What do lice transmit? - briefly
Head lice may transmit bacterial skin infections such as impetigo, but they are not major vectors of serious systemic disease. Body lice are confirmed carriers of epidemic typhus, relapsing fever and trench fever.
What do lice transmit? - in detail
Lice serve as vectors for a limited but clinically significant group of pathogens. The primary species involved are body lice (Pediculus humanus humanus), head lice (Pediculus humanus capitis), and pubic lice (Pthirus pubis).
Body lice are the only lice known to transmit bacterial infections. They harbor three obligate intracellular bacteria that cause distinct diseases:
- Epidemic typhus – caused by Rickettsia prowazekii. Transmission occurs when infected lice are crushed on the skin, releasing organisms that enter through abrasions. The incubation period is 5–14 days; symptoms include high fever, severe headache, macular rash beginning on the trunk, and potential complications such as pneumonitis or encephalitis. Diagnosis relies on serology or PCR; doxycycline is the treatment of choice.
- Trench fever – caused by Bartonella quintana. The organism is transmitted similarly through contaminated louse feces that are scratched into the skin. Clinical presentation consists of relapsing fever spikes, severe leg pain, and a “shin splint” sensation. The disease may become chronic, leading to endocarditis or bacillary angiomatosis. Doxycycline or azithromycin are effective.
- Louse‑borne relapsing fever – caused by Borrelia recurrentis. Infection follows contact with louse excreta; patients experience recurrent high fevers, headache, myalgia, and a characteristic “headache‑fever‑rash” triad. Mortality can exceed 30 % without treatment. Intravenous penicillin or tetracycline eradicates the pathogen.
Head lice are not recognized as disease vectors. Their impact is confined to local irritation, pruritus, and secondary bacterial infection of the scalp caused by Staphylococcus aureus or Streptococcus pyogenes. Such infections may progress to impetigo or cellulitis if untreated.
Pubic lice transmit no specific pathogens, but their presence can facilitate the spread of sexually transmitted infections indirectly by encouraging sexual contact and causing skin breaches that allow bacterial entry.
In summary, only the body louse functions as a competent vector for serious bacterial diseases—epidemic typhus, trench fever, and louse‑borne relapsing fever—while head and pubic lice primarily cause mechanical irritation and secondary bacterial complications. Effective control measures focus on hygiene, eradication of infestations, and prompt antimicrobial therapy for the associated infections.