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Lymphatic Filariasis
1. Tissue / Somatic Nematodes
By Dr. Rakesh Prasad Sah (Associate Professor Microbiology)
2. › Filarial nematodes – major group
› Family Filarioidea
› Filum – thread
› Slender, thread – like worms
› 8 species infect human being
3. Common Characteristics
• Require two hosts
– Need intermediate host
• Optimum/Definitive host – Man (the only reservoir host in W. bancrofti)
• Second host/Intermediate host – Insect vectors
• All species are transmitted by the bite of blood- sucking insect vectors.
4. Common Characteristics
Location (habitat)
› Tissue, blood or body cavities
› Adult worms seen in Lymphatic vessels and lymph nodes
› Embryonic forms seen in peripheral blood during night
› Female worms are Viviparous
– adult female give birth to larvae k/a microfilaria
5. › Highly motile, thread like pre larva
› Microfilaria are capable of living a long time in the vertebrate host,
but cannot develop further until ingested by an intermediate host.
› Microfilariae transforms into infective larvae in the insect and are
deposited in the next host when insect takes its blood meal.
› Some sp. retain their egg membranes which envelope them –k/a
‘Sheathed ‘microfilariae’
› In some it ruptures to become naked or ‘unsheathed’.
6. Most Important Species (according to habitat)
Lymphatic filaria
› Wuchereria bancrofti
› Brugia malayi
› Brugia timori
Subcutaneous tissue
› Onchocerca volvulus: river
blindness
› Loa loa: subcutaneous swelling
› Mansonella streptocerca
Serous cavity
› Mansonella perstans
› M. ozzardi
11. Location in the body
Worm Adult Microfilaria Periodicity of
microfilaria
Vector
Serous cavity filariasis
Mansonella
perstans
Body cavities Blood Non-periodic Culicoides
Mansonella ozzardi Body cavities Blood Non-periodic Culicoides
12. Periodicity
› Nocturnal periodicity : The microfilariae present in the peripheral
blood during daytime is very low in density. The number of
microfilariae gradually increases from evening to midnight
• W. bancrofti
• B. malayi
• B. timori
› Diurnal (daytime)
– L. loa
13. › Subperiodic (detected throughout the day but majority at night or late
afternoon)
– Some strains of W. bancrofti and B. malayi
› Nonperiodic - microfilariae circulating at some what constant levels
during day and night
– Mansonella
15. Lymphatic Filariasis
› Lymphatic filariasis is caused by the worms
– Wuchereria bancrofti
– Brugia malayi
– Brugia timori.
› These worms occupy the lymphatic system, including the lymph nodes.
› In chronic cases, these worms lead to the disease Elephantiasis.
17. Intermediate Host
› W. bancrofti is transmitted by
– Culex
– Aedes
– Anopheles species
Anopheles
Aedes
Culex
18. Morphology of Adult worm
• Long, thread-like nematodes
• Filiform in shape
• Tapering ends
• Creamy- white
› Sexually dimorphic species
› The adult male worm is 3 -5 cm in length, 0.1 cm in diameter.
› The female is 6 -10 cm long, 0.2-0.3 cm in diameter.
› Tail end of male worm is curved ventrally while that of female worm is narrow and
abruptly pointed.
22. Microfilaria
› Microfilariae are sheathed.
› Colourless and transparent.
› Approximately 245 - 300 μm in length.
› Sheath is longer (359 μm).
› Nocturnal periodicity.
› 10 PM ~ 2 AM.
23. Microfilariae measure 270 by 8 µm, have a sheath and a tail with terminal
constriction, elongated nuclei and absence of nuclei in the cephalic space. They
have nocturnal periodicity. (Wet mount preparation).
26. › Infective form - L3 larva.
› L1: 1-3 hours
› L2: 3-4 days
› L3: 5-6 days
› Clinical Incubation period: 8-16 months
› Inside the arthropod, the microfilariae develop in 1 to 2 weeks into infective
filariform (third stage larvae)
› Infective third stage larvae are transmitted to man by infected biting
arthropods during a blood meal
27. › The infective larvae migrate to the nearest lymph gland
where they mature into the thread like adult worms about 3
months to 1 year later.
› Mature adults can survive for 5 to 10 years.
28. Pathogenesis
› Main pathogenic factor
– Adult
› Manifestations are 2 types
1. Lymphatic Filariasis (caused by Adult worms)
2. Occult Filariasis (caused by embryos)
31. Acute inflammatory phase
› Recurrent attacks of lymphangitis and lymphadenitis due to blocking
of L. N. and lymph vessels.
› Blocking may be d/t
– toxic products
– mechanical irritation
– allergic reactions
– secondary bacterial infection.
32. Chronic Manifestation
› Chronic /Obstructive lesions takes 10-15 years.
› Most spectacular symptom of lymphatic filariasis is
– Elephantiasis - edema with thickening of the skin and underlying tissues
(especially in the legs and genitals)
› Wide spread fibrosis and damage of lymphatic vessels result in rupture
and discharge of lymph into the urinary system (chyluria) or hydrocoele.
35. Occult Filariasis
› Result of hypersensitivity to microfilarial antigens.
› Patients present with
– paroxysmal cough and wheezing
– low grade fever
– occasional haemoptysis
– massive eosinophilia
– Hepatosplenomegaly
– LAP.
› Microfilaria not seen.
36. Tropical Pulmonary Eosinophilia (TPE)
› Low grade fever, loss of weight
› No microfilaria in blood but appears in lung
› Lung opacities and cough and wheeze
› Marked eosionophilia
› Increased IgE
› Mottled shadows in Chest X-ray
37. Laboratory diagnosis
› Samples include
– Peripheral blood
– Chylous urine
– Exudate of lymph varix
– Hydrocele fluid
– Lymph node biopsy
– skin specimen
› Microscopic examination
– It deals with the detection of microfilariae.
› Macroscopic examination
– detection of adult worm (lymph node biopsy)
38. Microscopy
1. Demonstration of microfilariae in the peripheral blood
a. Thick blood smear: blood sample taken at night from 9pm-2am
by finger prick method, stained with Giemsa
41. Microscopy
1. Demonstration of microfilariae in the peripheral blood
b. Concentration techniques
i. Membrane filtration method: 1-2 ml intravenous blood filtered
through 3μm pore size membrane filter
ii. Knott's concentration method and sedimentation technique
42.
43.
44.
45. 1. Demonstration of microfilariae in the peripheral blood
C. DEC provocative test (2mg/Kg): After consuming DEC, mf enters into the
peripheral blood in day time within 15 – 20 minutes.
› Wet mount preparation.
› Immunochromatographic Test (ICT):
– Antigen detection assay can be done by Card test and through ELISA.
– Can detect antigen in amicrofilaraemic phase
› Circulating Filarial Antigen detection is regarded as “Gold Standard” for
diagnosing Wuchereria bancrofti infection.
46. › X-ray Diagnosis:
– Helpful in the diagnosis of Tropical pulmonary eosinophilia. Picture will show
interstial thickening, diffused nodular mottling.
– Calcified adult worms
› Immunodiagnosis:- (ELISA,IFAT,CFT,IHAT) detect antibodies using
Dirofilaria immitis antigen.
› PCR
› Eosinophilia(6-26%).
48. Management
› DEC – Drug of choice
› Kills microfilaria
› dose 6 mg/kg
› Lympangitis –
› Oral Antibiotics to cover against common skin pathogens Erythromycin
› Elevation
› Diuretics to reduce swelling – cosmetic/early recovery/ functional gain
49. Management
› Elephantiasis-
› Prophylaxis against bacterial skin sepsis
› [oral penicillin/ monthly benzathine penicillin ]
› Good foot hygiene, nail care, raising the foot at night appropriate footwear
› Periodic DEC to prevent re infection
50. Surgical Treatment
› Hydrocele: Excision
› Lymphoedema (Elephantiasis): Excision of redundant tissue, Excision of
subcutaneous and fatty tissues, postural drainage and physiotherapy
51. Prevention and control
› Destruction of breeding sites of vectors.
› Using bed nets while sleeping.
› Applying repellant creams on skin.
52. Brugia malayi
› Blood & lymphatics
› Causes elephantiasis, but is not as
disfiguring or common as with
Wuchereria bancrofti.
› Vectors – Mansonia (a mosquito that
usually bite during the night),
Anopheles & Aedes mosquitoes.
53. › Causes lymphatic filariasis in South East Asia (China, India, Indonesia,
Korea, Japan, Malaysia, and Philippines).
› There are two strains of B. malayi
1. The nocturnal periodic strain which is widely distributed in Asia.
2. The sub-periodic strain which is found in Malaysia, Indonesia and the
Philippines.
54. Morphology - B. malayi
› Microfilariae are sheathed
› About 200 - 275 μm and 6 μm in diameter.
› B. malayi microfilariae are slightly smaller
than those of W. bancrofti.
› Mf show nocturnal periodicity
55. Morphology
› One distinctive feature of B.malayi is that the microfilarial nuclei extends to
the tip of the tail with two nuclei near end of tail, one in a swelling just short
of tail’s end, the other in the end of the tail.
57. Brugia malayi: the tail is tapered and present a constriction.
The last two nuclei are divided by the constriction.
58. Brugia malayi: the cephalic space is longer than broad
(in W.bancrofti is as long as broad).
59. Differentiation of Mfs Between W.b. and B.m
W. b. B. m.
Size Large Small
Curvature Smooth Kinky
Cephalic space Short Long
Somatic nuclei Clear & separated Fused
Caudal nuclei None 2
60. Adult worms
› The adult worms of B. malayi are smaller than those of W. bancrofti
› Location : superficial e.g. mainly in lower limbs (W. bancrofti : superficial
and deeper e.g. lower limbs, groin, scrotum)
61. › L1 – L3 takes 6 -8 days
› Development of adult worms takes 7 months
63. Diagnosis
› Detection and identification of microfilaria in stained blood smears.
› Lymph node biopsy – adult worms
› PCR
› DNA probes
64. B. timori
› Exists only on islands of the Indonesian archipelago
› The lifecycle closely resembles that of Brugia malayi.
› Microfilariae - 310μm in length (larger)
› The sheath fails to stain pink with Giemsa
› Disease - Lesions are milder
65. Subcutaneous Filariasis
› Caused by the worms
– Loa loa
– Onchocerca volvulus
– Mansonella streptocerca
– Dracunculus medinensis (guinea worm)
