Some Biochemical Aspects of Clinical Johne’s Disease in Cattle

Abstract

Of 24 apparent cases of clinical Johne’s disease, the diagnosis was unequivocally confirmed by means of laboratory tests and post-mortem examination for 18 cows, 2 bulls and 2 steers. The present study constitutes a description of the chemical pathology of clinical Johne’s disease, based on the analysis of samples of blood, urine, faeces, skeletal muscle and intestinal mucosal tissue obtained from some or all of these 22 animals. Comparisons were made with data collected at the same time from suitable healthy control animals. The concentrations of total serum protein, albumin, β- and γ-globulins were lowered, but the concentration of α-globulin was unchanged in clinical disease. Although there were neither signs of acidosis nor alkalosis, concentrations of most of the electrolyte constituents of plasma were low. However, the concentration of inorganic phosphate was raised. The decrease in plasma potassium concentration was accentuated during terminal stages of the disease, falling some 40% during the last month of life. The hypokalaemia was accompanied by hypochloraemia without alkalosis. There was a correlation between the development of hypokalemia and the loss of intracellular potassium from muscular tissue. The output of potassium in the faeces and urine was increased. The decrease in concentration of many other plasma constituents probably resulted from a haemodilution, since the body tissues examined showed an increased water content. Wasting of muscle tissue was accompanied by an increased urinary output of creatine and amino-nitrogen. Elevated levels of plasma urea and non-esterified fatty acids were seen, particularly in terminal disease. In Johne’s disease, the urinary excretion of indican was increased above the normal levels for the ruminant. The inflammatory nature of the clinical condition was reflected in an increase in the concentration of serum glycoproteins and localized thickening of the intestinal mucosa, which appeared to be related to an increased concentration of mucopolysaccharide constituents. The biochemical changes described were not pronounced enough to constitute the basis for a diagnostic test.