[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Microbiology](https://durgical.com/en/microbiology/) › [Nematodes](https://durgical.com/en/microbiology/groups/nematodes/) › Wuchereria bancrofti / Brugia malayi

[Microbiology](https://durgical.com/en/microbiology/) · [Nematodes](https://durgical.com/en/microbiology/groups/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

## Key points

- Sheathed microfilariae with nocturnal periodicity: night-time thick smear.
- Elephantiasis and hydrocele.
- Vectors: mosquitoes (Culex, Anopheles, Aedes).
- Diethylcarbamazine is not used where onchocerciasis is present.
- Wolbachia as the target of doxycycline.

## 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

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

- Lymphatic filariasis [Lymphatic filariasis →](https://durgical.com/en/conditions/lymphatic-filariasis/)
- Chronic lymphoedema and elephantiasis of the limbs [Lymphoedema →](https://durgical.com/en/conditions/lymphoedema/)
- Hydrocele from damage to spermatic cord lymphatics [Hydrocele →](https://durgical.com/en/conditions/hydrocele/)

## 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:

- [Albendazole](https://durgical.com/en/pharmacology/albendazole/)
- [Ivermectin](https://durgical.com/en/pharmacology/ivermectin/)
- [Doxycycline](https://durgical.com/en/pharmacology/doxycycline/)

## Prevention

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

## In Colombia

In the Americas, transmission has shrunk to a few countries, and Brazil has eliminated it as a public health problem. In Colombia it is considered mainly in people arriving from endemic areas.

## Memory aid

The filaria works the night shift: to catch it in the blood, draw the sample when the mosquitoes come out to bite.

## 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.

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## Related

- [Onchocerca volvulus](https://durgical.com/en/microbiology/onchocerca-volvulus/)
- [Mansonella ozzardi / Mansonella perstans](https://durgical.com/en/microbiology/mansonella-ozzardi-mansonella-perstans/)

## Related conditions

- [Lymphatic filariasis](https://durgical.com/en/conditions/lymphatic-filariasis/)
- [Lymphoedema](https://durgical.com/en/conditions/lymphoedema/)
- [Hydrocele](https://durgical.com/en/conditions/hydrocele/)

## What the colours mean

**Gram-positive**
Thick peptidoglycan wall: stains purple.

**Gram-negative**
Thin wall with an outer membrane: stains pink.

**Acid-fast**
Lipid-rich wall (mycobacteria): Ziehl–Neelsen stain.

[← Back to the group: Nematodes](https://durgical.com/en/microbiology/groups/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](https://www.cdc.gov/dpdx/lymphaticfilariasis/index.html) (CDC, 2019); [Lymphatic filariasis](https://www.who.int/news-room/fact-sheets/detail/lymphatic-filariasis) (WHO, 2024).

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Representative model, for educational purposes only.

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License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/microbiology/wuchereria-bancrofti-brugia-malayi/