THE HEMATOLOGY OF ACUTE BACTERIAL-INFECTION IN FARMED RED DEER CERVUS-ELAPHUS - YERSINIA-PSEUDOTUBERCULOSIS

Haematological changes were followed in a field model of infection wit h Yersinia pseudotuberculosis using female weaner red deer, 109 animal s having blood samples taken before the challenge and at various times after challenge, a total of 553 blood samples being processed. Clinic al signs first developed 4 days after exposure, with a mode of 5 days and median of 7 days. Neutrophils rose sharply to well above the upper reference limit 1-2 days postexposure, but were within reference limi ts by days 3 to 4, before the development of clinical signs. Both hapt oglobin and fibrinogen levels increased within 24 h of exposure to lev els above the reference range, fibrinogen returning to within the refe rence range about day 14, though still highly significantly raised com pared to pre-exposure values. Haptoglobin levels were still greater th an the reference range upper limit 28 days after exposure.Mononuclear leucocytes were reduced in number 2 days after exposure reaching a min imum at 4 days and reaching pre-exposure values by day 6. Eosinophil n umbers were low at 2 days, all clinical cases having eosinophil counts round the low end of the reference range, counts remaining low and no t reaching pre-exposure levels until the 28th day sample. The basophil count decreased in animals with inflammation early in the infection a nd increased above pre-challenge values around the 28th day. Circulati ng platelet numbers decreased with a minimum 4 days after exposure, th en increased above pre-exposure values from day 6 to day 11. The mean platelet volume was low on day 5, returning gradually towards pre-expo sure values, but still low on day 28. Red cell mass indicators were hi gher and mononuclear leucocytes were lower in fatal cases than in nonf atal clinical cases. Fibrinogen level and neutrophil counts were highe r in animals with clinical signs that survived, compared to animals wi thout clinical signs but from which Yersinia were isolated. Subcutaneo us injection of killed Yersinia also invoked a neutrophil leucocytosis , reductions in circulating mononuclear leucocyte, eosinophil and baso phil numbers, and mean platelet volume. There were also increases in f ibrinogen and haptoglobin levels, and in circulating platelet numbers.