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Contributors: Edith Lederman MD, Noah Craft MD, PhD
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Lymphatic filariasis is an infection resulting from the transmission of Wuchereria bancrofti, Brugia malayi, and Brugia timori to humans by mosquitoes. It is estimated that 120 million people worldwide are infected with filariae. The disease is endemic in over 80 countries in Africa, Asia, South and Central America, and the Pacific Islands. More than two-thirds of infected people live in India or Africa.

Infection manifests as either acute lymphatic inflammation or chronic lymphatic obstruction resulting in hydrocele or elephantiasis of the limbs. Chronic lymphatic disease is rare in children under 10 years of age, but increases with age.

Usually the first manifestation of lymphatic filariasis is acute adenolymphangitis with fever ("filarial fever") and tender swelling of various lymph node groups. Chronic infection eventually results in swelling of the extremities (usually asymmetric and known as elephantiasis in the extreme forms) and swelling of the male genitalia (usually unilateral hydrocele) or female breast. Fever is usually associated with acute infections and also with acute bouts of epididymitis.

Risk factors include extended exposure to mosquitoes in endemic areas, especially near stagnant waters. The disease often presents asymptomatically, but the acute febrile stage lasts for 4-7 days. Patients from endemic areas may occasionally experience chyluria (milky urine) as renal lymphatics are blocked. Additionally, chronic infection may be associated with tropical pulmonary eosinophilia.

The disease course can be prolonged over years to decades.


B74.9 – Filariasis, unspecified

105706003 – Filariasis

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Differential Diagnosis & Pitfalls

Filarial fever and acute lymphadenopathy must be differentiated from other causes of tropical fevers and lymphadenopathy, and common viral infections (eg, influenza, mononucleosis, human immunodeficiency virus [HIV]).

  • Podoconiosis (nonfilarial elephantiasis) – Bilateral.
  • Other causes of lymphedema must be ruled out such as congestive heart failure, deep venous thrombosis, and subacute nephritis. Other causes of lymphatic blockage must be ruled out, such as pelvic tumors.
  • Inguinal hernia can sometimes be reduced or differentiated with a translucency test. Both may exist in the same patient.
  • Tumors of the testes are more solid (see testicular cancer).
  • Epididymitis caused by other infections such as tuberculosis or other bacterial causes can be ruled out by cultures.
  • Early scrotal elephantiasis needs to be distinguished from other causes of scrotal thickening such as fungal infections (more scale), scabies (more nodular), onchocerciasis, and chronic rubbing (lichen simplex chronicus, which presents with lichenification of the scrotum).
  • Tropical pulmonary eosinophilia must be distinguished from bronchial asthma, helminthic infections, tuberculosis, and neoplastic processes.

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Last Updated: 08/17/2017
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Filariasis (Chronic) : Lymphangitis, Regional lymphadenopathy, Scrotal edema, Peripheral leg edema, Upper extremity edema
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