Bovine leptospirosis: bacteriologic versus serologic diagnosis of cows at slaughter

Blood for serologic examination and kidneys for bacteriologic cultural examination were collected from 204 cows slaughtered in an Iowa packing plant during August to October 1981. By the microscopic agglutination test on the 200 serum samples which were collected, 29 (14.5%) were positive--22 samples (10.8%) had agglutinin titers to hardjo, 4 (2%) to pomona, and 5 (2.5%) to other serovars. With the enzyme-linked immunosorbent assay, 79 samples (39.5%) were positive--53 (26.5%) to hardjo and 36 (18%) to pomona. Leptospires were isolated from 13 (6.4%) of the kidneys (n = 204) examined. Characterization indicated that 7 isolates were hardjo; 3, grippotyphosa; and 2, pomona (1 isolate was lost during first subculture). Three of the hardjo isolates and 1 of the grippotyphosa isolates were obtained from cows that were seronegative by the microscopic agglutination test.