24. Nematode - Onchocerca volvulus.pdf slides
- 2. Nematodes 1. INTESTINAL NEMATODES WITH TISSUE STAGES Ascaris lumbricoides (Giant Roundworm; Common Roundworm) Strongyloides stercoralis HOOK WORMS:- Ancylostoma duodenale Cutaneous Larva Migrans Ancylostoma braziliense Ancylostoma caninum Necator americanus 2. INTESTINAL NEMATODES WITHOUT TISSUE STAGES Enterobius vermicularis (Pin Worm or Thread Worm) Trichuris trichuira (Whip Worm) 3. TISSUE AND BLOOD DWELLING NEMATODES Toxocara species (Toxocara canis; Toxocara cati) - Visceral Larva Migrans Trichinella spiralis Dracunculus medinensis FILARIAL WORMS:- Wuchereria bancrofti Onchocerca volvulus Loa loa (The Eye Worm) Mansonella species
- 3. Zoological Classication of Nematodes ORDER SUPER FAMILY FAMILY GENERA SPECIE Enoplida Trichinelloidea Trichinellidae Trichinella T. spiralis Trichuridae Trichuris T. trichiura Rhabditida Rhabditoidea Strongyloididae Strongyloides S. stercoralis Strongylida Ancylostomatoidea Ancylostomatidae Ancylostoma A. duodenale Metastrongyloidea Angiostrongylidae Necator N. americanus Ascaridida Ascaridoidea Ascarididae Ascaris A. lumbricoides Oxyurida Oxyuroidea Oxyuridae Enterobius E. vermicularis Spirurida Filarioidea Onchocercidae Wuchereria W. bancrofti Loa L. Ioa Mansonella M. perstans M. ozzardi M. streptocerca Onchocerca O. volvulus Dracunculoidea Dracunculidae Dracunculus D. medinensis
- 4. Onchocercavolvulus Prevalence and Geographical distribution Onchocerciasis (River Blindness) - Eye and Skin Disease 120 million people world-wide are at risk of Onchocerciasis 96% are in Africa Of the 36 countries where the disease is endemic 30 are in Sub-Sahara Africa (plus Yemen) 6 are in the Americas 18 million people are infected with the disease and have dermal microfilariae 99% are in Africa Over 6.5 million suffer from severe itching or dermatitis 270, 000 are blind
- 6. ParasiteMorphology Morphologies: • Adult worms are coiled within a fibrous tissue capsules (nodules) • Male: only about 5 cm long • Female: 30 - 50 cm long • Microfilariae: Unsheathed 150 – 350 μm long; & a pointed tail tip with NO nuclei Several Nuclei through-out the body Have a Diurnal Periodicity • Intermediate Host and Vector:- Female Simulium damnosum (Black Fly), found around Plantations; Rivers or River Basins
- 11. LifeCycle A Female Blackfly introduces 3rd Stage Filarial Larvae during it’s blood meal to a human host In subcutaneous tissues the Larvae develops into Adult Filariae (3 months to 1 year) commonly reside in nodules in subcutaneous connective tissues In the Subcutaneous Nodules, the female worms produces Microfilariae (thousands of new larvae daily) The Microfilariae are typically found in the Skin and in the Lymphatics of connective tissues occasionally found in peripheral blood, urine, and sputum The larvae become detectable in the skin 10 - 20 months after the initial infection A blackfly ingests the circulating Microfilariae during a blood meal After ingestion, the Microfilariae migrate from the Blackfly's Midgut through the hemocoele to the Thoracic muscles In Thoracic Muscles the Microfilariae develops into 1st Stage Larvae; 2nd Stage Larvae; 3rd Stage Larvae (Infective Stage), 10 - 12 days The 3rd Stage Larvae migrate to the Blackfly's Proboscis in readiness for infection Adults can live in the nodules for approximately 15 years
- 12. LifeCycle
- 13. FILARIALWORMS -CHARACTERISTICS PARASITE ADULTS LOCATION MICROFILARIA LOCATION MICROFILARIA CHARACTERISTICS MICROFILARIA PERIODICITY Lymphatic Filariasis Wuchereria bancrofti lymphatics Blood Sheathed, pointed tall tip free of nuclei Nocturnal Brugia malayi lymphatics Blood Sheathed, blunt tail tip with 2 terminal nuclei Nocturnal Brugia timori lymphatics Blood Sheathed Nocturnal Subcutaneous Filariasis Loa loa Connective tissue, conjunctiva Blood Sheathed, nuclei extending up to pointed tail tip Diurnal Onchocerca volvulus Subcutaneous nodules Skin, eyes Unsheathed, blunt tail tip free of nuclei Non periodic Mansonella streptocerca Subcutaneous Skin Unsheathed blunt tail tip with nuclei Non periodic Serous Cavity Filariasis Mansonella ozzardi Peritoneum and pleura Blood Unsheathed, pointed tail tip without nuclei Non periodic Mansonella perstans Peritoneum and pleura Blood Unsheathed, pointed tail tip with nuclei Non periodic
- 14. RiverBlindness(Onchocerciasis):ClinicalFeatures The symptoms are primarily caused by Microfilariae that move around the human body in the subcutaneous tissue or those that die and the body’s intense immunological response:- 1. Onchocerciasis - Skin disease Pruritus Acute skin inflammation Onchodermatitis Skin hypo- or hyper- pigmentation (due to antigenic material from dead Microfilaria) Hyperpigmented skin changes termed as Sowda (usually limited to one limb) Onchocercomata – Several skin fibrous nodules (1 -5 cm) enclosing Adult worms as a host-parasite reaction The skin becomes thickened and wrinkled, showing “lizard” or "leopard skin" appearance Elephantiasis of the external genitalia; hanging groin 2. Onchocerciasis - Eye disease Reversible lesions on the cornea Permanent clouding of the cornea and Blindness Inflammation/Atrophy of the Optic Nerve resulting in Vision Loss and eventually Blindness
- 15. Onchocerciasis - The Skin Disease (Thickened/Wrinkled Skin; Onchodermatitis)
- 19. Onchocerciasis - TheEye Disease
- 20. LaboratoryDiagnosis Skin Onchocerciasis The most common method - The skin snip:- A 1- 2 mg shaving or biopsy of the skin is done to identify larvae In patients with nodules in the skin :- Surgical removal and examination for adult worms Polymerase chain reaction (PCR) of the skin can allow for diagnosis if the larvae are not visualized Eye Onchocerciasis Slit-lamp examination of the anterior part of the eye
- 21. Treatment WHO recommends treating Onchocerciasis with Ivermectin every 6 months or once yearly for about 10 to 15 years Because it kills Microfilariae but not adult worms Exerts Microfilaricidal effects slowly – less severe side effects Doxycycline kills the adult worms kills Wolbachia bacteria on which the adult worms depend in order to survive Diethylcarbamazine (DEC) is the alternative drug kills the Microfilariae and Adult worms Very rapid onset of it’s action Should be used with care! The most common side effects are dizziness, nausea, fever, headache, or pain in muscles/joints
- 22. PreventionandControl 1. Targeting Vector control and elimination The Onchocerciasis Control Programme (OCP) launched in 1974 in West Africa The programme has been jointly sponsored by WHO, the World Bank, UNDP, FAO and more than 20 donor countries and agencies OCP's principal method for controlling Onchocerciasis:- Breaking the cycle of transmission by eliminating the black fly Simulium larvae are destroyed by application of selected Insecticides through aerial spraying of Breeding sites in fast-flowing rivers Once the cycle of river blindness has been interrupted for 14 years the reservoir of Adult worms dies out in the human population The parasite reservoir has now virtually died out in the original 7- country operations area OCP also distributes the drug Ivermectin where needed Program success When launched, more than 1 million people in West Africa suffered from Onchocerciasis Currently, number of infected people within the original area of operations is practically nil
- 23. PreventionandControl,continued 2. Personal protection measures against biting insects:- • Wearing insect repellant such as N,N-Diethyl-meta-toluamide (DEET) on exposed skin • Wearing long sleeves and long pants during the day when blackflies bite • Wearing Permethrin- treated clothing • Establishment of villages away from Simulium breeding places 3. Mass Distribution and Treatment : Ivermectin