sucking lice

Order: Phthiraptera
Anoplura – Sucking lice (human)
Mallophaga – Chewing lice (animals)

What order do sucking lice belong to, and what are its suborders?

Small, wingless ectoparasites
Head narrower than thorax
Soft, dorsoventrally flattened body
Mouthparts adapted for sucking blood and cutaneous fluids
Legs have a single tarsal segment with large claws for grasping hair
5-segmented antennae
Dorsal spiracles

Describe the general morphology of sucking lice.

hemimetabolous
Egg → Nymph → Adult

What type of metamorphosis do sucking lice undergo?

30–35 days

What is the complete life cycle duration of sucking lice?

Infective stage: Adult
Diagnostic stages: Egg, nymph, adult

Which stage is infective, and which are diagnostic?

Transmitted through head-to-head contact
Causes pruritus (itching), due to allergic reaction to bites
May lead to sores and secondary bacterial infections

: How is P. h. capitis transmitted and what symptoms does it cause?

Firmly attached to the hair shaft, near the scalp

Where are nits of P h. capitis commonly found?

Larger in size
Prefers clothing seams
Found in settings with poor hygiene, e.g., war, overcrowding

How does P. h. corporis differ from head lice?

Epidemic typhus – Rickettsia prowazekii
Trench fever – Bartonella quintana
Epidemic relapsing fever – Borrelia recurrentis

Which diseases can P. h. corporis transmit?

1.5–2.0 mm, crab-shaped body
Enlarged 2nd and 3rd legs for grasping coarse hair
Sexually transmitted – associated with other STIs
Prefers coarse, curly hair (pubic, axillary)

What are the key features and transmission mode of P. pubis?

pediculosis

Infestation with lice; causes irritation, allergic dermatitis, and sometimes secondary infection

Plica Polonica

Thickly matted hair caused by severe P. h. capitis infestation

Vagabond’s disease

Darkened, thickened skin from long-term P. h. corporis infestation

Phthiriasis palpebrarum

Eyelid infestation by Phthirus pubis; common in sexually abused children

Causative agent: Rickettsia prowazekii
Acute, febrile, epidemic disease
Historical outbreaks in wars and poor hygiene settings

What are the characteristics of louse-borne typhus?

Bartonella quintana (formerly Rochalimea quintana)
Known as Wolhynia fever or five-day fever

What causes trench fever, and what is its modern name?

Borrelia recurrentis
Associated with overcrowding, war, and disasters

What causes louse-borne relapsing fever?

Direct contact (skin, hair)
Contact with contaminated clothes, linens
Crushing lice on skin or mucosa
Feces from lice on broken skin or mucosa
Inhalation of dried feces (less common)

How can humans get infected by lice?

Shampoos: Pyrethrin 1%, Permethrin 1–5%, Lindane 1%
Ocular gel: Pilogel 4% for eyelid infestations
Manual removal: Fine-toothed comb (suyod)

What are effective treatments for lice infestations?

Wash clothing and linens in hot water (55°C/130°F)
Dry on hot cycle for 20 mins
Seal non-washables in bags for 2 weeks
Avoid sharing personal items
Assess and treat all household members

What are control measures?

Possibly yes, but conclusive studies are limited; more research is needed in the Philippines.

Can head lice also transmit pathogens?

Pediculus humanus corporis (body louse)

Which louse species is NOT reported in the Philippines?