Abstract
One hundred fifty lactating mink on one ranch in southern Ontario were monitored over the lactation period in 1989 for evidence of clinical disease, and serial blood samples were collected for biochemical analysis. Antemortem blood samples were collected and necropsies performed on the 17 females that developed nursing disease and on 17 controls matched to the same stage of lactation and on ten nonlactating controls. Twenty-two additional nursing disease cases were selected from seven ranches in the following year and processed similarly. The clinical signs typically observed in affected females were sudden onset lethargy and anorexia followed by dehydration, ataxia, and a reluctance to move. The major clinical-pathologic findings were a marked increase in serum osmolality and total protein, urea nitrogen, creatinine, phosphorus, glucose, and potassium concentrations and a decrease in sodium and chloride concentration. In addition, the animals were acidotic, there was a reduction in the urine specific gravity, and the hemogram was consistent with a stress response. Emaciation and dehydration were the only pathologic changes consistently present in cases of nursing discase and not in controls. In almost all cases, bacteria were not cultured from the liver, spleen, and mammary gland, but Campylobacter jejuni was cultured from the intestinal contents of 15/17 affected mink and 2/5 controls. Aleutian disease virus antibody was not present in any of the affected mink, Lipid vacuoles in hepatocytes and renal tubular epithelium, hypertrophy of cells in the adrenal cortex, and pulmonary congestion and atelectasis were present in both diseased females and controls, as were various sporadic inflammatory lesions. Nursing disease may result from energy depletion due to lactation. All lactating females are affected by this process: clinical disease reflects the terminal physiologic decompensation of the most susceptible individuals.