diseases caused by arthropods and Scabies

1. diseases caused by arthropods
&
Scabies
DR.UDAY

2. Arthropods
• Largest group in animal kingdom (80 % of all living animal species).
• Invertebrates with segmented bodies & jointed limbs .
 A hard outer body covering called an exoskeleton.
 Specialized mouth parts.

3. animal kingdom
Phylum Arthropoda
Class Insecta
Mosquitoes
Flies
Fleas
Bees, wasps, ants(hymenoptera)
Lice
Bugs (hemiptera)
Beetles (coleoptera)
Cockroaches (Dictyoptera)
Butter flies and moths (Lepidoptera),
Class Arachnida
Mites (Acari), Ticks (Acari),
Spiders (Araneae),
Scorpions (Scorpiones),
Class Chilopoda (centipedes)
Diplopoda (millipedes),

4. Classification
based on mechanism of disease they cause
Parasitic
arthropods
 Human parasites .
 That live most of their lives on or in the host.
 Eg- Lice , mites.
Stinging
arthropods
 Primarily use their stings to subdue prey & rarely offensively.
 The reaction to these stings ranges from pain and mild local edema to exaggerated reactions
that may last for days.
Eg- honeybees ,paper wasps , fire ants
Biting
arthropods
 Insects that bite humans.
 Eg- Bed bugs, horse flies , deer flies ,spiders , centipedes.
Dermatitis
producing artropods
 Cause blistering on human skin when touched & handled.
 Eg- Blister beetles, millipedes.
Arthropod
vectors
 Act as vectors for various diseases.

5. Arthropods act as vectors for various diseases.
• House fly
(musca domestica ,Musca
vicinia)
Typhoid & paratyphoid fever,
diarrhea , dysentery ,
cholera, gastroenteritis,
amoebiasis ,
helminthic infestations,
poliomyelitis,
conjunctivitis , trachoma
anthrax,
Sand-fly
Phlebotomus argentipes- kala-azar
Phlebotomus papatasii-sandfly fever
oriental sore
Mosquito
Anopheles-Malaria
Culex –bancroftian filariasis
Japanese encephalitis
west nail fever
Aedes- yellow fever (note India)
Dengue,
Dengue hemorrhagic
fever
Chikungunya fever
Tsetse fly -- Sleeping sickness
Hard tick
Tick typhus,
viral encephalitis,
viral fevers ,
viral hemorrhagic fever,
Bugs
Reduviid bugs –chagas disease
(Mexico ,South America)
Soft tick
Q fever,
relapsing fever,
Louse
Pediculus humanus capitis, - the head louse,
Pediculus humanus humanus, - the body
Phthirus pubis,- the pubic, or crab, louse.
Causative agent disease
Rickettsia prowazeki - Epidemic typhus
Rickettsia Quintana - Trench fever
excoriations noted on the scalp.
Secondary impetigo is common.

6. PAPULAR URTICARIA
• Chronic or recurrent eruption of pruritic papules.
• 3-10 mm,sometimes surmounted by vesicle , excoriation.
• Present on exposed areas (extensor surface of arms & legs).
• 2-7 year children
• Allergic hypersensitivity reaction to arthropod bite.
like- cat flea (centocephalides felis),
dog flea (centocephalides canis ),
human flea (pulex irritans) ,bed bugs,
mosquitoes & various mites.
• Papules may last from week to months.
• Usually in summer months, low socioeconomic groups.
• Seen with greater frequency among households with pets.
TREATMENT
 Identification & removal of cause
 Mild tropical steroids & systemic antihistamines
 Oral antibiotics for secondary infection
 Disinfection of pets along with fumigation of the home
 Patients should apply insect repellent to skin before they go outdoor
D/D-
• Scabies
• Urticaria
• Papular drug eruption
• Allergic contact dermatitis
• Atropic dermatitis
• Miliaria rubra

7.  Scabies
• caused by Sarcoptes scabiei var hominis (female gravid)
first described by the Italians Bonomo and cestoni in 1689 .
Phylum - Arthropod
Class - Arachnida
Subclass - Acari (Acarina)
Order - Astigmata
Family - Sarcoptidae
Genus - Sarcoptes
Species - Sarcoptes scabiei

8. Agent Factors-
Female mite Male mite
0.4 mm long 0.2mm long
0.3mm broad 0.15mm broad
four pairs of short legs; four pairs of short legs;
anterior two pairs end in elongated peduncles
tipped with small suckers
anterior two pairs end in elongated peduncles
tipped with small suckers
rear two pairs of legs end in long bristles bristles on the third pair
peduncles with suckers on the fourth pair
Creamy white color with brown sclerotized legs mouthparts.
 Body is oval.
 Dorsally convex and ventrally flattened.
on its dorsal surface by bristles and spines (denticles)
eggs and smaller fecal particles
Sarcoptes scabiei Female mite)

9. • life span 4–6 weeks; lays 40–50 eggs.
• Lays3 eggs per day in burrows;
• eggs hatch in 4 days. Burrow 2–3 mm daily, usually at night,
• lay eggs during the day.
The mites may crawl as fast as at the rate of 2.5cm/min on warm skin.

10. Host factors-
• -Scabies is most common in children and young adults, but may occur at any age.
Environmental factors
- Overcrowding,
- poverty and poor hygiene,
- close physical contact,
- sharing of clothing or bedding encourages the spread .
• Away from the host, scabies mites survive for 24–36 h at room conditions .
(21°C and 40–80% relative humidity)
• High humidity and low temperature favor survival, whereas high temperature and
low humidity lead to early death.

11. Life cycle of sarcoptes scabiei
MALE AND
FEMALE MITE
Lays Eggs
(40-50 eggs/life time)
Eggs (burrow)
Hatch in to larva
Moult into
protonymphs
Moult into
tritonymphs
Mite in burrow live in stratum corneum
Burrow at the rate of 0.5-5mm/day,
When male &female mites meet they mate in the burrow
Larva makes its way to skin surface and
Feed on skin debris in hair follicles and
the larva makes molting pocket
3days
10-13 days
2- 3days
Mite come in contact with skin it exudes a fluid ,
that dissolves skin surface, forming a well into which it sinks
after 50-53 hours

12. Immunology
• Allergic sensitivity to the mite or its products appears to play an important role in determining
the development of lesions other than burrows, and in producing pruritus.
• Evidence suggests that both immediate and delayed-type hypersensitivity are involved.
• During first infestation, pruritus occurs after sensitization to mite, usually within 4–6weeks.
• After reinfestation, pruritus may occur within 24 h
Other immunological findings include -
• high serum IgG and IgM,
• low IgA , } - levels returning to normal after treatment.

13. Types of scabies- • Classical scabies
• Scabies in clean
• Scabies incognito
• Infantile scabies
• Crusted scabies
• Nodular scabies
• Bullous scabies

14. C/F - (Classical scabies)
Symptoms - Generalized itching more severe at night, (nocturnal itching)
pruritic with skin rash
- Family members affected
Sign - papular lesions,
excoriations, and burrows.,
crusting , pyoderma,
vesicles are a prominent feature which may lead to blister formation .
Sites of predilection-
 the webs of the fingers ,flexor aspects of the wrists, elbows, anterior axillary folds,
umbilicus and periumbilical region, genitalia, and upper thighs, knees and ankles
 Adults, the scalp and face are usually spared,
 In infants lesions are commonly present over the entire cutaneous surface.
The lower parts of buttocks and natal cleft, scalp, face , palms, and soles are characteristically.
”.

15. the circle of Hebra
Common
sites
Burrows are most easy to identify on the web space of the hands, wrists, lateral aspects of the palms.
Scabietic nodules occur uncommonly, arising on the genitalia, especially the penis and scrotum, waist, axillae, and areolae.

16. Papules and burrows in typical location on the finger web.
(Burrows are tan or skin-colored ridges with linear configuration with a
minute vesicle or papule at the end of tunnel .)
Papulesburrows
multiple burrows

17. Scabies incognito
 The inappropriate use of topical steroids-
modify c/f of scabies ,mimic other dermatoses.
While corticosteroids reduce the itching ,
the Inflammatory lesions, the mite population increases.
Symptoms & signs while the infestation &transmissibility persist.
• The suspicious of scabies ,family history &response to t/t give a clue to diagnosis.
Infantile scabies
• m/c-Head, neck, palms, soles, secondary bacterial inf., vesicles found.
• The presence of lesions in mother gives a clue in many cases.
• vesicular and vesiculo pustular lesions on the hands and feet are frequent,
extensive eczematization is often present, and there may be multiple crusted
nodules on the trunk and limbs.

18. Crusted scabies (Norwegian Scabies)
hyperkeratotic scabies
• Severe variant of scabies ,highly contagious.
• Can easily trigger an epidemic of scabies.
• Itching is minimal or absent .
• It present as an eruption, slow in onset & insidious in progression.
• Typically in pt. with defective T-cell immune response.
• Characterized by hyperkeratotic ,scaly and crusted lesions
with large number of mites in them.
• lesions are seen on the scalp, face, palms, soles, neck,
and lumbosacral area. The helix of the ear is commonly involved.
• diagnosis by scraping and microscopy is easy because of the
high mite population ( over 1million/person).

19. Nodular scabies
• Lesions are reddish ,brown ,pruritic nodules , 5-8mm size.
• m/c in covered parts of body (groin, genitalia axillary region).
• Scabicides followed by intralesional steroids tar,
or excision are methods of treatment .
Bullous scabies
Present as intensely pruritic bullae on the extremities.
• Seen in school going age.
• Bullous lesions may contain many eosinophil ,
resembling bullous pemphigoid.
Nodular scabies in the axilla

20. Differential Diagnosis of Scabies
• Atopic dermatitis
• Dyshidrotic eczema (Pompholyx)
• Pyoderma
• Contact dermatitis
• Insect bite reaction
• Dermatitis herpetiformis
• Psoriasis
• Bullous pemphigoid
• Drug eruption
• Systemic causes of pruritus
• Delusions of parasitosis

21. Diagnosis
The four cardinal features in the clinical diagnosis are:
• The presence of the burrow, especially on the hands or penis.
• The characteristic distribution pattern of lesions.
• The presence or history of similar illness in other members of the household or
other contacts.
• Intense pruritus, which tends to worsen at night.

22. suggestive feature -
• Nocturnal pruritus, contact case
• Burrows are pathognomonic but seen less frequently.
To identify burrows -
(Burrows are tan or skin-colored ridges with linear configuration with
a minute vesicle or papule at the end of tunnel )
• quickly, a drop of India ink or gentian violet
can be applied to the infested area, then removed with alcohol.
Thin thread-like burrows retain the ink.
burrow

23. Diagnostic feature
Microscopic study
• surgical blade or sterile needle is used to remove the parasite. A drop
of mineral or immersion oil can be placed on a lesion and gently
scraped with the epidermis beneath it.
• Positive diagnosis is made only by the demonstration of the mite ,
eggs, fecal pellets (scybala) under the microscope .
• A burrow is sought and the position of the mite is determined.

24. TREATMENT-
- Treating the infestation with a scabicide ,
-Provide symptomatic relief with an antihistamine,
-Prevent of transmission and reinfection.
Drug Dose
• Permethrin 5% cream Apply for 8 hours, repeat in 7 days,
• Gamma benzene hexa chloride
1% lotion or cream Apply for 8 hours, repeat in7 days,
• Crotamiton 10% cream Apply for 8 hours on days 1,2, 3, and 8,
• Precipitated sulfur 5%–10% Apply for 8 hours on days1, 2, 3,
• Benzyl benzoate 10% lotion Apply for 24 hours,
• Ivermectin 200 μg/kg Taken orally on day 1 and 8.
• the rash and pruritus may persist for up to 4 weeks Instead, oral antihistamines and emollients
can be beneficial.

25. Treatment of scabies in special situation-
Drugs indicated Contraindicated
Pregnancy & lactation • 6% sulfur precipitate (Apply for 8 hours on days1, 2, 3)
• Permethrin
• Benzyl benzoate
• Ivermectin
• Gamma benzene hexa
chloride
Scabies in infants • Sulfur 2% ─10% in petrolatum
• > 2months – permethrin 5% cream
• Ivermectin
• Gamma benzene hexa
chloride
Scabies in children • permethrin 5% cream
• 12.5% benzyl benzoate emulsion
• Gamma benzene hexa
chloride
Nodular scabies Scabicides followed by intralesional steroids
Crusted scabies • Prolonged & persistent treatment
• Both oral (ivermectin) and topical scabicidal agents
• Keratolytic agents (5%-10% salicylic acid in petrolatum)

26. Instruction to parents/patients
• Medication should be rubbed in to the skin and all body parts.
• Topical agent should applied on clean & dry skin.
• Treatment is best done at night before going to bed.
• Change your under clothing & sheet Next day & launder them.
(i.e. washout ,dry & should be iron.)
• Everyone in the house should be treated at same time.
• Itching may persist for few days after treatment ,but never re-apply the medication
without doctor’s advice.
• Constantly retain the medicine out of reach from the minors.

27. Treatment failure -
The t/t can fail because of various reasons-
• Improper application-
-frequently made mistake ,drug applied only to the affected area.
• Inadequate application-
-drug dispensed should be used as such & it should not be diluted .
(when drug such as Gamma benzene hexa chloride are diluted ,their efficacy is reduced.)
• Reinfestation-
-common problem ,because of failure to treat contact cases,
• Resistance - to Gamma benzene hexa chloride ( reported in Peru,Panama,New Nealand,US,)
- it should be considered only if all the other causes for t/t failure are ruled out.
- In such areas combination of Gamma benzene hexa chloride &
benzylbenzoate or permethrin can be used .

28. Complication of scabies -
• Superadded bacterial infection -
–manifest as hundreds of crusted, purulent sores (ecthyma)
- clustered in scabies susceptible sites.
- Bullous impetigo- infection with staphylococcus aurous.
- Cellulitis, furunculosis.
• Post streptococcal glomerulonephritis ,
• Leucocytoclastic vasculitis ,
• Lymphangitis & septicemia .

29. PEDICUL0SIS
• Kingdom- Animal
• Phylum- Arthropoda
• Class - Insecta
• Order - Phthiraptera
• Suborder- Anoplura
• Family- Pediculidae
• Genus- Pediculus
• Species- Pediculus humanus
Pediculosis, the infestation of man by lice.
Lice are blood sucking, wingless,
2mm long with 3pairs of legs.
The female louse lays 5–10 eggs / day during her 30-day life span .

30. PEDICUL0SIS
Agent Factors-
Pediculosis, the infestation of man by lice, Three species of lice infest humans:
• Pediculus humanus capitis, - the head louse,
• Pediculus humanus humanus, - the body or clothing louse,
• Phthirus pubis,- the pubic, or crab, louse.
Host factors-
• Head lice infestations are most common in children between the ages of 3 and 12.
• Transmission is by direct head-to-head contact or by indirect transmission through combs,
brushes, blow-dryers, hair accessories, pillows, bedding

31. Environmental factors
Lice typically survive less than 2 days away from the scalp, although under favorable conditions
of heat and humidity, may survive up to 4 days.
• Nits can survive for 10 days away from the scalp.
CLINICAL FINDINGS
• Pediculosis capitis is confined to the scalp with nits found most readily in the occipital and
retro auricular regions
• Patients present with intense pruritus of the scalp often have posterior cervical
lymphadenopathy & excoriations noted on the scalp.
• secondary impetigo is common.
• Pruritic papular lesions may occur on the nape of the neck, and occasionally a generalized
nonspecific pruritic eruption develops .
• Pediculosis corporis -Generalized itching is accompanied by erythematous, blue and copper
colored macules, wheals, and lichenification

32. DIAGNOSIS
-Infestations are diagnosed by demonstrating egg capsules (nits) and live lice. Nits are readily
seen by the naked eye and are an efficient marker of past or present infestation.
The color of newly laid or viable eggs is tan to brown,
the eggs that have hatched are clear, white, or light in color.
COMPLICATIONS-
Secondary bacterial infections can occur with pediculosis capitis.
pyodermas of the scalp .
Several important human diseases are transmitted by the body louse.
The major diseases include epidemic typhus (caused by a rickettsiae,R. prowazekii),
trench fever (caused by B. quintana),
relapsing fever (caused by a spirochete)

33. Treatment of Pediculosis
drugs Administration
• Pyrethrins synergized Topically for 10 minutes
• Permethrin 1%a (Nix) Topically for 10 minutes
• Permethrin 5% Topically overnight
• Malathion 0.5% Topically overnight
• Carbaryl 0.5% Topically overnight
• Topical ivermectin Topically for 10 minutes
• Ivermectin, oral 200 μg/kg Orally on days 1, 8, and 15
• Application to dry scalp and hair followed by adequate wash out with non-medicated shampoo .
• Clothing placed in a dryer for 30 min at 65°C is reliably disinfected. Pressing clothing with an iron, especially the
seams, is also effective. Permethrin spray or 1% malathion powder can be used to treat clothing and reduce the
risk of reinfestation.