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How do filarial worms cause swelling in lymphatic filariasis?
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parasitic disease
Trypanosoma brucei in a blood smear (Giemsa-stained light photomicrograph).
In lymphatic filariasis, swelling occurs because adult nematodes reside within the lymph nodes and lymph vessels, where they induce allergic reactions in the surrounding tissues.1
Over time, these reactions lead to chronic inflammation and scarring. The lymph channels may become infiltrated and clogged with fibrous tissue, resulting in a blockage of the lymphatic system. This obstruction prevents the proper drainage of lymph fluid, causing it to accumulate in affected areas—most commonly the limbs and genitals. In severe, untreated cases, this process leads to elephantiasis, characterized by the gross enlargement, thickening, and hardening of the skin and underlying tissues.21