Genital infestations

Question 1

What is the incubation for scabies?

Answer 1

1-2 days

Question 2

Symptoms and signs of pubic lice?

Answer 2

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
• There may be either no symptoms or there may be itch due to
hypersensitivity to feeding lice
• Blue macules (maculae caeruleae) may be visible at feeding sites

Question 3

How do you diagnose pubic lice?

Answer 3

Finding adult lice and/or eggs

Examination under light microscopy can confirm the morphology if
necessary

Question 4

What should patients with pubic lice be advised?

Answer 4

• Avoid close body contact until they and their partner have completed treatment and follow-up
• Patients should be given a detailed explanation of their condition, and clear and accurate written information on applying the treatment

Question 5

Which products for pubic lice are more effective?

Answer 5

Lotions are likely to be more effective than shampoos, and should be applied to all body hair including the beard and moustache if necessary
A second application after 3-7 days is advised

Question 6

What are the recommended treatments for pubic lice?

Answer 6

Malathion 0.5%. Apply to dry hair and wash out after at least 2, and preferably, 12 hours ie overnight
• Permethrin 1% cream rinse. Apply to damp hair and wash out after 10 minutes
• Phenothrin 0.2%. Apply to dry hair and wash out after 2 hours
• Carbaryl 0.5 and 1% (unlicensed indication). Apply to dry hair and wash out 12 hours later

Question 7

How to treat pubic lice in eyelashes?

Answer 7

Infestation of eyelashes can be treated with permethrin 1% lotion
Keeping the eyes closed during the 10 minute application

Alternatively, an inert ophthalmic ointment with a white or yellow paraffin base such as simple eye ointment BP may be applied to the eyelashes twice daily for 8-10 days

This works by suffocating lice and avoids any risk of eye irritation by topical insecticide.

Question 8

What is the management of partners of patients with pubic lice?

Answer 8

Current sexual partners should be examined and treated

Question 9

What is the PN for pubic lice?

Answer 9

Contact tracing of partners from the previous 3 months should be undertaken

Question 10

Is follow up of pubic lice advised?

Answer 10

YES

Patients should be re-examined for absence of lice after 1 week

Question 11

What to do if treatment failure of pubic lice?

Answer 11

• Treatment failures should be given an alternative
• It should be explained to patients that dead nits may remain adherent to hairs. This does not imply treatment failure and the nits can be removed with a comb designed specifically for that purpose.

Question 12

Aetiology of scabies?

Answer 12

Parasitic mite
Female penetrates stratum corneum and lays eggs 1-3 daily
6 legged larvae hatch and then moult to form a 8 legged nymph

Question 13

What is lifespan of parasitic scabies mite?

Answer 13

4-6 weeks

Question 14

How do scabies mites feed?

Answer 14

On lymph and lysed tissue

Absorb oxygen through its surface

Question 15

How long can scabies mite survive outside of its host?

Answer 15

72 hours

Question 16

Classical scabies- how many mites?

Answer 16

In immunocomptent- 5-10

Question 17

What is different about norwegian scabies?

Answer 17

Found in immunocompromised or elderly
May be related to failure of sensitisation to mite antigen
Highly contagious
Honeycomb cavities in skin containing thousands of mites
Crusted lesions with hyperkeratosis over elbows, palms, knees and soles

Question 18

Most likely route of transmission of scabies?

Answer 18

Holding hands
Prolonged skin to skin
Although less likely- can remain viable on objects for 2-5 days

Question 19

Why itch with scabies?

Answer 19

Intense immunological reaction

Question 20

Where is usually affected in scabies?

Answer 20

Finger webs
Axilla
Wrists
Genitals
Buttocks
Extensor surfaces of elbows
- usually eczematous, associated with burrows

Question 21

How to diagnose scabies?

Answer 21

Identify burrows
Stain sites with washable felt tip
After washing, ink in burrow- delineated

Apply tetracycline- wash off excess
Burrows retain it
Shine under woods light where it will fluoresce

Microscopy- extract mites with needle

Question 22

What to tell patents about scabies treatment?

Answer 22

Wash clothes/bedding >50 degrees
Head to toe treatment
Minimum 12 hours
Repeat 1 week
Wash hands- reapply

Permethrin 5%
Malathion 0.5%

Ivmectin- norwegian

Question 23

Pubic lice- what is life cycle?

Answer 23

The nit- white oval egg attached to hair base

The nymph- resembles pubic louse but smaller
Hatches in 7 days
Migrates back to hair base to suck blood and mature

Adult- 1-2mm in length
3 pairs of claws with claw like appendages
Sensory attune that detect human smell
Almost blind- photophobic
Buries sharp mouthpiece stylets inside pubic hair follicle to get constant blood supply
Female lays 2-3 eggs / day
15-50 eggs over a lifetime

Question 24

Treatment of pubic lice

Answer 24

Malathion 0.5%
Permethrin 1%
Aqueous better than alcohol
Lotion better than shampoo
Repeat 7 days
Leave on 12 hours
Dead nits- fine tooth comb
Wash clothes etc >50 degrees

Question 25

Incubation period for scabies?

Answer 25

Reinfection incubation is 24-48 h

1st infection incubation is 4-6 weeks due to delayed type 4 hypersensitivity