Rain is pelting down on Doña Porcela's treatment room in Puerto Cabezas, the main town on Nicaragua's Northern Caribbean coast. The room is barren except for a few plastic chairs, a wooden table and some old plastic bottles balanced precariously on timber beams. Doña Porcela is a respected traditional healer here and the bottles are filled with her secret medicinal potions. Her patient today is a teenage girl asleep on a piece of cardboard, serving as a mattress on the dirt floor. "Grisi Siknis turns people into witches and they go crazy," she said. Last year there were 65 cases...