Lymphatic Filariasis

Lymphatic filariasis (LF, elephantiasis) is a mosquito borne infection by Wuchereria bancrofti (90%), Brugia malayi, and Brugia timori, with adult worms residing in the lymphatics.

• About 51 million people infected; 882 million at risk in 44 countries (India, Nigeria, Indonesia, Bangladesh, DRC, Ethiopia, Kenya coast, Tanzania).
• Vectors: Culex quinquefasciatus (urban), Anopheles (rural Africa), Aedes (Pacific), Mansonia (Brugia).
• Chronic disease from lymphatic dilatation and lymphoedema is a leading cause of disability worldwide.
• Global elimination programme through mass drug administration.

• Most infected people are asymptomatic with subclinical lymphatic damage.
• Acute adenolymphangitis (ADL): fever, painful lymph nodes and lymphatic channels, and retrograde spread with skin infection.
• Chronic: lymphoedema, elephantiasis (limbs, breasts, genitalia), hydrocele (most common in men), chyluria, and scrotal swelling.
• Tropical pulmonary eosinophilia (TPE): nocturnal cough, wheeze, dyspnoea, marked eosinophilia (above 3 x 10^9/L), and very high IgE.

• Night blood film (10 pm to 2 am for nocturnally periodic strains) for microfilariae, Knott concentration, and membrane filtration.
• Circulating filarial antigen (immunochromatographic card test, Filariasis Test Strip) in W. bancrofti infection, independent of time of day.
• Ultrasound of scrotum or lymphatics: "filarial dance sign" (live adult worms in motion).
• PCR, serology (anti-filarial IgG4), eosinophilia, chest X-ray in TPE (diffuse reticulonodular infiltrates).
• Exclude podoconiosis, venous or lymphatic obstruction, lymphoma, onchocerciasis, and loiasis.

• Individual treatment: diethylcarbamazine (DEC) 6 mg/kg/day in 3 doses for 12 days (or single 6 mg/kg); albendazole 400 mg twice daily for 21 days; and doxycycline 200 mg daily for 4 to 6 weeks (Wolbachia targeting; improves lymphoedema and reduces hydrocele progression).
• Mass drug administration (annual): albendazole 400 mg plus DEC 6 mg/kg, or triple drug therapy (IDA: ivermectin 200 micrograms/kg plus DEC 6 mg/kg plus albendazole 400 mg) in suitable areas; ivermectin plus albendazole where onchocerciasis or loiasis co-endemic (DEC contraindicated).
• TPE: DEC 6 mg/kg/day for 14 to 21 days.
• Morbidity management and disability prevention: strict limb hygiene (washing with soap and water, skin care, treating entry lesions such as fungal infection), elevation, exercise, compression bandaging, antibiotics for ADL episodes, and hydrocelectomy.
• Prevention with vector control and bed nets.