Lymphatic filariasis (LF)

The distribution of LF is linked to that of its mosquito vectors (Anopheles, Culex, Aedes, etc.):

• W. bancrofti: sub-Saharan Africa, Madagascar, Egypt, India, South East Asia, Pacific region, South America, The Caribbean
• B. malayi: South East Asia, China, India, Sri Lanka
• B. timori: Timor

90% of LF is due to W. bancrofti and 10% to Brugia spp.

Clinical features

• Acute recurrent inflammatory manifestations
  • Adenolymphangitis: lymph node(s) and red, warm, tender oedema along the length of a lymphatic channel, with or without systemic signs (e.g. fever, nausea, vomiting). The inflammation may involve the lower limbs, external genitalia and breast.
  •  In men: acute inflammation of the spermatic cord (funiculitis), epididymis and testicle (epididymo-orchitis).
  • Attacks resolve spontaneously within a week and recur regularly in patients with chronic disease.

• Chronic manifestations
  • Lymphoedema: oedema of the lower extremity or external genitalia or breast, secondary to obstruction of the lymphatics by macrofilariae. The oedema is reversible initially but then becomes chronic and increasingly severe: hypertrophy of the area affected, progressive thickening of the skin (fibrous thickening with formation of creases, initially superficial, but then deep, and verrucous lesions). The final stage of lymphoedema is elephantiasis.
  • In men: increase in volume of fluid due to accumulation within the tunica vaginalis (hydrocoele, lymphocoele, chylocoele); chronic epididymo-orchitis.
  • Chyluria: milky or rice-water urine (disruption of a lymphatic vessel in the urinary tract).
  • In patients parasitized by Brugia spp, genital lesions and chyluria are rare: lymphoedema is usually confined to below the knee.

Laboratory

• Detection of microfilariae in the peripheral blood (thick film) a Citation a. When test results are negative in a clinically suspect case, consider detection of antigens (ICT rapid test) and/or ultrasound of the inguinal area in search of the « filarial dance sign ». ; blood specimens should be collected between 9 pm and 3 am.
• In regions where loiasis and/or onchocerciasis are co-endemic, check for co-infection if the LF diagnosis is positive.

Treatment

Antiparasitic treatment

• Treatment is not administered during an acute attack.
• Doxycycline PO, when administered as a prolonged treatment, eliminates the majority of macrofilariae and reduces lymphoedema: 200 mg once daily for 4 weeks minimum. It is contraindicated in children < 8 years and pregnant or breast-feeding women.
• Diethylcarbamazine PO single dose (400 mg in adults; 3 mg/kg in children) may be an alternative but eliminates a variable proportion of adult worms (up to 40%) and does not relieve symptoms; a prolonged treatment is no more effective than single dose therapy. In addition, DEC is contra-indicated in patients with onchocerciasis or Loa loa microfilarial load > 2000 mf/ml and in pregnant and breast-feeding women.
• Ivermectin (weak or absent macrofilaricidal effect) and albendazole should not be used for the treatment of individual cases (no effect on symptoms).
• In the case of confirmed or probable co-infection with O. volvulus: treat onchocerciasis first, then administer doxycycline.

Control/prevention of inflammatory manifestations and infectious complications

• Acute attacks: bed rest, elevation of the affected limb without bandaging, cooling of the affected limb (wet cloth, cold bath) and analgesics; antibacterial or antifungal cream if necessary; antipyretics if fever (paracetamol) and hydration.
• Prevention of episodes of lymphangitis and lymphoedema: hygiene of the affected extremity b Citation b. Wash at least once daily (soap and water at room temperature), paying special attention to folds and interdigital areas; rinse thoroughly and dry with a clean cloth; nail care. , comfortable footwear, immediate attention to secondary bacterial/fungal infections and wounds.
• Established lymphoedema: bandaging of the affected limb by day, elevation of the affected extremity (after removal of the bandage) when at rest, simple exercises (flexion-extension of the feet when recumbent or upright, rotation of the ankles); skin hygiene, as above.

Surgery

May be indicated in the treatment of chronic manifestations: advanced lymphoedema (diversion-reconstruction), hydrocoele and its complications, chyluria.