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For further information, see CMDT Part 35-32: Lymphatic Filariasis

Key Features

Essentials of Diagnosis

  • Episodic attacks of lymphangitis, lymphadenitis, and fever

  • Chronic progressive swelling of extremities and genitals; hydrocele; chyluria; lymphedema

  • Microfilariae in blood, chyluria, or hydrocele fluid; positive serologic tests

General Considerations

  • Caused by filarial nematodes

    • Wuchereria bancrofti

    • Brugia malayi

    • Brugia timori

    • Mansonella perstans

    • Onchocerca volvulus

    • Loa loa

    • Mansonella streptocerca

    • Mansonella ozzardi

  • Humans are infected by bites of infected mosquitoes

  • Larvae move to the lymphatics and lymph nodes where they mature over months

  • The thread-like adult worms can live for many years and produce large numbers of microfilariae, which are infective to mosquitoes

  • Microfilariae are released into the circulation, usually at night except in the South Pacific where microfilaremia peaks during daylight hours

Demographics

  • Approximately 120 million people are infected with these organisms in tropical and subtropical countries

    • About one-third of these people suffer clinical consequences of the infections

    • Many are seriously disfigured

  • W bancrofti

    • Causes about 90% of episodes of lymphatic filariasis

    • Tansmitted by Culex, Aedes, and Anopheles mosquitoes

    • Widely distributed in the tropics and subtropics, including subsaharan Africa, southeast Asia, the western Pacific, India, South America, and the Caribbean

  • B malayi

    • Transmitted by Mansonia and Anopheles mosquitoes

    • Endemic in parts of China, India, southeast Asia, and the Pacific

  • B timori is found only in islands of southeastern Indonesia

  • Mansonella are filarial worms transmitted by midges and other insects in Africa and South America

Clinical Findings

Symptoms and Signs

  • Many infections remain asymptomatic despite circulating microfilariae

  • Clinical consequences of infection are principally due to inflammatory responses to developing, mature, and dying worms

Acute disease

  • Initial manifestation is often acute lymphangitis, with fever, painful lymph nodes, edema, and inflammation spreading peripherally from involved lymph nodes

  • Lymphangitis and lymphadenitis of the upper and lower extremities is common

  • Genital involvement occurs with W bancrofti infection

    • Epididymitis

    • Orchitis

    • Scrotal pain and tenderness

  • Acute attacks of lymphangitis last for a few days to a week and may recur a few times per year

  • Filarial fevers may also occur without lymphatic inflammation

Chronic disease

  • Most common manifestation is swelling of the extremities or genitals due to chronic lymphatic inflammation and obstruction

  • Extremities become increasingly swollen, with a progression from pitting edema to nonpitting edema to elephantiasis

  • Genital involvement, particularly with W bancrofti, occurs more commonly in men

    • Progresses from painful epididymitis to hydroceles, which are usually painless but can become very large

    • Inguinal lymphadenopathy

    • Thickening of the spermatic cord

    • Scrotal lymphedema

    • Thickening and fissuring of the scrotal skin

    • Chyluria (occasionally)

  • Lymphedema of the female genitalia and breasts may also occur

Tropical pulmonary eosinophilia

  • Infects young adult males with either W bancrofti or B malayi...

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