Systemic pathologic responses in experimental Psoroptes ovis infestation of Hereford calves

Nine Hereford calves were infested with Psoroptes ovis and were allowed to develop clinical mange during a 9-week period. Blood, serum, and urine samples were obtained before and after calves were infested and were compared with those from 3 noninfested control calves. All calves were euthanatized and necropsied 9 weeks after they were infested. Gross and microscopic anatomic changes occurred only in the skin. Calves developed typical exudative dermatitis, the extent of which was dependent on population density of mites. Severely infested calves (50% to 70% of skin with dermatitis) developed a mild anemia and lymphopenia with marked neutropenia and variable eosinophilia. There were also increases in fibrinogen, gamma-globulin, and in vitro lymphocyte response to mitogen stimulation and decreases in anion gap cortisol, albumin, albumin/globulin ratio, and fractional Na clearance values. The severity of many of the changes could be correlated with the extent of dermatitis.