Submitted to: Aquaculture America Conference
Publication Type: Abstract Only
Publication Acceptance Date: October 7, 2004
Publication Date: January 17, 2005
Citation: Xu, D., Klesius, P.H. 2005. Susceptibility of nile tilapia to infection of ichthyophthirius multifiliis. Aquaculture America Conference. Technical Abstract: The ciliated protozoan Ichthyophthirius multifiliis (Ich) is a parasite of freshwater fish. Nile tilapia Oreochromis niloticus are susceptible and suffer economic losses due to Ich infection. Little information is available about the pathogenicity of the Ich in this species. This study evaluated the susceptibility of tilapia to Ich infection by cohabiting with live Ich infected fish, exposure to dead Ich infected fish and theronts. The infectivity was evaluated by determining the percentage of fish infected, the infection level and the infection ratio of Ich infected fish to naive fish used in the infection trials. The percentage of fish infected was determined in each tank and the infection levels were determined by the numbers of trophonts on each fish. Tilapia were easily infected by these three methods when challenged with Ich from Ich passages or infection cycles 20-50. More than 94% of tilapia became infected by any of these 3 methods and the fish showed 50-100 or more visible trophonts per fish. Infection percentage and infection levels in tilapia were comparable to those in channel catfish. Tilapia were more tolerant to heavy Ich infection than channel catfish and a lower mortality was seen in tilapia than in channel catfish when exposed to high concentrations of infective theronts. Cohabitation with live Ich infected fish or exposure to dead Ich infected fish resulted in greater infection percentages and levels than exposure to theronts. Nile tilapia is a suitable host species to maintain Ich culture. The susceptibility of Nile tilapia to Ich infection is comparable to that of channel catfish, whether by cohabitation or by exposure to dead Ich infected fish.