What can be found on lice? - briefly
Lice harbor several disease‑causing agents, notably Rickettsia prowazekii (typhus), Bartonella quintana (trench fever), and Borrelia recurrentis (relapsing fever). They also maintain obligate symbiotic bacteria like Candidatus Riesia pediculicola that provide essential nutrients.
What can be found on lice? - in detail
Lice are obligate ectoparasites whose bodies host a range of biological and chemical elements. The adult insect consists of a head with compound eyes and antennae, a thorax bearing six legs each ending in grasping claws, and an abdomen containing digestive, reproductive, and excretory organs. The external cuticle is composed of chitin and proteins that provide structural integrity and protect internal tissues.
The surface of a louse carries several distinct materials:
- Eggs (nits): oval, firmly attached to host hair shafts by a cement-like secretion; each contains a developing embryo.
- Saliva: a complex mixture of enzymes, anticoagulants, and immunomodulatory proteins that facilitate blood feeding and can trigger allergic reactions in hosts.
- Excrement (frass): dark, digested blood residues expelled through the hindgut; often visible on clothing or bedding.
- Molted exoskeletons (exuviae): shed cuticle fragments from successive instars, composed primarily of chitin and sclerotized proteins.
- Endosymbiotic bacteria: intracellular microorganisms such as Candidatus Riesia pediculicola that supply essential B‑vitamins absent from the louse’s blood diet.
- Commensal microbiota: diverse bacterial taxa (e.g., Staphylococcus, Corynebacterium, Enterobacteriaceae) residing on the cuticle and within the gut, contributing to nutrient processing and pathogen resistance.
- Pathogenic agents: vectors for several human diseases, including Rickettsia prowazekii (epidemic typhus), Bartonella quintana (trench fever), Borrelia recurrentis (relapsing fever), and historically Yersinia pestis (plague). These organisms are transmitted through louse bites or contaminated feces.
- Allergenic proteins: specific salivary and cuticular proteins that elicit IgE‑mediated hypersensitivity in susceptible individuals, leading to pruritus and dermatitis.
In forensic contexts, louse DNA and associated microbial signatures can provide information about a host’s recent environment, personal hygiene, and geographic movement. The combination of structural components, reproductive elements, secretions, and microbial inhabitants defines the complete set of substances and organisms present on these ectoparasites.