Covers four blood-feeding human parasites in turn: the head and body louse, the crab louse, the bed bug and the human flea. For each, the note gives host range, stages of development, egg-laying and hatching timings, and key morphological features such as leg structure, body segments and wings. It also lists the diseases the body louse transmits, including typhus, trench fever and louse-borne relapsing fever.
Inside: 4 sections · 2 min
Topic 59 of 64 in the MU Sofia syllabus for Biology (Dental Medicine, Year 1). The free AceMed note covers it in 4 sections, about 320 words (2 min of reading).
In this note
Pediculus humanus (Human Louse)
Phthirus pubis (Crab Louse)
Cimex lectularius (Bed Bug)
Pulex irritans (Human Flea)
Pediculus humanus (Human Louse)
General Information
Types: Includes head louse (Pediculus humanus capitis) and body louse (Pediculus humanus corporis).
Transmission: Spread through direct contact and sharing of clothing.
Host: Exclusively humans, affecting the head and body.
Morphology
Life Stages: Nits (eggs), nymphs, and adults.
Nits: Lice eggs, oval-shaped, white.
Nymphs: Resemble smaller adults; mature in 9-12 days.
Adults: Have six legs attached to the midsection, three body segments, and require blood meals to survive.
Life Cycle
Egg Laying: Adults lay nits on the host.
Hatching: Nits hatch in 1-2 weeks.
Development: Nymphs appear and mature into adults over 9-12 days.
Diseases Transmitted
Transmits typhus, trench fever, and louse-borne relapsing fever through body louse.
Phthirus pubis (Crab Louse)
General Information
Common Name: Crab lice.
Host: Humans, typically found in pubic hair.
Morphology
Smaller and rounder than body and head louse.
Rearmost two pairs of legs are thicker, equipped with large claws for gripping.
Eggs resemble those of head and body louse.
Life Cycle
Egg Laying: Up to 3 eggs per day.
Hatching: Eggs take 6-8 days to hatch.
Nymphal Stages: Nymphs take 10-17 days to mature.
Adult Stage: Adults can live up to 30 days, feeding 4-5 times daily.
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