African Animal trypanosomosis is one of the most economically devastating diseases of livestock in sub-Saharan Africa. The persistence of its tsetse vectors and consequently the severity of the disease in a certain population largely depend on the maintenance of favorable ecological conditions in the area. This study was primarily initiated to assess spatial and temporal changes in tsetse distribution and trypanosome prevalence upstream (Loma District) and downstream (Kindo Didaye District) the Ghibe - III hydroelectric dam area to appreciate if the dam has any impact. Questionnaire surveys with 189 respondents using semi-structured questionnaire and focus group discussions (FGD) with 15 groups each containing 6-20 members were conducted by matrix scoring with local community to assess their perceptions on the disease situation and its tsetse fly vectors. Triangulation was done to evaluate the relationship between farmersâ€™ perception and trypanosomosis prevalence and impact in cattle. Tsetse flies were trapped by deploying 160 NGU traps at an interval of 200m air distance starting from the fringe of water bodies and animals were bled in dry and wet seasons from selected kebelesâ€™ of both districts to assess the situation as we go away from the Ghibe III dam reservoir in the upstream and from the Omo River downstream. The findings from the interviews and FGD revealed that: 1) cattle herd size greater or equal to six have significantly increased after dam construction in Loma district, whereas in Kindo Didaye farmers with such cattle herd size have declined, 2) Bovine trypanosomosis was ranked as number one disease priority in both Loma (upstream) and Kindo Didaye (downstream) Districts, and 3) Strong concordance observed between diseases and their clinical symptoms as well as impacts on animal health and production. Trypanosomosis prevalence and tsetse distribution studies showed: A) no difference between the two study districts in disease prevalence and tsetse apparent density (TAD) before dam construction, B) both TAD and trypanosomosis prevalence were significantly lower upstream the dam (Loma) than downstream (Kindo Didaye) study sites five years after dam construction (P