Lymphatic filariasis Infection with the filarial worms Wuchereria bancrofti and Brugia malayi is associated with clinical outcomes ranging from subclinical infection to hydrocele and elephantiasis. The infection is widespread in tropical Africa, the North African coast, coastal areas of Asia, Indonesia and northern Australia, the South Pacific islands, the West Indies and also in North and South America. Pathology Several factors contribute to the pathogenesis of lymphatic filariasis. 1- Toxins released by the adult worm cause lymphangiectasia; this dilatation of the lymphatic vessels leads to lymphatic dysfunction and the chronic clinical manifestations of lymphatic filariasis, lymphoedema and hydrocele. 2- Death of the adult worm results in acute filarial lymphangitis.Lymphatic obstruction persists after death of the adult worm. 3- Secondary bacterial infections cause tissue destruction. 4- The host response to microfilariae is central to the pathogenesis of tropical pulmonary eosinophilia.