Helminthic infections in man in relations to hygiene and environment in Zanzibar, Tanzania. A minor field study

control de enfermedades developing countries disease control disease transmission enfermedades humanas environmental factors facteur du milieu factores ambientales helminthose helminthoses helmintiasis higiene hogares households human diseases hygiene living standards maladie de l'homme niveau de vie nivel de vida pueblos tanzania tanzanie transmission des maladies village villages