Lymphatic Filariasis (Brugia malayi, Brugia timori, and Wuchereria bancrofti)

Chapter 288 Lymphatic Filariasis (Brugia malayi, Brugia timori, and Wuchereria bancrofti)



Arlene E. Dent, James W. Kazura



Etiology


The filarial worms Brugia malayi (Malayan filariasis), Brugia timori, and Wuchereria bancrofti (bancroftian filariasis) are threadlike nematodes that cause similar infections. Infective larvae are introduced into humans during blood feeding by the mosquito vector. Over a period of 4-6 mo, the larval forms develop into sexually mature adult worms. Once an adequate number of male and female worms accumulate in the afferent lymphatic vessels, adult female worms release large numbers of microfilariae that circulate in the bloodstream. The life cycle of the parasite is completed when mosquitoes ingest microfilariae in a blood meal, which molt to form infective larvae over a period of 10-14 days. Adult worms have a 5-7 yr life span.



Epidemiology


More than 120 million people living in tropical Africa, Asia, and Latin America are infected; approximately 10-20% of these individuals have clinically significant morbidity attributable to filariasis. W. bancrofti is transmitted in Africa, Asia, and Latin America and accounts for 90% of lymphatic filariasis. B. malayi is restricted to the South Pacific and Southeast Asia, and B. timori is restricted to several islands of Indonesia. Travelers from nonendemic areas of the world who spend brief periods of time in endemic areas are rarely infected. Global elimination has been targeted for 2020.



Clinical Manifestations


The clinical manifestations of B. malayi, B. timori, and W. bancrofti infection are similar; manifestations of acute infection include transient, recurrent lymphadenitis and lymphangitis, The early signs and symptoms include episodic fever, lymphangitis of an extremity, lymphadenitis (especially the inguinal and axillary areas), headaches, and myalgias that last a few days to several weeks. These symptoms are caused by an acute inflammatory response triggered by death of adult worms. Initial damage to lymphatic vessels may remain subclinical for years. The syndrome is most frequently observed in young persons 10-20 yr of age. Manifestations of chronic lymphatic filariasis occur mostly in adults 30 yr of age or older and result from anatomic and functional obstruction to lymph flow. This obstruction results in lymphedema of the legs, arms, breasts, and/or genitalia. Male genital involvement such as hydrocele is very common in W. bancrofti infection but uncommon in Brugia species infection. Chronic lymphedema predisposes affected extremities to bacterial superinfections, sclerosis, and verrucous skin changes, resulting in elephantitis, which may involve 1 or more limbs, the breasts, or genitalia. It is uncommon for children to have overt signs of chronic filariasis.



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Jun 18, 2016 | Posted by in PEDIATRICS | Comments Off on Lymphatic Filariasis (Brugia malayi, Brugia timori, and Wuchereria bancrofti)

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