What does a mite look like in demodicosis? - briefly
In demodicosis, the mite is a microscopic, spindle‑shaped organism about 0.2–0.4 mm long, residing in hair follicles and sebaceous glands with a translucent cuticle and short legs. Under light microscopy it shows a tapered anterior gnathosoma and a clearly visible posterior opisthosoma, often identified as «Demodex folliculorum» or «Demodex brevis».
What does a mite look like in demodicosis? - in detail
The mite responsible for demodicosis is a microscopic, elongated arachnid belonging to the genus Demodex. Its body measures approximately 0.2–0.4 mm in length, rendering it invisible to the naked eye and requiring light or electron microscopy for observation. The organism exhibits a cylindrical form divided into three distinct regions: an anterior segment containing the gnathosoma (mouthparts), a middle idiosoma (main body), and a posterior opisthosoma (tail). The gnathosoma houses short, cheliceral stylets used to pierce hair follicles or sebaceous glands. The idiosoma bears eight short, unsegmented legs, each terminating in a claw-like structure that facilitates attachment to the host’s skin. The legs are positioned in pairs on the ventral surface, allowing the mite to maneuver within the follicular canal.
Two species predominate in human demodicosis, each displaying subtle morphological differences:
- Demodex folliculorum – length ≈ 0.3–0.4 mm; rounded anterior end; prominent, curved opisthosoma; occupies the infundibulum of hair follicles; visible in clusters.
- Demodex brevis – length ≈ 0.2–0.3 mm; narrower, more tapered posterior; resides deeper within sebaceous glands; typically isolated.
The cuticle covering the mite is semi‑transparent, allowing internal structures to be discerned under high magnification. Internal anatomy includes a simple digestive tract extending the length of the body, a pair of spiracles situated laterally on the opisthosoma, and a reproductive system comprising paired ovaries in females and testes in males. Reproductive maturity is reached within 4–7 days, after which females lay 2–4 eggs within the follicular canal. Eggs appear oval, measuring about 0.05 mm, and hatch into six-legged larvae that develop into the eight‑legged adult within approximately 7 days.
Microscopic identification is aided by characteristic movement: the mite exhibits a slow, undulating locomotion, propelling itself forward by alternating leg strokes. In stained preparations, the gnathosoma appears darker due to the presence of chitinous sclerotization, while the opisthosoma often displays a slight curvature, a feature useful for differentiating species.
Overall, the mite’s minute size, elongated cylindrical shape, eight ventral legs, and species‑specific body proportions constitute the primary visual criteria for diagnosis of demodicosis under microscopic examination.