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Arthropods Attacks I IHAB YOUNIS, M.D.

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Presentation on theme: "Arthropods Attacks I IHAB YOUNIS, M.D."— Presentation transcript:

1 Arthropods Attacks I IHAB YOUNIS, M.D.

2 Etymology: L. [scabo,] to scratch
Scabies Etymology: L. [scabo,] to scratch

3 History " The seven year itch" was first used with
reference to persistent,undiagnosed infestationswith scabies Scabies has been reported for more than 2500 years

4 Aristotle discussed “lice in the flesh”
Celsus recommended sulfur mixed with liquid pitch as a remedy for the disease The disease was first ascribed to the mite by Bonomo in 1687 It was the first human disease recognized to be caused by a specific pathogen

5 Etiology About 300 million cases occur annually
Prevalence is higher in children and sexually active individuals It affects persons of all ages, races, and socioeconomic groups

6 Causative agent The Female Gravid Sarcoptes scabiei mite, var hominis
G: sarx (the flesh) and koptein (to cut)

7 Life cycle The entire life cycle of the mite lasts 30 days and is spent within the human epidermis After copulation, the male mite dies and the female mite burrows into the superficial skin layers and lays a total of eggs The ova require 10 days to progress through larval and nymph stages to become mature adult mites

8 Mites can survive up to 3 days away from human skin, so fomites such as infested bedding or clothing are an alternate but infrequent source of transmission Mites move through the top layers of skin by secreting proteases that degrade the stratum corneum creating burrows They feed on dissolved tissue but do not ingest blood

9 An affected individual harbors a variable number of living mites (10-15(
In immunocompromised hosts the number of mites can exceed 1 million (crusted scabies) Symptoms appear 2-6 weeks after infection as delayed-type IV hypersensitivity reaction to the mites, eggs, and scybala (packet of feces) occurs In reinfestation, the sensitized individual may develop a reaction within hours

10 Mode of transmission Epidemics or pandemics may occur in 30-year cycles Transmission is predominantly through direct skin-to-skin contact(10 minutes) Indirect contact through fomites such as infested bedding or clothing is possible, although not usual

11 Clinically The history is very important
Intractable pruritus that is worse at night Similar symptoms in close contacts History of itching for a short time. On the other hand, the infestation can persist indefinitely Occurs more commonly in fall and winter

12 A short (2-3 mm), elevated, serpiginous , gray brown track in the superficial epidermis, known as a burrow, is pathognomonic Occasionally, the mite is visible to the naked eye as a small white dot A small vesicle or papule may appear at the end of the burrow

13 Distribution Any pruritic papule on the penis or female
areola of breast or palms & sole of foot in an infant is scabies until proved otherwise

14 Scabies in infants tends to be more disseminated affecting head and face
Geriatric scabies demonstrates a propensity for the back, often appearing as excoriations

15 One- to 3-mm erythematous papules and vesicles are seen in typical distributions in adults and most likely represent a hypersensitivity reaction In very young children and infants, a widespread eczematous eruption primarily on the trunk is common



18 Histopathology

19 If a burrow is excised, mites, larvae, ova, and feces may be identified within the keratin
A superficial and deep dermal infiltrate composed of lymphocytes, histiocytes, mast cells, and eosinophils Spongiosis and vesicle formation with exocytosis of eosinophils

20 Crusted scabies demonstrates massive hyperkeratosis of the stratum corneum with innumerable mites in all stages of development Psoriasiform hyperplasia of the underlying epidermis with spongiotic foci and occasional epidermal microabscesses is present

21 Types 1-Crusted Scabies (Norwegian):
First described in 1848 by Danielssen and Boeck, who considered the disease to be a form of leprosy endemic to Norway May occur in almost any area of the body including the scalp Occurs in immunocompromised persons and in weak patients who can not scratch

22 Extensive, widespread, crusted lesions appear with thick, hyperkeratotic scales over the elbows, knees, palms, and soles Itching is minimal Serum IgE and IgG levels are extremely high


24 2-Animal scabies is characterized by absence of burrows since the animal mites cannot adapt themselves to human skin It is not transmitted from one human being to another

25 3-Scabies in the clean The disease is easily misdiagnosed because lesions are sparse and burrows are difficult to find

26 4-Scabies incognito Topical or systemic steroids may mask symptomsand signs of scabies, although the infestation remains freely transmissible This often results in unusual clinical presentations such as atypical and wide distribution

27 5-Nodular scabies Reddish-brown, pruritic nodules on covered parts (most frequently the male genitalia, groin, and axillary regions) Probably represents a hypersensitivity reaction to retained mite parts or antigens

28 6-Bullous scabies May mimic bullous pemphigoid clinically, pathologically, and immunopathologically Most patients are over 65 years of age. The duration of the scabies from onset until diagnosis is weeks to months, thereby exposing a number of individuals to the disease Burrows are present in most cases

29 complications Secondary bacterial infection may occur Nephritogenic
streptococcal strains may colonize scabietic lesions, leading to acute glomerulonephritis

30 Eczema, particularly in atopics, may be prominent in the active scabies and may continue as eczema after the scabies has cleared Acarophobia

31 Immunology Delayed:T-lymphocytes in inflammatory lesions
High IgG, IgM and IgA returning to normal after treatment IgM and C3 deposits at the DE junction in burrows

32 Lab tests Skin scraping: Place a drop of mineral oil on a glass slide, touch a No. 15 blade or a 7-mm curette to the oil, and scrape infested skin sites, preferably primary lesions such as vesicles, juicy papules, and burrows cover with a coverslip, and examine under a light microscope at 40X magnification

33 Multiple scrapings may be required to identify mites or their products
Multiple scrapings may be required to identify mites or their products. Persistence is key to accurate diagnosis Crusted scabies: Add 10% potassium hydroxide (KOH) to the skin scraping. This dissolves excess keratin and permits adequate microscopic examination

34 Treatment

35 Permethrin cream 5% (Ectomethrine)
Causes respiratory paralysis of parasite Recommended by CDC as first-line therapy Apply from chin to toes and shower off h later; repeat in 1 wk Not recommended for children <2 mo C - Safety for use during pregnancy has not been established More effective than a single dose of oral ivermectin, although it has equivalent efficacy when 2 doses of ivermectin are used at time zero and 2 weeks later

36 Lindane (Scabene) Stimulates nervous system of parasite, causing respiratory paralysis Second-line treatment if other agents fail or are not tolerated Not very safe in children as transcutaneous absorption leading to neurotoxicity Apply thin layer from chin to toes; use on dry skin and shower off 10 h later; repeat in 1 wk

37 Infants and children: Apply as adults but leave on 6-8 h before washing off and do not exceed 30 g/application Oil-based hairdressings may increase toxicity Safety in pregnancy:B - Usually safe but benefits must outweigh the risks

38 Sulfur in petrolatum (2 -10%, with 6% preferred)
May be used safely without fear of toxicity in very small children and in pregnant women It is malodorous, stains clothes & requires repeat applications, thus reducing compliance. It can cause a dermatitis in hot and humid climates Apply to entire body below head on 3 successive nights and bathe 24 h after each application

39 Crotamiton (Eurax) Mechanism of action is unknown
Apply thin layer onto skin of entire body from neck to toes; repeat in 24 h; take a cleansing bath 48 h after last application Do not apply to face, urethral meatus, eyes, mucous membranes, or swollen skin; can cause seizures

40 Benzyl benzoate(Benzanil)
Neurotoxic to mites Use 25% emulsion; apply below neck 3 times within 24 h without an intervening bath Safety in pregnancy:X - Contraindicated in pregnancy May cause stinging, if so reduce concentration

41 Ivermectin (Ivactin 6 mg tab)
Binds selectively with glutamate-gated chloride ion channels in invertebrate nerve and muscle cells, causing cell death 2 mg/10kg/d PO as single dose May cause nausea, vomiting, and mild CNS depression; may cause drowsiness

42 Etymology: L. [pediculus] louse +
Pediculosis Etymology: L. [pediculus] louse + G. [-osis] condition

43 Types Pediculosis capitis Pediculosis corboris Pediculosis pubis

44 Pediculosis capitis

45 Etiology The disease is spread from person to person by close physical contact or through fomites (eg, combs, clothes, hats, linens) Overcrowding encourages the spread of lice Head lice are very rare among negros due to the twisted nature of the hair shaft

46 Causative agent Pediculus humanus capitis (head louse)
Lice are ectoparasites that feed on human blood several times daily They have claws on their legs that are adapted for feeding and clinging to hair or clothing They move quickly(up to 23 cm/min) , which explains their ease of transmission

47 A fertilized female louse lays about 10 eggs a day for up to a month until it dies
The eggs (nits) are attached to the hair shaft, close to the skin surface, where the temperature is optimal for incubation Nits are cemented to the hair shaft with chitin and are very difficult to remove. Nits can survive for up to 10 days away from the human host

48 The eggs hatch in about 6-10 days
Lice develop into adults in 19 to 25 days from the time the egg is laid Live nits are fluorescent white when illuminated with a Wood’s lamp; empty nits are fluorescent gray

49 Clinically Itching is the most common symptom
Erythema and scaling may be present, as well as pruritic papules on the posterior neck There may be linear excoriations at the periphery of the hair area which frequently lead to pyoderma Cervical lymphadenopathy and febrile episodes are not uncommon


51 Pediculosis corporis

52 Etiology Infestations of body lice are found mainly in those with low income and poor hygiene, and homeless persons and refugees living in crowded conditions The infestation is transmitted chiefly by contaminated clothing or bedding

53 Causative agent Pediculus humanus corporis (body louse)
It is similar to the head louse but a little larger Body lice and their eggs are predominantly found on clothing and should be looked for in the seams of clothes

54 Early lesions consist of macules or papules at the site where the louse punctures the skin to obtain blood The characteristic eruption consists of numerous vertical excoriations, especially on the trunk and neck, caused by intense itching Crusts and at times pus or serum may stain the underclothing Transitory wheals and bacterial infections may complicate the process


56 Postinflammatory pigmentation is common
Few or no adult organisms are seen except in heavily infested persons Nnumerous nits are found in clothing seams, particularly in contact with the crotch, armpits, belt line, and collar

57 Pediculosis pubis

58 Etiology It is typically transmitted sexually, frequently coexisting with other sexually transmitted diseases Pubic lice were found in 1.7% of men and 1.1% of women in an STDs clinic

59 Causative agent Pthirus pubis (pubic or crab louse)
It is much shorter than other lice, being almost as wide as it is long

60 Lice have three pairs of legs
Lice have three pairs of legs. In the crab louse, the first set of legs terminates in a slender claw, while the second and third pairs have well-developed claws perfectly adapted for grasping the coarse, widely spaced hairs of the pubis It is sluggish, travelling a maximum of 10 cm/day

61 Clinically Pubic hair is the most common site
The crab louse is found firmly attached to the base of the pubic hair. Nits may also be found Pubic lice may spread to hair around the anus, abdomen, axillae, chest, and eyelashes Bluish grey macules, or maculae cerulea, may be seen on the abdomen or thighs and are secondary


63 Diseases transmitted by lice
Typhus: Caused by Rickettsia prowazekii high fever, petechial rash,CNS involvement Trench fever: Caued by Bartonella quintana fever similar to typhus, infective endocarditis Relapsing fever: Caused by the spirochete Borrelia recurrentis relapsing fever,rash

64 Treatment

65 General measures Nits are best removed with a very fine comb
Soaking the hair in a solution of equal parts water and white vinegar and then wrapping the wet scalp in a towel for at least 15 minutes may facilitate removal Treat all family members Discard infested clothing or wash in very hot water

66 Shaving of the scalp or body hair eradicates lice; if cosmetically acceptable by the patient
Wet combing or application of diluted vinegar or commercial preparations of 8% formic acid may help in the removal of nits or at least make the combing easier. Plastic or the sturdier metal nit combs may be used Multiple lice suffocation agents have been advocated, but most have not been scientifically evaluated. These include Vaseline; petroleum jelly; oils; mayonnaise

67 Drug therapy Treatment should be repeated in 7-10 days (the time needed for the eggs to hatch) because nits are less effectively killed than adults All contacts should be treated simultaneously Resistance to pediculicides has increased over recent years. Therapeutic agents can be rotated to slow the emergence

68 Same drugs as for scabies but:
Permethrin 5% :leave 5-10 min, then rinse Lindane 1% shampoo: Apply to dry head or pubic hair and surrounding areas; allow to set for 4 min, then lather for 4 min and rinse; repeat in 7 d prn

69 Malathion (Prioderm) : Irreversible cholinesterase inhibitor that is hydrolyzed and, therefore, detoxified rapidly by mammals but not by insects causing respiratory paralysis Ovicidal and pediculicidal. Binds to hair and provides some residual protection after therapy Available as 0.5% and 1% lotion

70 Apply lotion to dry hair; leave on 8-12 h, rinse; repeat in 7 d prn(as needed)
Contains flammable alcohol; do not expose lotion or wet hair to open flame or electric heat, eg, hair dryers (allow hair to dry naturally and uncovered following application); avoid contact with eyes (flush eyes immediately with water if contact)

71 Trimethoprim-sulfamethoxazole
The mechanism of action is postulated to be ingestion of the antibiotic by the louse as it takes its blood meal; subsequently the antibiotic kills the gut flora of the louse, with death ensuing from a deficiency of B vitamins The combination of permethrin and trimethoprim-sulfamethoxazole was more effective than either agent alone

72 Mercuric oxide Ointment (1%) is treatment of choice for Phthirus palpebrarum
Inspect eyelids and remove nits mechanically Apply to eyelashes qid for 14 d

73 Kerosene has shown pediculicidal activity in vitro, but safety and efficacy remain to be evaluated
DDT was the first pediculicide widely available. It was the main agent used in the treatment of body lice infestations during World War II. It was banned in the 1970s but about to be reintroduced as pesticide

74 Treatment failures Drug resistance
Improper dilution or duration of application Reinfestation from untreated contacts It may be best to assume that no product is reliably ovicidal and that patients will not comply fully with instructions. Retreatment in 1 week to 10 days is advisable to kill recently hatched nymphs

75 Drugs are often applied to wet hair, which dilutes the product and protects lice as they reflexively close their respiratory spiracles when exposed to water Hair conditioners may coat the hair shafts and prevent pediculicides from binding adequately to the hairs

76 Lice have been in existence for thousands of years
Lice have been in existence for thousands of years. Their extinction seems no more likely than our own

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