What diseases can affect lice? - briefly
«Borrelia recurrentis» (relapsing fever) and «Rickettsia prowazekii» (epidemic typhus) are bacterial agents transmitted by human lice, while «Bartonella quintana» causes trench fever. Lice may also act as reservoirs for some viruses, although confirmed viral transmission is rare.
What diseases can affect lice? - in detail
Lice (Pediculus humanus capitis, Pediculus humanus corporis, and Pthirus pubis) serve as carriers and, in some cases, biological hosts for several pathogenic microorganisms. The most significant agents are bacterial species transmitted to humans through the bite of an infected louse.
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« Rickettsia prowazekii » – causative agent of epidemic typhus. Transmitted primarily by body lice. After a bite, the bacterium enters the bloodstream, producing high fever, rash, and severe systemic complications. Outbreaks historically occurred in crowded, unhygienic settings such as war zones and refugee camps.
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« Bartonella quintana » – responsible for trench fever. Body lice acquire the bacterium during feeding and release it in feces, which enters the host through skin abrasions. Clinical presentation includes relapsing fever, painful shin splints, and prolonged fatigue. The disease remains endemic in homeless populations where lice infestations are common.
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« Borrelia recurrentis » – agent of louse‑borne relapsing fever. Transmission follows a similar route to trench fever, with the pathogen deposited in louse feces. Patients experience recurring episodes of high fever, headache, and myalgia, each lasting several days before remission.
In addition to these primary vectors, lice host obligate endosymbiotic bacteria essential for their nutrition, most notably « Candidatus Riesia pediculicola ». While not pathogenic to humans, the symbiont is crucial for louse survival and represents a target for novel control strategies.
Entomopathogenic fungi have been investigated for their capacity to infect and kill lice. Species such as « Beauveria bassiana » and « Metarhizium anisopliae » penetrate the cuticle, proliferate internally, and cause mortality within days. These biological agents do not transmit disease to humans but provide an alternative to chemical insecticides.
Viral agents are not commonly associated with lice as vectors. Experimental studies have identified limited replication of certain arboviruses within louse tissues, yet no natural transmission to humans has been documented.
Overall, the disease burden linked to lice derives mainly from bacterial pathogens transmitted by body lice, with head lice playing a minimal role in disease spread. Effective management requires hygiene improvement, regular delousing, and, where appropriate, targeted use of insecticidal or biological control measures.