The document provides an overview of somatic (tissue) nematodes, focusing on their classification, life cycle, pathogenesis, and laboratory diagnosis, particularly for species such as Wuchereria bancrofti, Brugia species, Loa loa, Onchocerca volvulus, and Dracunculus medinensis. It details their general properties, habitat, morphological characteristics, transmission vectors, and the clinical manifestations associated with infections they cause. Diagnostic methods are also outlined, emphasizing the importance of blood sampling and various laboratory techniques to identify and study these parasites.

1. Somatic (Tissue) nematodes
Mr. Gunjal Prasad Niranjan
M.Sc. Medical Microbiology,
PG Dip in Clinical Research.
Assistant Professor
Dept. of Microbiology,
UNDER GARADUATE STUDENT’S
PRACTICAL BRIFING ON

2. Aim and Objectives
• At the end of this session student must be able to understand
• Classification of Somatic (Tissue Nematodes)
• Life cycle, pathogenesis and laboratory diagnosis of the following tissue
nematodes.
• Wuchereria bancrofti
• Burgia species
• Loa loa
• Onchocerca volvulus
• Dracunculus medinesis
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3. General properties
• HABITAT:
• Filarial worm reside in the lymphatic system, skin, subcutaneous
tissue and rarely in the body cavity.
• Live upto 5 -7 yrs produces upto millions of offspring.
• Blocks the lymphatic system – Network of channels and lymph
nodes that helps maintain fluid levels in the body.
• Blockage leads to edema – collection of fluid in tissues.
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4. Morphology – General Properties
• ADULT WORM:
• Slender, Round 2 - 10 cm(except female of Onchocerca
35-50cm).
• Can survive for many years in humans causing chronic
obstructive and inflammatory conditions including
Elephantiasis & Hydrocele.
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5. General Properties
• Microfilaria:
• Female worm produces large number of L1 larvae
called as “Microfilaria”.
• Highly motile thread like larvae.
• Usually non-pathogenic, but sometimes ,
hypersensitivity reactions can occur against the
microfilarial antigen resulting in tropical pulmonary
eosinophilia (TEP) caused by an immune hyper-
responsiveness to microfilariae trapped in the lungs.
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6. Classification
• Filarial nematodes belongs to –
• Class – Secernentea
• Superfamily – Filarioidea
• Family – Onchocercidea
• They are differentiated on following properties
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7. Classification
• HABITAT:
• Where they reside – Lymphatics or Subcutaneous tissue or body
cavities.
• Geographical distribution.
• Vector responsible for transmission.
• Structure of their larvae for e.g. presence of sheath and nuclei at
the tail tip.
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8. Classification
• MICROFILARIAL PERIODICITY:
• It is defined as the time when most of the microfilariae are found in
peripheral blood.
• Microfilariae of various filarial worms exhibit different periodicity and
found at different time in peripheral blood.
• NOCTURANAL PERIODICITY – Night time between 9pm to 2am for e.g.
Wuchereria & Brugia.
• DIURNAL PERIODICITY – Day time for e.g. Loa loa.
• SUB-PERIODIC – Present throughout with slight increase in the
afternoon for e.g. rarely Wuchereria & Brugia.
• NON PERIODIC – Any time for e.g. Mansonella & Onchocerca.
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9. Classification
• Periodicity occurs due to biological and
evolutionary co-adaptation of the microfilariae to
the feeding habit of the mosquito for e.g. Culex
bites in night, Aedes bites in daytime.
• When not in peripheral blood, the microfilaria are
found in the pulmonary blood vessels.
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10. Difference between filarial nematodes
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Parasite Location of
adult
Location of
microfilaria
Microfilaria
periodicity
Vector Epidemiology
Lymphatic filariasis
W. bancrofti Lymphatic
tissue
Blood Nocturnal
(mostly)
Culex Cosmopolitan
(S. America , S.
Asia, Africa)
Subperiodic
(Rare)
Aedes Pacific islands
B. malayi Lymphatic
tissue
Blood Nocturnal
(mostly)
Mansonia,
Anopheles
South-East
Asia, Indonesia
and India
Subperiodic
(Rarely)
Coquillettidia
& Mansonia
South-East
Asia
B. tumori Lymphatic
tissue
Blood Nocturnal Anopheles Indonesia

11. Difference between filarial nematodes
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Parasite Location of
adult
Location of
microfilaria
Microfilaria
periodicity
Vector Epidemiology
Subcutaneous filariasis
Loa loa Subcutaneous
tissue &
conjunctiva
Blood Diurnal Chrysops
(Deer flies)
West & Central
Africa
Onchocerca
volvulus
Subcutaneous
tissue
Skin and eye None Simulium South &
Central
America &
Africa

12. Comparison of microfilariae
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A: Size, B: Periodicity, C: Sheath, D: Habitat

13. Classification – Tissue Nematodes
Lymphatic Wuchereria bancrofti
Brugia malayi
Skin and
Subcutaneous
Loa loa (African eye worm)
Onchocerca volvulus (blinding filaria)
Dracunculus medinensis (thread worm)
Brugia timori
Conjunctiva Loa loa
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14. Lymphatic filariasis
• Lymphatic filariasis is caused by Wuchereria bancrofti,
Brugia malayi, Brugia timori.
• WUCHERERIA BANCROFTI
• Most widely distributed,
• Affecting 8 crore people world wide.
• It is found in India, China, Far East, major parts of Africa, South
America & central America.
• In general it is nocturnal in periodicity except in Pacific islands
where it is sub periodic.
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15. Wuchereria bancrofti
• INDIA
• 600 million people at risk of 250 district of 20 states in India.
• Highly epidemic states –UP, Bihar, Jharkhand, Odisha, AP, TN,
Kerala and Gujrat.
• Low prevalence in J&K and Punjab.
• Sub-periodic W. bancrofti, transmitted by Aedes, reported from
Nicobar island.
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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.
Geographical
distribution
India, China, Far East, Africa,
South & Central America.

17. Wuchereria bancrofti – morphology
• Exists in 3 forms :
• ADULT :
• Worms are thread like, live in lymphatic tissue as
tightly coiled nodular mass.
• Long slender, creamy white thread like having
smooth cuticle, with ends rounded.
• ADULT MALE : Measures about 3.5 to 4.0cmX0.1 mm.
• ADULT FEMALE : Measures 6-10 cm x 0.2-0.3 mm.
• Average life span 4 to 5 years.
• Female worm (viviparous) liberates sheathed
embryos (Microfilaria).
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18. Wuchereria bancrofti – morphology
• ADULT WORM –
• Male can be differentiated from female by
• small size,
• crock screw tail and
• presence of two spicules at posterior end
which helps at time of copulation.
• Female are viviparous – directly discharge
larvae.
• LARVAE
• Like other nematodes – 4 larval stages
present.
• First stage larvae – Microfilaria.
• The third stage larvae – Filariform larva
(Infective from for humans).
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19. MICROFILARIA :
• Microfilaria of W. bancrofti lives
in blood vessels and are actively
motile.
• Diagnostic forms.
• Found in peripheral blood
between 10 pm to 4 am.
• Measures about 275 to 300 um x
8 to 10 um.
• Covered with hyline sheath
which is 350 um long.
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20. Microfilaria
• Head is blunt and tail is tapering. In unstained
preparations these are colourless.
• When stained with Giemsa or Romanowsky stains
– pink with column of purple to violet nuclei.
• These nuclei are absent at the head and tail ends.
• They develop in mosquitoes.
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21. Cultivation of filarial nematodes
• Success is limited in its cultivation.
• CELL LINES – W. bancrofti, B. malayi can be cultivated in mosquito cell
lines like Aedes togoi & Anopheles maculatus.
• Grown in modified RPIM-1640 medium or TC199 supplemented with
20% of newborn calf serum and LLC-MK2 cells.
• Human embryonic cell lines are also used as feeder layers.
• Microfilaria ex-sheath and molt twice to L3 stage larvae in 12-16 days.
• Culture method is not used for diagnosis but for maintenance of
parasite for Ag preparation, Antifilarial drug sensitivity and research
purpose.
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22. Life cycle of w. bancrofti
• Life cycle is complex. Requires 2 hosts.
• Humans are definitive hosts.
• While mosquitoes of the genera Culex , Aedes & Anopheles are
intermediate hosts.
• Infective form for humans – third stage larva, present in
proboscis sheath of mosquitoes.
• Mode of transmission - Larva (L3) are deposited on skin of
humans, near the site of bite, larva penetrate through puncture
skin or wound to reach subcutaneous tissues.
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23. Life cycle of w. bancrofti – human cycle
• Larva enter afferent lymphatics &
reach draining lymph nodes to develop
into adults in 3 to 15 months (4-6 wks
B. malayi).
• Male fertilize female, gravid female lays
sheathed embryos – the Microfilaria.
• Microfilaria enters efferent lymphatics
to reach blood circulation through
thoracic duct or right lymphatic duct.
• Come in peripheral blood between 10
pm to 4 am, this Nocturnal periodicity
is related the night biting habit of
mosquitoes.
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24. Life cycle of w. bancrofti -Mosquito cycle
• These sheathed microfilaria (L1) are ingested by mosquitoes with
their blood meal. (Culex – at night, Aedes – at day time).
• Microfilariae lose their sheath in stomach & penetrate the gut
wall to reach the thorax of the mosquitoes.
• Develop successively into second stage & third stage larvae
which is the infective form for humans.
• Third stage larvae measure about 1500 to 2000 um in length
and it enters the proboscis sheath, ready to infect a new host.
• Development in mosquitoes – 10 to 20 days.
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25. Life cycle of w. bancrofti
• This duration depends on atmospheric temperature, humidity, and
the species of mosquito.
• One microfilaria develops into one infective form third stage
larva.
• Multiplication of parasite does not occur in mosquitoes.
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27. Clinical features
• Infection - Wuchereriasis/ Lymphatic filariasis/ Bancroftian
filariasis.
• Disease manifestations are due to lymphatic dysfunctions
resulting from presence of living or dead worms lymph
thrombi, inflammation and immune reactions to worm and
worm products.
• Pathogenic states are produced only by adult worm (living/
dead) – Classical filariasis.
Occult filariasis – Lesions produced by microfilaria.
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28. Clinical Features
• Clinical states in classical filariasis can be classified
as:
1. Asymptomatic ( in endemic areas).
2. Inflammatory – lymphangitis and lymphadenitis
- Common lymph node enlarged are inguinal,
axillary, lymphatics of male genital organs are
commonly involved that leads to funiculitis,
epididymitis and orchitis.
3. Obstructive – Granuloma, thrombi formation,
fibrosis of lymph vessels leading to severe
lymphatic obstruction and pedal edema.
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29. Classical Filariasis -
1. Lymphangitis– Lymph vessels of extremities, testicles &
epididymis are inflamed due to -
• 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.
2. Lymphadenitis- Lymph Nodes of groin & axilla are inflamed.
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30. 3. Lymphoedema : with hypertrophy of the affected parts
( Elephantiasis - of organs like leg, scrotum, penis, vagina,
breast, arm etc – fibrotic thickening of skin & subcutaneous
tissue)
4. Lymphangiovarix- dilatation of afferent lymph vessels due to
obstruction.
5. Hydrocele – Commonest complication disorder in which
serous fluid accumulates in a body sac (especially in the
scrotum).
6. Chyluria – Excretion of chyle, a milky white fluid in urine
occurs rarely . (Rupture of renal lymphatic through the mucous
membrane of urinary tract).
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31. Lymphatic filariasis
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32. Occult filariasis –
Tropical pulmonary Eosinophilia / Weingarten’s syndrome
–Distinct syndrome in some individuals.
–Proximal cough and wheezing.
–Weight loss low grade fever.
–Pronounced blood eosinophilia.
–Total serum IgE and Antifilarial Ab titres are raised.
–Represents a hypersensitivity reaction to microfilarial antigen.
–Response well to treatment but in untreated cases can cause
progressive pulmonary damage.
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33. 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, Diethylcarbamazine
(DEC) 4-6mg/kg-12 days.
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34. Clinical features
• IMMUNE COMPLEX MEDIATED MANIFESTATION –
• Circulating immunocomplexes containing microfilarial
antigens are found to be deposited in various organs
such as –
• Kidney – causes nephrotic syndrome, haematuria and
proteinuria.
• Joints – Causes filarial arthritis of knee or ankle.
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35. Laboratory diagnosis
• SPECIMEN –
• Blood collected at night, preferably capillary blood
from ear lobes.
• Chylous urine,
• Hydrocele fluid,
• Exudates from Lymphangiovarix
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36. Microscopic examination
• Wet mount – A drop of blood is taken on a slide and
covered with cover slip.
• Microfilaria are easily identified under low power
(10x) due to their size and motility.
• Giemsa:
• To prepare a stained preparation.
• About 20 to 60 mm3 blood is streaked on a slide and
allowed to dry.
• Then stained with Giemsa stain.
• Sheathed microfilaria with no nuclei at tail tip
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37. Laboratory diagnosis
• Concentration techniques – for capillary blood, venous blood
(Knott’s technique)
• Diethylcarbamazine provocation test – 2mg/kg of DEC orally,
examine peripheral blood smear after 30 to 45 minutes.
• It provokes microfilaria to come in peripheral blood even during
day time.
• This test is contraindicated in Onchocerca & Loa loa.
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38. Laboratory diagnosis
• Quantative Buffy Coat examination (QBC) –
• Generally done for malaria, can be used for microfilariae.
• Blood is centrifuged in capillary tube, stained with acridine
organe and examine under fluorescent microscope.
• More sensitive than smear microscopy.
• Microfilaria may not be found in blood due to many reasons:
• Occult filariasis
• Chronic filariasis and endemic normal people
• Wrong time of blood collection
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39. Laboratory diagnosis
• ANTIGEN DETECTION
• Circulating Ag of W. bancrofti can be detected by using monoclonal
Abs against Og4C3 and AD12 Ags, by ELISA and ICT.
• Advantages : More sensitive than microscopy.
• Can be done at daytime.
• Differentiate in current and past infection.
• Can be detected in urine.
• Ag disappears after clinical cure.
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40. Laboratory diagnosis
• ANTIBODY DETECTION
• Crud parasitic extract was used to detect serum Abs previously.
• Using IHA, IFA and ELISA. Useful for seroepidemiological purposes.
• Low specificity – due to cross reactivity with other parasites.
• Can not differentiate between current and past infection as Abs
can persist even after clinical cure.
• PCR, RT PCR are developed for molecular diagnosis.
• Xenodiagnosis – mosquitoes are allowed to feed on infected
patients and dissected after 4-6 wks to demonstrate microfilariae.
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41. Treatment
• DEC (Diethylcarbamazine) –
microfilaricidal: 6mg/ kg/day for 12
days
• 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
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42. Brugia species
• 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
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43. Brugia species
– Children commonly affected.
– Rapid development of signs & symptoms.
– Elephantiasis affect lower extremities.
– Chyluria & Hydrocele rare.
– Microfilaria :
– Sheathed with 2 widely spaced nuclei & blunt tip at
tail end.
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44. Onchocerca volvulus
Definitive host Man.
Intermediate host Black flies (Simulium).
Infective form Larva.
Mode of transmission Inoculation.
Site of localization Subcutaneous tissue, dermis &
eye.
(Blinding filaria – 2nd most common cause of infectious blindness)
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45. 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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47. Diagnosis & Treatment
• Nodular biopsy – adult
worm
• Skin snip – unsheathed
microfilaria with no nuclei.
• Treatment –
• Ivermectin,
• Surgical removal,
• DEC in non ocular
onchocercosis
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49. Loa loa
Definitive host Man
Intermediate host Chrysops (deer fly)
Infective form Larva
Mode of transmission Inoculation
Site of localization Subcutaneous & deep
connective tissue
(African eye worm)
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50. Clinical features
• Subcutaneous swelling – Calabar (a dark
brown seed of Calabar vine) or fugitive
swelling, measuring 5 to 10 cm.
• Marked by erythema and angioedema,
usually in the extremities.
• Due to host inflammatory response to
migrating worms (1cm/min speed) or its
metabolic products.
• Migrating worm in subconjunctival
tissue- Causes conjunctival granuloma,
edema of eye lid leading to proptosis
(bulging).
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51. Diagnosis & Treatment
• Peripheral blood smear - Sheathed microfilaria
with nuclei up to rounded tail tip
• Isolation of worms from the conjunctiva or
subcutaneous biopsy
• Treatment - Ivermectin,
• surgical removal,
• DEC (effective against adult & microfilaria)
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52. Dracunculus medinensis
Adult worms Male 2 to 4 cm Female 70 –120 cm,
Viviparous
Infective form Larva inside Cyclops
Mode of transmission Ingestion of water contaminated
with cyclops
Site of localization Subcutaneous tissue
(Guinea Worm)
Human
Intermediate host
Definitive host
Cyclops
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54. 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
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55. 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
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56. Treatment –
1. Thiabendazole/ Metronodazole – symptomatic
relief, easy removal of worm.
2. Gradual extraction of worm by winding of a few
cm. on a matchstick per day, over 3 to 4 weeks.
3. Surgical excision
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57. 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
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58. Expected Questions
• Write essay on
• Describe life cycle, pathogenesis, and laboratory diagnosis of
bancroftian filariasis.
• Classify somatic nematodes? Describe their life cycle,
pathogenesis and laboratory diagnosis of Burgia malayi?
• Write short note on
• Onchocerciasis
• Loiasis
• Guinea worm infection
• Differentiate Between:
• Microfilaria of Wuchereria bancrofti and Burgia malayi.
• Classical filariasis and occult filariasis.
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59. MCQ
• Causative agent of Calabar swelling is:
• A. Dracunculus medinesis
• B. Wuchereria bancrofti
• C. Burgia malayi
• D. Loa loa
• Which of the following infection is eradicated from India:
• A. Wuchereria bancrofti
• B. Burgia malayi
• C. Dracunculus medinesis
• D. Ascaris lumbericoides
• Which of the following microfilariae is sheathed?
• A. Mansonella perstans
• B. Onchocerca volvulus
• C. Burgia malayi
• D. Mansonella streptocerca
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60. MCQ
• Microfilaria of Burgia malayi differs from that of Wuchereria bancrofti by
all except:
• A. Coarse, overlapping and darkly stained nuclei
• B. Tail tip free from nuclei
• C. Possesses secondary kinks
• D. Cephalic space longer
• Which of the following microfilaria comes to peripheral blood in the day
time?
• A. Wuchereria bancrofti
• B. Burgia malayi
• C. Loa loa
• D. Burgia tumori
• Answers : 1)D 2)C 3)C 4)B 5)C
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