Experimental infection of the possum (Trichosurus vulpecula) with Leptospira interrogans serovar balcanica II. A comparison of laboratory techniques for the detection of leptospiraemia and leptospiruria

Abstract

Leptospiruria in possums (Trichosurus vulpeculu) experimentally infected with balcanica was monitored for 13 months by dark-field microscopy, inoculation of hamsters and culture. Leptospiraemia was monitored by inoculation of hamsters and culture for the first 28 days post-inoculation.

Inoculation of hamsters for the detection of leptospiraemia had a sensitivity of 63.2%, whereas culture had a sensitivity of 36.8%. The use of hamsters enabled leptospires to be demonstrated in blood up to 15 days after inoculation by which time serum agglutination titres had reached peak levels.

Dark-field microscopy was the least sensitive method for the detection of leptospiruria (37.7%). Inoculation of hamsters and direct inoculation of media containing 400𝛍g 5-fluorouracil (5FU) had sensitivities higher than 70%. The incorporation of a high level of 5FU in media significantly improved isolation rates.

Differences were seen in the sensitivity of different methods at three different stages of leptospiruria. Inoculation of hamsters was the most sensitive method during the intial stage of leptospiruria, while direct inoculation of media containing 400𝛍g 5FU/ml was the most sensitive method during the chronic stage.