Medicine: Cow-Dung Cure

All over two of Brazil's states, Minas Gerais and Sáo Paulo, health workers were directing homeowners last week in what looked like a most unsanitary task: coating the walls inside thousands of mud huts with a mixture containing cow dung. As a result, Dr. Mario Pinotti, running the campaign from his modernistic 18th-floor office in Rio, was confident that thousands of lives would be saved.

The enemy was Chagas' disease, named 50 years ago for the late great Dr. Carlos Chagas, who found that this misnamed "South American sleeping sickness" was caused by a trypanosome, a microscopic animal with a complex life...