Don’t forget the fish : organ damage and hepatic lipid accumulation in carp after feed-borne exposure to DON

The occurrence of mycotoxins in fish nutrition increasingly gains attention. One of the most important contaminants in fish feeds is deoxynivalenol (DON). The investigations that will be presented show effects of DON on carp (Cyprinus carpio L.) using three different DON concentrations representative for commercial fish feeds including increased lipid peroxidation in liver, head kidney and spleen after four weeks of DON feeding of fish. Most of the effects of DON were reversible by two weeks of feeding the uncontaminated control diet. However, histopathological scoring revealed increased liver damage in DON-treated fish, which persisted even after the recovery phase. Biochemical analyses revealed a significantly higher fat content, and consequently an increased energy content in whole body homogenates of fish treated with the highest DON concentration. This suggests that DON affects nutrient metabolism in carp. Changes of lactate dehydrogenase activity in kidneys and muscle and high lactate levels in serum indicated an effect of DON on anaerobic metabolism. Thus, DON affects liver function and metabolism in carp. Effects on growth and mass of fish were not observed during these 6 weeks lasting experiments, and only marginal DON concentrations were found in muscle and plasma samples. Nevertheless, DON impaired innate immune responses whereby cytotoxic effects of DON partly contributed to this effect. Investigations of acute and chronic responses to DON revealed that the early responses of immune cells include increased expression of pro-inflammatory and anti-inflammatory genes whereas prolonged exposure to DON only led to the activation of anti-inflammatory genes. Consequently, these results raise concern about impaired immune function and animal welfare of fish raised in aquaculture