Interactive toxic effects of aflatoxin B1 and zearalenone on cellular and humoral immunity of rainbow trout (Oncorhynchus mykiss)

Feeds are widely exposed to various mycotoxin contaminations including aflatoxin and zearalenone. The present study was designed to investigate the simultaneous toxic effects of aflatoxin and zearalenone. To this end, 540 rainbow trout fingerlings (3.0 ± 0.2 g) were randomly allotted to nine different experimental groups composed of three different dietary aflatoxin (0, 25 and 50 ppb) and zearalenone (0, 200 and 400 ppb) levels. The experiment lasted 30 days. Red and white blood cell counts along with some immunological indices including serum lysozyme activity, antibody, lymphocyte proliferation, complementary pathway and phagocytic intensity of peripheral blood phagocytic cells (NR assay) were investigated. Results showed that lysozyme activity, serum antibody content, red and white blood cell counts were not significantly affected by dietary mycotoxin contamination (p>0.05). However, the complementary pathway was significantly affected by dietary aflatoxin B1 content (p<0.05) and the lowest and highest activity was observed in those fish received 50 ppb and diet lacking aflatoxin contamination, respectively. Aflatoxin B1 and zearalenone interactively affected lymphocyte proliferation and NR indices (p≤ 0.05) with the lowest and highest activities were recorded in those fish fed diet containing 50 ppb aflatoxin devoid of zearalenone and diet containing 50 ppb aflatoxin and 200 ppb zearalenone, respectively. It is conceivable that simultaneous dietary contamination of aflatoxin and zearalenone attenuates immune system functioning of rainbow trout.