Lymphatic Filariasis

Aka: Lymphatic Filariasis, Filarial Elephantiasis, Filarial Lymphatic Elephantiasis, Elephantiasis, Filariasis, Wucheria, Wuchereria Bancrofti, Filaria Bancrofti, Brugia Malayi, Brugia Timori, Timorian Filariasis

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II. Definitions

  1. Filariasis
    1. Nematode infections by organisms in the family Filarioidea (Filarial Infections)
    2. Often used to refer to Filarial Elephantiasis, but includes other organisms (e.g. Onchocerca Volvulus)

III. Pathophysiology

  1. Filarial Infection (Filariae, Family Filarioidea)
    1. Wucheria and Brugia are in the family Filarioidea and are considered filarial infections
    2. Filaria are blood and tissue Nematodes transmitted by Arthropod Bite
    3. Adult filariae, living in the Lymphatic System, birth prelarval microfilariae
    4. Microfilariae invade tissue and circulate in blood and lymph
      1. Microfilariae are transmitted between human hosts via Arthropod Bite
    5. Filariae are hosts to an endosymbiotic, Rickettsial-like Bacteria, Wolbachia
      1. Killing Wolbachia (e.g. doxycyline) decreases microfilaria and renders adult worms sterile
  2. Transmission of Mosquito-borne Roundworms
    1. Wucheria bancrofti (most prevalent)
      1. Regions: Central Africa, Nile Delta, South and Central America, tropical Asia (e.g. southern China, Pacific islands)
      2. Transmitted by Mosquito vectors in the genera Culex, Anopheles, Mansonia, and Aedes
    2. Brugia Malayi
      1. Regions of the Malay peninsula and southeast asia
      2. Transmitted by Mosquito vectors in the genus Mansonia
      3. Typically limited to manifestations below the knee
    3. Brugia Timori (Timorian Filariasis)
      1. https://en.wikipedia.org/wiki/Brugia_timori
      2. Limited to Lesser Sunda Islands (Indonesia)
      3. Transmitted by Mosquito vector Anopheles barbirostris, which breeds in rice fields
  3. Infects Lymphatics
    1. Microfilariae, transmitted by Mosquito Bite, invade genital and leg Lymphatics where they mature to adult worms
    2. Adult worms mate, giving rise to microfilariae which migrate to blood circulation
    3. Initially results in lymphatic inflammation
    4. Later scarring and obstruction result in severe Lymphedema

IV. Symptoms: Acute, Recurrent Infections in Endemic Regions

  1. Often asymptomatic with single infections (recurrent infections are more likely to be symptomatic)
  2. Headache
  3. Photophobia
  4. Vertigo
  5. Fatigue
  6. Low grade fever
  7. Myalgia

V. Signs

  1. Acute
    1. Conjunctivitis
    2. Orchitis
    3. Lymphangitis
    4. Lymphadenopathy
  2. Chronic: Lymphatic and Venous obstruction with recurrent infections
    1. Secondary scarring and fibrosis obstructs Lymphatics
    2. Edema distal to obstruction
    3. Hydrocele
    4. Elephantiasis of Breasts, Scrotum, vulva, legs
  3. Tropical Pulmonary Eosinophilia may occur with chronic recurrent infections
    1. Nocturnal Asthma
    2. Bilateral Interstitial Infiltrates

VI. Labs

  1. Filarial Antibodies
    1. Positive Antibody titers do not differentiate between the 8 species of filaria causing disease in humans
  2. Stained Blood Film (night-time sample is preferred due to nocturnal periodicity)
    1. Microfilariae seen
  3. Complete Blood Count
    1. Eosinophilia

VII. Differential Diagnosis

  1. Podoconiosis (endemic nonfilarial Elephantiasis)

VIII. Management

  1. Test and treat for coinfections with Lymphatic Filariasis
    1. Onchocerca Volvulus (River Blindness)
      1. Treat first with Ivermectin or Moxidectin
      2. Next Diethylcarbamazine (DEC) 6 mg/kg orally once AND Doxycycline 200 mg/day for 6 weeks
    2. Loa loa
      1. Loa loa blood concentration <2500 microfilaria/ml
        1. Diethylcarbamazine (DEC) 9 mg/kg divided three times daily orally for 21 days
      2. Loa loa blood concentration >2500 microfilaria/ml
        1. Severe encephalopathy risk if treated with DEC
        2. Consult local expert opinion
      3. Loa loa blood concentration >20,000 microfilaria/ml
        1. Doxycycline 200 mg/day for 6 weeks to treat ONLY Lymphatic Filariasis
  2. Treat Lymphatic Filariasis if no coinfections (monoinfections)
    1. Treat Diethylcarbamazine (DEC) 6 mg/kg orally once AND
    2. Doxycycline 200 mg/day for 6 weeks

IX. References

  1. Gladwin, Trattler and Mahan (2014) Clinical Microbiology, Medmaster, Fl, p. 367
  2. Freedman (2024) Sanford Guide, accessed on IOS 8/4/2025

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