THE PREVALENCE OF LEPTOSPIROSIS AND ITS ASSOCIATION WITH MULTIFOCAL INTERSTITIAL NEPHRITIS IN SWINE AT SLAUGHTER

Authors:
  • SMSA MCEWEN
    SA MCEWEN
  • JPJF PRESCOTT
    JF PRESCOTT
  • AMAH MEEK
    AH MEEK
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  • 1 July 1989
    • journal article
    • research article
Abstract
An abottoir survey was undertaken to determine the prevalence of leptospirosis and its association with lesions of multifocal interstitial nephritis (so-call "white spotted kidneys:) in swine at slaughter. Both cross-sectional and case-control study designs were used. Of 197 kidneys from hogs randomly selected at slaughter, 11 (5.6%) had generalized grey-white foci typical of multifocal interstitial nephritis (MFIN). Antibody titers .gtoreq. 1:80 against Leptospira pomona were detected in nine (4.6%) hogs and against L. bratislava in 63 (32%) of these hogs. Leptospira pomona (kennewicki) was detected by immunofluorescence in 5/197 (2.5%) of randomly selected hogs. Leptospires identified as genotype kennewicki were isolated from six (9.8%) of 61 kidneys cultured. Leptospira bratislava was not detected by immunofluorescence or culture. There was a highly significant (p = 0.00) and strong association (odds ratio (OR) = 195) between high L. pomona titer (.gtoreq. 1:80) and the presence of leptospires in the kidneys, as detected by culture. There was also a significant (p = 0.046) and strong (OR = 8.10) association between multifocal interstitial nephritis and the presence of renal leptospires as detected by culture. The association between leptospiral titer and MFIN lesions in the prevalence survey group of animals was statistically significant (p = 0.031), but this association was not significant in the cross-control study group (p = 0.071). The failure to identify L. bratislava despite serological evidence of infection suggests that some of these seropositive animals may have been transiently infected at an early age, that serological findings were falsely positive, or that immunofluorescence and isolation attempts failed to detect L. bratislava if they were indeed present in the kidneys. Thus, infection of hogs at slaughter with leptospires in Ontario is associated with multifocal interstitial nephritis, and this finding supports the continued condemnation of such kidneys at the slaughterhouse.

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