Effects Of Chicken Manure and Macrolesions on the Infectivity of Saprolegniasis (Saprolegniales Saprolegniaceae) on Nile Tilapia Oreochromis Niloticus Niloticus Fingerlings

Abstract

An investigation was carried out to determine the mycotic infectivity of Saprolegnia ferax an aquatic Oomycetes on the nile tilapia, Orochromis niloticus niloticus with macrolesions using chicken droppings as fertilizer. The development of saprologniasis and the outcome on histological sections of the gills, skin and kidneys on experimental fish were also evaluated. Physiochemical parameter of the water were investigated. Fifty ( 4 week old) fingerlings of the test fish O. niloticus nilotcus with average weight of 13.40 + 1.90g and average length of 8.80 + 0.91cm were distributed into 5 replicated tanks containing 5 fingerlings each. Saprolegnia ferax that was cultured and identified using cultural characteristics from hatchery pond water was introduced into the experimental tanks equally. Experimental fish was disinfected with Ippm malachite green solution by immersion following standard methods. Chicken manure was washed with distilled water to remove dirt and grit before using as fertilizer employing standard application rates. There was no significant difference in all the tanks in respect to temperature, pH, and unionized ammonia values (P < 0.05) using One Way Analysis of Variance (ANOVA) and Duncans Multiple Range test. However in the tanks treated with chicken manure there was depletion of oxygen, increase in values of both free carbon (iv) oxide and dissolved organic content. Mortality of fish fingerlings was lowest (10%) in the control tank and higher (95%) in tanks containing fish with macrolesioins by the 4th day of experiments respectively. Histological examinations of organs of the gill, kidney and skin revealed that the fingerlings in the control tank retained their gill filaments and lamellae while the treated fingerlings showed broken gill filaments and eroded gill lamellae. The mucus lining of the skin section was sloughed off and the lining underneath the mucus was thinnest in the control fingerlings and thickest in the fish treated with chicken manure. Kidney section of fish in the control tank showed fewer circular thyroid follicles as compared with treated tanks. The study has revealed that physico - chemical parameters especially the increase in free carbon (iv) oxide and dissolved organic content might have influenced the high rate of secondary pathogenicty of Saprolegnia ferax. Infection due to S. ferax greatly affected the mortality rates of experimental fish and caused pathological changes to the gill, skin and kidney of the Nile tilapia, Oreochromis niolticus niloticus.