A vector-borne parasitic disease caused by nematodes (filarial worms) transmitted to humans through the bite of infected mosquitoes.
Aetiology
Causative Organisms (Lymphatic Filariasis)
- Wuchereria bancrofti (most common worldwide)
Vectors
- Culex species (urban areas)
- Anopheles species (rural areas)
- Aedes species (Pacific islands)
Pathophysiology
- Adult worms reside in lymphatic vessels and lymph nodes
- Induce lymphatic dilation, valvular dysfunction, and obstruction
- Recurrent inflammation leads to:
- Lymphangitis
- Fibrosis
- Irreversible lymphedema
- Immune-mediated reactions to microfilariae and dead worms contribute to symptoms
Clinical presentation
Asymptomatic Stage
- Microfilaremia without clinical symptoms
- Subclinical lymphatic damage
Acute Filariasis
- Acute adenolymphangitis (ADL):
- Fever
- Painful lymphadenitis
- Lymphangitis
- Scrotal pain and swelling (epididymo-orchitis)
Chronic Filariasis
- Lymphedema (limbs, breast, genitalia)
- Hydrocele (most common chronic manifestation in males)
- Chyluria (milky urine due to lymphourinary fistula)
Occult Filariasis
- Tropical pulmonary eosinophilia:
- Nocturnal cough
- Wheezing
- Marked eosinophilia
Investigations
Parasitological Diagnosis
- Peripheral blood smear:
- Collected at night (10 pm–2 am)
- Demonstrates microfilariae
- Concentration techniques (Knott’s method)
Antigen Detection
- Circulating filarial antigen (CFA) assays
- Highly sensitive for W. bancrofti
Hematological Findings
Imaging
- Ultrasonography:
- “Filarial dance sign” (motile worms in lymphatics)
- Lymphoscintigraphy for lymphatic dysfunction
Management
- Diethylcarbamazine (DEC) 6 mg/kg/day divided in 3 doses for 12 days
- Combination regimens for mass drug administration:
- DEC 6 mg/kg/day × 12 days + Albendazole 400 mg SD or daily
- Ivermectin 150–200 µg/kg SD + Albendazole 400 mg SD
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