Lymphedema (elephantiasis)
The most obvious sign of infection, elephantiasis, is the enlargement of the limbs. A late complication of infection, elephantiasis is a form of lymphedema and is caused by repeated inflammation of the lymphatic vessels. Repeated inflammatory reactions causes vessel dilation and thickening of the affected lymphatic vessels, which can compromise function. The lymphatic system normally functions to maintain fluid balance between tissues and the blood and serves as an integral part of the immune system. Blockage of these vessels due to inflammatory induced fibrosis, dead worms, or granulomatous reactions can interfere with normal fluid balance, thus leading to swelling in the extremities.[14] Elephantiasis resulting from B. malayi infection typically affects the distal portions of the extremities. Unlike bancroftian filariasis, B. malayi rarely affects genitalia and does not cause funiculitis, orchitis, epididymitis, hydrocele, or chyuria, conditions more readily observed with bancroftian infection.