Immunohistochemical investigations of leptospira-infected golden hamsters in potency tests.

Golden hamsters taken from routine potency testing of leptospirosis vaccines were investigated for leptospirae after a challenge infection. Kidneys, livers, and spleens were examined immunohistochemically by the unlabelled antibody enzyme (PAP) method, and samples of these organs were additionally cultured for the evidence of living leptospirae. In non-vaccinated animals the recultivation method indicated leptospirae during the bacteraemic phase, beginning immediately after infection. Both methods resulted in positive reactions after organ manifestations. Intravascular evidence of leptospirae in the kidneys could be seen first on day 3 after infection. On day 7, there was intracellular and intratubular evidence as well, combined with tubulo-interstitial alterations. In vaccinated animals the bacteraemia after infection was reduced. Organ manifestations were seen rarely; there were less severe or no pathohistological alterations.