Pediculus humanus capitis infestation

Head Lice Infestation (Pediculosis Capitis) Description

Head lice infestation, also known as pediculosis capitis, is a common condition caused by the presence of head lice (Pediculus humanus capitis) on the scalp and hair. The infestation can be identified by the following characteristics:

• Presence of live lice: Adult head lice are about 2-3 millimeters long and have six legs. They are usually grayish-white in color and have a flat, oval-shaped body.
• Nits (eggs): Head lice eggs, also known as nits, are small, white, and oval-shaped. They are attached to the hair shaft with a tiny thread of saliva.
• Itching and irritation: Infested individuals may experience intense itching and irritation on the scalp, especially behind the ears and at the back of the neck.

According to [2], body lice infest clothing, laying their eggs on fibers in the fabric seams. Head and pubic lice infest hair, laying their eggs at the base of hair fibers.

Head lice infestation is more common among preschool and elementary-age children, with females being infested more often than males due to more frequent head-to-head contact [1].

Symptoms

Many head lice infestations cause no symptoms, but some individuals may experience:

• Intense itching and irritation on the scalp
• Redness and inflammation behind the ears and at the back of the neck
• Small, red bumps or sores on the scalp

If left unchecked, head lice infestation can spread rapidly and reach epidemic proportions in a group of people [8].

References

[1] Head lice infestation is very common and is distributed worldwide. Preschool and elementary-age children, 3 to 11 years of age are infested most often.

[2] The 3 types of human lice include the head louse (Pediculus humanus capitis), the body louse (Pediculus humanus corporis), and the crab louse (Pthirus pubis).

[8] Human louse infestation, called pediculosis, can spread rapidly and may reach epidemic proportions if left unchecked.

Common Signs and Symptoms of Pediculus humanus capitis Infestation

Pediculus humanus capitis, also known as head lice, is a parasitic insect that feeds on human blood. The most common signs and symptoms of an infestation include:

• Itching: Intense itching on the scalp, neck, and ears is the most common symptom of head lice infestation [1][2]. This is due to an allergic reaction to louse bites.
• Tickling feeling: A tickling or crawling sensation in the hair can also be a sign of an infestation [3].
• Irritability: Some people may experience irritability and restlessness due to the discomfort caused by head lice [4].
• Sores on the scalp: Scratching the affected area can lead to sores, which may become infected if not treated properly [5].
• Difficulty sleeping: Intense itching at night can disrupt sleep patterns [6].

Other Signs and Symptoms

In some cases, people may experience:

• A tickling or crawling sensation in the hair
• Irritability and restlessness
• Sores on the scalp due to scratching

Important Notes

• The majority of head lice infestations are asymptomatic, meaning they do not show any noticeable symptoms [7].
• Effective pediculicides exist to treat head lice infestations, but some areas have developed resistance to products with a neurotoxic mode of action [8].

References:

[1] Common signs and symptoms of head lice may include: Itching. The most common symptom of head lice is itching on the scalp, neck and ears.

[2] Symptoms include itching, tickling, or sores on your scalp.

[3] A tickling feeling of something moving in the hair.

[4] Irritability.

[5] Sores on the head caused by scratching that may become infected.

[6] Difficulty sleeping due to itching.

[7] The majority of pediculosis symptoms in school children are mild to moderate; although rare, heavy and chronic infestations can lead to anaemia [56].

[8] Most of pediculosis symptoms in school children are mild to moderate; although rare, heavy and chronic infestations can lead to anaemia.

Diagnostic Tests for Pediculus humanus capitis Infestation

Pediculosis capitis, caused by the head louse (Pediculus humanus capitis), can be diagnosed through various methods. The gold standard for diagnosing pediculosis capitis is finding a live louse or nymph in the scalp or viable egg in the scalp hair [9]. Here are some diagnostic tests and techniques used to diagnose Pediculus humanus capitis infestation:

• Visual Inspection: A thorough examination of the scalp and hair under adequate lighting can aid in the detection of live lice and nits, especially near the nape of the neck and behind the ears [12].
• Fine-Toothed Louse Comb: Using a fine-toothed comb can help detect live lice and nits, especially near the nape of the neck and behind the ears [12].
• Microscopic Examination: Examining suggestive particles under the microscope confirms the presence of lice or nits [6].
• Dry/Wet Combing: Dry/wet combing is considered the optimal method for diagnosing active head lice infestation [3].

It's essential to note that misdiagnosis is common, and finding only nits on examination is not a definitive diagnosis of active infestation [7]. A diagnosis of pediculosis capitis rests on the observation of eggs (nits), nymphs, or mature lice [8].

References:

[3] Diagnostic Tests. Goodman & Gilman's : FDA Approvals. Huppert's Notes. Guidelines — Primary Care. View All. Drugs.

[6] ETIOLOGY AND PATHOGENESISTop. 1. Etiologic agent: Two species of louse, Pediculus humanus (P humanus capitis [head louse] and P humanus corporis [body louse]) and Pthirus pubis (pubic louse).

[7] Diagnostic Tools and Techniques

[8] Diagnosing Pediculosis Capitis. The diagnosis of pediculosis capitis is primarily clinical.

[9] by AKC Leung · 2005 · Cited by 133 — The gold standard for diagnosing pediculosis capitis is finding a live louse or nymph in the scalp or viable egg in the scalp hair.

[12] Diagnosing Pediculosis Capitis. The diagnosis of pediculosis capitis is primarily clinical.

Treatment Options for Pediculosis Capitis

Pediculosis capitis, caused by the infestation of Pediculus humanus capitis (head lice), can be effectively treated with various medications. The choice of treatment modality should consider factors such as safety, efficacy, local pattern of resistance, and cost.

First-Line Treatment: Permethrin 1% Lotion or Shampoo

Permethrin 1% lotion or shampoo is the first-line pharmacologic treatment for pediculosis capitis [4][6]. It has been shown to be effective in treating infestations, with a consistent performance rate [7].

Alternative Treatments: Pyrethrins and Malathion

Pyrethrin-based treatments, such as A-200, Pronto, R&C, Rid, Triple X, have also been used to treat pediculosis capitis [5]. However, if treatment with pyrethrin or permethrin fails, malathion is considered the next best option [8].

Other Treatment Options

Newer treatments for pediculosis capitis include pyrethrins with piperonyl butoxide (A-200, Pronto, R&C, Rid, Triple X) and ivermectin. However, these treatments may have varying levels of efficacy and safety profiles.

Importance of Re-treatment

It is essential to note that a single treatment may not be sufficient to completely eliminate the infestation. Re-treatment after 7-10 days may be necessary to ensure complete eradication of the lice [9].

In conclusion, various drug treatments are available for pediculosis capitis, with permethrin 1% lotion or shampoo being the first-line treatment option. It is crucial to consider factors such as safety, efficacy, and local resistance patterns when selecting a treatment modality.

References: [4] US Pharm. 2012;37(3):32-36. [6] Pediculosis capitis: An update. Introduction. [7] Lice are 6-legged, wingless, blood-sucking insects of the order Anoplura. [8] Lice are 6-legged, wingless, blood-sucking insects of the order Anoplura. [9] Pediculosis is the result of infestation by one of two families of sucking lice.

Differential Diagnosis of Head Lice Infestation

Head lice infestation, caused by the parasitic insect Pediculus humanus capitis, can be challenging to diagnose due to its similarity in appearance to other hair and scalp conditions. The following are some common differential diagnoses for head louse infestation:

• Desquamated epithelial cells: These are dead skin cells that can resemble nits (eggs) of the head louse.
• Hair casts: Also known as "dandruff," these are small, white or yellowish scales that form on the scalp and can be mistaken for nits.
• Lint: This is a type of fabric residue that can accumulate on the hair and scalp, resembling nits.
• Sand: Sand particles can become lodged in the hair and scalp, causing irritation and potentially being mistaken for nits.
• Dried concretion of hair spray: This is a hardened deposit of hair spray or other styling products that can resemble nits.

These conditions can be distinguished from head louse infestation by their inability to move or attach to the scalp. Live nymphs (baby lice) or adult lice on the scalp or hair are the best indicators of an active head lice infestation [9][10].

References:

• [10] Pediculosis capitis, or head lice infestation, caused by Pediculus humanus capitis, is a worldwide public health concern (Ko & Elston, 2004).
• [9] Finding a live nymph (baby louse) or adult louse on the scalp or hair confirms the diagnosis of a head lice infestation.