INDUCTION OF TIBIAL DYSCHONDROPLASIA AND SUPPRESSION OF CELL-MEDIATED-IMMUNITY IN CHICKENS BY FUSARIUM-OXYSPORUM GROWN ON STERILE CORN

An isolate of Fusarium oxysporum from corn associated with Kaschin-Bec k disease in humans was tested for its ability to induce tibial dyscho ndroplasia (TD) and toxicity in chicks. Both leghorn and broiler chick s were fed diets in which corn was replaced with varied amounts (0% to 50%) of the F. oxysporum culture grown on sterile corn, or with known TD-inducing agents. F. oxysporum did not affect body weight in either type of chicks. In leghorn chicks, neither F. oxysporum nor the known TD-inducing agents (F. equiseti, 4%; tetramethylthiuram disulfide [Th iram], 35 ppm) caused TD. However, F, oxysporum at high levels (50%) a nd the two known TD-inducing agents reduced interdigital cutaneous res ponse to phytohemagglutinin-P challenge. In addition, Thiram also redu ced body-weight gain by more than 17%. In female broiler chicks (Corni sh Rock), F. oxysporum not only decreased cell-mediated cutaneous resp onse to phytohemagglutinin-P but also increased TD incidence; these sa me effects were observed with F. eqitiseti and Thiram. Histological ex aminations revealed similar pathological changes among dyschondroplast ic lesions induced by F, oxysporum, F. equiseti, and Thiram. Results o f this experiment indicate that the isolate of F. oxysporum from the r egion in which Kaschin-Beck disease is endemic can induce TD in broile r chicks and that it is immunosuppressive.