FACULTY OF VETERINARY MEDICINE
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Item Histology of selected organs of Clarias gariepinus infected with the metacercaria of a digenean trematode(Faculty of Veterinary Medicine, University of Ibadan (Ibadan, Nigeria, 2021) Adedokun, R. A. M.; Aina, O. O.; Oladosu, G. A.; Igado, O.O.; Tijani, I. D.Fish have become a major source of protein and essential fatty acid for fish lovers in the world. Thus, many farmers are venturing into fish farming but have challenges due to fish diseases and parasites. This study examined the possible pathological lesions associated with digenean trematode infections in the Clarias gariepinus. Clarias gariepinus juveniles reared in fibre-glass tanks under intensive, flow through system were obtained from a commercial farm. Aquatic snails were obtained from earthen ponds on three commercial fish farms. The presence of cercaria was established in these snails, which were reared in laboratory conditions with Clarias gariepinus juveniles, for two weeks, to cause infection. Age matched un-infected Clarias gariepinus served as controls. Presence or absence of metacercaria after histological examination was used to determine infected and controls, respectively. Fish were sacrificed after two weeks and organs reexamined for the presence and absence of metacercaria. Preliminary examination using wet mount revealed the presence of metacercaria only in the gills of juveniles reared with infected snails. Histological staining and examination using haematoxylin and eosin stain, revealed histopathological lesions in the gills, kidneys, liver, spleen, brain and skin. Lesions included loss of secondary filaments in the gills, tubular degeneration and necrosis in the kidneys, vacuolations and spongiosis in the cerebellum and liver, and loss of pigmentation in the skin. There were no lesions observable in the intestine and stomach. Findings obtained from this experiment indicate that the presence of parasites in the gills alone is cause for concern, especially in commercial fish farming. It is postulated that the lesions in other organs may be partly due to the disruptive effect on the gills resulting in oxygen deprivation. In conclusion, there was significant disruption of these organs due to massive invasiveness of metacercaria in the gills, which may lead to economic losses and possible zoonosis. Measures targeted at snail control in earthen ponds with fiches, will break the transmission chain, and prevent digenea infestation in cultured fish.Item Causal Factors of Mass Mortality of Hatchery Reared Clarias gariepinus fry during Exogenous Feeding(AkiNik Publications, 2021) Anifowose, O. R.; Oladosu, G. A.; Oladele, O. O.The study investigated the causal factors associated with mass mortality of hatchery-reared Clarias gariepinus Burchell 1822 fry during exogenous feeding. A feeding trial and fry re-infection trial were conducted using four different starter diets. The food samples were fed to 480 post-yolk-absorbed fries for 21 days in two replicates. Samples of dead fry were cultured for bacteria using standard methods. The total aerobic and coliform were significantly higher in all food samples, meanwhile, alkaline pH (9.25±0.34) and low dissolved oxygen (4.5±1.08) were not significantly different (P>0.05) in all water tanks. The bacterial pathogens isolated from dead fries were Aeromonas hydrophila Stainer, 1943 and Pseudomonas aeruginosa Migula, 1990, whereas significantly higher mortality in experimentally infected fry was observed (α < 0.05). Mass mortality of C.gariepinus fry observed in this study was associated with bacterial pathogens, bacterial contamination of food, alkaline pH, and low dissolved oxygenItem Histology of selected organs of Clarias gariepinus infected with the metacercaria of a digenean trematode(University of Ibadan, Faculty of Veterinary Medicine, 2021) Adedokun, R. A. M.; Aina, O. O.; Oladosu, G. A.; Igado, O. O.; Tijani, I. D.Fish have become a major source of protein and essential fatty acid for fish lovers in the world. Thus, many farmers are venturing into fish farming but have challenges due to fish diseases and parasites. This study examined the possible pathological lesions associated with digenean trematode infections in the Clarias gariepinus. Clarias gariepinus juveniles reared in fibre-glass tanks under intensive, flow through system were obtained from a commercial farm. Aquatic snails were obtained from earthen ponds on three commercial fish farms. The presence of cercaria was established in these snails, which were reared in laboratory conditions with Clarias gariepinus juveniles, for two weeks, to cause infection. Age matched un-infected Clarias gariepinus served as controls. Presence or absence of metacercaria after histological examination was used to determine infected and controls, respectively. Fish were sacrificed after two weeks and organs re examined for the presence and absence of metacercaria. Preliminary examination using wet mount revealed the presence of metacercaria only in the gills of juveniles reared with infected snails. Histological staining and examination using haematoxylin and eosin stain, revealed histopathological lesions in the gills, kidneys, liver, spleen, brain and skin. Lesions included loss of secondary filaments in the gills, tubular degeneration and necrosis in the kidneys, vacuolations and spongiosis in the cerebellum and liver, and loss of pigmentation in the skin. There were no lesions observable in the intestine and stomach. Findings obtained from this experiment indicate that the presence of parasites in the gills alone is cause for concern, especially in commercial fish farming. It is postulated that the lesions in other organs may be partly due to the disruptive effect on the gills resulting in oxygen deprivation. In conclusion, there was significant disruption of these organs due to massive invasiveness of metacercaria in the gills, which may lead to economic losses and possible zoonosis. Measures targeted at snail control in earthen ponds with fiches, will break the transmission chain, and prevent digenea infestation in cultured fish.Item Prevalence of Monogenea Trematodes in different developmental stages of Clarias gariepinus in Delta State, Nigeria(Fisheries Society of Nigeria, 2018) Okunade, O. A.; Oladosu, G. A.; Adeogun, O. A.; Akinwale, M. M. A.; Akintayo, I. A.; Peters, O. S.; Odusanya, A. F.Monogenea trematodes are ectoparasitic worms of numerous species including the two super-genera (Dactylogyrus and Gyrodactylus). They infect freshwater organisms, primarily fishes. They are harmless at low infestation, but heavy infestations cause wounds and gills hypertrophy which compromises respiratory functions. Out of 231 fish examined in this study, a total of 72 specimens were infected with an overall prevalence of monogenea trematodes infections of 31.17%. Dactylogyrus sp. was recorded in juveniles, post juveniles, and adults with a total prevalence of 23.6% No Dactylogyrus sp. was found in fry and fingerlings. The total prevalence of 76.39% was recorded for Gyrodactylus sp across all stages. Gyrodactylus sp. infected the gills of all the stages in different frequencies, juvenile recorded the highest and fry the least. Dactylogyrus sp were found more on the skin of adult Clarias gariepinus than the gill. The water quality parameters recorded were pH, dissolved oxygen, ammonia, water and atmospheric temperatures.