoparasites in cases of unexplained dermatoses. Biological agriculture avoiding insecticides may cause reappearance of this almost forgotten skin disease.
We describe here the first documented case in Austria of the cattle ear mite Raillietia auris in a four-year-old dairy cow. The cow was mildly depressed, and keratoconjunctivitis was diagnosed in both eyes with Horner's syndrome in the left eye. The animal showed a mild head tilt to the left and a generalized ataxia with a tendency to move to the right side, which became exacerbated if the animal was blind-folded. Head pressing to the right side, dysphagia and a dropped jaw were also observed. Numerous rather mobile ear mites were observed at necropsy in the basal part of the left ear canal. The clinical significance of the cattle ear mite is uncertain and the clinical signs could have been caused by listerial encephalitis, which was also confirmed histologically in this case.
This is the first report describing the finding of the canine nasal mite, Pneumonyssoides caninum, in a silver fox (Vulpes vulpes). It is also the first time P. caninum has been found in a species other than the dog (Canis familiaris). A severely debilitated 10-month-old, male silver fox was euthanised due to suspected renal failure. During autopsy, a female mite matching the description of P. caninum was found in the nasal cavity of the fox. The finding of P. caninum in the fox suggests the existence of a new host, or at the very least a transient host. The fox's role in maintaining and/or propagating canine nasal mite infection needs to be explored.
Phosphatases, C4 and C8 esterases, leucine and valine aminopeptidases, n-acetyl-beta-glucosaminidase, beta-glucosidase, beta-galactosidase and beta-glucuronidase were active in extracts of scab mites (Psoroptes spp.) raised on sheep or rabbits. Trypsin and chymotrypsin activities were not detected. Haemoglobin was hydrolysed by a detergent-soluble fraction of the mite extracts in a pH-dependent fashion with an optimum of pH 3-5. Acid proteinase activity was greater in mites raised on rabbits than in those raised on sheep. Inhibitors of cysteine, serine and metallo-proteinases failed to inhibit the hydrolysis of H-Pro-Thr-Glu-Phe-Phe(NO2)Arg-Leu-OH while pepstatin A, a specific inhibitor of aspartic proteinases, totally inhibited its hydrolysis at a concentration of 1 nM.
The natural control of the tracheal mite, Acarapis woodi, of the honey bee depends greatly on good foraging opportunities for bee colonies and on limited competition between colonies. The severe, widely-publicised disease of bees, referred to as 'the Isle of Wight disease' in Britain early in the last century when colonies were more numerous than subsequently, was wrongly attributed to the mite, which causes no overt symptoms. The disease was almost certainly caused by bee paralysis virus, which does cause the symptoms and is independent of the mite, and which is similarly associated with large densities of bee colonies.
In Italian nurseries and young groves of evergreen cypress (Cupressus sempervirens L.), the eriophyoid mite Trisetacus juniperinus (Nal.) is considered a very serious pest. A rating system of damage symptoms was developed to investigate the susceptibility of different cypress seedling families to the mite. Based on this system, the seedlings were evaluated for three years in the nursery and in two field locations after transplanting. Data obtained in the nursery allowed the cypress families to be allocated to at least two different levels of susceptibility. These levels of susceptibility were generally also maintained in the field. However, the environmental conditions of the two transplanting localities significantly affected the susceptibility of each family. In all families, scores for each of the damage categories were strongly correlated positively to each other and negatively with the average increment in the height of plant over the duration of the field experiment. Assessment of the intensity of the symptoms peculiar to damage category A (buds enlarged, deformed, russet and/or branch apex folded) was sufficient to give the same susceptibility evaluation as if data for all damage categories were used. The evaluation of susceptibility on the basis of injury pattern may return very useful information for selection and certification of families of known susceptibility to eriophyoid mites.
The use of Parafilm membranes for in-vitro feeding of northern fowl mites, Ornithonyssus sylviarum (Canestrini & Fanzago), is described. A membrane stretched in two perpendicular directions, folded, heat-sealed, inflated, and twisted at the ends to form a sphere allowed a high percentage (greater than 80%) of surviving adult female mites to feed on whole chicken blood. A high percentage (7 of 10) of protonymphs also fed through the membrane. Mites were able to feed from the same sac for 3 d and oviposited on the sac. This technology has potential applications for use in rearing O. sylviarum and other hematophagous arthropods, and for physiological experimentation.
Dermatophagoides mite concentrations in household dust have been measured in three Australian towns with contrasting geographical features, climate, and degree of urbanisation. Mite allergen skin tests on school children living in these areas showed that the prevalence of positive reactions varied with mite concentrations. In Belmont, D. farinae as well as D. pteronyssinus were present in some of the dust samples. Skin test weals were larger in Busselton than in either Wagga Wagga or Belmont. The importance and practical implications of these findings are discussed.
Infestation with a short-tailed demodectic mite and Demodex canis was diagnosed in both a six-and-a-half-year-old and a four-year-old dog. The clinical picture was compatible with generalised demodicosis complicated by staphylococcal pyoderma (case 1), or localised demodicosis (case 2). In both cases, the short-tailed demodectic mite outnumbered D canis in superficial skin scrapings. The laboratory findings (lymphopenia, eosinopenia, increased serum alkaline phosphatase and alanine aminotransferase activities, diluted urine and proteinuria) and the results of a low dose dexamethasone suppression test were suggestive of underlying hyperadrenocorticism in the first case. Hypothyroidism was considered a possibility in the second case, owing to the sustained bradycardia and the extremely low basal total thyroxine value. Systemic treatment with ivermectin and cephalexin (case 1), or topical application of an amitraz solution in mineral oil, along with sodium levothyroxine replacement therapy (case 2), resulted in a complete resolution of the skin lesions and the disappearance of both types of demodectic mite after two and one and a half months, respectively.
Adult females of the two-spotted spider mite (Tetranychus urticae Koch), showed a daily rhythm of sensitivity to DDVP (dimethyl 2,2-dichlorovinyl phosphate). When the mites were maintained in alternating light-dark conditions, maximum susceptibility to the chemical occurred 2 hours after dawn and the mites were least sensitive 2 hours after nightfall.
The richness, diversity, abundance and prevalence of mite species associated with sigmodontine rodents of different species in Entre Ríos province, Argentina are studied. Five of the six species of mites were reported for the first time in the study area. The richness and diversity of mites was higher on Oligoryzomys flavescens and O. delticola than on Akodon azarae. Androlaelaps rotundus was dominant and exhibited higher values of mean abundance and prevalence on A. azarae, Mysolaelaps microspinosus on O. flavescens and Gigantolaelaps mattogrossensis on O. delticola.
We studied the parasitism by larvae of the chigger mite Eutrombicula alfreddugesi on the lizard community of Restinga de Jurubatiba, Rio de Janeiro State, Southeastern Brazil. We investigated the patterns of infestation (prevalence and intensity) of chigger mites in four sympatric lizards: Tropidurus torquatus, Mabuya agilis, M. macrorhyncha and Cnemidophorus littoralis. All lizards collected were checked for the presence of mites, which were counted under stereomicroscope. We tested the relationship between intensity of infestation and lizard body size for each species using regression analysis. The prevalences and mean intensities (+ one standard deviation) of infestation on each host species were, respectively: 100%; 86.4 + 94.6 in T. torquatus (n = 62); 100%; 20.9 + 9.3 in M. agilis (n = 7); 100%; 11.1 + 13.1 in M. macrorhyncha (n = 12); and 95.2%; 19.1 + 16.8 in C. littoralis (n = 21). Only for C. littoralis did body size significantly affect the intensity of infestation (r = 0.27, p = 0.02). For all lizard species, the body parts where chiggers occurred with the highest intensity were those of skin folds and joint regions.
Caged-layer hens were scored as infested or uninfested by visual examination of the vent region, and the number of northern fowl mite, Ornithonyssus sylviarum (Canestrini & Fanzago), per hen was estimated. The proportion infested and average number of mites per hen were shown to have a highly significant, positive relationship (r = 0.936). Sampling among houses within a flock, and rows and sections within houses were analyzed to determine the reliability of sampling a representative portion of a flock. Low- and moderate-tolerance treatment thresholds, based on percentage of hens infested with mites, were developed from sampling 1 wk before and 1 wk after acaricide treatments determined necessary by the producer. These thresholds were used to compare a fixed (single) sampling plan, a curtailed procedure of the fixed sampling plan, and a sequential sampling plan based on a sequential probability ratio test, by sampling 174 hens (the maximum number needed for the single sampling plan). The sequential sampling plan required fewer hen examinations on average to reach a treatment decision than did the other plans, depending on the infestation tolerance limits. Using a low tolerance approach in which infestations below 15% are considered noneconomic (safe threshold) and infestations above 25% are considered economically important (action threshold), as few as 5 hens required examination to reach a treatment decision. Sequential sampling plan graphs are presented for 2 tolerance threshold scenarios (a 15% safe-threshold paired with a 25% action threshold and a 35% safe-threshold paired with a 45% action threshold). These sequential sampling plans using presence absence assessments should greatly facilitate monitoring and treatment decisions for this important pest.
An intensive survey of ectoparasitic arthropods associated with small mammals in upland forests near Manaus, Brazil, provides information on the taxonomy and host distribution of laelapine mites in the Amazonian Region. We identified 5 genera and 21 species of these mites by comparison with representative museum specimens, the taxonomic literature, and, when possible, the original type specimens. These mites are host specific, with associations ranging from strict monoxeny (18 species) to oligoxeny (1 species) and pleioxeny (2 species). Marsupials were infested with species of Androlaelaps, echimyid rodents with Tur, and sigmodontine rodents with Gigantolaelaps, Laelaps, and Mysolaelaps. Androlaelaps bergalloi, a new species of Laelapinae, is described from the pelage of the marsupial Monodelphis brevicaudata.
In collections of ectoparasites from 368 small ground finches, Geospiza fuliginosa, in populations from the islands of Isabela, Santa Cruz, San Cristóbal, and Santa Fé, in the Galápagos Archipelago, Ecuador, we found 8 species of mites. Four mite species were common on all islands sampled, i.e., Mesalgoides geospizae Mironov and Pérez (Psoroptoididae), Xolalges palmai Mironov and Pérez (Xolalgidae), and 2 new species, Trouessartia geospiza n. sp. (Trouessartiidae) and Proctophyllodes darwini n. sp. (Proctophyllodidae). Four other species were represented by single collections from G. fuliginosa, i.e., Pterodectes atyeoi n. sp. (Proctophyllodidae), Strelkoviacarus sp. (Analgidae), Dermoglyphus sp. (Dermoglyphidae), and Dermanyssus sp. (Dermanyssidae). Authorship of new species names is attributed to the 3 authors who prepared the descriptions (B.M.O.C., J.F., D.L.). Trouessartia geospiza and P. atyeoi were also found on previously collected specimens of other Geospiza species in museum collections. For the 4 common species, we found no differences in prevalence among the 4 island populations, but infection prevalence differed among the 4 species. The mean infection prevalence was high for T. geospizae (89%), moderate for M. geospizae (58%) and X. palmai (44%), and low for P. darwini (26%) in all populations. The feather mite fauna of G. fuliginosa was similar to that of other Geospiza species, and generally related to communities found on other emberizid finches.
In a laboratory study to evaluate the efficacy of selamectin for treatment of canine nasal mite infection, 12 purpose-bred beagles were experimentally infected with Pneumonyssoides caninum (P. caninum). Six of the dogs were treated with selamectin applied to the skin of the back at dosages of 6 to 24 mg/kg for three times at 2-week intervals. The remaining six dogs were an untreated control group. At necropsy 39 to 46 days after inoculation, no P. caninum mites were found in any of the treated dogs. In contrast, nasal mites were found in five of the untreated dogs. This difference was statistically significant at P=0.015.