DurgicalDurgical
EN
Open the app

Microbiology · Nematodes

Wuchereria bancrofti / Brugia malayi !

  • Parasite
  • Exam priority: medium

A mosquito-borne worm that lives in lymph vessels. Over the years it causes massive leg swelling (elephantiasis) and hydrocele.

Updated 2026-11-01

Also called: lymphatic filaria, elephantiasis

At a glance

Shape
Threadlike adults coiled in lymph vessels
Family
Onchocercidae
Type
Filarial nematode (tissue, lymphatic)
Stain
Giemsa thick smear: sheathed microfilaria
Size
Female up to about 10 cm; microfilaria about 250 µm

Morphology

  • Sheathed microfilariae in blood, with nocturnal periodicity in most regions.
  • W. bancrofti: the tail tip has no nuclei; Brugia: two terminal nuclei.
  • Adults in the lymphatics, sometimes seen moving on ultrasound.

Transmission

  • Bites of infected mosquitoes that leave L3 larvae on the skin.
  • Many bites over months or years are needed; it affects people living in endemic areas.

Reservoir: Humans (W. bancrofti); Some Brugia have animal reservoirs

Vector: Mosquitoes: Culex, Anopheles and Aedes for W. bancrofti; Mansonia and Aedes for Brugia.

Isolation precautions

What the care team adds to standard precautions.

  • Standard

Life cycle

  1. An infected mosquito leaves L3 larvae on the skin while biting; they enter through the wound.
  2. The larvae travel to the lymph vessels and mature into adults over months.
  3. Females release sheathed microfilariae that enter the blood, mainly at night.
  4. A mosquito swallows them while biting; they shed the sheath and develop to L3 in its thoracic muscles.
  5. The L3 reaches the proboscis and is passed on at the next bite.

Virulence factors

  • Adults dilate and damage lymphatics (lymphangiectasia) even without symptoms.
  • The endosymbiotic bacterium Wolbachia contributes to inflammation.
  • Recurrent bacterial skin infections (adenolymphangitis) worsen lymphoedema.
  • An exaggerated lung response to microfilariae causes tropical pulmonary eosinophilia.

Diseases it causes

Clinical picture

  • Many infected people have no symptoms despite lymphatic damage.
  • Acute attacks of adenolymphangitis with fever.
  • Progressive lymphoedema of legs, arms, breasts or genitals; hydrocele.
  • Chyluria and tropical pulmonary eosinophilia (night cough, wheeze).

Diagnosis

  • Microfilariae on Giemsa thick smear of blood drawn at night; Knott concentration or filtration.
  • Circulating filarial antigen (rapid test) on blood drawn at any hour.
  • Antifilarial IgG4 antibodies.
  • Ultrasound: moving adults in lymphatics ('filarial dance').

Treatment

Antifilarials: diethylcarbamazine, albendazole and ivermectin, combined in mass drug administration depending on whether onchocerciasis is present; doxycycline targets Wolbachia. Lymphoedema is managed with skin hygiene and hydrocele with surgery.

Drug class only; doses and regimens are set by the clinician from the current guideline.

In Pharmacology:

Prevention

  • Annual mass drug administration in endemic communities.
  • Bed nets, repellents and mosquito control.
  • Morbidity management: lymphoedema care and hydrocele surgery.

Test yourself

Think of the answer, then tap the question to see it.

Why is the W. bancrofti thick smear taken at night?

Because its microfilariae have nocturnal periodicity and are most abundant in peripheral blood at night.

Which test diagnoses lymphatic filariasis on blood drawn at any hour?

Circulating filarial antigen detection, for example with a rapid test.

What chronic manifestations does lymphatic filariasis cause?

Progressive lymphoedema up to elephantiasis, and hydrocele.

Why is diethylcarbamazine avoided where onchocerciasis exists?

It can cause severe inflammatory reactions by killing Onchocerca microfilariae, so ivermectin plus albendazole is used there instead.

Add to my cards (4)

← Back to the group: Nematodes

Educational content on microorganisms; not a treatment guide and no substitute for a health professional's advice. No doses are given.

Sources: CDC - DPDx - Lymphatic Filariasis (CDC, 2019); Lymphatic filariasis (WHO, 2024).

Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake

Representative model, for educational purposes only.