Zinc and copper plasma levels in Icelandic horses with Culicoides hypersensitivity

Zinc concentration has been shown to have a potent immunomodullatory capaci ty, particularly influencing T helper cell organisation and cytokine secret ion. Culicoides hypersensitivity (CHS) in horses resembles the early and la te phase of type I hypersensitive reactions in man, characterised by a shif t from T helper cell subtype I to T helper cell subtype 2 cytokine profile. In this pilot study, zinc and copper levels were measured in the plasma of 48 CHS-affected and 56 healthy Icelandic horses age 4-25 years (mean simil ar to 11 years) kept on 7 farms. Affected horses were divided into 3 groups according to the severity of disease. Time of blood collection and feeding management was constant. No differences in zinc or copper plasma levels and plasma copper/zinc ratio were determined among CHS horses and controls by univariate analysis of va riance. Therefore, the most significant influences on zinc and copper plasm a levels were affected by the location of housing. However, Spearman correl ation showed a negative coefficient between the plasma zinc concentration a nd the severity of CHS (r = -0.31). Due to a probability value of P = 0.002 the null hypothesis r = 0 is rejected, although only 9% of the total varia tion of plasma zinc is presently explained by its relationship to CHS. In c ontrast, the Spearman correlation coefficient between plasma copper levels and severity of CHS was not significant (r = -0.14; P = 0.16). The minor de viations in plasma zinc concentrations in association with the severity of CHS may be real or due to neurohumoral or cytokine-mediated mechanisms, but appear too minimal to be relevant.