How to identify a pubic louse? - briefly
Pubic lice are tiny, crab‑shaped parasites about 1‑2 mm long that cling to the base of coarse hair, appearing as gray‑brown insects or as oval, white nits glued to hair shafts. Intense itching and the visual presence of live insects or attached eggs near the genital region confirm an infestation.
How to identify a pubic louse? - in detail
Pubic lice, also known as Pthirus pubis, can be distinguished by several physical and clinical characteristics. The adult insect measures 1–2 mm in length, has a broad, crab‑like body, and three pairs of short legs adapted for grasping coarse hair. Its coloration ranges from gray‑white to brown, often appearing translucent when unfed. The head bears a pair of tiny, forward‑pointing antennae and compound eyes that are difficult to see without magnification.
The abdomen contains a pair of genitalia located near the rear, a feature that separates it from head lice, which have a more elongated abdomen and lack visible genital structures. The ventral surface bears a row of clawed legs that cling tightly to pubic or other coarse hair, such as that on the beard, armpits, chest, or perianal region. Eggs (nits) are oval, about 0.8 mm, and attached firmly to the hair shaft at a 45‑degree angle, often within 1 mm of the skin surface. Nits are creamy‑white and become darker as the embryo develops.
Clinical signs accompany infestation:
- Persistent itching in the affected area, caused by the louse’s saliva.
- Small, bluish‑gray macules or papules where the insects feed.
- Visible adult lice or nits during close inspection.
Diagnosis relies on direct visual examination. A fine‑toothed comb or magnifying lens (10–20×) can reveal live insects and attached eggs. Dermatoscopic devices provide enhanced clarity, allowing observation of the characteristic crab‑like morphology and the angle of nit attachment. In uncertain cases, a sample of hair can be examined under a light microscope at 40–100× magnification to confirm species identification.
Key steps for accurate identification:
- Inspect the pubic region and other coarse‑hair sites for live insects and nits.
- Use magnification to assess body shape, leg configuration, and nit attachment angle.
- Differentiate from head lice by noting the broader body and the presence of visible genitalia.
- Confirm with microscopic examination if visual assessment is inconclusive.
These criteria enable reliable detection of Pthirus pubis and distinguish it from other ectoparasites.