Genital Infestations Flashcards
What is phthirus pubis
Pubic lice
How is phthiriasis diagnosed?
Pubic lice - Can be seen by the naked eye
Nits (eggs) - seen with naked eye - adhere to hairs
Examination under light microscopy can confirm morphology if necessary
Treatment of phthiriasis
Malathion lotion or permethrin cream.
All body hair should be treated.
All bedding should be washed at high temperatures.
Sexual partners need treatment.
Transmission of phthirus
public lice transmitted by close body contact
incubation period for phthirus (lice)
incubation period usually 5 days to several weeks
Symptoms / signs of phthirus (lice)
itching
can be asymptomatic
visible lice or nits (eggs)
Blue macules (maculae caeruleae) may be visible at feeding sites
What areas can be affected by phthirus (lice)
Adult lice infest coarse hairs of the pubic area, body hair and, rarely, eyebrows and eyelashes
Eggs (nits) are laid which adhere to the hairs
Management of phthirus pubis (lice)
Lotions more effective than shampoos
apply to all body hair including beard + moustache
A second application after 3-7 days
- Malathion 0.5%. Apply to dry hair- wash out 2 - 12hrs
- Permethrin 1% cream - Apply to damp hair- wash out 10min
- Phenothrin 0.2% - apply to dry hair - wash out 2hr
- Carbaryl 0.5 and 1% - Apply to dry hair - wash out 12 hr
avoid close body contact until they + partner(s) completed treatment + follow-up
full STI screen
Treatment of pubic lice infestation of eyelashes
permethrin 1% lotion - keep eyes closed - 10 minute application
OR
inert ophthalmic ointment with white / yellow paraffin base applied to the eyelashes BD for 8-10 days - works by suffocating lice - avoids risk of eye irritation
treatment of phthirus pubis (lice) in pregnancy or breastfeeding
Permethrin is safe
Permethrin 1% cream - Apply to damp hair- wash out 10min
Advice for sexual partners of patients with phthirus pubis (lice)
Examine and treat current sexual partners should be examined and treated
Contact tracing - partners in last 3 months
follow up for patients treated for phthirus pubis (lice)
Review at 1 week - re-examine for absence of lice
Treatment failure should be given an alternative
Dead nits may remain adherent to hairs - does not imply treatment failure - nits can be removed with a nit comb
What is scabies
Sarcoptes scabiei var hominis
human itch mite
Lifecycle of scabies mite
lifecycle of sarcoptes = 4-6 weeks Mites burrow into skin + lay eggs eggs hatch ~10% grow into adults in 10 - 15 days female lays ~25 eggs and dies
Transmission of scabies
close skin contact
frequently sexually acquired
mites can live off a host for 24-36 hours
Fomite transmission is uncommon but can occur
Why is format transmission more common in crusted scabies
greater number of mites present
and mites can survive longer - up to 7 days
Symptoms of classical scabies infection
intense generalised itching
worse at night
due to delayed type-IV hypersensitivity reaction to mites, and mite faeces + eggs
How long after primary infestation do symptoms of scabies occur
Symptoms begin 3-6 weeks after primary infestation
earlier ( 1-3 days) in a re- infested person
Scabies is infectious before the rash develops
signs of scabies infestation
most common = erythematous papules excoriation characteristic distribution pathognomonic lesion= burrow -linear intra-epidermal tunnel = short wavy greyish/ white threadlike elevations of 2-10mm length Nodular lesions
Anatomical sites commonly affected by scabies
interdigital webspaces / sides of fingers / under finger nails
flexor aspects of wrists / extensor aspects of elbows
anterior + posterior axillary folds
around nipples / penis + scrotum / umbilicus
upper medial thighs / buttocks / sides + back of feet
Spares face + scalp
what is Norwegian scabies
Crusted scabies / Scabies crustosa / Norwegian scabies) occur in immunocompromised states
When does crusted scabies occur
occur in immunocompromised states
e.g. in AIDS, leprosy, lymphoma, systemic or potent topical steroids, organ transplant recipients, elderly
what proportion of patents with crusted scabies have no identifiable risk factor (e.g. no immunocompromised)
40%
suggests possible genetic susceptibility
Symptoms / signs of crusted scabies
Erythematous scaly crusted lesions can be malodorous associated with fissuring can affect any part of the body including the face and scalp itching may be mild or absent
If a healthy patient contracts scabies from a patient with crusted scabies what type of scabies will they develop?
classical scabies
unless also immunocompromised / genetically susceptible to crusted scabies
complications of crusted scabies
Sepsis - as fissures associated with crusted scabies provide an entry point for bacteria
Can humans contract animal scabies?
Humans can rarely contract scabies from pet dogs (canine scabies = Sarcoptes scabiei var canis) or cats (feline scabies = Notoedres cati.)
incubation period is shorter
lesion distribution confined to sites of contact with the animal
burrows not seen
self-limiting as mites do not reproduce in humans hosts
treatment of animal only
what is Scabies Incognito
altered clinical presentation following use of topical steroids widespread atypical papular lesions may mimic generalized eczema Symptoms are masked but patient remains infectious
Diagnosis of scabies
clinical history and distribution / appearance of skin lesions.
+/- Microscopic identification of mites / eggs / faecal pellets (scybala) from scrapings
+/- burrow ink test
+/- dermoscopy
Preparation of a skin scraping for microscopy in suspected scabies
Scraping of the skin burrows with a scalpel blade Place specimen on a glass slide Add 10% potassium hydroxide ( dissolves excess keratin) OR
Apply a drop of mineral oil to the lesion
Scrape away the entire lesion with the scalpel blade
transfer to slide
What is the burrow ink test for suspected scabies
Apply black / blue ink to suspected papule
remove surface ink with alcohol wipe t
positive test = characteristic dark zigzagged line running away from the lesion = ink tracking down mite burrow
Differential diagnosis for scabies
Impetigo folliculitis papular urticaria atopic dermatitis contact dermatitis dermatitis herpetiformis psoriasis seborrhoeic dermatitis pytiriasis rosea secondary syphilis lymphoma
Complications of scabies
Secondary bacterial infection - staph aureus / group A β-haemolytic strep / peptostreptococci
resulting in impetigo / folliculitis / furunculosis / ecthyma / abscess
Secondary eczematisation due to constant scratching / irritant effects of medication
glomerulonephritis
leucocytoclastic vasculitis
what is furunculosis
a deep infection of the hair follicle leading to abscess formation with accumulation of pus and necrotic tissue
= furuncle (i.e. boil)
treatment options for scabies
- permethrin 5% cream
- malathion aqueous 0.5% liquid
- benzyl benzoate 25% emulsion (not recommended)
- oral ivermectin (less effective than permethrin) [topical ivermectin not available in UK]
why is benzyl benzoate 25% emulsion not recommended as treatment for scabies
not as effective as Permethrin or Malathion
may cause skin irritation
General advice for patients with scabies
Hot wash (60°C) - bedding / clothing / towels used during the previous four days before
or by dry-cleaning
or by sealing in a plastic bag for at least 72 hours
Recommended regimen for Permethrin 5% cream to treat scabies
Permethrin 5% cream
- apply to whole body from the chin + ears downwards
- pay special attention to areas between the fingers / toes / under nails
- apply treatment to cool dry skin
- allow lotion / cream to dry before dressing in clean clothing
- Wash off cream after 8 - 12 hr
- reapply 1 week later.
- if hands are washed with soap within 8 hours then reapply cream
Which groups of patients with scabies should be advised to apply permethrin cream to the whole body including face + scalp
people who are immunosuppressed
the very young
the elderly people
Recommended regimen for Malathion 0.5% aqueous lotion to treat scabies
Malathion 0.5% aqueous lotion
- apply to whole body from the chin + ears downwards
- pay special attention to areas between the fingers / toes / under nails
- apply treatment to cool dry skin
- allow lotion / cream to dry before dressing in clean clothing
- Wash off cream after 24 hr
- reapply 1 week later.
- if hands are washed with soap within 24 hours then reapply
Alternative regimen for scabies treatment
i.e not Malathion or Permethrin
Ivermectin - oral - dose 200 mcg/kg 2 weeks apart -
available on a named patient basis.
- used in the treatment of crusted scabies that does not respond to topical treatment alone
- adverse events associated with ivermectin = rash / vomiting / abdominal pain
Treatment of crusted scabies
Combination treatment
topical permethrin cream OD for 7 days
then 2x weekly until cure
+ oral ivermectin (200 mcg/kg) on days 1,2,8,9 and 15
should be isolated + barrier nursing
Treat all household members
Management of post scabetic itch
crotamiton 10% cream (2-3 times a day)
Or - if the scabies mites have definitely been eradicated - use topical hydrocortisone 1%
Night time sedative antihistamine may help
emollients for dry skin/eczema
What is post scabetic itch
Itching may continue up to 2 weeks after successful scabies treatment
Treatment failure suspected if new burrows appear or if itching persists >2-4 weeks
Treatment of scabies in pregnancy and breastfeeding
Permethrin 5% cream.
Alternatively use Malathion 0.5% aqueous liquid
remove the liquid or cream from the nipples before
breastfeeding and reapply afterwards
Avoid oral antihistamines during pregnancy
Treatment of sexual partners of patients with scabies
Examine and treat
- Current sexual partners
- household members
- others with close personal contact
Contact tracing = 1 month
Follow-up for scabies
not generally required
Return if pruritus persists >2 weeks
Return if new burrows appear
for scabies which treatments has there been documented resistance to?
documented resistance for both permethrin and ivermectin
