How can lice be identified? - briefly
Lice are detected by closely examining the scalp or body hair for live insects and for oval, white‑colored nits firmly attached to the shaft within a millimeter of the skin. Confirmation is achieved with a fine‑tooth comb to remove specimens and, if needed, microscopic review to distinguish them from dandruff or hair debris.
How can lice be identified? - in detail
Lice detection relies on a combination of visual assessment, mechanical extraction, and laboratory analysis.
A trained examiner inspects the scalp, hair shafts, and body hair under adequate lighting. Adult specimens measure 2–4 mm, have a flattened body, six legs, and a gray‑white coloration. Nymphs appear smaller, with translucent bodies. Eggs (nits) are firmly attached to the hair shaft within 1 mm of the scalp, exhibiting a concave, oval shape and a brownish hue.
Mechanical methods improve accuracy. A fine‑tooth comb, spaced at 0.2–0.3 mm, is run through wet or conditioned hair from the scalp outward. Each pass removes live insects and dislodges nits for visual confirmation. Repeating the process at 2‑day intervals for one week captures newly hatched nymphs that may have been missed initially.
Microscopic examination provides definitive identification. Collected specimens are placed on a slide with a drop of saline solution and examined at 40–100× magnification. Diagnostic features include the presence of clawed tarsi, a shortened abdomen in females, and the characteristic “crab‑like” body shape.
Molecular techniques are employed when morphological assessment is ambiguous or for epidemiological studies. DNA is extracted from a single louse or egg, followed by polymerase chain reaction (PCR) amplification of species‑specific gene regions such as cytochrome c oxidase I (COI). Sequencing the amplicon confirms species identity and can detect resistance‑associated mutations.
In practice, a stepwise protocol maximizes detection reliability:
- Initial visual inspection of scalp and hair.
- Application of a fine‑tooth comb to collect specimens.
- Microscopic verification of collected material.
- PCR analysis for species confirmation or resistance profiling, if required.
Combining these approaches yields a comprehensive assessment, enabling effective treatment and control measures.