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DPDx

DPDx is an education resource designed for health professionals and laboratory scientists. For an overview including prevention and control visit www.cdc.gov/parasites/lymphaticFilariasis/.

Lymphatic Filariasis

[Brugia malayi] [Brugia timori] [Wuchereria bancrofti]

Microfilariae of W. bancrofti in a thick blood smear stained with Giemsa. Image courtesy of the Oregon State Public Health Laboratory.

Microfilaria of W. bancrofti in a thick blood smear stained with Giemsa. Image courtesy of the Oregon State Public Health Laboratory.


Adults of W. bancrofti. The male worm is on the left; the female is on the right.

Adults of W. bancrofti. The male worm is on the left; the female is on the right.


Microfilaria of B. malayi in a thin blood smear, stained with Giemsa.

Microfilaria of B. malayi in a thin blood smear, stained with Giemsa.

Causal Agent

The filarid nematodes Wuchereria bancrofti, Brugia malayi, and (less-commonly) B. timori. Humans can also be infected with several zoonotic Brugia species.

Life Cycles

Brugia Malayi

Life cycle of Brugia malayi

The typical vector for Brugia malayi filariasis are mosquito species in the genera Mansonia and Aedes. During a blood meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound The number 1. They develop into adults that commonly reside in the lymphatics The number 2. The adult worms resemble those of Wuchereria bancrofti but are smaller. Female worms measure 43 to 55 mm in length by 130 to 170 μm in width, and males measure 13 to 23 mm in length by 70 to 80 μm in width. Adults produce microfilariae, measuring 177 to 230 μm in length and 5 to 7 μm in width, which are sheathed and have nocturnal periodicity. The microfilariae migrate into lymph and enter the blood stream reaching the peripheral blood The number 3. A mosquito ingests the microfilariae during a blood meal The number 4. After ingestion, the microfilariae lose their sheaths and work their way through the wall of the proventriculus and cardiac portion of the midgut to reach the thoracic muscles The number 5. There the microfilariae develop into first-stage larvae The number 6 and subsequently into third-stage larvae The number 7. The third-stage larvae migrate through the hemocoel to the mosquito's proboscis The number 8 and can infect another human when the mosquito takes a blood meal The number 1.

Wuchereria bancrofti

Life cycle of Wuchereria bancrofti

Different species of the following genera of mosquitoes are vectors of W. bancrofti filariasis depending on geographical distribution. Among them are: Culex (C. annulirostris, C. bitaeniorhynchus, C. quinquefasciatus, and C. pipiens); Anopheles (A. arabinensis, A. bancroftii, A. farauti, A. funestus, A. gambiae, A. koliensis, A. melas, A. merus, A. punctulatus and A. wellcomei); Aedes (A. aegypti, A. aquasalis, A. bellator, A. cooki, A. darlingi, A. kochi, A. polynesiensis, A. pseudoscutellaris, A. rotumae, A. scapularis, and A. vigilax); Mansonia (M. pseudotitillans, M. uniformis); Coquillettidia (C. juxtamansonia). During a blood meal, an infected mosquito introduces third-stage filarial larvae onto the skin of the human host, where they penetrate into the bite wound The number 1. They develop in adults that commonly reside in the lymphatics The number 2. The female worms measure 80 to 100 mm in length and 0.24 to 0.30 mm in diameter, while the males measure about 40 mm by .1 mm. Adults produce microfilariae measuring 244 to 296 μm by 7.5 to 10 μm, which are sheathed and have nocturnal periodicity, except the South Pacific microfilariae which have the absence of marked periodicity. The microfilariae migrate into lymph and blood channels moving actively through lymph and blood The number 3. A mosquito ingests the microfilariae during a blood meal The number 4. After ingestion, the microfilariae lose their sheaths and some of them work their way through the wall of the proventriculus and cardiac portion of the mosquito's midgut and reach the thoracic muscles The number 5. There the microfilariae develop into first-stage larvae The number 6 and subsequently into third-stage infective larvae The number 7. The third-stage infective larvae migrate through the hemocoel to the mosquito's prosbocis The number 8 and can infect another human when the mosquito takes a blood meal The number 1.

Geographic Distribution

Among the agents of lymphatic filariasis, Wuchereria bancrofti is encountered in tropical areas worldwide; Brugia malayi is limited to Asia; and Brugia timori is restricted to some islands of Indonesia.

Clinical Presentation

Lymphatic filariasis most often consists of asymptomatic microfilaremia. Some patients develop lymphatic dysfunction causing lymphedema and elephantiasis (frequently in the lower extremities) and, with Wuchereria bancrofti, hydrocele and scrotal elephantiasis. Episodes of febrile lymphangitis and lymphadenitis may occur. Persons who have newly arrived in disease-endemic areas can develop afebrile episodes of lymphangitis and lymphadenitis. An additional manifestation of filarial infection, mostly in Asia, is pulmonary tropical eosinophilia syndrome, with nocturnal cough and wheezing, fever, and eosinophilia.

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  • Page last reviewed November 29, 2013
  • Page last updated November 29, 2013
  • Content source: Global Health - Division of Parasitic Diseases and Malaria
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