Submitted to: World Aquaculture Society Meeting
Publication Type: Abstract Only
Publication Acceptance Date: November 28, 2001
Publication Date: February 1, 2002
Citation: Griffin, B.R., Davis Jr., K.B. Quantitive bioassay of the sensitivity of channel catfish to infestation by ichthyopthirus multifillis and the effects of stress. 2002. Abstract p. 87. Technical Abstract: A quantitative bioassay to determine the sensitivity of channel catfish to infestation by the obligate external protozoan parasite Ichthyopthiriliis multifiliis was developed. Infestation was counted as the number of trophonts/cm2 after 4 to 5 days of infection. Consistent counts could be made up to eight days after fixing the fish in 10% formalin. Infestation was proportional to the concentration of the tomite stage, the infective form, and was linear from 1.25 to 10 K tomites per liter. Infestation of fish subjected to a low water crowding exposure for 2h or 6h were compared to non-crowded controls. Fish stressed for 6h had significantly higher trophont counts than control fish and fish stressed for 2h had intermediate infestations. Plasma cortisol concentrations increase due to low water stress and is thought to suppress the resistance of the fish. Fish fed 200 mg cortisol per kg of feed developed trophont infestations significantly higher than fish fed control feed. These data support the idea that cortisol secretion induced by exposure to stressors increase the susceptibility of channel catfish to Ichthyopthirius multifiliis.