How to identify a scabies mite in a person? - briefly
Look for intense nocturnal itching and the presence of thin, grayish burrows or tiny raised tunnels on wrists, finger webs, elbows, and the genital area. Microscopic analysis of skin scrapings confirms Sarcoptes scabiei infestation.
How to identify a scabies mite in a person? - in detail
Scabies is diagnosed by recognizing characteristic skin findings, confirming the presence of the mite, and excluding other pruritic conditions.
The first step is a thorough patient history. Key points include intense nocturnal itching, recent close contact with an infected individual, and a rapid spread of lesions among household members.
Physical examination focuses on typical lesion sites: finger webs, wrists, elbows, axillae, waistline, genitals, and feet. Look for:
- Fine, grayish‑white tunnels (burrows) that follow the skin’s stratum corneum.
- Papules or vesicles at the ends of burrows.
- Nodular eruptions in the flexor surfaces of the wrists or the penis in adults.
- Crusted plaques in immunocompromised patients.
When lesions are present, collect specimens for microscopic confirmation. The preferred technique is a skin scraping:
- Apply a drop of mineral oil to a glass slide.
- Use a sterile scalpel blade to scrape the edge of a suspected burrow or papule.
- Transfer the material onto the slide, add a cover slip, and examine under 10–40× magnification.
- Identify the mite, its eggs, or fecal pellets (scybala). The adult mite appears as an oval organism about 0.3‑0.4 mm long, with four pairs of legs.
If microscopy is unavailable, dermoscopy provides a rapid bedside alternative. A handheld dermatoscope reveals the “jet‑liner” sign—a dark, linear structure corresponding to the burrow—and occasionally the mite itself as a translucent oval within the tunnel.
In ambiguous cases, a skin biopsy can be performed. Histopathology shows a mite within the epidermis, an inflammatory infiltrate rich in eosinophils, and epidermal hyperkeratosis.
Differential diagnosis includes:
- Atopic dermatitis (distribution differs, no burrows).
- Contact dermatitis (history of exposure, lack of mites).
- Pediculosis (lice are larger and found on hair shafts).
- Fungal infections (scale and positive KOH test).
Treatment decisions rely on confirming scabies. Accurate identification prevents unnecessary therapy and curtails transmission.