1. Dr.R.Jayaprada
LYMPHATIC FILARIASIS

2. Outline of presentation
Lymphatic Filariasis
 Introduction
 History
 Epidemiology
 Morphology
 Mode of transmission
 Life cycle
 Pathogenesis
 Signs and symptoms
 Laboratory diagnosis
 Prevention and Control

3. Lymphatic Filariasis
 WHO has identified lymphatic filariasis (LF) as the second leading cause of
permanent and long-term disability after leprosy(1-3).
 Filariasis is the pathological condition caused by infection of filarial
nematodes transmitted by different vectors.
Infection with 3 closely related Nematodes
 Wuchereria bancrofti (90%)
 Brugia malayi
 Brugia timori (10%)
1.Centers for Disease Control and Prevention (CDC). Morbidity & Mortality Weekly Report. 2011; 60(24):814-18.
2. Addiss DG, Brady MA. Morbidity Management in the Global Programme to Eliminate Lymphatic Filariasis: A Review of
the Scientific Literature. Filaria J 2007;6:2.
3.National Vector Borne Disease Control Programme, Directorate General of Health Services, Ministry of Health and
Family Welfare, Government of India. Website: Available from: http://nvbdcp.
gov.in/filariasis-new.html. [Assessed on 2011 Sept 23].

4. Lymphatic Filariasis
• Transmitted by the bite of infected mosquito responsible for
considerable sufferings/deformity and disability
• Infection occurs in blood vessels, lymphatic system , connective
tissues and serous cavities of man
* All the parasites have similar life cycle in man
* Adults are seen in Lymphatic vessels
* Off springs seen in peripheral blood during night

5. History
 Symptoms of bancroftian filariasis had been mentioned as elephantiasis
arabicum in the ancient hindu literature ( Susruta, 600 BC).
 Demarquay (1863) first demonstrated the microfilariae in hydrocele fluid.
 Subsequently, Wucherer in brazil described the microfilariae in chylous
urine in 1866.
 Lewis (1872) in India demonstrated the microfilariae in the peripheral
blood.
 Bancroft (1876-77) first demonstrated adult females & Sibthorpe (1888)
first found males.
 Manson(1878) first demonstrated the culex mosquitoes as the
intermediate host & also described the nocturnal periodicity of
microfilariae in the peripheral blood.

6. EPIDEMIOLOGY
 W. bancrofti occurs in sub-Saharan Africa, Southeast Asia, the Indian
subcontinent, many of the Pacific islands, and focal areas of Latin
America and the Caribbean (including Haiti).
 B. malayi occurs mainly in China, India, Malaysia, the Philippines,
Indonesia, and various Pacific islands.
 B. timori occurs on the Timor Island of Indonesia.
 Overall, approximately two-thirds of individuals infected with lymphatic
filariasis are in Asia.

7. Vectors of Lymphatic filariasis
 The major vectors of W. bancrofti are mosquitoes of the genus Culex (in
urban and semi-urban areas), Anopheles (in rural areas of Africa and
elsewhere) and Aedes(in islands of the Pacific).
 The parasites of B. malayi are transmitted by various species of the
genus Mansonia; in some areas, anopheline mosquitoes are responsible
for transmitting infection.
 Brugian parasites are confined to areas of east and south Asia, notably
India, Indonesia, Malaysia and the Philippines.
 An estimated 120 million people in tropical and subtropical areas of the
world are infected with lymphatic filariasis; of these, almost 25 million men
have genital disease (most commonly hydrocele) and almost 15 million,
mostly women, have lymphoedema or elephantiasis of the leg.
 Approximately 66% of those at risk of infection live in the South-East Asia
Region and 33% in the African Region.

8. EPIDEMIOLOGY

9. Global Scenario
 Population
at risk : 120 million
 No. of countries : > 80
 Mf carriers : 76 million
 Diseased : 44 million
 Hydrocele : 27 million
 Lymphoedema : 16 million
 TPE : 1 million

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

11. Taxonomic classification
 Kingdom : Animalia.
 Phylum : Nemathehelminthes.
 Class : Nematoda.
 Subclass : Phasmidia.
 Super family : Filariodea.
 Family : Acanthocheilonematidae.
 Genus : Wucheraria, Brugia.
 Species : bancrofti, malayi, timori.

12. Morphology of W . bancrofti
 Adult worm: long, thread like, minute, whitish, transparent nematodes.
 Filariform in shape.
 Anterior end is surrounded by 2 rows of ten sessile papillae.
 Posterior end contains anus at its terminal end.
 Male measures 2.5 to 4 cm in length by 0.1 mm in thickness and female
measures 8 to 10 cm in length and 0.3 mm in thickness
 Male: Tail end is sharply curved ventrally with 2 spicules of unequal
length.
 Female: Tail end is narrow & abruptly pointed.
 Females are ovoviviparous ( Laying eggs with well developed
embroyos).
 Life span is usually 5-10 years.

13. Morphology of Brugia
Brugia malayi
 The adult females of B malayi resembles to W. bancrofti but the
adult males differ .
Brugia timori
 Similar to B. malayi .

14. Morphology of microfilaria
 First stage larva is called microfilaria.
 Microfilaria are found in the peripheral blood, hydrocele fluid and chylous
urine.
 It has a
 A . Hyaline sheath
 B . Cuticle lined by subcuticular cells & is seen only with vital stains.
 C. Somatic cells or nuclei : These appear as granules in central axis of
the body & extend from head to the tail end. Granules do not extend upto
the tip of the nuclei & serve as distinguishing feature of Mf. bancrofti.

15. Morphology of microfilaria
 Granules are broken at definite places serving as the landmarks for
identification of the species. They include the following:
 A. Nerve ring, an oblique space.
 B. Anterior ‘V’ spot, represents rudimentary excretory system.
 C. Posterior ‘V’ spot, represents the terminal part of the alimentary canal
(anus/cloaca).
 D.G-cells, also called genital cells.
 E.Innenkorper of fulleborn or Central body of manson: Represents the
rudimentary alimentary canal.

16. Differences b/n microfilaria of bancrofti, malayi & timori
Microfilariae Periodicity Sheath Size Body &tail
Mf. bancrofti Nocturnal Sheathed Large & thick Body curves are graceful
& sweeping.
Tail is tapering &pointed.
No nuclei are in the tail
end.
Mf. malayi Nocturnal Sheathed Large & thick Body is coiled & kinked.
Nuclei are large& dense.
Tail is tapering.
Two nuclei are present in
the tail end.
Mf.timori Sub-periodic Sheathed Large & thick Body stains lightly.
Tail is irregularly tapering.
Two nuclei are present at
the tail end.

17. Microfilaria of Brugia
malayi. Figure B:
Microfilaria of B. malayi in
a thick blood smear,
stained with Giemsa and
captured at 500x oil
magnification
Microfilaria of Wuchereria
bancrofti. Figure A:
Microfilaria of W. bancrofti in
a thick blood smear stained
with Giemsa and captured at
500x oil magnification
Microfilaria of B.
timori in a thick blood
smear, stained with
Giemsa and captured
at 500x oil
magnification.
Courtesy:
CDC

18. Micro filarial periodicity
 Nocturnal periodicity: Mf are present in the peripheral blood between
10 P.M to 4 A.M. Mechanism is presumed to be related with night feeding
habit of culex pipens fatigans.
 Nocturnal periodicity is shown by Mf.bancrofti, B.malayi & B.timori
 Diurnal periodicity: Mf are present in large number in peripheral blood
during day hours. Eg: Loa loa.
 Nocturnal sub-periodicity & diurnal sub-periodicity: Mf are present in the
peripheral blood continuously throughout day & night with a slight
increase in number during afternoon & evening. Eg: Sub-periodic W.
bancrofti & B.malayi.

19. Modes 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. Life cycle
 W. bancrofti passes its life cycle in 2 hosts: Man & Mosquito ( Culex
quinquefasciatus, Anopheles, Aedes).
 Mode of transmission: Bite of infected female mosquito.
 Infective form : Third stage larva.
 In India & china: Culex pipens fatigans.
 In pacific islands: Anopheles punctulatus.
 In polynesian islands: Aedes polysienensis.

21. Life cycle in mosquito
 Sheathed microfilaria ingested by mosquito during its blood meal, loses
its sheath with in 1 hour or 2 hour
Migrates to thoracic muscles of the mosquito
next 48 hrs
First stage larva (L1) ( Thick, short, sausage shaped forms with short spicy
tail )
Moults once/ twice in 3-7 days time
Second stage larva (L2) ( Larger sausage shaped larva
on 10th or 11th day
Third stage larva (L3)Infective stage.
Enters the proboscis of the mosquito on 14th day.
Development in mosquito is completed within 10-20 days.
In mosquitoes, Mf do not multiply to increase in number, each microfilara
develops into one L3 larva.

22. Life cycle in man
Mosquito with Mf bites a man
Third stage larva (L3) deposited on the skin
Reach lymphatic channels
Migrates to the inguinal lymph nodes
Develop into adult worm & sexually mature
Adult male & female worms are coiled up in the regional lymphatics &lymph
nodes
Fertilization
Gravid female gives birth to Mf Reach the thoracic/R. lymphatic duct
Venous system
Peripheral blood

23. Life cycle

24. Pathogenesis
 Pathogenic effects seen in wuchereriasis are produced by the adult worm
(living/ dead).
 L3 larva & microfilaria are not pathogenic.
 Following stages occur sequentially in the pathogenesis of lymphatic
filariasis:
 1.Dilatation of lymphatic vessels.
 2.Infecion of the lymphatics ( Lymphangitis).
 3. Obstruction of the lymph nodes.

25. Causes of lymphangitis
 1.Mechanical irritation caused by the movement of adult worms inside
the lymphatic system.
 2. Liberation of toxic metabolites by the growing larvae & secretion of
some toxic fluid by fertilized females Allergic manifestations like
urticaria, fugitive swellings & lymphedema.
 3. Absorption of toxic products liberated from dead worms undergoing
disintegration Allergic manifestations.
 4.Bacterial infection---secondary invaders.

26. Causes for lymphatic obstruction
 1. Mechanical blocking of the lumen by dead worms which act as an
embolus.
 2.Obliterative endolymphangitis: Endothelial proliferation &
inflammatory thickening of the walls of the lymphatic vessels.
 3.Excessive fibrosis of the lymphatic vessels: caused by recurrent &
repeated attacks of lymphangitis.
 4.Fibrosis of the afferent lymph nodes draining the particular area.
Effects of lymphatic obstruction: Two types of conditions are produced:
 A. Lymph varix —varicosity of lymphatic vessels.
 B. Elephantiasis ---Hypertrophy of the affected part.

27. Factors affecting pathogenesis
 Factors affecting pathogenesis of filarial manifestations include
 1.Cumulative exposure to bites,
 2.Quantity of accumulating adults,
 3. Number of secondary infections,
 4.Degree and type of host immune response (Th1/Th2) and
 5.Genetic predisposition (4-6).
 Hydrocele is less common in microfilaria carriers than endemic normals.
 Lymphatic filarial parasites also harbor an endosymbiont – Wolbachia -
that contributes to inflammation (7).
4.Adjobimey T, Hoerauf A. Induction of Immunoglobulin G4 in Human Filariasis: An Indicator of Immunoregulation.
Ann Trop Med arasitol 2010; 104:55-64.
5.Ravichandran M, Reghunathan J, Narayanan RB, Jayaram K, Kaliraj P. Modulation of Cellular Immune Responses
by Cytokines in Bancroftian Filariasis. Ind J Clin Biochem 1997; 12(1):27-31.
6.Lammie PJ, Cuenco KT, Punkosdy GA. The Pathogenesis of Filarial Lymphedema: Is it the Worm or is it the Host?
Ann NY Acad Sci 2002; 979:131-42.
7.Debrah AY, Mand S, Specht S, Marfo-Debrekyei Y, Batsa L, Pfarr K et al. Doxycycline Reduces Plasma VEGF-
C/sVEGFR-3 and Improves Pathology in Lymphatic Filariasis. PLoS Pathogens 2006;

28. Different stages of lymphatic vessel remodeling and modulation of lymphatic flow during
progression of filarial infection. (A) Normal lymphatic collecting vessel showing normal flow
patterns and lymphatic drainage regulated by the unidirectional valves in the absence of filarial
parasitic infection.
(B) Onset and progression of acute filarial infection with microfilariae and adult worms lodged
within the vessel. Normal host immune response is initiated. Slight hypertrophy of the lymphatic
muscle cell layers is observed with a partial impairment of lymph flow. (C) Chronic filarial infection
results in a major host immune response due to toxins released by dead or live parasites. Various
immune cells are observed at the site of infection leading to a strong inflammatory reaction.
Secondary infections with bacteria harboring Wolbachia exacerbates the condition leading to a
chronic infection state or elephantiasis. The lymphatic vessels exhibit largely dysfunctional valves,
vessel dilation, impaired lymphatic muscle contractility and insufficient drainage. The resultant
fluid accumulation and retrograde lymph flow associated with severe lymphedema. Activation and
remodeling of lymphatic endothelial cells during this chronic stage could potentially result in either
endothelial dysfunction or promote lymphangiogenesis.

29. Pathogenesis

31. Immunopathogenesis
Microfilaria Adult
worm
Wolbachi
a
Dead/Decalcifyin
g
Worm
Secondary
infection
Parasitic secretory/excretory
Products (over 850 identified)
Immunomodulatory Gly p (ES-
62),
Circulating microbial products
Early activation of immune
response Th2 response
Antiinflammatory cytokine
production
IL-4, IL-10, TGF-ß
Wolbachia ligands(>90
identi)
SP, HSP, LPS
Inflammatory
Cytokine
prodution
IL1,6,IFNγ,TNFα,N
O
Upregulation of pro inflammatory
Cyto IL6,12,17,22, IFNγ,TNFα, GM
CSF
Desensitisation
to TLR & CD 40
pathways
Activation of inflammatory
mediators
Lymphangiogenic &
Angiogenic factors, VEGF-
A,C, D, Ang 1,2.
Upregulated acute phase
proteins
CRP, Haptoglobin..
Early activation of immune
response
Th1 & Th2Depressed & Desensitized host immune
response
Acute inflammatory
response Inflammatory host immune response
Asymptomatic or Acute pathology Chronic pathology
Lymphatic endothelial cells Lymphatic muscle cells
Proliferation
morphological changes..<
permeability
Fibrosis
Cellular hyperplasia,
impaired contractility

32. Immunopathogenesis

33. Clinical manifestations
 Two distinct groups of clinical entities caused by W.bancrofti are:
 1. Lymphatic filariasis
 2. Occult filariasis.
 Clinical manifestations depend on stages of the disease lymphatic
filariasis as follows:
 1.Endemic normal
 2.Asymptomatic stage
 3. Acute filariasis
 4.Chronic filariasis
 5.Occult filariasis
 6.Less frequent lesions: granuloma of spleen & other organs, presence
of adult W. bancrofti in the anterior chamber of the eye.

34. Clinical manifestations
 1.Endemic normal/ Asymptomatic amicrofilaremia : In endemic areas
of filariasis, a certain proportion of population living in these areas do
not develop overt clinical features or any microfilaria in the peripheral
blood after an exposure to L 3 larva.
 2. Asymptomatic stage:
 Persons in this stage have microfilaraemia in their blood & do not
show any clinical manifestations.
 It is suggested that in these people, TH1 component of inflammatory
response is down regulated & TH2 component is stimulatory. Cytokine
IFNα is depressed & IL-4 is elevated.
 After many years later, Hyporesponsiveness breaks down
Inflammation begins

35. Clinical manifestations
 3) Acute –
 Fever with chills and rigors, lymphedema with pain, lymphadenopathy
(cervical, axillary, inguinal and generalised – Acute Filarial
Lymphangitis/Acute Dermatolymphangioadenitis), chyluria, hematuria,
inflammatory granuloma or abscesses, pain in testes, funiculitis,
epididymoorchitis.
 4) Chronic - funiculitis, epididymoorchitis, hydrocele, lymph varices,
chyluria, elephantiasis, breast edema(1-3,8-10).
8.Sabesan S, Palaniyandi M, Das PK, Michael E. Mapping of lymphatic filariasis in India. Ann Trop Med Parasitol 2000;
94:591-606.
9.Hotez, PJ., Molyneux, DH., Fenwick A., Kumaresan, J, Sachs SE, Sachs JD et al. Control of Neglected Tropical
Diseases. N Engl J Med 2007; 357:1018-27.
10.Lahariya C, Tomar SS. How Endemic Countries can Accelerate Lymphatic Filariasis Elimination? An Analytic Review
to Identify Strategic and Programmatic Interventions. J Vector Borne Dis
2011; 48:1-6.

36. Clinical manifestations
 5) Occult filariasis ( Meyers-Kouwenaar syndrome):
 a)Condition in which there is massive eosinophilia (30-80%),
 b)Absolute eosinophilic count >3000/ mm3,
 c) Generalized lymphadenopathy
 d) Hepatosplenomegaly
 e) Pulmonary symptoms
 f) Absence of microfilaraemia.
 Adult worm produces Mf continuously, but they do not reach the peripheral
blood because they are destroyed in the tissues.

37. Tropical pulmonary eosinophilia (Eosinophilic lung Or Weingarten’s
syndrome)
• First described in 1940 and labelled as “pseudotuberculosis with
eosinophilia”(11).
• Term tropical pulmonary eosinophilia (TPE) was first coined by Weingarten in
1932 to a syndrome of wheezing, fever, eosinophilia, cough with scanty
sputum (blood tinged), spleenomegaly and bilateral mottling of the lungs.
• Mf may be demonstrated in the lung biopsy specimens.
• TPE is caused by a type 1 hypersensitivity reaction to filarial antigens (W.
bancrofti or B. malayi). It presents as an eosinophilic alveolitis with an airway
component.
• Total serum IgE levels (10,000 to 100,000 ng/mL) and antifilarial antibody
titers are characteristically elevated.
11.Frimod1. t-Moller C, Barton RM. A pseudo-tuberculosis condition associated with eosinophilia. Indian Med Gaz
1940; 75 : 607-13.

38. Laboratory diagnosis of Wuchereriasis
 Samples includes :
Peripheral blood , Chylous urine, Exudate of lymph varix, Hydrocele fluid,
Lymph node biopsy, skin specimen
 Diagnosis of Bancroftian filariasis
 Direct evidence /Specific tests Indirect evidence/ Non specific test
 Microfilariae in Peripheral blood, Adult worms
Chylous urine, Hydrocele fluid in biopsied L.node
Allergic tests Serological tests
1. Blood for eosinophilia
2. Intradermal test for immediate hypersensitivity

39. Methods of examination
 1. Blood Microscopy
 2. DEC provocation test
 3.Quantitative buffy coat examination
 4. Urine microscopy
 5.Microscopy of hydrocele fluid & lymph node aspiration.

40. Blood Microscopy
 2 or 3 drops of peripheral blood are collected by finger prick.
 Blood is collected as follows:
 Nocturnal periodic W.bancrofti: Between 10 P.M & 4 A.M in the night.
 Sub-periodic Nocturnal W.bancrofti : Between 8 P.M & 4 A.M during
night.
 Sub-periodic diurnal W.bancrofti : Between 2 P.M & 6 P.M in the after
noon.

41. Blood Microscopy
 Microfilaria can be demonstrated in the blood by microscopy by following
methods:
 1.Direct wet mount: 2-3 drops of blood is collected on a clean glass slide &
examined after placing a cover slip on it. Live microfilariae are identified by
characteristic serpentine movement in the blood plasma.
 2.Stained thick blood smear: Thick blood smear stained with giemsa or
leishman or wright or delafield’s hematoxylin stain is most commonly used
method for demonstration of Mf.
 Sheathed Mf with absence of nuclei in the tail tip is diagnostic of W. bancrofti
Mf.
 Delafield’s hematoxylin stain is used widely to demonstrate the greater
structural detail of Mf. This stain enhances the nuclei & sheath.

42. Blood Microscopy
 3. DEC provocation test:
 In this test, 2-8 mg/ kg of Diethyl carbamazepine (DEC) is given
orally to stimulate nocturnal periodic Mf to circulate in the peripheral
blood during the day time.
 After 30 minutes, capillary blood is collected by finger prick for
demonstration of Mf by direct wet mount or by staining the blood
smear.
 This test is contraindicated in the areas where Loa loa or
Onchocerca volvulus infections are also found because of Mazzotti
reaction & blindness in onchocerciasis.

43. Blood Microscopy
 4.Quantitative buffy coat examination:
 Quantitative buffy coat system (which requires commercial
equipment and fluorescence microscopy) may be used to enhance
sensitivity.
 Additional thin smears would be required to determine identification
of any microfilaria present.

44. Concentration of blood
 Various concentration methods are available for recovery of Mf.
 a. Knott’s method of concentration by sedimentation.
 b. Membrane filtration concentration methods using nuclepore
membrane filter or millipore membrane filter Most sensitive method
for recovery of Mf.

45. Knott’s method of concentration by sedimentation.
 Principle : This technique is used to recover low number of microfilariae
from blood.
 Formalin solution is used to lyse the RBC’s in a large blood sample,
and the organisms are concentrated in sediment by centrifugation.
 Disadvantage of this technique is that the Mf are killed & immobilized
and are therefore not readily revealed by any motility.
 Limitations:
 A. Motility will not be visible after formalin fixation.
 B. Identification to the species may be difficult without additional
staining.

46. Knott’s method of concentration by sedimentation
 Procedure: 1)1 ml of fresh whole blood or anticoagulated blood ( 9ml
of blood + 1 ml of 5% sodium citrate) in a centrifuged tube containing
10 ml of 2% formalin is mixed thoroughly.
 2. Centrifuge for 5 min at 300 Χ g.
 3. Pour off the supernant fluid without disturbing the sediment.
 4. A portion of sediment is placed on the slide & a cover slip is
applied and examined microscopically under low power (10X) & high
power (40X).
 5. If Mf are present, a thick film is prepared from the remainder
sediment, air dried, fixed in absolute methanol for 5 min, air dried
again & stained with giemsa/ Delafield haematoxylin.

47. Membrane filtration concentration
 Principle: Membrane filtration method have been developed for
recovering from patients with light infections
 It is one of the most efficient for the clinical laboratory when other
procedures used to recover Mf are unsatisfactory.
 Limitations:
 A. Giemsa or hematoxylin staining may be necessary to identify
the organisms to species level.
 B. Identification of Mf on filters to the species level may be difficult.

48. Membrane filtration concentration
 Procedure:
 1. 1 ml of fresh whole blood or anticoagulated blood into a 15 ml syringe
containing 10 ml of distiiled water.
 2. Mixture is shaken for 2-3 min to ensure that all blood cells are lysed
 3. A 25 mm Nuclepore filter (5µm porosity ) is placed over a moist 25 mm
filter paper pad, & placed in a swiney filter adapter.
 4. Swiney filter adapter is attached to the syringe containing the lysed blood.
 5. Lysed blood is pushed through the filter with gentle steady pressure on the
piston.

49. Membrane filtration concentration
 6. Without disturbing the filter, Swiney adapter is removed from the
syringe, and approx 10 ml of distilled water is drawn into the syringe.
Adapter is replaced & gently water is pushed through the filter to wash the
debris from the filter.
 7. Filter is removed from the adapter, placed it on the slide & allowed it air
dry.
 8.Then stained with giemsa / Delafield hematoxylin.

50. Microscopy
 5.Urine Microscopy: Mf are demonstrated in the chylous urine.
 Usually 10-20 ml of early morning sample is collected, centrifuged
& sediment is examined under microscope for Mf.
 6.Microscopy of hydrocele fluid/ L.node aspiration:
 Ether/ Chloroform /xylol is used dissolve the fat globules & same
method as urine is employed.

51. Immunodiagnosis
 Immunodiagnostic methods include:
 1.Serological tests & 2. Cellular assays.
 Serology-based diagnosis tools can be divided into two categories:
 a) Antigen-detection assays and b) Antibody-detection assays.
 These include the enzyme-linked immunosorbent assay (ELISA), also
called enzyme immunoassay (EIA), and all its derived tests such as the
Falcon assay screening test ELISA (FAST-ELISA) and the dot-ELISA.
 Other assays include the hemagglutination (HA) test, indirect or direct
immunofluorescent antibody (IFA or DFA) tests, complement fixation (CF)
test, and immunoblotting and rapid diagnostic tests (RDTs)(12).
12.Ndao M. Diagnosis of parasitic diseases: old and new approaches. Interdiscip Perspect Infect Dis. 2009

52. Antibody-detection assays
 These include:
 1.IHA, 2.IFA, 3.ELISA, 4.RIA,5.Luminescence immunoassay.
 Native antigen is W.bancrofti Mf obtained from microfilaraemic cases or
heterologous filarial worms ( Brugia.malayi, Dirofilaria immitis, etc).
 Most of the newer tests are using recombinant filarial antigen.
 Falcon assay screening test ELISA (FAST-ELISA) consists of using
synthetic and recombinant peptides to evaluate antibody responses to
an antigen

53. Antibody-detection assays
 Antibody-based diagnostic assays using four recombinant antigens,
WbSXP are commercially available.
 They are based on the detection of antifilarial IgG4 antibodies.
 Disadvantages: These assays show cross reactivity with sera from
other filarial & helminthic infections.
 These cannot discriminate between past & current infections as
filarial antibodies persist longer even after clinical cure.

54. Antigen-detection assays
 These assays are useful in distinguishing recent & past infection.
 Two monoclonal antibody based ELISA’s that detect circulating filarial
antigen in the serum are available.
 A) ELISA employing mab AD12 detects a 200 KD antigen of adult
W.bancrofti in the serum.
 B) ELISA using the mab Og43C that detects adult W.bancrofti as well as Mf
antigen in the serum.
 Immunochromatography test (ICT) filariasis card test is a new & rapid filarial
antigen test that detects soluble W.bancrofti antigens in the serum of the
infected patients.
 This test is developed by ICT diagnostics (Balgowlah, New South Wales,
Australia).
 It uses mab AD12 to detect the antigen.

55. Antigen-detection assays
 ICT card has a sensitivity of 96-100% & specificity is 100 %.
 Main advantage of antigen based assays are:
 1.Blood can be collected during daytime for demonstration of the
antigen.
 2. Demonstration of antigen in the urine is a most recent approach for
the diagnosis of bancroftian filariasis.

56. Serodiagnosis Contd
 ‘Seva Filachek’ is a dipstick based ELISA system which has been permitted
by government of India (Signal MF) for microfilarial antigen(IC-Ag) as well as
filarial antibodies (IgG4) in diagnosis of filarial infection in different clinical
groups.
 The detection of IgG4 antibody titre of 1:300 and above against specific
microfilarial antigen was found to be useful.

57. Cellular assays
• These include:
• 1.Filarial skin test (Intradermal test ): It is an immediate hypersensitivity
test. Filarial antigen is injected on skin. After 30 minutes a wheal over 2
cm appears.
• 2. Invitro lymphocyte responses to filarial antigens.
• Disadvantage of cellular assay being neither of the two are specific.

58. Other
 Molecular methods
 PCR: It has been developed which can detect as low as 1 pg of filarial
DNA.
 PCR is positive only when circulating Mf are found in the peripheral
blood.
 So PCR is negative in cases of chronic infections.
 Xenodiagnosis:
 Demonstration of Mf in the stomach-blood of the specific mosquito vector
which was allowed to bite an infected individual.
 Imaging methods : Chest X-ray, Ultrasound.
 Haemogram shows eosinophilia.

59. Treatment
 Diethyl carbamazepine is the drug of choice for Lymphatic filariasis.
 It is filaricidal in action.
 1st day—50 mg after food.
 2nd day---50 mg tid daily.
 3rd day--- 100 mg tid daily.
 4th day to 21st day– 5mg/kg /day in 3 divided doses.
 Use of tetracycline to kill the adult worm & to kill wolbachia bacteria which
is having a symbiotic relation with W.bancrofti.
 Other drugs include: Ivermectin-single oral dose-150µg/kg is used to
destroy the Mf, but not the adult worm.
 Recently evaluated drugs include Levamisole, mebendazole and
centprazine ( CDRI, Lucknow).

60. Prevention & Control
 Prevention & Control depends upon:
 1.Mosquito control 2. Chemotherapeutic control.
 Mosquito control:
 a) Clinical control– By spraying insecticides like DDT, Malathion etc.
 b) Biological control– By the use of carnivorous bacteria ( Bacillus sphaericus,
strain 1593), carnivorous fish (Poecilia reticulata molliensis) &
spore forming bacterium ( Bacillus thuringenesis serotype 11-14).
c) Environmental control– By efficient drainage & sewage system to eliminate the
mosquito breeding places.
d) Reduction of non vector contact by use of mosquito nets & house screens.
 Chemotherapeutic control:
 It is based on the mass or selective treatment of the cases by administering DEC
or use of DEC medicated salt in the populations exposed to filarial infections.

61. Brugia. malayi
 Adult Brugia is distinctly dilated at the anterior end & has a
complete spicule.
 Mf is sheathed & has nuclei at the end of the tail. One nucleus is
present at the external end of the tail.
 Adult always inhabits the lymphatics. Mf are present in the
peripheral blood.
 Brugia has 9 species.
 Species pathogenic to man are:
 B. malayi, B.timori, B. pahangi, B.beaveri.

62. Brugia. malayi
 Brugia. malayi causes malayan filariasis.
 It has both nocturnal periodicity– 10 P.M to 4 A.M & sub-periodic diurnal
periodicity.
 Life cycle is same as that of W.bancrofti.
 It is transmitted by mosquito vectors– Mansonia, A.barbirostris, but not by
Culex.
 Man is the definitive host, apart from humans leaf monkeys ( Presbytis spp)
are also definitive hosts.
 Infective form : Third stage larva (L3) similar to W.bancrofti.
 Pathogenesis & pathology:
 Like W.bancrofti, it causes lymphangitis & elephantiasis.
 Malayan filariasis is characterized by absence of chyluria and genital
involvement.

63.  Laboratory diagnosis is similar to bancroftian filariasis.
 Antibody-based diagnostic assays using four recombinant antigens,
Bm14,BmSXP, and BmR1 have become commercially available.
 They are based on the detection of antifilarial IgG4 antibodies.
 The BmR1 ELISA as well as dipstick (Brugia Rapid immunochromatography
based) antibody tests have very high sensitivity for Brugia malayi (~100%),
Bm14 ELISA is sensitive for both Wuchereria bancrofti and Brugia malayi
(~91%-96%).
 A sandwich ELISA detecting antibodies to recombinant antigen Bm-SXP-1
has been found useful to detect B. malayi infection.
 Treatment: same as bancroftian filariasis.
 Prophylaxis: In India, removal of water plant, Pistia stratiodes, Water hyacinth
reduced the breeding of Mansonioides annulifera, mosquito vector.

64. B. timori
 Human infection with B.timori is found in Timor island at the eastern end of the
Indonesian archipelago.
 No animal reservoir host has yet been discovered.
 Natural vector mosquito is A. barbirostris.
 Adults are found in lymphatic system.
 Clinical manifestations are milder than other lymphatic filariasis.
 Lymphangitis, lymphadenitis, lymphedema (confined below knee) & abscess
along the lymph trunk or nodes are common clinical features.
 Diagnosis depends on the detection of Mf in the peripheral blood collected
during night.
 Mf.timori has a length: width ratio of cephalic space of 3:1 (Mf.malayi 2:1), 5 -7
terminal nuclei, sheath not stained with giemsa stain.
 Laboratory diagnosis, treatment & prophylaxis are similar to those of B.malayi.