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  1. 1. Filarial WormsRumala MorelDept. of ParasitologyPeradeniyaY2S2
  2. 2. Teaching Learning Objectives: Name the major tissue nematodes of humans indicating theirlocation in the human body. List the major characteristics of the filarial parasites ofhumans indicating those found in Sri Lanka Name the vectors of those parasites found in Sri Lanka Outline the life cycle of a typical filarial parasite Describe the life cycle of Wuchereria bancroftiDescribe the phenomenon ‘Periodicity of microfilaria’ State the stages that cause pathogenic effects Identify stages of diagnostic importance Outline laboratory methods of visualization/identification ofparasites/products Identify points in the life cycle where preventive measuresare applicable
  3. 3. FILARIAL WORMS: Filariasis tissue nematodes adults thread like; female embryos (early first stage larvae)microfilariae (mf)• transmitted by insect vectors• adults in different habitats in body• mf in blood/ subcutaneous tissue
  4. 4. Human filarial parasites grouped according toHABITAT of the ADULT WORM in man Lymphatic filariae Subcutaneous filariae filarial infections of the body cavities& associated tissue
  5. 5. LIFE CYCLEMAN2 moults Adultsmf in blood /subcutaneous tissueINSECT VECTOR2-moultsNO multiplicationInfective larva-L3
  6. 6. Microfilaria- periodicityIn some species mf in peripheral blood onlyduring certain times during 24 h period. Non periodic Periodic - nocturnally- diurnally Sub periodic- mf present at all timesbut peak nocturnally or during daytime
  7. 7. Periodicity of microfilariaphysiological adaptation to biting habits of vectorMf bldpatency6h 12h 24h 2h 6hNocturnallyperiodicNonperiodicDiurnallyperiodicSub periodic
  8. 8. LYMPHATIC FILARIAEmosquito borneadults in lymphatics / mf in blood Wuchereria bancrofti-widespread tropics Brugia malayi- SE Asia, India Brugia timori- Timor island,other islands nearby
  9. 9. HydrocoeleLymphoedema
  10. 10. Distribution of lymphatic filariaeSub periodic W. b
  11. 11.  Dog filarial wormDirofilaria repens- zoonosis in Sri LankaFilarial infections of Man in Sri Lanka Bancroftian filariasis- W bancrofti(nocturnally periodic)
  12. 12. Wuchereria bancrofti (nocturnally periodic)High prevalence in hot,humid, tropics.associated with ‘poor’ urbanizationVector-common urban mosquitoCulex quinquefasciatusIn E Africa- vector rural-Anopheles gambiaePacific islands- diurnally sub periodicvector day biting -Aedes spp
  13. 13. life span 7-16 yrs
  14. 14. Larva developing in themosquito thoracic muscle
  15. 15. Infective larvae L3 emerging from proboscisof mosquito
  16. 16. Adults ofWuchereria bancroftiare long and threadlike.MALES (left) measureup to 40 mm longand FEMALES (right)are 80-100 mm long.
  17. 17. tail nucleiWuchereria bancrofti -mf Brugia malayi300 x10 µm 260 µmLie- graceful curves kinked (acute angles)head space- short longnuclei- countable, overlapping,tail nuclei+head space
  18. 18. Laboratory Diagnosis of Filariasis:Direct Detection of mf in bloodThick film- 10pm-2 am (20-60µl)wet mount/ stain GiemsaConcentration-•Knott’s method-1ml blood +2% formalin, centrifuge,examine deposit for mf•Membrane filtration- pore size 5µmDetection of adults in biopsy- rareDetection of Filarial Specific AbDetection of Circulating Filarial Ag.Indirect
  19. 19. A). Detection of filarial antibodies in serum Indirect immunofluorescent test- IFA/FATAntigen used - microfilariae of W bancroftisections of adult worms (cattle filariae) ELISA (enzyme linked immunosorbent assay)Disadvantage: Ab long lastingB). Detection of Circulating Filarial Ag•Antigen detection ELISA•Immunochromatographic [ICT] Card TestINDIRECT TESTS
  20. 20. Antigen detection strip (card) tests- RDTsSample origin(whole bloodserum/plasma)polyclonal Ab+ colloidal goldMabW bancroftiT Cabsorbent padtest controlRDT = Rapid Detection TestsImmunochromatographic Card Test=
  21. 21. ImmunochromatographicCard TestAg detectionELISA plate
  22. 22. ICT card testImmunochromatographic card test-detects specific circulating W bancrofti Agin serum/whole blood using monoclonal Ab IgG4 simple, no equipment required quick results <15 min no need for night blood 100% sensitive in mf +s Not quantitative (+/-)But disease severity not dependant on mf densityDisadvantage: High cost > Rs. 1600/test
  23. 23. Filariasis in Sri Lanka-1937-39: Brugia malayi predominant1947: Anti Filariasis Campaign1960’s: Brugian filariasis eradicatedcontrol of larval breedingresidual action of DDT on adultstreatment with DECBancroftian filariasis is the ONLYlymphatic filariasis in SL now
  24. 24. LF is endemicin eight of the25 districts.Confined tourbanizedcoastal belt:9.5 million(50%)populationexposedinland foci:Gampaha,WarakapolaVeyangoda
  25. 25. Global Elimination of LymphaticFilariasis• Global Programme to Eliminate Lymphatic Filariasis -WHO 1998• Global Alliance to Eliminate Lymphatic Filariasis - 2000– public-private partnership– WHO, national Ministries of Health,– Private drug companies donating albendazole &ivermectin (Mectizan®)– NGOs• 1 billion at risk population• > 120 million people are already infected• > 40 million incapacitated or disfigured
  26. 26. Bancroftian filariasis control in Sri Lankavector control:prevent mosquito breedingclear drains, cess pits, sealing of septic tankslarviciding with insecticides, larvivorous fish Selective treatment of mf + caseswith 2-week DEC (6 mg/kg) Mass chemotherapy- eradication of parasite bykilling mf and disrupting transmission- continued for4-5 yearsMorbidity control clinics – disability managementtraining
  27. 27. Culex quinquefasciatus breeding sitesDirty water in blocked drains, cess pits etc.
  28. 28. Brugia malayi - Confined to AsiaNot detected in Sri Lanka since 1962aduAdults in lymphatics of lower limbs, groin. Rare in genitalia.Mf sheathed, characteristic morphologyPre patent period- 1-3 monthsSub periodic form- SE Asia-zoonoses(monkeys,dogs & cats)B malayi- nocturnally periodicVector: Mansonia speciesFemale mosquito of Mansonia spplays eggs on the under surface ofleaves of water plantseg. Pistia, Salvinia, Eichonia
  29. 29. Subcutaneous filariasis of humansdifferent fly vectorsmf in blood / subcutaneous tissuebiting habits of vectorOnchocerca volvulus- OnchocerciasisMajor public health problem - tropical Africavector- black flies, mf – subcutaneousLoa loa- Tabanids, mf in bloodBody cavities:Mansonella spp- culicoides, mf in blood
  30. 30. Dirofilaria repens - DirofilariasisZoonotic filariasis in Sri Lankaa common subcutaneous filarial infection of dogs inSri LankaTransmitted by several species of mosquitoesAedes, Armigeres & Mansonia spp.Human disease commonCauses subcutaneous nodulesdue to granulomatous reactionto adult wormbutnot known toproduce microfilariaein humansD.repens adult
  31. 31. Cross-sections of Dirofilaria sp. from a subcutaneous nodulestained with hematoxylin and eosin (H&E).100x 200x
  32. 32. Onchocerciasis = River BlindnessSimulium (black fly)fast flowing riversRiver Volta-W Africa
  33. 33. mff causes eye lesions:blindnessIn skin: itching, depigmentationloss of elasticityAdults cause subcutaneous nodules
  34. 34. Loa loa- loasisAdults in subcutaneous tissueMf in blood- diurnally periodictransmitted by blood sucking day-biting fliesVectors: Tabanid fliesConfined to Tropical Africa where vectors arefoundMf in bloodAdult worm underthe conjunctiva- 10 mmTransient swellings-days
  35. 35. Tabanid flyadult worm underthe conjunctiva
  36. 36. Filarial worms- Wucheraria bancrofti [SRI LANKA]Brugia malayi• Subcutaneous filariae- Onchocerca volvulus [River blindness]- Loa loa- Dirofilaria repens [ZOONOSIS in SRI LANKA]• filarial infections of the body cavities& associated tissue•Lymphatic filariae