Onchocerchiasis

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Onchocerchiasis

  1. 1. ONCHOCERCIASISONCHOCERCIASIS
  2. 2. ONCHOCERCIASISONCHOCERCIASIS Synonyms  Onchocercosis  Blinding filariasis  River blindness
  3. 3. a chronic parasitic disease filarial nematode Onchocerca volvulus. multiple organ systems cutaneous and ophthalmologic complications. multiple organ systems primarily affects people living near fast- flowing rivers where blackflies breed.
  4. 4. EPIDEMIOLOGYEPIDEMIOLOGY occurs worldwide  Africa, Central and South America, and the Middle East. ~ 18 million people are currently infected. Of those infected:- ◦ about 1.5% are blind, ◦ additional 2.8% have severe visual impairment.
  5. 5. ◦ Greater morbidity with age is the result of cumulative exposure in endemic areas. ◦ Blindness tends to occur in adulthood after many years of infection.
  6. 6. PATHOPHYSIOLOGYPATHOPHYSIOLOGY humans are the only definitive hosts. Simulium black flies - obligate intermediate hosts The species Simulium damnosum in africa African Simulium species tend to bite the ribs, hips, iliac crests and lower limbs,
  7. 7. Female worm length ranges from 30-80 cm, Male adult worms are usually 3-5 cm in length migrate between various subcutaneous nodules to inseminate females. life span of up to 14 years for adults MF live for 6-30 months;
  8. 8. the female worms produce 1000-3000 MF daily. can migrate throughout the subcutaneous tissues and skin; they have a particular affinity for ocular tissues.  most die without completing their life cycle. with heavy infection, as many as 100,000 MF die each day. The predominant immune response is production of antibodies against dead/dying MF
  9. 9. LIFE CYCLELIFE CYCLE  Blackflies bite an individual infected with O.volvulus.  Fly saliva acts as a chemoattractant for microfilariae in the surrounding subcutaneous tissues  The microfilariae develope in the thoracic muscles within the blackfly,  in a 2- to 3-week period they become infective-stage larvae.  fully develop in the labium of the proboscis of the fly  which passes larvae to another human when taking a blood meal.  In the human host, the larvae developesto male and female adult worms
  10. 10. CLINICALCLINICAL  years after initial infection.  initial bite go unnoticed.  A 1- to 2-year latent period afer initial bite  Pruritus is the most common early symptom  Lymphadenopathy inguinal and femoral regions→ .  Subcutaneous nodules → (onchocercomata)  Visual symptoms itching, redness, photophobia, and→ blurred vision vision loss and frank→ blindness
  11. 11. PHYSICAL FINDINGS  diverse  range from early mild inflammatory lesions to chronic debilitating cutaneous and ophthalmic lesions.
  12. 12.  OnchodermatitisOnchodermatitis ◦ refers to the various cutaneous findings ◦ classified into 6 diseases 1. Acute papular onchodermatitis (APOD) 2. Chronic papular onchodermatitis (CPOD) 3. Lichenified onchodermatitis (LOD) 4. Atrophy 5. Depigmentation 6. onchocercomata
  13. 13. ACUTE PAPULAR DERMATITISACUTE PAPULAR DERMATITIS  Widespread small pruritic papules that may progress to vesicles and/or pustules in the most severe cases.  There may be associated erythema and edema.  most often involves the face, shoulders, trunk, and extremities.
  14. 14. CHRONIC PAPULAR DERMATITISCHRONIC PAPULAR DERMATITIS Larger (3 to 9 mm in diam.), flat-topped, lichenoid papules distributed symmetrically Pruritus is common post-inflammatory hyperpigmentation may be present. hyperpigmented papules, regional lymphadenopathy, and edema The most commonly affected anatomic areas are the buttocks, shoulders, and waist area.
  15. 15. LICHENIFIED ONCHODERMATITISLICHENIFIED ONCHODERMATITIS  an intensely pruritic dermatitis  excoriations and hyperpigmented and hyperkeratotic papules and plaques.  Become lichenified in time  The plaques have an asymmetric distribution  lower extremity is the most commonly affected anatomic location.  There is often associated lymphadenopathy.
  16. 16. ATROPHYATROPHY  Atrophy, also known as “lizard skin”  degeneration of elastic fibers and other structural elements of the skin due to chronic infection.  The skin appears wrinkled and thin  most commonly the buttocks and, less commonly, the extremities.  It may develop after any of the patterns described previously, or arise de novo.
  17. 17. DEPIGMENTATIONDEPIGMENTATION  is also known as “leopard skin.”  common finding in advanced onchocerciasis.  lesions resemble vitiligo  is ass. with perifollicular pigmentation  Pruritus is rarely seen  commonly found on the shins bilaterally.  useful method to screen for onchocerciasis in endemic areas.  Less commonly the buttocks, lateral groin, and lower abdomen are involved.
  18. 18. ONCHOCERCOMATAONCHOCERCOMATA Palpable onchocercal nodules containing the adult worm, involve the deep dermis and subcutaneous tissue. are typically asymptomatic occur over bony prominences such as ◦ the skull, -iliac crest, ◦ knee, -rib, ◦ sacrum, -scapula ◦ trochanter.
  19. 19. OCULAR FINDINGSOCULAR FINDINGS ◦ MF enter the eye by direct invasion from the conjunctiva into the sclera or cornea. ◦ inflammatory responses to MF ◦ intense host immune inflammatory reaction ◦ intensifies when MF die. ◦ causes the following ocular findings, which are typically bilateral:-
  20. 20. →Punctate keratitis →Sclerosing keratitis. →Anterior uveitis → Posterior segment lesions →optic neuritis
  21. 21. DDX.DDX.  hypersensitivity reactions Leprosy Yaws Pinta Treponematosis (endemic syphilis) Vit. A deficiency Atopic dermatitis Contact dermatitis Insect bites Scabies Chronic eczema Superficial mycoses Glaucoma Trachoma Vitiligo
  22. 22. DIAGNOSISDIAGNOSIS  dermatitis, subcutaneous nodules, or ocular lesions.  Peripheral eosinophilia and elevated IgE levels are common  Identification of the MF in a skin snip (100% specific)  6 samples are usually obtained: 1 from each scapula, iliac crest, and lateral calf  Demonstration of adult worms in an excised nodule.  Free floating MF can easily be seen in the anterior chamber of the eye on slit- lamp examination.
  23. 23. DIAGNOSIS…DIAGNOSIS…  Mazzotti test ◦ Performed when infection is suspected and skin snip test results are negative. ◦ 6 mg of DEC is administered ◦ Pt. observed for development of pruritus with or without erythema ◦ indicates the death of microfilariae in the skin. ◦ The reaction may occur from 15 minutes to 24 hours after DEC administration. ◦ Severe reactions may occur in both the skin and the eyes, and other adverse effects include vomiting, conjunctivitis, hypotension, and sudden death.  DEC patch test ◦ A mixture of 10% DEC and Nivea cream is applied under an occlusive dressing; ◦ the occurrence of a localized inflammatory response indicates a positive test result. ◦ This test is a safer alternative to the Mazzotti test. ◦ sensitivity is 30-80%.
  24. 24. Histologic Findings:-  Microscopic examination of excised onchocercomata reveals  cross-sections of adult worms and a collection of eosinophils and lymphocytes at the periphery of the nodule. and sometimes giant cells tend to accumulate around the worms. Calcification may also be seen
  25. 25. TREATMENTTREATMENT The current mainstay of treatment is ivermectin. Mass treatment campaigns (WHO) ◦ ivermectin is a microfilaricide ◦ and does not kill adult worms, ◦ does not cure the disease. ◦ significantly reduces microfilarial burden ◦ decreases transmission and ◦ 150 mcg/kg/d PO as single dose q6-12mo ◦ administered for the life span of the adult worm.
  26. 26. Doxycycline 100 mg/d administered for 6-8 weeks targets bacteria of the Wolbachia species, known endosymbionts in O.volvulus. Reduces microfilarial loads, sterilizes adult worms, decreases adult worm viability.
  27. 27. Treatment…Treatment… Diethyl carbamazine kills the MF and is given as follows:- first 3 days 1mg/kg body weight once; Next 4 days 2mg/kg body weight once; second week 4mg/kg body weight three times a day; third week 4mg/kg body weight three times a day.
  28. 28. Treatment…Treatment… In heavily infected patients,  or in those with severe dermatitis  or with eye involvement,  prednisone 40mg should be given at a daily dose in adults, starting the day before DEC and continuing for a few days until the reaction has settled.  Ocular reactions need treatment with corticosteroid eye drops and mydriatics.
  29. 29. Treatment…Treatment…  Suramin ◦ Extremely toxic ◦ in selected individuals for curative treatment of severe hyperreactive onchodermatitis uncontrolled by repeated ivermectin treatment. ◦ is a drug that kills adult worms and MF ◦ Parenteral/IV: >60 kg: 0.2 g week 1; 0.4 g week 2; 0.6 g week 3; 0.8 g week 4; 1 g week 5 and 6; total dose 4 g  nodulectomy, usually combined with a microfilaricide.
  30. 30. PREVENTIONPREVENTION Vector control ◦ larvicides to reduce the black fly population. Mass treatment with ivermectin ◦ is employed in areas of high endemicity ◦ reduces the microfilarial burden in the population. Education of people in endemic areas
  31. 31. Mass RMass Rxx

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