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Infectious Disease and Microbiology - Lice
Lice infestation, also known as pediculosis, is caused by ectoparasitic insects of the order Phthiraptera that live on human hair and skin. It is not an infection but an infestation, involving three main types depending on location: head lice, body lice, and pubic lice. The causative organisms include Pediculus humanus capitis, Pediculus humanus corporis, and Phthirus pubis. These parasites feed on human blood and complete their life cycle entirely on the host, with eggs (nits) hatching into nymphs that mature into adults within a few weeks.
Head lice infestation is particularly common among school-aged children and spreads mainly through close personal contact. It is not strongly linked to poor hygiene but is associated with crowding and household size. Body lice are more commonly seen in individuals with poor hygiene, especially among homeless populations or in crowded environments such as refugee camps. Pubic lice are typically transmitted through sexual contact and are therefore considered a sexually transmitted condition, often associated with other sexually transmitted infections.
The main symptom of lice infestation is pruritus, which results from a hypersensitivity reaction to lice saliva. The itching varies depending on the site of infestation and may lead to excoriations and secondary bacterial infections. Physical examination is diagnostic, revealing live lice or nits attached to hair shafts or clothing fibers. In head lice, careful combing of wet hair can improve detection. Pubic lice may also affect other coarse hair regions, including eyelashes, and characteristic bluish-gray skin lesions known as maculae ceruleae may appear.
Diagnosis is clinical and does not require laboratory testing. However, in cases of pubic lice, evaluation for coexisting sexually transmitted diseases is recommended. Body lice infestations may be associated with transmission of certain pathogens, including Bartonella quintana and, less commonly, Rickettsia prowazekii, making recognition important in vulnerable populations.
Treatment primarily involves topical insecticides, with permethrin 1% being the first-line therapy for most infestations. Reapplication after 7 to 10 days is often necessary to eradicate newly hatched lice. Alternative treatments include malathion, lindane (with caution due to potential toxicity), and oral ivermectin in selected cases. Proper application technique is essential for treatment success, as resistance or improper use may lead to persistence of infestation.
Supportive measures include washing clothing, bedding, and personal items in hot water, particularly for body lice. For pubic lice affecting the eyelashes, petroleum jelly may be used. Mechanical removal of lice and nits can be helpful but is generally less effective when used alone. The prognosis is excellent with appropriate treatment, although reinfestation can occur if contacts are not treated simultaneously.
Complications are usually mild and include secondary bacterial skin infections due to scratching. In certain cases, particularly with body lice, there is a risk of transmission of systemic infections. Psychological distress, especially among children and caregivers, is also a notable consequence of infestation.
Lice infestation, also known as pediculosis, is caused by ectoparasitic insects of the order Phthiraptera that live on human hair and skin. It is not an infection but an infestation, involving three main types depending on location: head lice, body lice, and pubic lice. The causative organisms include Pediculus humanus capitis, Pediculus humanus corporis, and Phthirus pubis. These parasites feed on human blood and complete their life cycle entirely on the host, with eggs (nits) hatching into nymphs that mature into adults within a few weeks.
Head lice infestation is particularly common among school-aged children and spreads mainly through close personal contact. It is not strongly linked to poor hygiene but is associated with crowding and household size. Body lice are more commonly seen in individuals with poor hygiene, especially among homeless populations or in crowded environments such as refugee camps. Pubic lice are typically transmitted through sexual contact and are therefore considered a sexually transmitted condition, often associated with other sexually transmitted infections.
The main symptom of lice infestation is pruritus, which results from a hypersensitivity reaction to lice saliva. The itching varies depending on the site of infestation and may lead to excoriations and secondary bacterial infections. Physical examination is diagnostic, revealing live lice or nits attached to hair shafts or clothing fibers. In head lice, careful combing of wet hair can improve detection. Pubic lice may also affect other coarse hair regions, including eyelashes, and characteristic bluish-gray skin lesions known as maculae ceruleae may appear.
Diagnosis is clinical and does not require laboratory testing. However, in cases of pubic lice, evaluation for coexisting sexually transmitted diseases is recommended. Body lice infestations may be associated with transmission of certain pathogens, including Bartonella quintana and, less commonly, Rickettsia prowazekii, making recognition important in vulnerable populations.
Treatment primarily involves topical insecticides, with permethrin 1% being the first-line therapy for most infestations. Reapplication after 7 to 10 days is often necessary to eradicate newly hatched lice. Alternative treatments include malathion, lindane (with caution due to potential toxicity), and oral ivermectin in selected cases. Proper application technique is essential for treatment success, as resistance or improper use may lead to persistence of infestation.
Supportive measures include washing clothing, bedding, and personal items in hot water, particularly for body lice. For pubic lice affecting the eyelashes, petroleum jelly may be used. Mechanical removal of lice and nits can be helpful but is generally less effective when used alone. The prognosis is excellent with appropriate treatment, although reinfestation can occur if contacts are not treated simultaneously.
Complications are usually mild and include secondary bacterial skin infections due to scratching. In certain cases, particularly with body lice, there is a risk of transmission of systemic infections. Psychological distress, especially among children and caregivers, is also a notable consequence of infestation.
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