Immunosuppressive effects of Ochratoxin a in young Turkeys¹

Abstract

SUMMARYOchratoxin 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.

Immunotoxicity of ochratoxin A and citrinin in New Zealand White rabbits.

“…Several studies revealed that OTA affected the structural components of the immune system. Immune suppression due to regression of immunological organs such as the bursa of Fabricius and the thymus and their lymphoid cell population in the OTA treated chicks, resulted in a decline in IgG, IgA and IgM levels in serum (Dwivedi and Burns, 1985). This result lends further support to the present findings.…”

“…The stimulation index of the lymphocyte transformation test in rabbits indicated a significantly lower cellular immune response in OTA and combination groups. This may be due to the effect of these toxins on the immunocompetent organs (Chang, 1979;Dwivedi and Burns, 1985). These findings were further supported by a reduced cellular reaction in the dermis at the skin test site, as histopathologically noted.…”

Immunological responses of male White Leghorn chicks kept on ochratoxin A (OTA)-contaminated feed

“…The finding of our study is in line with results shown by Elaroussi et al (2006) that reported significant decreases in the skin thickness response to PHA-P in male broiler chicks kept on an OTA-contaminated ration (i.e., at 0.4 and 0.8 mg/Kg diet) for 5 weeks. The significant decrease in the thymus weight and depletion of lymphoid cells noted here-and also reported earlier by Elauorssi et al (2006), Al-Anati andPetzinger (2006), andDwividi andBurns (1985)-provide significant clues to allow us to better understand the depression in T-lymphocyte functions in OTA-treated birds.…”

Experimental ochratoxicosis in broiler chickens

“…Furthermore, OTA fed to broilers alone (4 parts/ 10 6 ) decreased humoral immunity, and in combination with aflatoxin (2 parts/10 6 ) decreased humoral and cellular immunity (Verma et al ., 2004). OTA was detrimental also to quail (Farshid & Rajan, 1996) and turkey immunity (Dwivedi & Burns, 1985). Suppression of humoral and cellular immunity by OTA reduces the immune response of chickens to vaccination against Newcastle disease virus strain B1 (Stoev et al, 2000(Stoev et al, , 2002 or LaSota strain (Santin et al ., 2002), and allows development of secondary bacterial infections (Kumar et al ., 2003(Kumar et al ., , 2004 Two findings that were reported in this study, a reduced leucocyte count and thymus weight, implied that the functioning of the immune system is altered.…”