Parasitic Infestations PDF

Parasitic infestations  Parasitic infestations: pediculosis Scabies Myiasis Tungiasis Cutaneous larva migrans Onchocerciasis pediculosis Pediculosis is an ectoparasitosis caused by haematogenous blood sucking ,wingless insects (lice) In humans, infestation is caused by : Pedic...

Parasitic infestations  Parasitic infestations: pediculosis Scabies Myiasis Tungiasis Cutaneous larva migrans Onchocerciasis pediculosis Pediculosis is an ectoparasitosis caused by haematogenous blood sucking ,wingless insects (lice) In humans, infestation is caused by : Pediculus humanus capitis or head louse, Pediculus humanus corporis or body louse, and Phthirus pubis or pubic louse. Clinical types (a) Pediculosis Capitis (b) Pediculosis Corporis (c) Pediculosis Pubis (a) Pediculosis capitis Synonym: Head lice. Cause: Pediculus humanus capitis. Epidemiology: Common in children Spread from person to person is achieved by head-to head contact, and by shared combs or hats. Often seen in epidemics among kindergarten and school children Also common in homeless people. Con- Pediculosis capitis Pathogenesis: Lice live on the scalp and suck blood They firmly attach their eggs (nits) to the hair shaft just at the skin surface The head louse measures some 3–4 mm in length and is greyish, and often rather hard to find Con- Pediculosis capitis Clinical features: Pruritic eruption on back of scalp and nape Excoriations and secondary infections (lice dermatitis) The hairs may become matted from repeated scratching Lice identified, especially when combing the hair Nits may be present throughout the scalp, but most common in the retro auricular region (ova close to scalp are viable). Diagnostic approach Look for nits on the hair shafts (retro-auricular) lice on the scalp. (a) Pediculosis capitis …….cont. Therapy Effective therapeutic agents must kill/remove both lice and ova. 1) Pyrethrins and the synthetic permethrin: - 1% and 5% cream - is marketed for the treatment of scabies - must be applied (10 min) after shampooing and drying the hair completely - No hair washing for 24 hours (a)Pediculosis capitis …….cont. 2) Malathion 0.5% lotion is most effective but can be irritating to the eyes. 3) Lindane (gamma benzene hexachloride) is widely used, but relatively less effective Has potential neurotoxicity if abused. 4) Crotamiton (Eurax)10% cream or lotion (a) Pediculosis capitis ……cont. Nits treatment: The nits are always a problem Many schools have rules banning children returning as long as nits are present. No treatment is available Re-treatment in a week is reasonable for all patients. Combing with a metal or plastic nit comb (fine-toothed) is an important adjunctive measure (b) Pediculosis corporis Synonym: Body lice. Cause: Pediculus humanus corporis. Epidemiology: Is primarily a disease of the unwashed “Vagabond's disease" It is common in homeless people and during wars and other disasters (b) Pediculosis corporis Pathogenesis: The lice feed on the body, but live in the clothing The parasite obtains its nourishment by descending to the skin and taking a blood meal. Lay their eggs in the seams of clothing (b) Pediculosis corporis Clinical features: Pruritus. Itching is accompanied by erythematous and copper-colored macules, wheals Excoriations and secondary infections (lice dermatitis) on trunk (vagabond skin) are common. (b) Pediculosis corporis Diagnostic approach: Look for the lice and nits on the clothing, not on the skin. Is differentiated from scabies by the lack of involvement of the hands and feet (b) Pediculosis corporis Therapy: Same pediculicides as for Pediculus humanus capitis can be used Lice may live in clothing for 1 month without a blood meal. Disinfection of clothing and bedding (boiling, hot ironing). Attempt to change living conditions. (c) Pediculosis pubis Synonym: Pubic lice. Cause: Phthirus pubis Epidemiology: Is found in the pubic region, as well as hairy areas of legs, abdomen, chest, axillae, arms Spread through close physical contact Usually transmitted by sexual contacts Con- Pediculosis pubis Clinical features: Lice and nits present in the hair The signs and symptoms are similar to those of body louse infestation. Patients usually identify moving lice on their pubic hairs associated with pruritus Nits usually on pubic hair, occasionally elsewhere C0n- Pediculosis pubis Clinical features: The feeding sites turn into distinctive blue-gray hemorrhagic macules “maculae cerulenne” are located chiefly on the sides of the trunk and on the inner aspects of the thighs They are probably caused by altered blood pigments Con- Pediculosis pubis Therapy: Malathion lotion and Permethrin cream or shampoo are the treatment of choice They kill lice and eggs effectively Malathion has the extra value of sticking to the hair and so protecting against re-infection for 6 weeks. Lindane lotion or shampoo is also effective The application should be repeated after 1 week so that any lice that survive the first application and hatch out in that interval can be killed. Scabies Introduction Scabies is an intensely pruritic skin infestation The term scabies is derived from Latin word scabere (to scratch). Prevalence rates are higher in children and sexually active individuals than in other persons. Caused by the host-specific mite, Sarcoptes scabiei var hominis Is an obligate human parasite Pathophysiology Transmission is via direct and prolonged contact with an infected individual (not via inanimate objects) Mites can survive up to 3 days away from human skin The entire life cycle of the mite lasts 30 days and is spent within the human epidermis. Pathophysiology After copulation, the male mite dies and the female mite burrows into the superficial skin layers Once on the skin, fertilized female mites burrow through the stratum corneum at the rate of about 2 mm per day, and produce two or three oval eggs each day (total of 60-90 eggs) The ova require 10 days to 3 weeks to become mature adult mites Pathophysiology … cont. Mites move through the top layers of skin by secreting proteases that degrade the stratum corneum. They feed on dissolved tissue Scybala (feces) are left behind as they travel through the epidermis, creating linear lesions clinically recognized as burrows. Pathophysiology … cont. Upon initial infestation, a delayed type IV hypersensitivity reaction to the mites, eggs, or scybala develops over 4-6 weeks. Previously sensitized can develop symptoms within hours of reexposure. The hypersensitivity reaction is responsible for the intense pruritus that is the clinical hallmark of the disease. Clinical features Distribution of the lesion differs in adults and children. Adults Lesions manifest primarily on the flexure aspects of the wrists, the interdigital web spaces of the hands, the dorsal feet, axillae, elbows, waist, buttocks, and genitalia. Pruritic papules and vesicles on the scrotum and penis in men and areolae in women characteristic Clinical features … cont. Infants and children Lesions are on the face, scalp, neck, palms, and soles, although any site may be involved. The diagnosis of scabies is considered in any patient presenting with a recent onset of intense itching that is accentuated at night. Similar symptoms in close contacts should immediately rank scabies at the top of the clinical differential diagnosis. Clinical features … cont. Primary and secondary lesions: Primary lesions include small papules, vesicles, and burrows. Burrows are a pathognomonic sign and represent the intraepidermal tunnel created by the moving female mite. Secondary lesions are the result of rubbing and scratching, and they may be the only clinical manifestation of the disease Management Treatment includes administration of : scabicidal agents antipruritic agent (e.g. sedating antihistamine) antimicrobial agent if secondarily infected All family members and close contacts must be evaluated and treated All clothing, bed linens, and towels used within the last week to be launder in hot water the day after treatment and again in 1 week. Management … cont. Application of topical antiscabietic agents, with repeat application in 7 days. These include: Permethrin 5% cream is the drug of choice, especially for infants >2 months and small children Lindane1% lotion or cream Sulfur 6% in petrolatum Crotamiton (Eurax)10% cream or lotion for treatment of scabies An oral agent, ivermectin. Dose of 200-250 mcg/ kg given at diagnosis and repeated in 7-14 days Myiasis Introduction Infestation of body tissue of humans and animals by the larva (maggots) Clinical classification DERMAL / SUBDERMAL CUTANEOUS Creeping Furuncular Traumatic NASOPHARENGEAL OPHTHALMOMYIASIS INTESTINAL UROGENITAL ETIOLOGY Dermatobia hominis Cordylobia anthropophaga Clinical features FACULTATIVE /TRAUMATIC WOUND MYIASIS Egg larvae in suppurating tissues OBLIGATORY CUTANOUS MYIASIS Creeping eruptions Frunucular myiasis Furuncular myiasis Insiduous , tender boils central punctum ,serosanguinous discharge Posterior end of the larvae , spiracles visible in punctum Rapid resolution on removal of larva Lymphangitis Creeping eruption Resemble cutaneous larvae migrans Tortuous , thread –like red line with terminal vesicle marks the passage of the larvae Treatment Debridement and irrigation (chloroform , turpentine guaze , ether ,paraffin) Treatment of secondary infections Mechanical forceps extraction  Furuncular myiasis Traditional methods: pork fat , mineral oil ,petroleum ,butter , beewax Surgical (I &D------extraction) Creeping eruptions Extraction beyond the vesicle Ethyl chloride freeze Ivermectin 12mg Tungiasis A disease caused by flea called tunga penetrans (jiggers) It is not contagious , so it is not transmitted from one person to person but it is always through external environment. Jiggers are common in some rural locations and transmission is by penetration to skin Both male and female jigger fleas are blood suckers of all warm blooded animals The male leaves its host after obtaining the meal , but the female when pregnant ,burrow into soft skin commonly between the toes where they lay eggs In children other part of the body e.g buttocks can also be infested by the flea Clinical feature and treatment After penetration and burrowing into the skin , the result is a small ,round itching ,painful swelling with point Secondary bacterial infection is common Treatment is by mechanical removal of the flea by sterile pin fallowed by antiseptics dressing NYDA (dimeticone 0ils) Prevention : Wearing shoes provide protection Keeping house and environment clean Cutaneous larva migrans CLM is parasitic skin infection caused by hookworm larvae Common causes :Ancylostoma braziliense ,Anclyostoma caninmum People of all ages ,sex ,and race can be affected Most commonly found in tropical area or subtropical geographic locations Group at risk include :farmers , gardeners Clinical features & treatment A non- specific eruption occurs at the site of pentration Tingling or pricking sensation Snake like tracks stretching 3-4cm from penetrating site Slightly rasied ,flesh –colored or pink and caused intense itching Treatment : Is a self – limiting , humens are an accidental and dead-end host so hookworm larvae eventually die In most cases the lesions will resolve without treatment within 4-8 weeks  Antihelmenintics such as tiabendazole , mebendazole , albendazole and ivermectin are used Liquid nitrogen cryotherapy or carbon dioxide laser may be dystrod the larvae Antihistamin and topical corticosteroids may also be used Antibiotics for secondary bacterial infection Onchocercasis Onchocerciasis is a chronic and progressive skin, eye, and neurological disease caused by Onchocerca volvulus, a filarial nematode (worm). The eye disease is often called river blindness. initial infestation may occur in childhood and produce no symptoms for long periods. However the neurological manifestations mainly affect children. What causes onchocerciasis? O. volvulus is transmitted to humans through the bite of a female blackfly (Simulium spp)  Skin disease in onchocerciasis Classification Skin features Widespread itchy eczema -like rash Acute papular onchodermatitis with multiple small itchy papules which progress to become vesicles and pustules. The face, trunk, and extremities are often affected. Severely itchy rash with scattered flat-topped papules and areas of hyperpigmentation. The shoulders, Chronic papular onchodermatitis buttocks, and extremities are typically affected. The most common pattern of skin disease. Thickened scaly and hyperpigmented itchy plaques. The lower extremities are commonly affected, Lichenified onchodermatitis and lymph nodes are often enlarged. Onchocercal atrophy Large areas of wrinkled thin, dry inelastic skin. Commonly affects buttocks and lower back. Also called “leopard skin”. Areas of pigment loss (leukoderma), with islands of normally pigmented skin Onchocercal depigmentation surrounding hair follicles. Often affects the shins in a symmetrical pattern and is not usually itchy. Subcutaneous lumps found over bony prominences contain the adult worms. The subcutaneous nodules Palpable onchocercal nodules (oncocercoma) range in size from a few millimetres to several centimetres, and each contains 2 to 4 adult worms that can reach a length of 80 cm.  clinical presentations of onchocerciasis include: Early due to acute and chronic onchodermatits( itchy eczematous rash with macules and papule scaling and then lichenifiction) Subcutaneous nodules (oncocercoma) lymphadenopathy Sowda(sever pruritus with darkening of skin often on the limb)  late manifestation 'Lizard skin' – dry, scaly skin resembling ichthyosis 'Hanging groin' – (sac of atrophic skin containing inguinal or femoral lymph node) scarring atrophy Elephantiasis may occur leopard skin (depigmentation of lower extremities)  Eye disease in onchocerciasis Inflammation and bleeding in an eye occurs when microfilariae in the cornea and/or back of the eye die. Early symptoms include itching, redness, pain and photophobia. Repeated episodes of inflammation in the cornea cause a chronic keratitis and sclerosis affecting the clarity of the cornea. Blurring of vision, night blindness, glaucoma, visual field loss, and eventually blindness may develop in the affected eye. Complication Psychosocial effects Inability to work Significant disability due to blindness and neurological effects diagnoses Identifying microfilariae in six skin snips(thin skin biopsy and examined microscopically ) In early or mild disease when larvae are not seen, polymerase chain reaction (PCR) is used to amplify the larval DNA. Adult worms are seen in excised nodules under a light microscope. Microfilariae may be directly observed during slit lamp examination of the eye. Detection of antibodies against O. volvulus in blood samples – however, this test cannot reliably distinguish between past and present infection so is used for diagnosing patients with a brief exposure history. treatment Prevention No vaccine available Prevent blackfly bites Use of insect repellents such as DEET Wearing long-sleeved shirts and pants  Systemic treatment Oral ivermectin kills the microfilariae but not the adult worm. One dose every 3 months is required. New agents under investigation to kill the adult worm include suramin and moxidectin. Diethylcarbamazine(hetrazan,banocide) ; Microfilaricidial but uncertain effect on adult worm Nodulectomy  What is the outlook for onchocerciasis? Onchocerciasis has been successfully eradicated from some countries and programmes continue in many others. Treatment of established infestation is not curative, but aims to stop progression of disease. Prevention is the most cost-effective measure. Papular urticaria Papular urticarial is a papulovesicular reaction to insect bites more common in children than in adults.. It is also called a persistent insect bite reaction. Who gets papular urticaria? Papular urticaria most often occurs in children. This is because desensitisation to insect bites has not yet developed. It may also occur in adults, especially in travellers to new environments.  What is the cause of papular urticaria? Papular urticaria is thought to be an immunological reaction to insect bites. The reaction settles after a few months or years, as the person becomes desensitised to the bites. The initial bite is rarely noticed. clinical features of papular urticaria Papular urticaria presents with clusters of itchy red bumps (papules) without systemic symptoms. Most often on legs and other uncovered areas such as forearms and face Sometimes scattered in small groups all over the body Range from 0.2–2 cm in diameter Each papule has a central punctum May present as crops of fluid-filled blisters New lesions develop just as old ones start to clear A new bite may provoke reactivation of old ones complications of papular urticaria Secondary bacterial infection following scratching causes painful pustules and scabs (impetiginisation) Infected insect bites can lead to cellulitis and rarely, bacteraemia (sepsis) Localised cutaneous vasculitis diagnoses Papular urticaria is usually a clinical diagnosis. A biopsy may support the diagnosis, as insect bites have a characteristic microscopic appearance. The histopathology of papular urticaria includes mild dermal oedema, extravasation of erythrocytes, interstitial eosinophils, and exocytosis of lymphocytes. Vasculitic features may be noted. Treatment Preventative measures Wear protective clothing Insect repellents can be applied to exposed skin to prevent insect bites when outdoors Insecticides can rid the house, workplace, or school, of insects. Obtain professional help from a pest control company if necessary.  Symptomatic measures Topical steroid cream – this should be applied as soon as the itchy spots appear Antihistamine tablets – may reduce the size and severity of the spots and reduce itching Antiseptic cream can reduce or avoid secondary infection