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Lymphatic filariasis
Microfilariae
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The disease
Lymphatic filariasis, more commonly known as elephantiasis, is a painful and profoundly disfiguring disease. While the disease is usually acquired in childhood its visible manifestations occur in adults leading to temporary and permanent disability. It has a major social and economic impact on endemic countries.
The disease is caused by thread-like worms of genus Wuchereria and Brugia., known as filariae, that lodge in the lymphatic system, the network of nodes and vessels that maintain the delicate fluid balance between the tissues and blood and which are an essential component of the body's immune system.
Filariae are responsible for a variety of clinical manifestations, including lymphoedema of the limbs, genital disease (hydrocele, chylocele and swelling of the scrotum and penis) and acute, recurrent secondary bacterial infections known as "acute attacks". The vast majority of infected people are asymptomatic but virtually all of them have sub clinical lymphatic damage and as many as 40% have renal involvement with proteinuria and haematuria.
The transmission cycle
Filariea are transmitted through mosquitoes. When an infected mosquito takes a blood meal, the parasites are deposited on the person's skin from where they enter through the skin. These larvae then migrate to the lymphatic vessels and develop into adult worms, over a period of 6 to 12 months, causing damage and dilatation of the lymphatic vessels. The filariae live for several years in the human host. During this period they produce millions of immature microfilariae that circulate in the peripheral blood and are ingested by mosquitoes when the latter bite infected humans. The larval forms further develop inside the mosquito before becoming infectious to man. Thus, a cycle of transmission is established.
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