How are lice harmful to humans? - briefly
Lice feed on blood, producing itching, skin irritation, and secondary bacterial infections from scratching; severe infestations may cause anemia, particularly in children. Certain types also transmit pathogens such as Rickettsia prowazekii (epidemic typhus) and Bartonella quintana (trench fever).
How are lice harmful to humans? - in detail
Lice feed on blood, injecting saliva that contains proteins triggering an intense itch. Repeated scratching can break the skin, allowing bacteria such as Staphylococcus aureus or Streptococcus pyogenes to enter and cause secondary infections. These infections may develop into impetigo, cellulitis, or, in rare cases, more serious systemic conditions.
The presence of lice also creates an environment for allergic reactions. Some individuals develop hypersensitivity to louse saliva, resulting in erythema, swelling, and prolonged discomfort long after the infestation has been cleared.
Body lice act as vectors for several bacterial diseases. They transmit Rickettsia prowazekii, the agent of epidemic typhus, Bartonella quintana, responsible for trench fever, and Borrelia recurrentis, which causes relapsing fever. Transmission occurs when lice are crushed against the skin, releasing infected feces that contaminate scratches or wounds.
Heavy infestations can lead to measurable blood loss, especially in children and individuals with compromised nutrition. Chronic blood depletion may contribute to anemia, fatigue, and reduced cognitive performance.
Psychological effects are significant. Persistent itching and visible infestation generate embarrassment, social stigma, and anxiety. In school settings, outbreaks often result in absenteeism, disruption of learning, and increased administrative burden.
Key adverse outcomes include:
- Persistent pruritus and skin irritation
- Secondary bacterial infections (impetigo, cellulitis)
- Allergic dermatitis from saliva proteins
- Transmission of epidemic typhus, trench fever, relapsing fever
- Anemia from chronic blood loss in severe cases
- Psychological distress, social stigma, and school absenteeism
Effective control requires prompt removal of lice, thorough cleaning of personal items, and, when necessary, use of pediculicidal agents. Resistance to common insecticides is rising, making proper diagnosis and integrated management essential to minimize health risks.