Aquatic vegetation harms human health in several ways since water-related diseases are part of our environment. Malaria has receded internationally due to chemo-thera-peutic-insecticidal programs, but recently has resisted both medicines and insecticides. Lately, active malaria cases in the U.S. were kept to fewer than a dozen annually; in 1967, the figure was about 700, almost all traceable to returning military personnel. Other diseases exist whose transmission is indirectly affected by aquatic weed conditions: filariasis, and various trematodiases especially the schistosomes, Chinese liver fluke, cattle liver fluke, Guinea worm, giant intestinal fluke, Asiatic lung fluke, and the broad tapeworm.