Filaria microbiology

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 see n: 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.

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

9. 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 mosquito by 14 th day Within 1-2 hours In 2 days In 3-7 days 10 th -11 th day

10. 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 (inguinal , 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 system and pulmonary capillaries and finally reach systemic circulation 5-18 months

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

12. 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.

13. 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

14. 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.

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

16. Mansonia annulifera Mansonia uniformis

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

18. 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 .

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