What are Demodex mites and how can they be identified from a photograph? - briefly
Demodex are microscopic, elongated arthropods inhabiting human hair follicles and sebaceous glands, with the species D. folliculorum and D. brevis being the most prevalent. In a photograph they appear as tiny, translucent, worm‑like bodies about 0.2–0.4 mm long, showing a clear, elongated shape and a slightly thicker anterior end when captured with high‑magnification light microscopy or dermatoscopic imaging.
What are Demodex mites and how can they be identified from a photograph? - in detail
Demodex mites are microscopic arthropods belonging to the order Trombidiformes. Two species dominate human infestation: Demodex folliculorum, residing in hair follicles, and Demodex brevis, inhabiting sebaceous glands. Adult mites measure 0.2–0.4 mm, elongated, sausage‑shaped, with eight short legs positioned near the anterior end. Their transparent cuticle renders internal structures invisible under routine light microscopy, but the external morphology—rounded anterior, tapered posterior, and distinct dorsal surface—remains discernible.
Photographic identification relies on specific preparation and imaging techniques:
- Sample collection – obtain superficial skin scrapings, eyelash clippings, or follicular contents with a sterile blade or forceps.
- Mounting medium – place material on a glass slide with a drop of mineral oil or lactophenol cotton blue to preserve morphology and enhance contrast.
- Microscope settings – employ a compound light microscope at 100–400× magnification; oil immersion (1000×) may be used for detailed examination.
- Image capture – attach a digital camera or smartphone adapter to the eyepiece; adjust focus, exposure, and white balance to avoid over‑exposure.
- Diagnostic criteria – verify the following features in the captured image:
- Length of 200–400 µm, visible as an elongated oval.
- Eight legs clustered near the head, each with two short segments.
- Dorsal ridge or striations along the body surface.
- Absence of visible segmentation; body appears smooth.
- Presence of a terminal caudal shield in D. brevis or a broader posterior in D. folliculorum.
Interpretation of the photograph should compare the observed morphology with reference images from reputable dermatological atlases. Consistency with the listed criteria confirms the presence of Demodex mites, differentiating them from other ectoparasites such as scabies or lice, which exhibit distinct body shapes, leg counts, and size ranges.