A DissertationLeptospirosis is a neglected zoonotic disease of world wide public health importance. Rodents are major reservoirs of leptospira although wetland and aquatic migratory birds also carry and transmit leptospira. Studies on leptospirosis in fish are few in African countries, including Tanzania, despite favourable environment and abundant reservoirs, which can spread leptospires into aquatic habitats and infect fish. The objective of this study was to determine the presence of Leptospira spp in fish; the prevalent Leptospira serovars and whether they are related to serovars reported in animals; and their potential public health risk. A Multistage sampling technique was performed in Morogoro municipality, Tanzania, between November- 2016 and February -2017. Before the sampling, knowledge, attitude and practices (KAP) questionnaire was administered to assess the awareness of people (fishermen, fish mongers) on risk factors that might lead to the diversity of Leptospira species and water quality for pH , Dissolved Oxygen and Temperature was measured using Meter Sensor at Sample sites in Morogoro Municipality.Live catfish (n=193) were caught from five different locations, namely Sokoine University of Agriculture Magadu farm, Mzumbe University waste water pond, Morogoro Urban Water Supply and Sanitation Authority (MORUWASA)- Mafisa waste water ponds , Kingolwira Centre for Fish Farming and Fingering Production and Mkindo Fish Farmers in Morogoro Urban and mvomero districts Tanzania where blood and biopsy samples were collected. Microscopic agglutination test (MAT) was used to detect antibody against four leptospiral antigens, including local serovars Sokoine (serogroup Icterohaemorrhagiae); Hebdomadis (serogroup Hebdomadis); Kenya (serogroup Ballum) and Pomona (serogroup Pomona). Samples with MAT titers ≥ 1:160 were scored as higher values while samples with MAT titers ranging from 1:20 to1:80 were scored as lower values for seropositivity. Absence of agglutination titers was scored as negative. All MAT samples, including the low titre samples were subjected to PCR using Lepat and Sapro primers for the pathogenic and non-pathogenic species (saprophytic) respectively. Tissue samples were prepared by grinding freshly obtained kidneys of sharptooth catfish (Clarias gariepinus) for culturing in Fletchers medium. Dark-field microscopy readings of each of the tubes were performed at first,second, fourth, and sixth week after culturing at 20 X magnification to assess bacterial growth, of the total 193 samples tested, 29 (15 %) were positive with MAT. The major circulating leptospiral serovars were Pomona (11.4 %,), Kenya (1.55%), Hebdomadis (1.55%) and Sokoine (0.52%). By using PCR methods and of the 193 samples screened, 4 (2%) were positive for pathogenic leptospira. No isolation of leptospira was achieved from the kidney cultures. This study has shown a relatively high seroprevalence 15% of leptospirosis in common fresh water fish type, compared to warm blooded animals hence indicate an extended public health risk, of leptospirosis to fish handlers and consumers .To minmize leptospirosis transmission in Morogoro region, and Tanzania at large, where the disease is little known and thus neglected, it is recommended, to increase public awareness of leptospirosis in the general public, and particularly those groups at risk such as farmers, livestock keepers, fishermen, sewerage and abbatoir workers. Routine screening for leptospirosis should be considered in people engaged with occupational activities that increase contact with environments likely to contain leptospires. This is especially important in situation where malaria, typhoid and other common febrile diseases are ruled out; Isolation of leptospires from different hosts and sources should be emphasized in order to understand the sources of infections, infecting serovars and developing a protocol for the diagnosis of this infectious disease appropriate for different areas. Rapid serological tests not involving live microorganisms for routine diagnosis is highly recommended.