What does a louse transmit? - briefly
The human body louse transmits Rickettsia prowazekii (epidemic typhus), Bartonella quintana (trench fever) and Borrelia recurrentis (relapsing fever); the head louse is not a disease vector.
What does a louse transmit? - in detail
Lice are capable of moving disease‑causing agents from one host to another. The body louse (Pediculus humanus corporis) is the primary vector; the head louse (Pediculus humanus capitis) rarely transmits infections, while the crab louse (Pthirus pubis) is not a known vector.
Pathogens linked to louse bites or contamination of louse feces include:
- Rickettsia prowazekii – agent of epidemic (louse‑borne) typhus; transmitted when infected feces are scratched into skin.
- Bartonella quintana – cause of trench fever; spread through contaminated feces entering broken skin or mucous membranes.
- Borrelia recurrentis – responsible for louse‑borne relapsing fever; transferred in the same manner as typhus.
- Yersinia pestis – historically implicated in plague outbreaks; occasional reports of transmission via body lice.
- Acinetobacter spp. and Streptococcus pneumoniae – occasionally isolated from lice, but their role in human disease remains uncertain.
Transmission occurs when a louse feeds on an infected individual, acquires the pathogen, and later defecates on the skin of a new host. Subsequent scratching introduces the contaminated feces into the bloodstream or mucosal surfaces. Direct bite inoculation is rare; the primary risk is the mechanical transfer of pathogen‑laden excreta.
Risk factors for louse‑borne disease include crowded living conditions, poor hygiene, lack of access to clean clothing, and prolonged contact with infested individuals. Control measures focus on regular laundering of clothing at temperatures above 55 °C, use of insecticidal powders, and treatment of affected persons with pediculicidal agents. Prompt identification of outbreaks and antibiotic therapy (doxycycline for typhus and trench fever, penicillin for relapsing fever) reduce morbidity and mortality.