Cross-Protection Between hardjo and balcanica

Abstract

Extract

Sir, — We were interested to see the results of the trial conducted by Flint and Liardet ⁽²⁾ which showed that the antibodies produced by hamsters in response to a hardjo bacterin protects them against balcanica infection. Their results complement those from a passive hamster protection test conducted by ourselves. In this test 10 hamsters were each injected intraperitoneally with 0.5 ml of bovine anti-Pithardjo serum. This serum had been collected from a heifer which had received a 2 ml dose of a commercial hardjo/pomona bacterin* eight weeks previously and had a titre of 1:96 to hardjo. Twenty-four hours later these 10 hamsters were challenged: 5 received an intraperitoneal inoculation of approximately 2 x 10⁷ bakanica organisms and 5 received a similar inoculum of hardjo organisms. At the same time, 2 control groups of 5 hamsters were challenged with balcanica and hardjo by the same route. Leptospires could not be isolated from any of the challenged hamsters which received anti-hardjo serum when their kidneys were cultured 18 days post-inoculation. However, leptospires were isolated from the kidneys of 5 out of 5 control hamsters inoculated with hardjo and 4 out of 5 control hamsters inoculated with balcanica. An analogous trial using bovine anti-balcanica serum, collected from cattle experimentally infected with balcanica, gave almost identical results to the above trial.

Notes

* Leptavoid, Wellcome (N.Z.) Ltd.