Demodectic oviposition in the eyelid.

The normally torpid existence of demodectic mites of the eyelid changes with the onset of oviposition. There occurs a burst of activity characterized by flexion, extension and rotation.

Demodicosis and symbiophobia: status, terminology, and treatments.

All patients are undoubtedly parasitized by hair follicle mites (D. brevis and/or D. folliculorum). Recovery of these may trigger or exacerbate phobias, so they should not be demonstrated on primary presentation. As adjunct treatment for all patients, one can recommend avoidance of long-term topical sterate or corticosteroid preparations, followed by use of daily lavage with soap and water. This is doubly important in sensitive or phobic patients, because ubiquitous demodecids may increase from 'normal' (greater than 5 per pilosebaceous complex) demodiciasis to marked (less than 10 mites) demodicosis. Evidence of phobia should, provisionally, be labelled with the nonperjorative term symbiophobia (herein coined for "fear of association with organisms"), and the causative organisms, if present, treated. Nonremission of phobias, despite counselling and treatment, should be referred to a sensitive, competent, medically trained psychiatrist.

Demodicosis of ophthalmic concern.

Hair-follicle mites are the only metazoan organism commonly found in the pilosebaceous components of the eyelid of man. Our study showed that Demodex folliculorum in all stages is found in the small hair follicles and the eyelash hair follicles. This species, in adult and immature forms, consumes epithelial cells, produces follicular distension and hyperplasia, and increases keratinization leading, in eyelashes, to cuffing consisting of keratin and lipid moieties. Demodex brevis (in all stages) is present in the eyelash sebaceous glands, small hair sebaceous glands, and in the lobules of the meibomian glands. Adults and immature forms consume the gland cells in all of these loci and, when infestations are heavy, can affect the formation of the superficial lipid layer of the tear film coacervate. Comparative studies of demodicids from man and other mammals suggest that keratinization, hyperplasia, distension, and melanocyte aggregation may be even more extensive if large populations of D. folliculorum build up in the follicles of the eyelid. Large populations of D. brevis may destroy the glandular cells, produce granuloma in the eyelid, and plug the ducts of the meibomian or sebaceous glands. Further studies may incriminate either or both species, in conjunction with microorganisms, as transfer agents or synergists, or both, in producing ocular disease in man. Prevention and control of these mites must await experimental studies with infested laboratory animals (such as the squirrel monkey, Saimiri sciureus). These mites are probably most vulnerable during transfer stages, when they leave their glandular or follicular habitats.

Demodex cati Hirst 1919: a redescription.

All life stages of Demodex cati are described and compared with D. canis. Presence of D. cati is reported for the first time from the external auditory meatus. In the two cases examined mites occurred in large numbers with little pathogenic effect.

Demodex canis: redescription and reevaluation.

A brief review of the taxonomy of Demodex canis is followed by a complete redescription. Demodex canis is diagnosed with D. odocoilei of the white-tailed deer. In view of the continued speculation that dogs and man share the same demodicid, simple morphological characters are noted which distinguish D. canis from D. folliculorum and D. brevis in all stages of their life cycles.

Hair follicle mites (Demodex spp.) of medical and veterinary concern.

A review is presented, including some new data, of the biology of ten species of hair follicle mites (Demodex spp.) of man and domestic animals. Major topics covered are taxonomy, host-parasite interactions, and problems in need of resolution. To this last, some information is provided on the question of species validity, the degree of host specificity and synhospitaly, population dynamics and incidence, transference and host behavior, pathogenesis and disease transmission, and control. A key is provided for species discrimination.

Pathogenesis associated with hair follicle mites (Demodex spp.) in Australian Aborigines.

Demodex folliculorum and D. brevis are found in different habitats in the skin: the former in the hair follicles, the latter in the sebaceous glands. Both seem minor pathogens--merely harvesting the cells of their respective habitats. D. folliculorum was found aggregated (all stages) and plugging the follicular orifices; D. brevis, on the other hand, was usually solitary. In one case marked degeneration of the sebaceous gland, with leukocyte invasion, was associated with D. brevis. No correlations were discovered between either of these species and the gross condition of the skin. Positive samples were obtained from both mainland and island populationf of Aborigines. Incidence values obtained were 66.6% for males and 80% for females; in the latter, the sample was small (5) and their ages over 34 years.