Microbiology of Filaria

1. Filariaris
 The causative agents of filariasis are of the
phylum: Nemathelminthes belonging to the
Superfamily FILARIOIDEA.
 The genus Wuchereria and Brugia are
implicated in lymphatic filariasis caused in
man.

2. Wuchereria bancrofti
Common name: Bancroft’s
filaria
 Class : NEMATODA
 Subclass : PHASMIDIA
 Superfamily : FILARIOIDEA
 Subfamily :
ACANTHOCHEILONEMANTINAE
 Genus : WUCHERERIA
 Species : BANCROFTI

3. Wuchereria bancrofti
Common name: Bancroft’s
filaria
 Demarquay (1863): found larval forms in
hydrocele fluid of man.
 Wucherer (1866): found them in chylous urine.
 Bancroft (1876): found adult females.
 Geographical distribution: Tropics and
subtropics. India, West Indies, Southern
China, Japan. Along sea coasts and banks of
big rivers.
 Habitat: Adult worms in lymphatic vessels and
lymph nodes of man only.

4. Morphology of W. bancrofti
 Adult worms:
Long hair like, transparent nematodes.
Filiform in shape, ends tapering. Head end
terminating in a slightly rounded swelling.
Male: 2.5-4 cm length. 0.1 mm thick. Tail end curved
ventrally. Contains two spicules of unequal length.
Female: 8-10 cm length. 0.2-0.3 mm thick. Tail end
narrow and abruptly pointed.

5.  Embyos(Microfilariae):
Unstained: Colourless and transparent bodies with blunt heads
and pointed tails.
290 micrometre length. 6-7 micrometre breadth.
Stained with Romanowsky’s stains, following features are
seen:
i) A hyaline sheath
ii) Cuticula
iii) Somatic cells or nuclei
iv) G-cells
v) Innenkorper of Fulleborn or Central Body of Manson

6. Microfilaria of Wuchereria bancrofti

7. Vectors of W. bancrofti filaria
 Mode of infection – Inoculative method, bite of
mosquito.
 Transmitting Agent – Female mosquitoes :Culex
:Aedes
:Anopheles
 In India and China – Culex pipiens fatigans (C. p.
quinquefasciatus).
 In Pacific islands: Anopheles punctulatus and in
Polynesian islands: Aedes polynesiensis.
 Infective form: Third stage larvae of developing
Microfilaria bancrofti.
 Portal of entry: Skin.

9. Life cycle of W. bancrofti
 2 hosts:
Definitive host : man
Adult worm in the lymphatic system
Intermediate host : mosquito
microfilaria undergo further development

11. Stage in mosquito
Sheathed microfilariae ingested by mosquito, collect at anterior
end of
stomach
Sheaths are cast off, they penetrate the gut-wall and migrate to
the thoracic muscles.
First-stage larva arises.
Larva grows rapidly, moults once or twice and develops to second
stage larva
Metamorphosis is complete. Third stage larva having 3 subterminal
caudal papillae arises
Note:At this stage it is infective to man and enters the proboscis
sheath of
Within 1-2 hours
In 2 days
In 3-7 days
10th -11th day

12. Stages in man
Upon bite of an infected mosquito, the third stage larvae are
deposited on the skin
Attracted by the warmth of the skin, the larvae penetrate through
The larvae reach the lymphatic channels, settle down at some spot (ingu
scrotal or abdominal lymphatics) and begin to grow into adult worms.
They become sexually mature. Male fertilises the female and
microfilarae are produced.
Pass through the thoracic duct or right lymphatic duct, to the venous syst
pulmonary capillaries and finally reach systemic circulation
5-18 months

13. Brugia malayi and Brugia
timori
 Class : : NEMATODA
 Subclass : : PHASMIDIA
 Superfamily : FILARIOIDEA
 Subfamily : :
ACANTHOCHEILONEMANTINAE
 Genus: : BRUGIA
 Species : : MALAYI, TIMORI

14. Brugia malayi
Common name: Malayan filaria
 Geographical distribution: Malaysia,
Indonesia, Borneo, Thailand, Vietnam, India.
In India: Kerala, Orissa, Madhya Pradesh and
Assam.
 Habitat: The adult form is found in the
lymphatic system.

15. Morphology of B. malayi
 Adult worm: delicate
whitish thread-like.
Mature females
Length :4.3-5.5 cm
Breadth :0.13-0.17 mm.
Mature males
Length :1.3-2.3 cm
Breadth :0.07-0.08 mm
Microfilaria of Brugia malayi

16. Morphology of Mf. malayi
 Smaller in size; lies folded with head close to
tail.
 Possesses secondary kinks.
 Double stylets at the anterior end.
 The cephalic space is longer.
 The nuclei are blurred.
 Tail tip is not free from nuclei.

17. Vectors of B. malayi filaria
 Intermediate hosts in India are various
species of Mansonia: M. annulifera
M. indiana
M. uniformis
and one species of Anopheles: A. barbirostris
 Reservoirs of infection: Domestic animals,
cats, dogs, leaf monkey (Presbytis sp.)

18. Mansonia annuliferaMansonia uniformis

20. Life cycle of B. malayi
 Similar to W. bancrofti.
 Intermediate host : Mosquito
Definitive host : Man
 Larval development is completed in 6-8 days.

21. Brugia timori
Common name: The Timor filaria
 Geographical distribution: B. timori is found
in Timor Island.
 Habitat- Adult worms are found in the
lymphatic system.
 Vectors- No animal reserviors.
 Natural vector : Anopheles barbirostris
Aedes togoi.
 Infective form – microfilariae.

22. Morphology of B. timori
MORPHOLOGY OF MICROFILARIAE :
 Length which is 310 micrometre.
 Length:width ratio of cephalic space- 3:1.
 5-7 terminal nuclei.
 Sheath not stained with Giemsa stain.