Lymphatic Filariasis

Introduction

Lymphatic filariasis is a disease associated with parasitic infection of one of three different nematodes: Wuchereria bancrofti, Brugia malayi, or Brugia timori.
The microscopic worms enter the human body through mosquito transmission. After Infection, the worm can live up to 5-7 years in the lymphatic system.
The distribution of lymphatic filariasis is linked to that of its mosquito vectors (Anopheles, Culex, Aedes, etc.).

Clinical features of lymphatic filariasis

Acute recurrent inflammatory manifestations 

  • Adenolymphangitis
  • Filarial fever
  • Tropical pulmonary eosinophilia

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: funiculitis, epididymis and epididymo-orchitis
  • Attacks resolve spontaneously within a week and recur regularly in patients with chronic disease.

Chronic manifestations

  • Lymphedema
  • Renal Pathology
  • Secondary infections

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 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), blood specimens should be collected between 9 pm and 3 am. The recommended collection of sample at night is because the microfilariae that cause lymphatic filariasis circulate in the blood at night (called nocturnal periodicity). After collection, a thick smear should be made and stained with Giemsa or hematoxylin and eosin.
  • Check for co-infection if the LF diagnosis is positive.

Treatment for lymphatic filariasis

  • Diethylcarbamazine (DEC) is the drug of choice.
  • In settings where onchoceriasis is present, Ivermectin is the drug of choice to treat LF.
  • People with lymphedema and elephantiasis are unlikely to benefit from DEC treatment as most of them are not actively infected with the filarial parasite.

Antiparasitic treatment

Treatment is not administered during an acute attack.
Doxycycline
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 (DEC)

  • Treatment of lymphatic filariasis in adults and children > 18 months of age involves either a 1 day or 12 day treatment course of DEC (6mg/kg/day).
  • One day treatment is generally as effective as the 12-day regimen
  • For tropical pulmonary eosinophilia (TPE), a longer DEC treatment course of 14-21 days is generally recommended
  • DEC PO single dose (400 mg in adults; 3 mg/kg in children) eliminates a variable proportion of adult worms (up to 40%) and does not relieve symptoms.
  • DEC is contraindicated in patients with onchocerciasis or Loa loa microfilarial load > 2000 mf/ml and in pregnant and breast-feeding women.

Ivermectin and albendazole should not be used for the treatment of individual cases. Ivermectin has weak or absent macrofilaricidal effect while albendazole has 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 & 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 and hydration.

Prevention of episodes of lymphangitis and lymphoedema:

  • hygiene of the affected extremity, 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

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

Prevention

Avoid mosquito bites especially if you live in an area with lymphatic filariasis.

References