178: Scabies, Other Mites and Pediculosis Flashcards
What is the prevalence of scabies in underdeveloped countries?
The prevalence rates of scabies in underdeveloped countries range from 4% to 100%.
What are the primary routes of transmission for scabies?
The primary routes of transmission for scabies include:
- Close personal contact
- Transmission via inanimate objects (especially in cases of crusted scabies)
- Sometimes considered a sexually transmitted disease.
What are the characteristic clinical findings associated with scabies?
The diagnosis of scabies is suspected by:
- Pruritus
- Associated with a characteristic distribution of lesions
- Epidemiologic history
- Onset is typically insidious with intense nocturnal pruritus.
- Symptoms may develop 4 to 6 weeks after initial infestation, and some patients may not develop symptoms for 3 months.
What is the life cycle of the scabies mite?
The life cycle of the scabies mite includes:
- Female mite excavates a burrow in the skin, laying 0-4 eggs per day.
- Eggs hatch in 10-12 days, and larvae leave the burrow to mature on the skin surface.
- After molting, they become nymphs (can survive 2 to 5 days off host).
- The male mite lives on the skin surface and enters burrows to procreate.
- The entire life cycle is completed on human skin.
What are the physical examination findings in a patient with scabies?
Physical examination findings in scabies may include:
- Excoriations and eczematous dermatitis
- Lesions in:
- Interdigital webs
- Sides of fingers
- Volar aspects of wrists and lateral palms
- Elbows, axillae, scrotum, penis, labia, and areolae (women)
- The head and neck are typically spared in healthy adults, but all skin surfaces may be affected in infants, elderly, and immunocompromised individuals.
What is a pathognomonic lesion for scabies and how is it identified?
The pathognomonic lesion for scabies is the burrow, which is:
- Thin, thread-like, linear, or J-shaped structure
- Ranges from 1 to 10 mm in length
- Best seen in the interdigital webs and wrists
Identification can be done by rubbing a black felt-tip marker across an affected area, then wiping excess ink away with an alcohol pad; the burrow will appear darker due to ink accumulation.
A patient presents with intense nocturnal pruritus and burrows on the interdigital webs. What diagnostic steps should you take to confirm scabies?
To confirm scabies, perform a microscopic identification of scabies mites, eggs, or fecal pellets (scybala) by applying a drop of mineral oil over a burrow, scraping longitudinally with a scalpel blade, and examining the scrapings under low power. Alternatively, use dermoscopy to identify the ‘delta-wing jet’ sign.
A patient with scabies has a history of leprosy and presents with minimal pruritus but hyperkeratotic plaques. What is the diagnosis?
The diagnosis is crusted scabies, which occurs in individuals with defective immunologic or sensory responses, such as those with leprosy.
A patient with scabies presents with burrows on the palms and soles. What population is this finding common in?
Burrows on the palms and soles are common in infants and young children, who are less effective scratchers.
What is the typical life cycle of the Sarcoptes scabiei mite, including its egg-laying habits?
The female Sarcoptes scabiei mite lays between 0 to 4 eggs a day, up to 50 eggs during her lifespan of about 30 days. The eggs hatch in 10 to 12 days, and the larvae leave the burrow to mature on the skin surface. After molting, they become nymphs, which can only survive 2 to 5 days off the host.
What are the common clinical findings associated with scabies infestation?
Common clinical findings include:
- Pruritus: Intense itching, especially nocturnal.
- Lesion Distribution: Characteristic distribution of lesions, often in interdigital webs, sides of fingers, and other areas.
- Epidemiologic History: Recent exposure to infested individuals.
- Physical Examination: May reveal excoriations, eczematous dermatitis, and pathognomonic burrows.
How does the presentation of crusted scabies differ from typical scabies?
Crusted scabies presents with hyperkeratotic plaques diffusely on the palmar and plantar regions, thickening and dystrophy of toenails and fingernails, and an enormous mite burden with few or no symptoms. In contrast, typical scabies usually presents with intense pruritus and characteristic lesions without the extensive crusting seen in crusted scabies.
What factors contribute to the transmission of scabies in a population?
Factors contributing to the transmission of scabies include:
- Close Personal Contact: A prime route of transmission, often considered sexually transmitted.
- Inanimate Objects: Transmission can occur via contaminated items, especially in cases of crusted scabies.
- High Contagion in Crusted Scabies: Individuals in close proximity to crusted scabies patients are at high risk of infestation due to the high number of mites present in their environment.
What is the significance of identifying a burrow in diagnosing scabies?
Identifying a burrow is significant because it is a pathognomonic lesion for scabies. A burrow appears as a thin, thread-like, or J-shaped structure in the stratum corneum, typically found in areas like the interdigital webs and wrists. Rubbing a black felt-tip marker over an affected area can help visualize the burrow, which will appear darker than the surrounding skin due to ink accumulation.
What are the implications of being a ‘carrier’ of scabies?
Individuals considered ‘carriers’ of scabies may remain asymptomatic despite being infested. This can lead to unintentional transmission to others, as they may not exhibit the typical symptoms of pruritus or visible lesions, making it difficult to identify and control outbreaks.
What are the challenges in diagnosing scabies in infants and young children?
Challenges in diagnosing scabies in infants and young children include:
- Less Effective Scratchers: Infants may not scratch effectively, making lesions less apparent.
- Burrow Locations: Burrows may be found in less typical areas such as palms, soles, and intertriginous areas, complicating diagnosis.
- Indurated Nodules: Crusted nodules can be mistaken for other conditions, leading to misdiagnosis.
What is the role of the immune response in the severity of scabies infestation?
The immune response plays a crucial role in the severity of scabies infestation. Individuals with defective immunologic responses, such as those with leprosy, paraplegia, or HIV, may harbor millions of mites with minimal pruritus, leading to crusted scabies. In contrast, healthy individuals typically experience intense pruritus and characteristic lesions due to a more effective immune response.
How can the presence of scabies mites be definitively diagnosed?
Definitive diagnosis of scabies can be achieved through microscopic identification of scabies mites, eggs, or fecal pellets (scybala). This is done by scraping a burrow or suspicious skin area with a scalpel blade and applying the scrapings to a glass slide for examination under a microscope.
What are the potential complications of untreated scabies?
Potential complications of untreated scabies include:
- Secondary Bacterial Infections: Due to excoriation and skin breakdown.
- Crusted Scabies: Can develop in immunocompromised individuals, leading to extensive mite burden and severe skin issues.
- Psychosocial Impact: Persistent itching and visible lesions can lead to anxiety, social stigma, and decreased quality of life.
What are the common diagnostic methods used to identify scabies?
- Confocal microscopy and dermoscopy can be used to examine the mite in vivo.
- Classic dermoscopic finding: ‘delta-wing jet’ sign of dense scabies head parts and body, eggs, and a burrow.
- Skin biopsy: diagnostic if the mite is transected in the stratum corneum.
- Enzyme-linked immunosorbent assay: used in animals, not humans.
- Diagnosis is usually based on clinical impression and solidified by response to treatment.
What are the complications associated with scabies?
- Secondary impetiginization
- Poststreptococcal glomerulonephritis from scabies-induced pyodermas caused by Streptococcus pyogenes
- Crusted scabies: can lead to lymphangitis and septicemia
- Can trigger bullous pemphigoid.
What is the recommended treatment approach for scabies?
- Combination of a scabicide and fomite control.
- A second application is usually required a week after the initial treatment to prevent reinfestation.
- All household and close contacts must be treated simultaneously to prevent reinfestation from symptomatic and asymptomatic carriers.
- Topical scabicides should be applied overnight to the entire skin surface, with special attention to areas like finger and toe creases, cleft of the buttocks, and beneath the fingernails and toenails.
What precautions should be taken to prevent reinfestation of scabies?
- All family members and close contacts should be treated simultaneously due to common occurrence of asymptomatic mite carriers.
- Wear clean clothing.
- Wash all clothing, pillow cases, towels, and bedding used during the previous week in hot water and dry at high heat.
- Nonwashables should be dry-cleaned, ironed, or stored in a sealed plastic bag in a warm area for 2 weeks.
- Floors, carpets, and upholstery should be carefully vacuumed.
What are the considerations for using ivermectin in the treatment of scabies?
- Ivermectin is an anthelmintic agent approved for treatment of scabies at a dosage of 200 μg/kg given twice, one week apart.
- It is extremely safe but not recommended for children weighing less than 15 kg (33 lbs) or in pregnant/lactating women due to potential effects on the developing nervous system.
- Success rates approach 100% in studies for crusted scabies when combined with a topical scabicide.
A child presents with crusted scabies. What treatment regimen should be followed?
For crusted scabies, a combination of oral ivermectin and a topical scabicide is recommended. Oral ivermectin is effective but does not penetrate the keratinous debris under the nails, so topical treatment is essential.
A patient with scabies is treated with permethrin but continues to experience pruritus for weeks. What is the likely cause and how should it be managed?
The persistent pruritus is likely due to ‘postscabetic itch,’ which can last up to 4 weeks after adequate scabicidal therapy. Manage it with oral antihistamines and emollients, and educate the patient to avoid excessive washing with harsh soaps.
A family member of a scabies patient is asymptomatic. Should they be treated? Why or why not?
Yes, all household and close contacts should be treated simultaneously to prevent reinfestation, as asymptomatic carriers are common.
A patient with scabies is advised to avoid excessive washing with harsh soaps. Why is this recommendation given?
Excessive washing with harsh soaps can aggravate skin irritation and worsen symptoms.
A patient with scabies is prescribed ivermectin. Why is this drug not recommended for young children?
Ivermectin is not recommended for young children because their blood-brain barrier is not fully developed, and the drug acts on nerve synapses that utilize glutamate or γ-aminobutyric acid.
A patient with scabies is treated with sulfur ointment. What are the advantages and disadvantages of this treatment?
Sulfur ointment is inexpensive and considered safe for neonates and pregnant females, but it is messy, malodorous, stains, and can cause irritant dermatitis.
A patient with scabies is diagnosed using dermoscopy. What is the classic finding?
The classic dermoscopic finding for scabies is the ‘delta-wing jet’ sign, representing dense scabies head parts, body, eggs, and a burrow.
A patient with scabies is advised to vacuum their home. What areas should be targeted and why?
Vacuum floors, carpets, upholstery, play areas, and furniture to remove mites and prevent reinfestation.
A patient with scabies is treated but their pet is not. Is this a concern?
No, pets do not harbor the human scabies mite and do not need to be treated.
A patient with scabies is treated with permethrin. How should the application be performed?
Apply permethrin overnight to the entire skin surface, paying special attention to finger and toe creases, the cleft of the buttocks, the belly button, and beneath the fingernails and toenails.
A patient with scabies is advised to treat nonwashable items. What methods can be used?
Nonwashable items should be dry-cleaned, ironed, put in a clothes dryer without washing, or stored in a sealed plastic bag in a warm area for 2 weeks.
A patient with scabies is advised to treat all household members. Why is this necessary?
Treating all household members simultaneously prevents reinfestation from asymptomatic carriers.
A patient with scabies is treated with ivermectin. What is the recommended dosage and schedule?
The recommended dosage of ivermectin is 200 μg/kg, given twice 1 week apart.
A patient with scabies is advised to avoid fumigation of living spaces. Why is this recommendation made?
Fumigation of living spaces is not recommended because it is unnecessary for controlling scabies mites.
What is the significance of the ‘delta-wing jet’ sign in the diagnosis of scabies?
The ‘delta-wing jet’ sign is a classic dermoscopic finding indicating the presence of dense scabies head parts, body, eggs, and burrows, which aids in the diagnosis of scabies.
What are the recommended treatments for crusted scabies?
The recommended treatment for crusted scabies is a combination of oral ivermectin and a topical scabicide, as the oral medication does not penetrate the thickness of keratinous debris under the nails.
What precautions should be taken when using ivermectin for treating scabies in children?
Ivermectin is not recommended for use in children weighing less than 15 kg (33 lbs) or in pregnant or lactating women due to the risk associated with the drug acting on nerve synapses that utilize glutamate or γ-aminobutyric acid.
What is the importance of a second application of scabicide after the initial treatment?
A second application of scabicide is important to reduce the potential for reinfestation from fomites and to kill any nymphs that may have hatched after the initial treatment.
What are the potential complications associated with untreated scabies?
Potential complications of untreated scabies include secondary impetiginization, poststreptococcal glomerulonephritis, lymphangitis, septicemia, and triggering bullous pemphigoid.
How should clothing and bedding be managed to prevent scabies reinfestation?
Clothing, pillowcases, towels, and bedding used during the previous week should be washed in hot water and dried at high heat to prevent reinfestation from scabies mites.
What is the role of topical scabicides in the treatment of scabies?
Topical scabicides are applied overnight to the entire skin surface, focusing on areas like finger and toe creases, and provide relief from symptoms within 3 days, although rash and pruritus may persist for up to 4 weeks.
What are the recommendations for treating family members and close contacts of a scabies patient?
All family members and close contacts should be treated simultaneously to address the common occurrence of asymptomatic mite carriers in the household.
What is the clinical efficacy of ivermectin for treating scabies?
Ivermectin has shown impressive clinical efficacy for scabies at a dosage of 200 μg/kg given twice, one week apart, with success rates approaching 100% in studies.
What are the contraindications for using lindane in scabies treatment?
Lindane has a ‘black box’ warning and is banned in California due to safety concerns of uncontrolled seizures.
What is the recommended approach for preventing scabies in a household?
Preventive measures include treating all family members simultaneously, wearing clean clothing, washing bedding and clothing in hot water, and vacuuming living spaces carefully.
What is the significance of enzyme-linked immunosorbent assay in scabies diagnosis?
The enzyme-linked immunosorbent assay is used in animals for diagnosing scabies but is not applicable in humans; diagnosis is primarily based on clinical impression and response to treatment.
What are the characteristics of 5-10% sulfur as a treatment option for scabies?
5-10% sulfur is messy, malodorous, inexpensive, and may cause irritant dermatitis; it is considered the safest choice for neonates and pregnant females in areas with limited resources.
What is the clinical significance of postscabetic itch?
Postscabetic itch refers to the persistence of rash and pruritus for up to 4 weeks after adequate scabicidal therapy, indicating that patients should be informed about this potential outcome.
What are the implications of excessive washing of the skin for scabies patients?
Excessive washing of the skin with harsh soaps can aggravate skin irritation in scabies patients; therefore, oral antihistamines and emollients may be beneficial.
What is the role of confocal microscopy in the diagnosis of scabies?
Confocal microscopy can be used to examine the mite in vivo, providing a detailed view that aids in the diagnosis of scabies.
What are the recommended cleaning practices for non-washable items in a scabies outbreak?
Non-washable items should be dry-cleaned, ironed, or stored in a sealed plastic bag in a warm area for 2 weeks to prevent scabies transmission.
What is the significance of the ‘black box’ warning associated with lindane?
The ‘black box’ warning indicates serious safety concerns regarding the use of lindane, leading to its ban in California and restrictions on its use in certain populations.
What is the recommended dosage of ivermectin for treating scabies?
The recommended dosage of ivermectin for treating scabies is 200 μg/kg given twice, one week apart, to achieve clinical efficacy.
What are the common symptoms that patients may experience after scabicidal therapy?
Patients may experience a rash and pruritus that can persist for up to 4 weeks after adequate scabicidal therapy, known as postscabetic itch.
What is the importance of treating asymptomatic carriers in a scabies outbreak?
Treating asymptomatic carriers is crucial to prevent reinfestation and further spread of scabies within the household.
What are the potential side effects of using 5-10% sulfur for scabies treatment?
Potential side effects of using 5-10% sulfur include messiness, malodor, staining, and irritant dermatitis.
What is the recommended approach for managing pets in a scabies outbreak?
Pets do not need to be treated for scabies as they do not harbor the human scabies mite, thus no specific management is required for them.
What is the role of topical scabicides in the management of scabies?
Topical scabicides are applied to the entire skin surface to eliminate scabies mites and provide symptom relief, with specific attention to skin folds and creases.
What are the implications of permethrin use for pregnant females, breastfeeding mothers and children <2 years?
Pregnant females should limit its use to 2 applications, spaced one week apart, for no more than 2 hours due to potential risks.
What is the clinical efficacy of crotamiton compared to other scabicides?
Crotamiton is considered less effective than other scabicide options available for treating scabies.
What are the key considerations for using oral ivermectin in scabies treatment?
Oral ivermectin is extremely safe and effective, but it is not recommended for young children under 15 kg or for pregnant/lactating women due to safety concerns.
What is the significance of skin biopsy in diagnosing scabies?
Skin biopsy is diagnostic for scabies if the mite is transected in the stratum corneum, providing a definitive diagnosis when clinical findings are inconclusive.
What are the recommended practices for cleaning living spaces to prevent scabies?
Living spaces should be carefully vacuumed, and fumigation is not recommended as a preventive measure against scabies.
What is the role of oral antihistamines in the management of scabies symptoms?
Oral antihistamines can be beneficial in managing skin irritation and pruritus associated with scabies, especially after treatment.
What are the characteristics and effects of Demodex folliculorum and Demodex brevis on humans?
Demodex folliculorum and Demodex brevis are the only mites that routinely live on humans.
- D. folliculorum: Found in the hair follicle.
-
D. brevis: Located in the infundibulum of the sebaceous gland.
They are linked with conditions such as:
1. Rosacea
2. Perioral dermatitis
3. Suppurative folliculitis (causal role not established).
What are the symptoms and causes associated with Pyemotes species?
Pyemotes species, also known as straw itch or itch mite, are not primary parasites of humans but can cause dermatitis outbreaks in several Mid-westerns states
- Red macules with a small blister center, occurring 10 to 16 hours after contact.
- Pyemotes ventricosus and tritici: animal handlers and farmers involved in grain harvesting.
- Pyemotes herfsi: Leaf galls on oak trees, affecting people who spend time outdoors in wooded areas.
What are the characteristics and clinical significance of harvest mites?
Harvest mites, also known as berry bugs, red bugs, scrub-itch mites, and chiggers, belong to the family Trombiculidae.
- Found in grasslands, forests, and damp areas along lakes and streams.
- Humans are susceptible to larvae from April until the first frost.
- Minute, reddish larvae feed on skin cells, injecting digestive enzymes that cause severe reactions and swelling.
- Characteristic red papule with a white, hard central area.
- Itching from chigger bites may not develop until 1 to 2 days after the bite.
- Prefer warm, covered areas of the body, often clustering behind the knees or beneath tight undergarments.
What role do house dust mites play in human health?
House dust mites are cosmopolitan guests in human habitation, feeding off flakes of shed human skin.
- Harmless: Generally considered harmless to humans.
- Bodies and excreta can play a role in human disease.
- Common precipitant of asthma, hay fever, and allergic respiratory symptoms worldwide.
- May exacerbate atopic dermatitis in some individuals.
A patient presents with dermatitis after spending time in a wooded area. Red macules with small blister centers appear 10-16 hours after exposure. What mite is likely responsible?
The likely culprit is Pyemotes herfsi, an itch mite associated with leaf galls on oak trees. These mites cause dermatitis on exposed skin.
A patient reports severe itching 1-2 days after being in a grassy area. Red papules with a white, hard central area are observed. What is the diagnosis and cause?
The diagnosis is chigger bites, caused by larvae of harvest mites (family Trombiculidae). These mites inject digestive enzymes into the skin, causing severe reactions.
A patient with asthma experiences worsening symptoms. House dust mites are suspected. What role do these mites play in human disease?
House dust mites are harmless themselves, but their bodies and excreta are common precipitants of asthma, hay fever, and allergic respiratory symptoms.
What are the characteristics and potential health impacts of Demodex folliculorum and Demodex brevis on humans?
Demodex folliculorum and Demodex brevis are mites that live on humans.
- D. folliculorum: Found in hair follicles.
-
D. brevis: Located in the infundibulum of sebaceous glands.
They are linked with conditions such as:
1. Rosacea
2. Perioral dermatitis
3. Suppurative folliculitis
However, a causal role in these conditions has not been established.
What are the symptoms and causes of Pyemotes mite infestations in humans?
Pyemotes mites, also known as straw itch or itch mites, can cause skin eruptions.
- They are not primary parasites of humans but can lead to epidemics of dermatitis.
- Commonly associated with:
- Pyemotes ventricosus and Pyemotes tritici: Affect animal handlers and farmers during grain harvesting.
-
Pyemotes herfsi: Found on oak trees, affecting people outdoors in wooded areas.
Symptoms include: - Red macules with a small blister center, appearing 10 to 16 hours after contact.
What are the characteristics and clinical significance of harvest mites?
Harvest mites, also known as berry bugs, red bugs, scrub-itch mites, and chiggers, belong to the family Trombiculidae.
- Habitat: Found in grasslands, forests, and damp areas near lakes and streams.
- Lifecycle: Humans are susceptible to larvae from April until the first frost.
- Feeding: Minute, reddish larvae feed on skin cells and inject digestive enzymes, causing severe reactions and swelling.
- Symptoms: Characteristic red papule with a white, hard central area.
- Bite reaction: Itching may not develop until 1 to 2 days after the bite, often unnoticed at the time of occurrence.
- Preferred areas: Warm, covered areas of the body, often behind the knees or under tight clothing.
How do house dust mites contribute to respiratory diseases in humans?
House dust mites are cosmopolitan guests in human habitats, feeding on shed human skin.
- Health impacts: Although harmless themselves, their bodies and excreta can play a role in human disease.
- Common conditions: They are known to precipitate asthma, hay fever, and allergic respiratory symptoms worldwide.
- Atopic dermatitis: This condition may be exacerbated in some individuals due to exposure to house dust mites.
What are the three species of lice that infest humans?
- Pediculus humanus capitis - the head louse
- Pediculus humanus humanus - the body or clothing louse
- Phthirus pubis - the pubic or crab louse
What is the average incubation period for head lice infestation?
The average incubation period for head lice infestation is 4 to 6 weeks.
How is head lice primarily transmitted?
Head lice are primarily transmitted through direct head-to-head contact. Indirect transmission can occur through fomites such as combs, brushes, and bedding.
What are the clinical findings associated with head lice infestation?
Clinical findings include:
- Pruritus (itching)
- Nits (eggs) most readily found in the occipital and retroauricular regions
- Erythematous macules or papules
- Other findings: low-grade fever, regional lymphadenopathy, and irritability.
What is the life cycle of the female louse?
The female louse lays 5 to 10 eggs per day during her 30-day life span. After 10 days, the eggs hatch into larvae, referred to as nymphs or instars, which go through 3 stages of development and take 14 days for full maturation.
What are the characteristics of nits in head lice infestation?
Nits are:
- Readily seen by the naked eye and serve as an efficient marker of past or present infestation.
- Firmly attached to individual hairs with a proteinaceous glue.
- Newly laid or viable eggs are tan to brown, while remains of hatched eggs are clear, white, or light in color.
A child presents with pruritus and nits in the occipital region. What is the most likely diagnosis and how is it confirmed?
The most likely diagnosis is pediculosis capitis (head lice). Confirm by demonstrating egg capsules (nits) and live lice, which can be identified through fine combing or dermoscopy.
A patient with head lice is advised to use wet combing. How does this method improve detection?
Wet combing with water and conditioner pries adult lice from hair follicles, increasing the yield of detection.
A patient with head lice is advised to use a nit comb. What is the purpose of this tool?
A nit comb is used to remove nits and live lice from the hair, improving the effectiveness of treatment.
What are the three species of lice that infest humans and their specific names?
- Pediculus humanus capitis - the head louse
- Pediculus humanus humanus - the body or clothing louse
- Phthirus pubis - the pubic or crab louse
What is the typical length of time for pruritus to appear after exposure to lice?
After initial exposure: 2 to 6 weeks.
Subsequent exposure: 1 to 2 days.
What are the common clinical findings associated with pediculosis capitis?
- Pruritus (itching)
- Nits (eggs) most readily found in the occipital and retroauricular regions
- Erythematous macules or papules
- Excoriations, erythema, and scaling
- Possible low-grade fever, regional lymphadenopathy, and irritability
How is pediculosis capitis diagnosed?
Diagnosis is made by demonstrating:
1. Egg capsules (nits) - visible to the naked eye, indicating past or present infestation.
2. Live lice - presence confirms active infestation.
3. Differentiation from dandruff and hair.
What are common clinical findings in the scalp of a person infested with lice?
Common findings include erythematous macules or papules, excoriations, erythema, and scaling.
Possible low-grade fever and regional lymphadenopathy may also be present.
How is pediculosis capitis diagnosed?
Diagnosis is made by demonstrating egg capsules (nits), live lice, and differentiating from dandruff and hair casts.
Nits are not easily removed from the hair shaft.
What is the life cycle of the female louse in terms of egg laying?
The female louse lays 5 to 10 eggs per day during her 30-day life span. After 10 days, the eggs hatch into larvae, referred to as nymphs.
What factors contribute to the transmission of head lice?
Direct head-to-head contact is the primary mode of transmission, while indirect (fomite) transmission can occur through various objects.
What is the average incubation period for lice infestation symptoms?
The average incubation period for symptoms of lice infestation is 4 to 6 weeks.
What are the characteristics of nits and how can they be identified?
Nits are readily seen by the naked eye, firmly attached to individual hairs with a proteinaceous glue, and typically found within a few millimeters of the scalp. Newly laid or viable eggs are tan to brown, while hatched eggs are clear, white, or light in color.
What is the significance of the presence of adult lice in diagnosing pediculosis capitis?
The presence of adult lice confirms active infestation, which is necessary for appropriate treatment.
What are the survival conditions for lice and nits away from the scalp?
Lice typically survive less than 2 days away from the scalp, but under favorable conditions, they can survive up to 4 days. Nits can survive for 10 days.
What is the role of wet combing in the treatment of head lice?
Wet combing involves applying water and conditioner to the hair prior to using a nit comb, which increases the yield by prying the adult lice from the hair follicles.
What is the typical demographic most affected by pediculosis capitis?
Pediculosis capitis is most common in children aged 3 to 12 years and affects all levels of society and ethnic groups.
What are the stages of development for lice nymphs?
Nymphs go through 3 stages of development and take approximately 14 days for full maturation after hatching from the eggs.
What is the significance of the trend in prescriptions for lice treatments?
The increase in prescriptions may suggest either an increase in the number of infestations or a failure rate of nonprescription home regimens.
What is the anatomical adaptation of lice that aids in their survival on the scalp?
Lice have 3 pairs of claw-like legs that are well adapted for grasping hair, aiding in their survival and feeding on the scalp.
What are the common symptoms experienced by individuals infested with lice?
Common symptoms include pruritus, low-grade fever, regional lymphadenopathy, and irritability.
What is the role of the proteinaceous glue secreted by female lice?
The proteinaceous glue is used to firmly attach the eggs (nits) to individual hairs, ensuring they remain in place for development.
What is the typical behavior of lice in terms of movement and hiding?
Lice are typically fast, avoid light, and blend in with the hair, making them difficult to find during examination.
What are the implications of finding hatched nits during a lice examination?
Hatched nits indicate a past infestation but do not confirm current active infestation.
What is the significance of the low incidence of head lice among African Americans in the US?
The low incidence may be due to an anatomic inability of female lice to deposit eggs on coarse curly hair.
What are the potential complications of untreated pediculosis capitis?
Potential complications include secondary bacterial infections, persistent pruritus, and social stigma.
What is the primary method of lice transmission in schools and daycare settings?
The primary method of transmission is through direct head-to-head contact among children.
What are the characteristics of lice that make them highly host-specific?
Lice are blood-sucking, wingless insects that are highly adapted to their specific host, which is humans.
What is the role of environmental conditions in the survival of lice?
Heat and humidity can extend the survival of lice away from the scalp, allowing them to live up to 4 days.
What is the importance of identifying the presence of adult lice during diagnosis?
Identifying adult lice is crucial as it confirms active infestation necessary for treatment.
What are the common misconceptions about lice transmission?
Common misconceptions include the belief that lice can jump or fly; however, lice can only crawl.
What is the typical lifespan of a female louse and its reproductive capacity?
A female louse has a lifespan of about 30 days and can lay 5 to 10 eggs per day.
What are the signs that indicate a person may be a carrier of lice?
A person may be considered a carrier if they remain asymptomatic despite infestation.
What is the significance of the nits’ attachment to hair in the diagnosis of lice?
The attachment of nits indicates a current or past infestation, differentiating them from other debris.
What are the standard treatment recommendations for head lice infestation?
Confirm active infestation with live lice and treat with a nonprescription or prescription pediculicidal therapy.
What are the physical methods recommended for treating head lice?
Shaving one’s head and combing nits out after applying a hair moisturizer like Cetaphil are recommended.
What factors contribute to the increasing number of lice infestations?
Resistance to topical therapies, highest success rates with malathion and ivermectin, and local resistance patterns.
What are the recommended measures to prevent reinfestation of lice?
Wear clean clothing, wash all items in hot water, and clean combs and brushes in very hot water.
What is the life span and reproductive capacity of body lice?
Body lice have a life span of 20 days during which the female may lay up to 300 eggs.
What populations are most commonly affected by body lice?
Homeless individuals, refugees, and those in crowded living conditions with poor hygiene.
What are the clinical findings associated with body lice infestation?
Pruritus (itching) is a common symptom associated with body lice infestation.
What is the relationship between head lice and body lice in terms of disease transmission?
Head lice and body lice are closely related and can transmit diseases.
What is the recommended approach for treating lice with increasing resistance to pediculicides?
Treatment decisions should be based on local resistance patterns and patient characteristics.
What is the impact of a strict ‘no nit’ policy in schools regarding lice treatment?
It results in significant absence from school, and the American Academy of Pediatrics does not recommend it.
What are the occlusive and suffocation methods for treating lice?
Occlusive methods include petrolatum, mayonnaise, and dimethicone, but their efficacy is not well established.
What psychological impact might shaving one’s head have on girls as a treatment for head lice?
Shaving one’s head can be psychologically traumatic for girls.
What is the role of patient compliance in the effectiveness of pediculicides?
Variable compliance can affect effectiveness, leading to treatment failures.
How does the morphology of body lice differ from that of head lice?
Body lice are 30% larger than head lice.
What is the recommended duration for washing nonwashable items to prevent lice reinfestation?
Nonwashable items should be stored in a sealed plastic bag for 2 weeks.
What is the significance of combing nits out after applying a hair moisturizer for lice treatment?
It can help achieve high cure rates but should not be relied upon as the sole treatment method.
What are the implications of lice being able to survive without a blood meal?
They can persist in environments where hosts may not be available for feeding.
What are the challenges associated with treating lice in populations with poor hygiene?
An inability to wash and change clothing allows infestations to persist and spread.
What is the recommended method for cleaning combs and brushes used for lice treatment?
Wash in very hot water (65°C [149°F]) or coat with pediculicide for 15 minutes.
What is the clinical significance of secondary bacterial infections in lice infestations?
They are a common complication and the most common cause of pyodermas of the scalp.
What is the role of the World Health Organization in lice treatment recommendations?
They recommend pediculicidal testing to avoid overestimation of mortality rates.
What are the potential consequences of not treating lice infestations effectively?
Persistent infestations, increased risk of secondary infections, and social stigma.
What is the importance of confirming active infestation before treatment?
It ensures treatment is necessary and avoids unnecessary use of pediculicides.
What are the implications of lice resistance to malathion and ivermectin?
Resistance can lead to treatment failures, necessitating alternative therapies.
What is the significance of the life cycle of body lice in relation to their transmission?
Their ability to lay eggs in clothing seams and survive without a blood meal facilitates transmission.
Why is it crucial to ensure treatment for lice?
To ensure that treatment is necessary and to avoid unnecessary use of pediculicides.
What are the implications of lice resistance to malathion and ivermectin?
Resistance can lead to treatment failures, necessitating the need for alternative therapies and strategies.
What is the significance of the life cycle of body lice in relation to their transmission?
Their ability to lay eggs in clothing seams and survive without a blood meal facilitates transmission in crowded living conditions.
What are the recommended practices for treating infestations in crowded living conditions?
Proper hygiene, regular washing of clothing, and treatment of all individuals in close contact are essential to prevent reinfestation.
What are the clinical findings associated with pruritus in lice infestations?
Pruritus is often due to an allergic reaction to louse saliva during feeding.
What is the role of environmental cleaning in managing lice infestations?
Environmental cleaning is crucial to remove viable eggs and lice from the environment.
What are the psychological effects of lice infestations on affected individuals?
They can lead to embarrassment, anxiety, and social stigma, particularly in children and adolescents.
What is the significance of the American Academy of Pediatrics’ stance on ‘no nit’ policies?
It emphasizes the need for evidence-based practices that do not unnecessarily exclude children from school.
What are the implications of lice being able to ‘resurrect’ from seeming death?
This complicates treatment efforts and may lead to misinterpretation of treatment efficacy.
What are the challenges in treating lice in populations with high resistance to pediculicides?
High resistance can lead to treatment failures, necessitating exploration of alternative treatment options.
What are the major diseases transmitted by body lice?
- Epidemic typhus (caused by Rickettsia prowazekii)
- Murine typhus (caused by Rickettsia typhi)
- Trench fever (caused by B. quintana)
- Relapsing fever (caused by Borrelia recurrentis)
What is the most important treatment for pediculosis pubis?
- Disinfestation of all clothing and bedding
- Beds should be burned or sprayed with lice sprays.
- Clothing should be treated as biohazardous waste, bagged, and sealed.
- Waste should be handled separately and incinerated at 65°C (149°F) for 30 minutes.
- If incineration is not possible, clothing should be fumigated, washed in hot water, and dried on high heat or dry-cleaned.
- Treated from head to toe with a topical insecticide or given oral ivermectin.
What are the clinical findings associated with pediculosis pubis?
- All hairy parts of the body should be examined, including eyelashes, eyebrows, and perianal area.
- Infestation can be mistaken for scabs or moles.
- Average of 10 to 25 adult organisms on the body.
- Nits identified near the base of hairs.
- Diagnosis confirmed by microscopic examination of plucked hair for nits and adult lice.
- Maculae caerulea may be present, representing hemorrhage, and appear as slate gray to bluish irregular-shaped macules (~1 cm in diameter).
What is the life span of a crab louse and how many eggs do they lay?
- The life span of a crab louse is less than 3 weeks, during which they lay approximately 25 eggs on human hairs.
What precautions should be taken to prevent reinfestation of pediculosis pubis?
- All hairy areas of the body should be treated to prevent migration of lice.
- Oral ivermectin is recommended, requiring repeat doses on day 8 and day 15.
- Fomite precautions should be the same as for pediculosis capitis.
- Other household members should be questioned for symptoms and examined.
A patient with body lice is at risk of secondary infections. What are the major diseases transmitted by body lice?
Body lice can transmit epidemic typhus (R. prowazekii), murine typhus (R. typhi), trench fever (B. quintana), and relapsing fever (B. recurrentis).
A patient presents with pubic lice. What areas of the body should be examined and why?
Examine all hairy parts of the body, including pubic and perianal regions, eyelashes, eyebrows, and other hair-bearing areas, as lice can migrate and infest multiple sites.
A patient with pubic lice is treated but reinfestation occurs. What might have been overlooked?
Reinfestation may occur if all hairy areas of the body are not treated or if sexual contacts and household members are not treated.
A patient with body lice is advised to treat their clothing as biohazardous waste. Why is this necessary?
Body lice lay eggs in the seams of clothing, and treating clothing as biohazardous waste ensures complete disinfestation.
A patient with pubic lice is treated with ivermectin. Why must the treatment be repeated?
Ivermectin relies on the louse obtaining a blood meal, so nits are not affected. Repeat treatment is required on day 8 and day 15 to ensure all lice are eradicated.
A patient with body lice is at risk of secondary infections. What bacteria are commonly involved?
Secondary infections with S. aureus, S. pyogenes, and other bacteria can occur due to excoriations.
A patient with pubic lice presents with slate gray macules. What is the diagnosis?
The diagnosis is maculae caerulea, which are slate gray to bluish macules representing hemorrhage.
A patient with body lice is advised to avoid infested items for 2 weeks. Why is this duration recommended?
Avoiding infested items for 2 weeks ensures that any lice or eggs present have died, as lice cannot survive without a host for more than 3 days and eggs hatch within 10 days.
A patient with pubic lice is treated but presents with infestation of eyelashes. What is the condition and treatment?
The condition is pediculosis palpebrarum (infestation of eyelashes). Treat with petrolatum applied at least 5 times a day for weeks or with ivermectin.
What are the major diseases transmitted by body lice and their causative agents?
- Epidemic typhus (caused by Rickettsia prowazekii)
- Murine typhus (caused by Rickettsia typhi)
- Trench fever (caused by Bartonella quintana)
- Relapsing fever (caused by Borrelia recurrentis)
What is the most important treatment for body lice infestation?
- Disinfestation of all clothing and bedding
- Burning or spraying beds with lice sprays
- Clothing treated as biohazardous waste
- Waste handled separately and incinerated at 65°C (149°F) for 30 minutes
- Fumigation or washing clothing in hot water and drying on high heat
- Topical insecticide or oral ivermectin treatment
What are the clinical findings associated with pediculosis pubis?
- Examination of all hairy parts of the body, including eyelashes, eyebrows, and perianal area.
- Identification of 2 different hair-bearing sites infested.
- Average of 10 to 25 adult organisms on the body.
- Nits identified near the base of hairs.
- Diagnosis confirmed by microscopic examination of plucked hair.
How does the life span of crab lice compare to that of body lice?
- Crab lice: Life span is less than 3 weeks, laying approximately 25 eggs on human hairs.
- Body lice: Adult lice can survive for 36 hours off the human host, while their eggs are viable for up to 10 days.
What are the recommended precautions to prevent reinfestation of lice?
- Treat all hairy areas of the body to prevent migration of lice.
- Repeat oral ivermectin on day 8 and day 15.
- Carefully question and examine household members for symptoms of infestation.
What is the significance of maculae caerulea in the diagnosis of crab lice infestation?
- Maculae caerulea are rare findings representing hemorrhage, appearing as slate gray to bluish, irregular-shaped macules approximately 1 cm in diameter.
What are the common sites of infestation for crab lice?
- Most commonly found in the pubic and perianal region.
- Occasionally found in mustache, beard, axillae, eyelashes, eyebrows, and scalp hair.
What are the potential complications associated with body lice?
- Secondary infections with Staphylococcus aureus, Streptococcus pyogenes, and other bacteria due to excoriation.
- Transmission of microorganisms leading to diseases such as epidemic typhus, murine typhus, trench fever, and relapsing fever.
What is the role of ivermectin in the treatment of pediculosis pubis?
Ivermectin is recommended for treatment, relying on the insect obtaining a blood meal, but it does not affect nits. Requires repeat doses on day 8 and day 15.
What are the signs of body lice infestation?
The only sign is typically excoriations which are linear and found on the back, neck, shoulders, and waist.
What type of mites do infested hosts usually harbor?
Infested hosts usually harbor oviparous female mites.
What is the life span of a female scabies mite?
The life span of a female mite is approximately 30 days.
What is the prime route of transmission for scabies?
The prime route of transmission is direct skin-to-skin contact.
How long can nymphs survive off the host?
Nymphs can survive up to 3 days off the host.
What is the recommended therapy for crusted scabies?
The recommended therapy for crusted scabies is oral ivermectin and topical permethrin, as the oral medication will not penetrate into the thickness of the keratinous debris under the nails.
What is the most effective treatment for Pediculosis capitis?
The most effective treatment for P. capitis is topical insecticides, and must be repeated in 7-10 days.
What is the life span of P. humanus humanus?
P. humanus humanus has a life span of about 30 days during which the female may lay up to 300 eggs.
What are the major diseases transmitted by P. humanus humanus?
The 4 major diseases transmitted by P. humanus humanus are:
1. Typhus
2. Trench fever
3. Relapsing fever
4. Louse-borne diseases.
What is the classic dermoscopic finding in scabies?
The classic dermoscopic finding is burrows.
What is the typical survival time of P. capitis lice away from the scalp?
P. capitis lice typically survive less than 24 hours away from the scalp.
What is the primary route of transmission for scabies?
Direct skin-to-skin contact.
How long can a scabies mite live outside the host in a sterile test tube?
Up to 4 days.
What is the life span of a female scabies mite?
Approximately 30 days.
How many eggs can a female scabies mite lay in a day?
Anywhere from 10 to 25 eggs.
What is the typical survival duration of nymphs off the host?
Up to 3 days.
What is the recommended therapy for crusted scabies?
Oral ivermectin and topical scabicides.
What are the efficient markers of past and present P. capitis infestation?
Nits (lice eggs).
What is the most effective treatment for P. capitis?
Permethrin or pyrethrin, repeated in 7-10 days.
What is the life span of P. humanus humanus?
Approximately 30 days.
How long can P. humanus humanus survive without a blood meal?
Up to 2 days.
What is the primary transmission method for P. capitis?
Direct head-to-head contact.
What is the typical survival duration of P. capitis lice away from the scalp?
Less than 24 hours.
What is the common area where P. pubis is found?
Pubic region and sometimes the armpits.
How many eggs does a female P. pubis lay on human hairs?
Approximately 3 eggs per day.
What are the major diseases transmitted by P. humanus humanus?
Typhus fever, trench fever, relapsing fever, and epidemic typhus.
What is the classic dermoscopic finding in scabies?
Burrows or tracks in the skin.
What is the duration for which the rash and pruritus may persist after adequate scabicidal therapy?
Up to 2 weeks, known as post-scabetic pruritus.
What is the recommended application frequency of permethrin for young children?
Once every week for 2 applications.
What is the survival duration of P. corporis on the human host?
Up to 2 days.
What are the common presentations of P. corporis?
Itching and secondary bacterial infections.
What is the appearance of macules that represent hemorrhage in pediculosis?
Slate gray to bluish, irregular-shaped macules.
How often is ivermectin therapy repeated for lice treatment?
Every 7-14 days.
What is the typical duration for which nonwashables should be stored in a sealed plastic bag?
At least 2 weeks.
What is the typical survival duration of nits away from the scalp?
Up to 2 weeks.
What is the primary method of transmission for P. corporis?
Close contact with infested clothing or bedding.
What is the pathognomonic lesion associated with scabies?
Burrows in the skin.
What is the typical duration for which the rash and pruritus may persist after treatment for scabies?
Up to 2 weeks.
What is the typical survival duration of adult crab louse off the human host?
Up to 2 days.
What is the appearance of nits in pediculosis?
Small, white or yellowish oval eggs attached to hair shafts.
Incubation period of scabies?
4-6 weeks. Thus pruritus also happens 4-6 weeks after infestation.
Patients with crusted scabies shed how many mites per gram of debris from sheets, floor, screening curtains and nearby chairs?
6000.
Sarcoptes scabiei var. homini is able to live for how many days away from the host in a sterile test tube and how many days if placed in mineral oil mounts?
3 days - sterile test tube.
7 days - mineral oil mounts.
Describe how the female scabies mite excavates the skin, how it lays its eggs, and how it reproduces.
- By a combination of chewing and body motions, it excavates a slopiing burrow of 0.5-5mm/day in the stratum corneum to the boundary of the stratum granulosum.
- This path can be 1 cm long, and along this she lays anywhere from 0-4 eggs/day or up to 50 eggs during her lifespan (30 days).
- The eggs hatch after 10-12 days and the larvae mature at the skin surface.
- The larvae molts and the nymphs can only survive 2-5 days off the host.
- Male mite lives on the skin surface and enters burrows to procreate.
In infants and children who are less effective scratchers, burrows are located on what areas?
Palms and soles, intertriginous areas, and trunk.
Ivermectin is approved by the FDA for treatment of what 2 diseases?
Onchocerciasis and stronglyloides.
Most common demographic for head lice?
Children, 3 - 12 years.
Enumerate some important points of the life cycle of the head louse.
- entire life cycle is on the scalp
- female louse lays up to 5-10 eggs/day during her 30-day life span
- after 10 days the eggs hatch
- larvae are referred to as instars or nymphs and take 14 days for full maturation
- eggs are laid approximately 1 cm from scalp surface
- lice typically survive less than 2 days away (up to 4 days) from the scalp, while nits survive longer (10 days)
Efficient marker of past or present head lice infection?
Nits.
What is the cure rate of combing the nits out after application of a hair moisturizer such as Cetaphil?
95%.
What is the most effective treatment for pediculosis capitis?
Pediculosides. It is recommended to repeat treatment with all insecticidal treatments in 1 week.
It is though to be the most common cause of pyodermas of the scalp in the developed world.
Head lice.
What is the mechanism of action of occlusive and suffocation methods (petrolatum, mayonnaise, dimethicone, vegetable oil, hair pomade, olive oil) for pediculosis capitis and are they effective?
They slow the movement of mites to allow combing. There are no studies establishing their safety and efficacy.
To manage pediculosis capitis, combs and brushes may be washed in hot water for how many degrees or may be coated with the pediculocide for how long?
- 65 C / 149 F
- 15 minutes
T or F: In the treatment of head lice, fumigaton and treatment of pets are recommended.
False.
This is commonly the only sign of body lice.
Excoriations.
Areas affected frequently in body lice?
Back, neck, shoulders, waist.
Crab lice infects what areas of the body?
Pubic, perianal, mustache, beard, axillae, eyelashes, eyebrows, scalp hair.
Preferred treatment for crab lice?
Oral ivermectin.
Treatment for phthiriasis palpebrarum?
- Traditional: petrolatum - slow and needs to be applied at least 5x a day for weeks
- 1st line: ivermectin
T or F: Shaving is curative for pediculosis pubis.
False.
T or F: Ivermectin targets nits.
False. It relies on the insect obtaining a blood meal so the nits are not affected.
