MBBS UG MICROBIOLOGY THEORY CLASS LECTURE POWERPOINT PPT KARPAGAM FACULTY OF MEDICAL SCIENCES AND RESEARCH, COIMBATORE

1. FILARIAL WORMS
Dr. R.Someshwaran, MBBS, MD., Assistant Professor,
Department of Microbiology,
Karpagam Faculty of Medical Sciences and Research,
Othakalmandapam, Coimbatore-641032

2. Objectives of today’s class
• To enlist the human filarial worms (Nematodes)
• To understand and explain the morphology, life
cycle, clinical presentation and pathogenesis of
various filarial worms infecting humans
• To understand and explain the lab diagnosis,
treatment and prevention of various filarial
worms infecting humans

3. HELMINTHOLOGY
• Helminths are multicellular, bilaterally
symmetrical animals
• Helminths – 2 Phylum
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Nemahelminthes
Nematodes
Platyhelminthes
Cestodes &
Trematodes

4. Differences between Cestodes, Trematodes & Nematodes
CESTODES TREMATODES NEMATODES
Shape Tape like
segmented
Leaf like
unsegmented
Elongated,
cylindrical,
unsegmented
Sexes Sexes not separate
Monoecious
Hermaphrodite
Sexes not separate
Monoecious except
Schistosoma
Sexes are separate
Diecious
Head end Suckers, often with
hooks
Suckers, no hooks No suckers, no
hooks, well
developed
Alimentary
canal
Absent Present,
incomplete, no
anus
Present, complete,
anus present
Body cavity Absent Absent Present
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5. NEMATODES CLASSIFICATION
(LOCATION OF ADULT IN BODY)
• INTESTINAL NEMATODES:
a. Small intestine: Ascaris, Ancylostoma, Necator,
Strongyloides, Trichinella.
b. Large intestine: Enterobius, Trichuris
• TISSUE NEMATODES (Somatic nematodes):
a. Lymphatic: Wuchereria, Brugia
b. Sub-cutaneous: Loa loa, Onchocerca, Dracunculus
c. Mesentry: Mansonella spp.,
d. Conjucntiva: Loa loa
e. Zoonotic filariasis: Dirofilaria spp.,

6. NEMATODES CLASSIFICATION
(MODE OF INFECTION)
i. By ingestion:
a. Eggs: Ascaris, Enterobius, Trichuris
b. Larvae within intermediate host: Dracunculus
c. Encysted larvae in the muscle: Trichinella
ii. By Penetration of Skin: Ancylostoma, Necator,
Strongyloides
iii. By blood sucking insects: Filariae
iv. By inhalation of dust containing eggs: Ascaris,
Enterobius

7. NEMATODES CLASSIFICATION
(BASED ON THEY LAY EGGS/LARVAE)
i. Oviparous: Egg laying nematodes
a. Unsegmented eggs: Ascaris, trichuris
b. Segmented eggs: Ancylostoma, Necator
c. Eggs containing larvae: Enterobius
ii. Viviparous: Producing larvae
Ex: Trichinella, Wuchereria, Brugia, Dracunculus
iii. Ovoviviparous: Laying eggs containing fully
formed larvae which hatch out immediately:
Strongyloides.

8. HUMAN FILARIAL WORMS
• Filarial worms belong to Superfamily:
Filarioideae.
• Thread like worms transmitted by blood
sucking insects (Arthropods)
• Vector borne disease / Zoonotic disease
• Infection by any filarial worm is called as
‘Filariasis’.
• Morphological forms: Adult worm &
Microfilariae (embryo)

9. HUMAN FILARIAL WORMS
• Microfilaria (mf): Sheathed & Unsheathed/naked
• Sheathed mf: Retain their egg membrane
• Unsheathed mf: Ruptures out from the egg
membranes
• 8 species of filarial worms infect humans
• Humans are the Definite hosts

10. Classification of Human filarial worms
A. Lymphatic filariasis:
a. Wuchereria bancrofti (Bancroftian filariasis)
b. Brugia malayi (Malayan filariasis)
c. Brugia timori
B. Subcutaneous filariasis:
a. Loa loa (Calabar swelling/Fugitive swelling)
b. Onchocerca volvulus (River blindness, dermatitis) &
c. Mansonella streptocerca (Skin diseases)
C. Serous cavity filariasis:
a. Mansonella ozzardi (Non-pathogenic) &
b. Mansonella perstans (Non-pathogenic)

11. Classification of Human filarial worms
D. Zoonotic filariasis:
a. Dirofilaria immitis
b. Dirofilaria repens
c. Brugia pahangi
d. Brugia beaveri
e. Brugia leporis

12. Filarial
nematode
Habitat of Adults Habitat of
Microfilaria
Vector Microfilaria
periodicity
LYMPHATIC FILARIASIS
Wuchereria
bancrofti
Lymphatic tissue Blood Culex quinquefasciatus (W)
Anopheles in rural Africa
Aedes spp.,
Nocturnal (M)
Sub-periodic (R)
Brugia malayi Lymphatic tissue Blood Mansonia spp., Anopheles
Mansonia spp., Coquillettidia
Nocturnal (M)
Sub-periodic (R)
Brugia timori Lymphatic tissue Blood Anopheles barbirostris Nocturnal
SUBCUTANEOUS FILARIASIS
Loa loa Subcutaneous
tissue, Conjunctiva
Blood Chrysops (Deer fly) Diurnal
Onchocerca
volvulus
Subcutaneous
tissue
Skin and eye Simulium (Black fly) None
Mansonella
streptocerca
Subcutaneous
tissue
Skin Culicoides (Midges) None
SEROUS CAVITY FILARIASIS
Mansonella
perstans
Body cavities,
Mesentry
Blood Culicoides (Midges) None
Mansonella ozzardi Body cavities Blood Culicoides (Midges)
Simulium (Black fly)
None

13. Filarial nematode Characteristic feature of Microfilaria Epidemiology
LYMPHATIC FILARIASIS
Wuchereria bancrofti Sheathed, Pointed tail tip free of nuclei South America,
Africa, Asia
Brugia malayi Sheathed, blunted tail tip with two terminal
nuclei
Pacific Islands
Brugia timori Sheathed longer than Mf. malayi SE Asia, India,
Indonesia
SUBCUTANEOUS FILARIASIS
Loa loa Sheathed, nuclei extending up to pointed tail tip West and Central
Africa
Onchocerca volvulus Unsheathed, blunt tail tip free of nuclei S. And C. America
and Africa
Mansonella
streptocerca
Unsheathed, blunt tail tip with nuclei W. And C. Africa
SEROUS CAVITY FILARIASIS
Mansonella perstans Unsheathed, pointed tail tip free of nuclei S. And C. America
Mansonella ozzardi Unsheathed, pointed tail tip with nuclei S. And C. America
Carribean Islands

14. Head and Tail ends of Microfilariae

15. LYMPHATIC FILARIASIS
• Wuchereria bancrofti
• Brugia malayi
• Brugia timoria

16. Global Scenario
• Population
at risk : 1.2 Billion
• No. of countries : > 80
• Mf carriers : 76 Million
• Diseased : 44 Million
• Hydrocele : 27 Million
• Lymphoedema : 16 Million
• TPE : 1 Million

17. National Scenario
• Total Population : 110 C
• Population at risk : 45.4 C
(in 16 States & 5 UT’s)
• Total infected : 51.7 M
(Wb - 99.4 % and Bm - 0.6 %)
• No. of diseased : 22.5 M
• Mf carriers : 29.2 M
• Hydrocele : 12.9 M

18. EPIDEMIOLOGY

19. Mode of Transmission &
Incubation Period
• Lymphatic Filariasis is transmitted by the bite
of Infected mosquito which harbours L3 larva.
• L1: 1-3 hours
• L2: 3-4 days
• L3: 5-6 days
• Pre-patent period: (L3 to Mf) Not known
• Clinical Incubation period: 8-16 months

20. Clinical Manifestations
• Manifestations are 2 types
1. Lymphatic Filariasis (Presence of Adult
worms)
2. Occult Filariasis (Immuno hyper
responsiveness)
Clinical Spectrum
None Asymptomatic
microfilaremia
Filarial
fever
Chronic
pathology
TPE

21. Stages in Lymphatic Filariasis
• There are 4 stages :
1. Asymptomatic amicrofilariaemic stage
2. Asymptomatic microfilariaemic stage
3. Stage of Acute manifestation
4. Stage of Obstructive (Chronic) lesions

23. Wuchereria bancrofti
Bancroftian Filariasis

24. Wuchereria bancrofti

25. Wuchereria bancrofti - Adult

26. LIFECYCLE OF W. bancrofti

28. Filarial fever

29. Complications

30. Lab diagnosis

31. Laboratory Diagnosis
1. Demonstration of microfilarae in the
peripheral blood
a. Thick blood smear: 2-3 drops of free flowing
blood by finger prick method, stained with JSB-II
b. Membrane filtration method: 1-2 ml
intravenous blood filtered through 3µm pore
size membrane filter
c. DEC provocative test (2mg/Kg): After
consuming DEC, mf enters into the peripheral
blood in day time within 30 - 45 minutes.

32. 2. Immuno Chromatographic Test (ICT): Antigen
detection assay can be done by Card test and
through ELISA. Circulating Filarial Antigen
detection is regarded as “Gold Standard” for
diagnosing Wuchereria bancrofti infection.
Specificity is near complete, sensitivity is
greater than all other parasite detection assays,
will detect antigen in amicrofilaraemic as well
as with clinical manifestations like
lymphoedema, elephantiasis.

33. 3. Quantitative Blood Count (QBC):
QBC will identify the microfilariae and will help in
studying the morphology. Though quick it is not
sensitive than blood smear examination.
4. Ultrasonography:
Ultrasonography using a 7.5 MHz or 10 MHz probe can
locate and visualize the movements of living adult
worms of W.b. in the scrotal lymphatics of
asymptomatic males with microfilaraemia. The
constant thrashing movements described as “Filaria
dance sign” can be visualized.

34. 5. Lymphoscintigraphy:
The structure and function of the lymphatics of the
involved limbs can be assessed by lymphoscintigraphy
after injecting radio-labelled albumin or dextran in the
web space of the toes. The structural changes can be
imaged using a Gamma camera. Lymphatic dilation &
obstruction can be directly demonstrated even in early
clinically asymptomatic stage of the disease.
6. X-ray Diagnosis:
X-ray are helpful in the diagnosis of Tropical pulmonary
eosinophilia.
Picture will show interstial thickening, diffused nodular
mottling.
7. Haematology : Increase in eosinophil count

35. Peripheral smear showing Microfilaria

36. CLASSICAL FILARIASIS vs OCCULT FILARIASIS
CLASSICAL FILARIASIS OCCULT FILARIASIS
CAUSE Inflammatory changes to
Devoloping worms and
adult
Hypersensitivity reaction
to Microfilaria antigen
PATHOLOGY Acute inflammation and
epitheloid granuloma
Eosinophilic granuloma
ORGANS AFFECTED Lymph nodes &
Lymphatic system
Lung, liver and spleen
MICROFILARIA Present in blood Present in affected
tissues & absent in blood
THERAPEUTIC RESPONSE No response Responds to
microfilaricidal agent
SEROLOGICAL TESTS Antobody not diagnostic IgE Ab Highly sensitive

38. DEC PROVOCATION TEST
• Diethyl carbamazine 2mg/kg Body weight
• 20-50 mins later – peripheral smear for
microfilariae.

39. Post DEC Provocation test

40. Tropical Pulmonary
Eosinophilia

41. Brugia malayi
Malayan Filariasis

42. LIFE CYCLE

43. Brugia malayi

44. Brugia malayi

45. Microfilaria of Wuchereria bancrofti
& Brugia malayi
Features Wuchereria bancrofti Brugia malayi
Appearance Graceful sweeping curves Kinky with 2⁰ curves
Size 250-300 micrometres long 175 to 230 micrometres
Cephalic space Length to width ratio 1:1 Length to width ratio 2:1
Stylet at anterior end Single Double
Excretory pore Not prominent Prominent
Nuclei column Large coarse discrete nuclei Overlapping blurred nuclei
Tail Pointed & free of nuclei Pointed with 2 distinct nuclei
Sheath Faintly stained Well stained

47. Wuchereria bancrofti

48. Brugia timori
Lymphatic filariasis

49. Brugia timori

50. Loa loa
• African eye worm
• Calabar swelling
• Fugitive swelling
• Adult: 3-7cm long
• Treatment: Dec. Surgical removal

51. CALABAR SWELLING

52. Loa loa Subcutaneous nodules

53. LIFE CYCLE

54. Loa loa

55. Onchocerca volvulus
River blindness
Convoluted or Blinding filaria
50cm long adult worm

56. Onchocerca volvulus

57. Onchocerca volvulus

58. Mazzotti reaction
• DEC treatment causes intense reaction with
rash, pruritus, facial edema, fever,
hypotension, lymphadenopathy and occ. Eye
damage.
• Drug of choice is Ivermectin

59. Life cycle

60. Mansonella streptocerca
• Subcutaneous filariasis

61. Life cycle

62. Mansonella ozzardi

63. Mansonella perstans
• Usually nonpathogenic

64. Mansonella perstans

65. Zoonotic filariasis
• Dirofilaria immitis – Dog heart worm
• Dirofilaria repens (dogs) – subcutaneous
and conjunctival nodules in humans
• Dirofilaria conjunctivae (humans)
• Brugia pahangi- cats and dogs

66. Dirofilaria immitis

67. Dirofilaria immitis

68. Dirofilaria repens

69. Brugia pahangi

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