Lymphatic filariasis test. Health worker holding a test card used for the diagnosis of lymphatic filariasis. This is a negative result for the Wuchereria bancrofti worm's antigen. Infected people may not show immediate signs of the disease. An early diagnosis allows drug therapy to be started. The disease progesses slowly, and can eventually result in elephantiasis: grossly swollen limbs. The disease is caused by parasitic nemotode worms transmitted in larval form by the bite of mosquitoes. The condition is rarely fatal, but causes widespread suffering in tropical areas. Photographed in Haiti.