The use of aqueous extracts of Vernonia amygdalina in the control of saprolegniasis in Clarias gariepinus, a freshwater fish

Abstract

Saprolegniasis infection causes severe damage to fish integument. To control this fungal infection in the fish environment, Asteraceous plant (Vernonia amygdalina) extract at varying concentrations (50, 40, 30, 20%, control) was used to test its potency in controlling the infection and to ascertain its inhibitory capacity. The axenic culture of the test fungus was maintained on PDA at 28oC. The rate of the colony forming units was determined and the test inocula adjusted to 1.5 X 105 spores per ml. The Asteraceous plant extract generally depressed the growth of the fungi and cleared the spores earlier noticed on the fish integument. The potency of inhibition of the growth of Saprolegnia increased with increase in concentration. The control fish without the plant extract showed fluffy tufts growing on their body after 28 days and they appeared lethargic. This research hold great promise in elucidating the potency of the plant extract (V. amygdalina) in suppressing fungal growth in the integument of Clarias gariepinus, a freshwater fish.