Helminths > Nematodes > Filaria

Filaria

Filiaria Cause filariasis 8 species of filariae found in human body 2 of them are of great medical importance, which are named Wuchereria bancrofti Brugia malayi

Wuchereria bancrofti Brugia malayi

1. Morphology

1.1 Adult

Adult

Adults are slender, thread-like, milk white Female of W. bancrofti: 58.5~105 mm; Male of W. bancrofti: 28.2~42 mm, having a curled tail. Adults of B. malayi slightly smaller than those of W. bancrofti

1.2 larva A female adult of filaria don’t lay eggs, but give birth to larvae named microfilaria ( mf )

Microfilaria

Colorless, about 200 um long, having a sharp tail

Cephalic space

Sheath Body nuclei

Terminal nuclei W. bancrofti

B. malayi

Morphological difference between two species of microfilaria W. bancrofti

B. malayi

Size

larger

smaller

Cephalic space

shorter

longer

Body nuclei

equal sized

unequal sized

clear

unclear

no

two

Terminal nuclei

W. bancrofti

B. malayi

Cephalic space

Body nuclei

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Terminal nuclei

W. bancrofti

B. malayi

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2. Life cycle

microfilaria Lymph node adult In human lymphatic

patient

Healthy person Filariform larva

In mosquito

microfilaria Thoracic muscle

Sausage-like larva

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Nocturnal Periodicity Definition: In human body, the microfilariae present in the blood vessels of skin at night, and absent during daytime. This phenomenon is called nocturnal periodicity.

Filariform larva

3. Pathogenesis and Symptom

Acute stage

Chronic stage

Pathogenesis In acute stage, the adults cause allergic reaction and inflammation by producing toxin, antigens and mechanical irritation. In chronic stage, the wall of lymphatics become thickened, the dead microfilariae and remains of adults form stone, therefore the lymphatic will become obstructed,and the trapped lymph will break some lymphatic wall,and flow into tissues.

Pathogenesis In early chronic stage, although the lambs become enlarged due to filling with lymph, the skin is still as normal as healthy person. The symptom is called lymph edma In late chronic stage, the skin become darker, thicker, harder and coarser than normal, the symptom is called elephantiasis

symptom In acute stage Lymphangiitis Lymphadenitis Inflammation of testes Filarial fever

symptom In chronic stage Lymph edema Elephantiasis Hydrocele Chyluria

Hydrocele Lymph flow into scrotum,and make it be enlarged. Chyluria In abdomen, the lymph with chyle flow into kidney or urethra.

lymphangiitis

Elephantiasis of a leg

Elephantiasis due to Brugia malayi, complicated by severe dermatitis and secondary bacterial infection.

Elephantiasis of scrotum

Lymph edema and elephantiasis

Hydrocele

Chyluria

4. Diagnosis

5. Epidemiology

Distribution W. bancrofti : the area between 30 。 N and 30 。 S in the Western Hemisphere and 41 。 N and 28 。 N in the eastern hemisphere. B. malayi: Far east. In China, filariasis is prevalent in 15 province.

Factors for epidemic of this disease Sources of infection: patients and carriers with mf in their blood. In addition, some monkeys and cats also transmit B. malayi. Vector: Culex, for W. bancrofti; Anopheles, for B. malayi.

6. Treatment and prevention Eradication of sources of infection Diethylcarbamazine (DEC, Hetrazan) Elimination of the vectors Protection of people from infection Mosquito net, some drugs,vaccine