Filariasis

Filariasis

Dr. Mejbah Uddin Ahmed

Tissue nematode

Classification

A) According to habitat:

a) Lymphatic system: W. bancrofti, B. malyai, B. timori

b) Subcutaneous tissue: D. medinensis, O.volvulus, Loa loa

c) Mesentery: D. perstans, M. ozzardi

d) Conjunctiva: Loa loa.

B) According to disease:

Disease Parasite

Lymphatic filariasis W.bancrofti,B. malyai, B. timori

Loiasis/ calabar swelling Loa loa

Onchocerciasis / River blindness

O. volvulus

Dracunculiasis D. medinensis

Tissue nematode

Filariasis

Filariasis are a group of parasitic diseases

caused by nematodes reside in the lymphatic and

connective tissue (W. bancrofti, B. malyai, B.

Timori).

Lymphatic filarisis is a debilitating and disfiguring

chronic disease (lyphoedema, elephantiasis and

hydrocele).

Lymphatic filarisis

Morphological forms:

Adult worms

Microfilaria

Adult worms:

The adult worms are white

Females are larger than males and

viviparous.

Wuchereria bancrofti

Microfilaria:

Average microfilaria measures 240–300 μm in

length. A thin delicate sheath surrounds the

organism. The head is blunt and round and the tail

is pointed. Except the tail tip numerous nuclei are

contained in the body.


Periodicity: The microfilarias are not constantly

found in the peripheral blood, but show nocturnal

periodicity. The exact mechanism is not fully

understood. It is determined by species and life

style of host and can be altered.


Life cycle:

Definitive host: Man.

Intermediate Host: Mosquito.

Infective form: Microfilaria.

Portal of entry: Skin, by mosquito bite.

Site of localization: Lymphatic system.


Filariasis

Pathology & Clinical feature :

May be asymptomatic

Adult and developing worm causes classical

filariasis

Microfilaria causes occult filariasis .


Classical filariasis:

Acute lymphatic filariasis: In the acute form

there are recurrent attacks of fever with

lymphadenitis and lymphangitis. The lymphatics

involved are those of the limbs, genital organs

(specially spermatic cord) and breasts.


Causes of lymphangitis: Mechanical irritation,

liberation of metabolites, bacterial infection.

Obstruction of lymphatics: Mechanical,

excessive fibrosis of lymph vessels and fibrosis of

afferent nodes.

Filariasis

Dilatation of lymphatics- Lymphangiovarix.

Rupture of lymphnagiovarix

Lymphorrhgia– Lymphscrotum, Lymphuria

Lymphocoele.

Chylorrhagia–Chylocoele, chyluria, chylorrhgia or

hematochyluria, chylus diarrhoea, chylus ascitis

and chylothorax. .

Filariasis

Elephantiasis: Affected part

becomes enlarged and

tumor like solidity due to

hypertrophy & hyperplasia of

skin and connective tissues

of various parts of the body.

Secondary bacterial

infections: Septic

lymphangitis, abscess and

septicemia.

Filariasis

Elephantiasis

Occult filariasis:

The condition when adult worm produces

microfilaria continuously but absent in the

peripheral blood because they are destroyed in

the tissues. This is characterized by massive

eosinophilia, hepatosplenomegali, generalized

lymphadenopathy & pulmonary symptoms..

Filariasis

Filariasis

Tropical pulmonary eosinophilia: A syndrome

of immunological hyper responsiveness of Mf in

the lung. It is particularly found in filaria endemic

areas. There is a marked eosinophilia, raised

ESR and high levels of filarial antibody including

high titers of IgE.

Laboratory Diagnosis:

Sample: Peripheral blood, chylous urine, hydrocele

fluid and exudates of lymph varix.

Microscopy: Detection of microfilaria stained with

Leishman, Giemsa or hematoxylin and eosin stain.

Antigen detection: Using an immunoassay for

circulating filarial antigens constitutes a useful

diagnostic approach.

Filariasis

Molecular diagnosis: Polymerase chain reaction

is available for W. bancrofti and B. malayi.

Identification of adult worms: is possible from

tissue samples collected from subcutaneous

biopsies.

Antibody detection: Is of limited value.

Complement fixation test.

Filariasis

Filariasis

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