How can lice be examined? - briefly
Lice are identified through close visual inspection of the scalp and hair, typically employing a fine‑toothed comb to collect specimens for microscopic confirmation. Laboratory analysis then mounts retrieved nits on a slide to examine morphological characteristics such as body size and claw structure for species differentiation.
How can lice be examined? - in detail
Lice inspection begins with a thorough visual survey of the scalp and hair. The examiner separates strands using a fine‑toothed comb, moving from the root toward the tip. Any live insects, nymphs, or viable eggs (nits) attached to the shaft are recorded.
A systematic approach includes:
- Direct observation: magnifying lenses (10–30×) reveal morphology, allowing differentiation between head lice, body lice, and crab lice.
- Combing technique: a metal or plastic nit‑comb, applied in sections of 1 cm, ensures complete coverage; each pass is examined for attached specimens.
- Microscopic analysis: collected samples are placed on a slide with a drop of saline solution, covered with a coverslip, and examined under a light microscope (400–1000×). Key diagnostic features—such as the shape of the thorax, presence of a dorsal shield, and the pattern of setae—confirm species identification.
- Laboratory culture: live lice may be transferred to a controlled environment (temperature 30 °C, humidity 70 %) on a host‑derived blood medium to observe life‑cycle stages and assess insecticide resistance.
- Molecular testing: DNA extracted from a single specimen undergoes polymerase chain reaction (PCR) targeting the COI gene; sequencing provides definitive species confirmation and can detect resistance‑associated mutations.
Documentation of findings requires recording the number of adults, nymphs, and nits, their location on the host, and any signs of secondary infection. Photographic evidence captured with a macro camera attached to the microscope supports clinical reports.
Interpretation of results follows established criteria: the presence of live lice or viable nits within 1 cm of the scalp indicates an active infestation; solitary nits without viable embryos suggest past exposure. Comprehensive assessment combines visual, microscopic, and molecular data to deliver an accurate diagnosis and guide treatment decisions.