1. Chapter 17
Infestation

2. Generalised itching/Pruritus
Definition: unpleasant sensation that causes the desire or reflex to scratch
Causes
Infections and infestations
Dermatological disorders
Medical disorders
Drugs (diuretics, morphine)
Psychiatric disease

3. Infestations
Scabies
Head lice
Pubic lice
Body louse
Dermatological disorders
Xerosis (dry skin)
Skin conditions
Psoriasis
Eczema
Sunburn
Athlete's foot
Hidradenitis suppurativa…
Medical disorders
Malignancy |(lymphoma, Hodgkin's disease)
Diabetes Mellitus
Liver diseases (jaundice and Cholestasis)
Renal diseases
Thyroid illness.
Hyperparathyroidism
Polycythemia, esp. after hot path.
Uraemia.
Iron deficiency anemia.
Menopause

4. Infestations Presence of animal parasites on or in the body
2 main groups, caused by:
Arthropods
Worms

5. Pediculosis (Lice infestations)
Flattened wingless insects
Suck blood
Nits: eggs, attached to hairs or clothing
Features:
Severe itching
Followed by scratching and secondary infection
2 species, obligate parasites in humans:
Pediculus humanus
P. humanus capitis (head louse)
P. humanus corporis (body louse)
Phthirus pubis (pubic louse)

6. Head lice Up to 10% of children Peak: 4 - 11 years,
More common in girls
Typical infested scalp will carry about 10 adult lice
Adult lice
3–4 mm in length
Greyish
Hard to find
Nits
Seen easily
Firmly stuck to the hair shafts
Spread from person to person
Head-to-head contact
Shared combs or hats.
Fig Head louse. Blood from a recent meal can be seen in the gut of this adult louse.

7. Presentation and course
Itching (may take several months to develop)
At first the itching is mainly around the sides and back of the scalp:
Later it spreads generally over the scalp.
Followed by scratching and secondary infection
Heavy infestations, the hair becomes matted and smelly.
Lymphadenopathy: draining lymph nodes often enlarge.
Complications:
Secondary bacterial infection
DDx:
Recurrent impetigo
Crusted eczema
Investigations: None are usually required
Finding of living moving lice means current and active infestation
Empty egg (past infestation, need periodic re-inspection)

8. Treatment
Malathion (sticking to the hair and so protecting against re-infection for 6 weeks)
Carbaryl
Permethrin
Lotion ( better than shampoo) should remain on the scalp for at least 12 h
Pediculicide is more effective than physical methods.
Toothcomb (remove nits)
Systemic antibiotic (severe secondary infection)
Pillow cases, towels, hats and scarves should be laundered or dry cleaned.
Other members of the family and school mates should be checked.
Systemic ivermectin (resisting cases)

9. Body lice Uncommon More in the unhygienic and socially deprived
Like the head louse
Lays its eggs in the seams of clothing
Transmission is via infested bedding or clothing.
Presentation and course
Self-neglect
Severe and widespread itching, esp. on the trunk.
The bites are obscured by excoriations and crusts
Vagabond’s disease
Chronic untreated cases
Skin becomes generally thickened, eczematized and pigmented
Lymphadenopathy

10. DDx:
Scabies
Eczema
Lymphomas
Investigations:
Clothing examined for the presence of eggs in the inner seams.
Treatment:
Treat the infested clothing & bedding (lice & eggs can be killed by high temperature laundering, dry cleaning and tumbledrying).
Less competent patients
5% permethrin cream
1% lindane lotion

11. Pubic lice Crabs are broader than scalp and body lice
Their 2nd & 3rd pairs of legs are well adapted to cling on to hair
Spread by sexual contact
Most commonly infest young adults
Presentation:
Severe itching in the pubic area
Followed by eczematization and secondary infection.
Small blue–grey macules of altered blood at the site of bites
The shiny translucent nits are less obvious
Spread most extensively in
Hairy males
May even affect the eyelashes

12. Eczema of the pubic area Investigations:
DDx:
Eczema of the pubic area
Investigations:
For other sexual transmitted diseases
Fig Pediculosis pubis. Numerous eggs (nits) can be seen on the plucked pubic hairs.

13. Treatment Carbaryl Permethrin Malathion
They should be applied for 12 h or overnight
Applied to all surfaces of the body (perianal area, limbs, scalp, neck, ears and face especially the eyebrows and the beard)
Treatment ahould be repeated after 1 week
The infected sexual partners should also be treated
Shaving the area is not necessary.
Infestation of the eyelashes
Hard to treat
Applying a thick layer of petrolatum twice a day for 2 weeks
Patients should avoid close bodily contact until be treated

14. Scabies Caused by the mite Sarcoptes scabiei var. hominis
More in poverty, overcrowding and poor hygiene areas
Adult mites is 0.3–0.4 mm long (visible by lens)
Transferred from person to person by
Close bodily contact
Not via inanimate objects
Fertilized female mites can
Move at up to 2 cm/min
Burrow through the stratum corneum 2 mm/day.
Produce 2-3 oval eggs each day, which turn into sexually mature mites in 2–3 weeks
Cause of itching (mite itself or it’s products)
adult female acarus

15. Presentation 1st infestation: Itching after 4–6 weeks Bad at night
+ve family history
2nd attack:
Itching starts within 1-2 day (already have immunity)
Excoriated, eczematized or urticarial papules, usually on the trunk & marks feeding spots
Burrows (diagnostic)
erythematous rubbery nodules (genitals)
The acarus may be seen through a lens as a small dark dot at the most recent least scaly end of the burrow. With experience it can be removed for microscopic confirmation

16. Typical burrows seen on the side of the thumb.
Easily missed
Grey–white
Slightly scaly
Tortuous lines
Up to 1 cm in length

17. Most burrows lie on the
Sides of the fingers
Finger webs
Sides of the hand
Flexural aspects of the wrists
Elbows
Ankles
Feet (especially in infants)
Nipples
Genitals (rubbery pink nodules)
Face (only in infancy)

18. Fig. 17.6 The characteristic plantar lesions of scabies in infancy.

19. Fig. 17.8 Unmistakable rubbery nodules on the penis, diagnostic of scabies.

20. Course:
Scabies persists indefinitely unless treated.
Chronic stage  diagnosis is difficult(small no. of mites).
Relapses are common (from untreated contacts).
Complications:
Secondary infection with pustulation is common( Rarely GN)
Skin irritation and eczema (repeated applications of scabicides).
Persistent itchy red nodules may remain on the genitals or armpits of children for some months after adequate treatment.
Venereal disease may be acquired at the same time as scabies.
Crusted (Norwegian) scabies
May not be itchy
Widespread crusted eruption
Vast numbers of mites are found
Affects people with mental retardation / immunosuppression.

21. Fig. 17.9 Scabies with bacterial superinfection.

22. DDx:
Animal scabies from pets (itchy rash without burrows).
Papular urticaria (excoriated papules, groups, legs).
Late-onset atopic eczema
Cholinergic urticaria
Lichen planus
Neurotic excoriations
Dermatitis herpetiformis
Investigations:
Microscopically can be seen:
Acarus (picked with a needle from the end of its burrow)
Eggs and mites from burrow scrapings mounted in KOH or mineral oil.
Dermatoscopy a quick and reliable way to find the mite.

23. Treatment Permethrin or malathion (2nd choice)
Topical treatment plus ivermectin (200 μg/kg by mouth), is effective for
Norwegian scabies
Unresponding scabies
Calamine lotion (itching)
Started if the diagnosis seems likely on clinical grounds
Treat all members of the family & sexual contacts (whether itching or not)
Scabicide must be applied to all areas below the neck
The scabicide should be re-applied if the hands are washed.
A 2nd application, a week after the first, is then essential.
Mites d
For babies, toddlers and children up to 2 years we use
Permethrin cream + 25% benzyl benzoate emulsion diluted with 3 parts of water
6-10% sulphar in white soft parfine (vazline).
ie in clothing unworn for 1 week.