Filariasis, Lymphatic

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 three filarial nematodes

  • Wuchereria bancrofti

  • Brugia malayi

  • Brugia timori

• 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

• Among the most important parasitic diseases of humans

• 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 ...