Immunosuppressive effects of ochratoxin A in young turkeys.

Ochratoxin A (OA), a potent nephrotoxic mycotoxin, was fed to day-old turkey poults at 0 and 4 parts/10(6) dietary levels for 4 and 10 weeks, and its effects, particularly on the immune system, were studied. OA resulted in a significant retardation of growth in both males and females. OA caused a regression of the thymus and bursa of Fabricius and lymphoid depletion in these and other lymphoid organs. Analysis of covariance revealed an enlargement of the kidneys at 10 weeks of age in OA-treated birds; the liver and spleen were enlarged in birds treated with bovine serum albumin (BSA). Cell-mediated immune responses, as measured by delayed hypersensitivity (DH) reactions to avian tuberculin and to BSA in pre-sensitised birds, were significantly depressed in OA-treated birds. The results suggest that the DH immune responses of turkeys differ from those in fowls in some respects; turkeys do not show a typical Arthus reaction and respond poorly to avian tuberculin PPD sensitisation. In a comparative evaluation of skin test sites for the study of DH responses in turkeys, the earskin area was found to be an easy and convenient site for injection, measurement and observation of cutaneous reactions.