Book excerpt: Helminths include one of the most diverse and geographically widespread groups of parasites which infect humans and animals. About 100 species have been reported from humans, usually producing asymptomatic infection or mild symptoms. However, about 20 species are of public health importance causing severe or even fatal infections. In many parts of Africa parasitic helminths are responsible for enormous economic losses, hampering rural development programmes and reducing the pace of economic growth. Many parasitic helminths are either zoonoses (diseases naturally transmitted between vertebrate animals and man) or have evolved from animal parasites. The modification of the environment through wars, famine and the ever expanding and increasingly mobile human population brings people into close contact with new environments and wildlife species which makes the study and control of zoonoses of special interest and complexity. In Africa, the transmission of helminth parasites is highly influenced by the ever changing social and cultural differences between diverse groups of peoples and their interaction with wild and domestic animals. It is not surprising, therefore, that approaches to the study and control of parasitic zoonoses require intersectoral cooperation between physicians, veterinarians, parasitologists, zoologists, demographers, anthropologists, engineers and economists to provide the breadth of knowledge and expertise required to develop our understanding of these diseases and to devise methods for their control. This book provides a selective compilation of parasitic helminths, many of which are zoonoses which create important economic and public health problems in Africa.