1. Tissue Nematodes
II BPT

2. 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

3. 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

4. Life cycle
08/04/09

5. 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
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6. 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

7. 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
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8. Lymphatic filariasis
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9. chyluria
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10. 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

11. 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

12. 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

13. 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

14. 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

15. (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

16. 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.
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17. 08/04/09

18. 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

19. 08/04/09

20. 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

21. 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
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22. 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

23. 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

24. 08/04/09

25. 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

26. 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

27. 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