Filariasis

On this page

Filariasis Basics - Wormy Intruders

  • Lymphatic Filariasis (LF): Chronic parasitic disease; affects lymphatics.
  • Causative Agents: Nematodes (filarial worms).
    • Wuchereria bancrofti (~90% cases).
    • Brugia malayi.
    • Brugia timori.
  • Vectors: Mosquitoes.
    • Culex quinquefasciatus (urban W. bancrofti).
    • Anopheles spp. (rural W. bancrofti).
    • Mansonia spp. (Brugia).
  • Transmission: Infective L3 larvae from mosquito bite. Microfilariae (mf) in blood.
  • Endemic in India.

Wuchereria bancrofti exhibits nocturnal periodicity (mf peak in peripheral blood at night, 10 PM - 2 AM).

Vectors & Lifecycle - Mosquito Mailmen

  • Vectors (Mosquitoes):
    • W. bancrofti: Culex (urban), Anopheles (rural), Aedes.
    • B. malayi: Mansonia, Anopheles.
    • B. timori: Anopheles barbirostris.
  • Lifecycle:
    • Mosquito (intermediate host) deposits L3 larvae on skin.
    • L3 larvae enter skin, migrate to lymphatics.
    • Mature into adult worms (human: definitive host).
    • Adults release microfilariae (L1) into blood.
    • Mosquito ingests L1; develop to L3 in mosquito.

image

W. bancrofti microfilariae show nocturnal periodicity (peak 10 PM - 2 AM). (📌 Mnemonic: "Bankers work late")

Clinical Picture - Elephant Tales & More

  • Asymptomatic Microfilaremia: Common; asymptomatic despite blood microfilariae.
  • Acute Lymphatic Filariasis:
    • Adenolymphangitis (ADL) / Filarial Fever: Recurrent fever, chills, painful lymphadenopathy & retrograde lymphangitis.
    • Acute epididymo-orchitis, funiculitis (esp. males).
  • Chronic Lymphatic Disease (Develops over years):
    • Lymphedema: Progressive: pitting → brawny, non-pitting edema.
    • Hydrocele: Most common in Bancroftian filariasis; scrotal swelling.
    • Elephantiasis: Irreversible enlargement (limbs, scrotum, penis, vulva, breasts). Skin hyperkeratotic, coarse, fissured. Massive leg lymphedema due to filariasis
    • Chyluria: Milky urine (lymphatic fluid, chyle).
  • Occult Filariasis (e.g., Tropical Pulmonary Eosinophilia - TPE):
    • Blood microfilariae absent (sequestered in lungs/tissues).
    • Nocturnal cough, wheeze, dyspnea, marked eosinophilia, ↑IgE.

    ⭐ Hydrocele is the most common chronic manifestation of Bancroftian filariasis.

Diagnosis Decoded - Finding Filaments

  • Microfilariae (MF) Detection: Key for diagnosis.
    • Peripheral Blood Smear (PBS): Gold standard.
      • Timing: Nocturnal sample (10 PM - 2 AM) for W. bancrofti, B. malayi.
      • Stain: Giemsa. Thick/thin smears examined.
    • Concentration Methods: ↑ sensitivity (e.g., Knott's, membrane filtration).
    • QBC (Quantitative Buffy Coat): For MF detection using fluorescence microscopy.
    • DEC Provocation Test: Induces daytime appearance of MF after 2 mg/kg DEC dose.
  • Adult Worm Detection:
    • Ultrasound (USG): "Filarial dance sign" (visualization of live, motile adult worms in lymphatics).
    • Biopsy: Lymph node or nodule biopsy may show adult worms.
  • Antigen Detection (W. bancrofti):
    • Immunochromatographic Card Test (ICT): Detects Circulating Filarial Antigen (CFA).

    ⭐ CFA tests (e.g., ICT) can be positive even in amicrofilaremic (occult) filariasis and chronic infections.

Management & Defense - Worm Warfare

  • Drug of Choice (DOC): Diethylcarbamazine (DEC).
    • Regimen: 6 mg/kg/day orally for 12 days.
    • Action: Potent microfilaricidal; also damages adult worms.
    • ⚠️ Caution: Mazzotti reaction (systemic/local inflammation from dying mf); manage with antihistamines/corticosteroids.
  • Lymphedema Care: Meticulous hygiene, limb elevation, exercises, compression; Complex Decongestive Therapy (CDT).
  • Hydrocele: Surgical management (hydrocelectomy).
  • Mass Drug Administration (MDA): Annual single dose of DEC (6 mg/kg) with Albendazole; or Ivermectin + Albendazole.
  • Vector Control: Integrated strategies against mosquito vectors (IRS, larviciding, LLINs).

⭐ DEC is the only drug effective against adult filarial worms (macrofilaricidal), particularly W. bancrofti.

High‑Yield Points - ⚡ Biggest Takeaways

  • Causative agents: Wuchereria bancrofti, Brugia spp.; Vector: Mosquitoes.
  • Hallmark: Chronic lymphedema leading to elephantiasis and hydrocele.
  • Acute episodes: Recurrent adenolymphangitis (ADL) with fever and painful lymphadenopathy.
  • Diagnosis: Nocturnal blood smear for microfilariae; ICT card test for W. bancrofti antigen.
  • Treatment: Diethylcarbamazine (DEC) is mainstay; doxycycline for Wolbachia.
  • Tropical Pulmonary Eosinophilia (TPE): Occult filariasis with nocturnal cough, marked eosinophilia.
  • Control: Mass Drug Administration (MDA); vector control.

Practice Questions: Filariasis

Test your understanding with these related questions

In a patient presented with a fever and a positive filarial antigen test, what is the next appropriate method of management?

1 of 5

Flashcards: Filariasis

1/10

In Lepromin test, early or Fernandez test is positive within _____ hours if there is the erythema measuring >10 mm

TAP TO REVEAL ANSWER

In Lepromin test, early or Fernandez test is positive within _____ hours if there is the erythema measuring >10 mm

48-72

browseSpaceflip

Enjoying this lesson?

Get full access to all lessons, practice questions, and more.

Start Your Free Trial