Tissue Nematodes II BPT

Classification – Tissue Nematodes Lymphatic Wuchereria bancrofti Brugia malayi Brugia timori Subcutaneous Loa loa (african eye worm) Onchocerca volvulus (blinding filaria) Dracunculus medinensis (thread worm) Conjunctiva Loa loa 08/04/09

Wuchereria bancrofti (Filarial worm) Definitive host Man Intermediate host Female Culex, Aedes or Anopheles mosquito Infective form Third stage larva Mode of transmission Inoculation – bite of mosquito Site of localization Lymphatics / lymph nodes of man 08/04/09

Life cycle 08/04/09

Clinical features Infection - Wuchereriasis/ Lymphatic filarisis/ Bancroftian filariasis Pathogenic states are produced only by adult worm (living/ dead) – classical filariasis Occult filariasis – lesions produced by microfilaria Clinical states in classical filariasis can be classified as: Asymptomatic ( in endemic areas) Inflammatory – lymphadenitis, lymphangitis, fever, lymphoedema Obstructive – elephantiasis, lymphangiovarix, chyluria, hydrocele Tropical pulmonary eosinophilia A. Lymphadenitis – LNs of groin & axilla B. Lymphangitis – lymphatics of extremities, testicles & epididymis. Causes of lymphangitis: Mechanical irritation – movement of adult parasite inside lymphatics Liberation of metabolites of growing larvae Secretion of toxic fluid by fertilized female worms Absorption of toxic products liberated from dead worms C. Filarial fever – high grade fever with chills, Fever subsides in 7-10 days but such inflammatory attack recurs every month D. Repeated attacks – damage lymphatics – chronic lymphoedema 08/04/09

Obstructive stage Lymphatic obstruction – occurs with the death of worms Causes of obstruction – Blocking of lumen by dead worms Excessive proliferation & thickening of walls of lymphatic vessels Fibrosis of lymphatic vessels 08/04/09

Consequences of Lymphatic Obstruction Elephantiasis of organs like leg, scrotum, penis, vagina, breast, arm etc – fibrotic thickening of skin & subcutaneous tissue Lymphangiovarix – dilatation of afferent lymphatics. Rupture of Lymphangiovarix into urinary tract – chyluria Hydrocele 08/04/09

Lymphatic filariasis 08/04/09

chyluria 08/04/09

Classical v/s Occult filariasis Classical filariasis Occult filariasis Cause Developing worms & adults Microfilariae Basic lesions Acute inflammation followed by an epitheloid granuloma surrounding the adult worm & a fibrous scar An eosinophilic granuloma (hypersensitivity reaction) Organs involved Lymphatic system Lymphatic system, lungs, liver & spleen Microfilaria Present in Blood Present in affected tissues not in blood Therapeutic response No response to any drug Responds to microfilaricidal drug, DEC. 08/04/09

Laboratory diagnosis Specimen - blood collected at night, preferably capillary blood from ear lobes, chylous urine, hydrocele fluid, exudate from lymphangiovarix Microscopic examination – wet mount or stained with giemsa: sheathed microfilaria with no nuclei at tail tip 08/04/09

Laboratory diagnosis Concentration techniques – for capillary blood, venous blood (Knott’s technique) DEC provocation test – 100 mg of DEC orally, examine peripheral blood smear after 30 to 45 minutes Serology – using non specific Ags Passive hemagglutination test Fluoresecent ab test ELISA 08/04/09

Treatment DEC (Diethylcarbamazine) – microfilaricidal: 6mg/ kg/day for 2-3 weeks Elevation of the affected limbs, use of elastic bandages & local foot care – reduces symptoms of lymphatic obstruction Surgical treatment of hydrocele Prevention Destruction of mosquitoes Protection against mosquito bites Treatment of carriers 08/04/09

Brugia sps Two species infect humans : B.malayi & B.timori Causes lymphatic filariasis Transmitted by Mansonia & Anopheles species of mosquitoes Life cycle, pathogenesis, clinical features, diagnosis & treatment – similar to W. bancrofti, with a following differences Children commonly affected Rapid development of signs & symptoms Elephantiasis affect lower extremities Chyluria & hydrocele rare 08/04/09

(Blinding filaria – 2nd most common cause of infectious blindness) Onchocerca volvulus (Blinding filaria – 2nd most common cause of infectious blindness) Definitive host Man Intermediate host Black flies (simulium) Infective form Larva Mode of transmission Inoculation Site of localization Subcutaneous tissue, dermis & eye 08/04/09

Clinical features Incubation period - 10 to 12 months Eosinophilia and urticaria. Nodular and erythematous lesions (Onchocercomata) in the skin and subcutaneous tissue Photophobia, lacrimation, keratitis and blindness – due to trapping of microfilaria in the cornea, choroid, iris and anterior chambers. 08/04/09

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Diagnosis & Treatment Nodular biopsy – adult worm Skin snip – unsheathed microfilaria with no nuclei Treatment – Ivermectin, surgical removal, DEC in non ocular onchocercosis 08/04/09

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Loa loa (African eye worm) Definitive host Man Intermediate host Chrysops (deer fly) Infective form Larva Mode of transmission Inoculation Site of localization Subcutaneous & deep connective tissue 08/04/09

Clinical features Subcutaneous swelling – Calabar or fugitive swelling, measuring 5 to 10 cm, marked by erythema and angioedema, usually in the extremities Migrating worm in subconjunctival tissue 08/04/09

Diagnosis & Treatment Peripheral blood smear - Sheathed microfilaria with nuclei upto rounded tail tip Isolation of worms from the conjunctiva or subcutaneous biopsy Treatment - Ivermectin, surgical removal, DEC (effective against adult & microfilaria) 08/04/09

Dracunculus medinensis (Guinea Worm) Adult worms Male 2 to 4 cm Female 70 –120 cms, viviparous Definitive host Human Intermediate host Cyclops Infective form Larva inside Cyclops Mode of transmission Ingestion of water contaminated with cyclops Site of localization Subcutaneous tissue 08/04/09

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Clinical Features Disease – Dracunculosis Clinical features develop an year after infection following the migration of worm to the subcutaneous tissue of the leg Blister formation – rupture of blister when in contact with water - ulceration – release of larvae by adult female worm Secondary bacterial infection of ulcer 08/04/09

Diagnosis & Treatment Detection of adult worm – when it appears at the surface of skin Detection of larva – in milky fluid released by worm on exposure to water Radiology – calcified worm in deeper tissues Treatment – Thiabendazole/ Metronodazole – symptomatic relief, easy removal of worm Gradual extraction of worm by winding of a few cms on a matchstick per day, over 3 to 4 weeks Surgical excision 08/04/09

Prevention Provision of safe water supply Education to discourage people from entering water source Filtering water through a double folded cloth Boiling water before drinking Discouraging the use of step wells 08/04/09