What can lice do? - briefly
Lice consume host blood, resulting in itching and skin irritation; severe infestations may provoke secondary bacterial infections. Their presence can also cause discomfort, distraction, and reduced quality of life.
What can lice do? - in detail
Lice are obligate ectoparasites that obtain nutrients exclusively from the blood of their hosts. Their mouthparts are adapted for piercing the epidermis and drawing plasma, which sustains growth, development, and egg production.
Feeding behavior is rapid; an adult consumes several microliters of blood per day, sufficient to cause localized irritation and, in heavy infestations, anemia. The saliva contains anticoagulants and anti‑inflammatory compounds that facilitate prolonged attachment and reduce host detection.
Reproduction proceeds through a three‑stage life cycle: egg (nits), nymph, and adult. Females lay 1–10 eggs per day, attaching them to hair shafts with a cementing protein. Incubation lasts 7–10 days, after which nymphs emerge and undergo three molts over 9–12 days before reaching maturity. High fecundity enables rapid population expansion on a single host.
Transmission occurs primarily by direct contact, such as head‑to‑head or body‑to‑body interaction. Some species, notably body lice, can be transferred via contaminated clothing or bedding. Mechanical vectors, they may carry bacterial pathogens (e.g., Rickettsia prowazekii, Borrelia recurrentis) without being infected themselves, facilitating epidemic typhus and relapsing fever.
Resistance to insecticidal treatments has emerged through mutations in target-site proteins and increased activity of detoxifying enzymes. Documented mechanisms include:
- Knock‑down resistance (kdr) mutations reducing sensitivity to pyrethroids.
- Enhanced esterases and glutathione‑S‑transferases degrading organophosphates.
- Behavioral avoidance of treated surfaces.
Control strategies therefore combine chemical agents with mechanical measures: regular combing, laundering at ≥ 60 °C, and environmental sanitation.
In animal hosts, lice can impair wool quality, reduce weight gain, and predispose to secondary infections. Their presence may also serve as an indicator of poor husbandry or compromised immunity.
Overall, lice exhibit specialized feeding apparatus, accelerated reproductive cycles, capacity for pathogen transmission, and evolving chemical resistance, all of which influence public health and veterinary management.