Abstract
This study examined the prevalence of Listeria species in fish (Clarias gariepinus and Oreochromis niloticus). The total number sixty (60) of fishes were randomly selected from commercial outlet in Ibadan and examined. Sex, Total Length, and Total Weight were determined in respect to occurrence of Listeria spp. Simple percentages were adopted to analyze the data. The results show that 12 out of 60 (20%) were positive for Listeria species. The three species identified were L. monocytogenes, L. innocua, and L. grayii. Male has highest rate of infection (18.91%), fishes with average length of 20-30 cm had 41.17%, 351-400 g has highest number of infection (28.57%). C. gariepinus shows the highest presence of Listeria spp with over 26.67% (L. monocytogenes 16.67%; L. innocua = 6.67%; and L. grayii = 3.33%) while O. niloticus shows total of 13.33% presence of Listeria species (L. monocytogenes 10.00%; L. innocua = 3.33%; and L. grayii = 0.00%). Isolation of L. monocytogenes in fish (Clarias and Tilapia) in Ibadan in this study indicates that there is high presence of Listeria species and this further suggested that there is high risk of contacting listeriosis in the study area. It was recommended that proper hygiene and cooking to at least 70 oC is recommended since the bacteria can be killed at that temperature. Attention should be given to avoid cross-contamination and re-contamination from the chain, especially ready- to- eat fish such as fried fish, smoked fish and so on.

Key words: Listeria monocytogenes, Listeria innocua, Listeria gravii, Prevalence, Infection, Claris gariepinus