The Effects of Foodborne Deoxynivalenol Exposure in Rainbow Trout (Oncorhynchus mykiss) Experimentally Infected with F. psychrophilum
Diets containing deoxynivalenol (DON) from a naturally contaminated or artificially produced source were investigated for potential impacts on the disease susceptibility, respiratory burst response and hematological parameters of rainbow trout. The ability of DON to inhibit the growth of Flavobacterium psychrophilum was also examined. Rainbow trout experienced significantly reduced (p<0.05) mortality after experimental infection with F. psychrophilum (5x107 CFU ml-1) when offered either diets containing corn naturally contaminated with DON (3.3, 4.1 and 5.9 ppm) or diets spiked with purified DON (3.8 ppm) for four weeks prior to infection in comparison to controls. Pair-fed trout also consistently had a significant reduction in mortality compared to fish fed the control diet to apparent satiation. Reduced feed intake and weight gain were also evident with increasing DON concentrations. At 35 d post-exposure to their respective diets, head kidney leukocytes isolated from rainbow trout offered diets spiked with purified DON (3.8 ppm) produced a significantly enhanced (p<0.05) respiratory burst response. Hematological parameters including PCV and WBC counts remained unaffected. In vitro, DON was inhibitory to the growth of F. psychrophilum but only well above relevant concentrations. These studies indicate that diets contaminated with DON may provide a protective effect for rainbow trout experimentally infected with F. psychrophilum, although further research is required.