Natural occurrence of Diplostomum spp. in farm-raised African catfish (Clarias gariepinus) from Oyo state, Nigeria

Diplostomum species are the parasites responsible for diplostomiasis in fish which may cause blindness, eyefluke, severe ocular disease, opacity of the lens and many other affections. The parasites use many organisms including fish as a host. African catfish is one of the widely distributed fish species in tropical Africa and has become one of the most important culturable fish species in Africa especially in Nigeria. This study examined the occurrence of Diplostomum species in farm raised African catfish in Oyo state. A total of two hundred and sixteen eye samples were collected from 108 fishes in 36 farms. The eye lens and vitreous body were examined for the presence of Diplostomum species. The data obtained were analysed using descriptive statistics and regression analysis to the relationship between the eye size and parasite occurrence. The result shows that 33.18% of the samples had Diplostomum species. Males had higher occurrence (23.53%) than the females (9.65%). There were statistically significant differences in the percentage, intensity and index of infection between males and females (p = 0.010, p = 0.003, and p = 0.012 respectively) while the density of infection between both sexes was not statistically significant (p = 0.063). The relationship between eye diameter and occurrence of the parasites shows positive relationship Pearson correlation (R(2) = 0.125). In conclusion, Diplostomum species are present in farm raised African catfish in Oyo state-Nigeria with a positive relationship between the eye diameter and occurrence of the parasites.