In tropical countries like Ethiopia where the wet seasons are restricted to less than fivernmonths of the year, wetlands such as those found around Lake Zwai provide idealrnenvironments for water-related diseases of sheep and humans. As a consequence, thisrnstudy was conducted over a 2-year period to study the gastro-intestinal parasites of sheeprnand humans (schoolchildren) that frequently visit the wetlands of Lake Zwai, thernintermediate hosts (snails) inhabiting the same wetlands and the effectiveness of drugs onrnthe gastro-intestinal parasites identified in the wetlands. The results generally showed thatrnthe wetlands of Lake Zwai are infested with gastro-intestinal parasites as shown in therntracer animals used (sheep) and by a different set of parasites picked by schoolchildrenrnvisiting the same wetlands. The snail vectors surveyed in these wetlands were generallyrnfound to host the diseases of the sheep rather than those diseases of the schoolchildren.rnThe drug effectiveness trials conducted of the livestock gastro-intestinal nematodernparasites were found to be susceptible in Tetramizole and Ivermectine, with lowerrnresistance in only one drug (Albendazole). It was concluded that Zwai wetlands thatrnprovide fresh herbage to sheep throughout the year and attractive playing grounds tornschoolchildren of a nearby school, provide conducive environments mostly to waterbornerngastro-intestinal parasites of sheep and to a lesser extent to humans (schoolchildren). Inrnall cases of the definitive hosts (sheep and humans), their performance in life is severelyrnaffected, if in rare cases deaths do not occur. It was, therefore, recommended that visits ofrnsheep and humans to the wetlands should be restricted particularly at peak infectionrnmonths, inflow of animal wastes with parasite eggs be diverted for treatment, regimes ofrnprophylactic treatments should be introduced and generally awareness of the diseaserncycles, herbages for animals should be collected and treated before feeding the sheep,rnsafe wetland playing-grounds for schoolchildren should be identified and safe wastehandlingrnmethods should be introduced into the local population and sheep owners.