Experimental infection with the virulent, Central-European, murine Leptospira pomona strain in the pig.

The virulent, murine Leptospira pomona strain isolated from Apodemus agrarius was used in an experimental infection of six pigs aged 4--5 months. The clinical course of the infection was inapparent, both the blood picture and the uptake of food were normal. All infected pigs produced antibodies against L. pomona at titres from 1:3 200 to 1:50 000. The reisolation of leptospires from the blood of the infected pigs was successful in one case only, and that on day two p.i. Throughout the course of our experiment, no microscopic evidence was obtained of the presence of leptospires in the blood of the infected animals. Of the six guinea pigs injected repeatedly with the urine of the infected pigs, antibodies against L. pomona were detected in two of these at titres 1:3 200 and 1:6 400. However, no direct proof was obtained of leptospires in their kidneys. Leptospires were isolated from the kidneys of two of the infected pigs, at days 10 and 21 p.i. respectively. As suggested by our results, the Central European, murine Leptospira pomona strain should be regarded as an independent biovar incapable of causing a long-term leptospiruria and, hence, apparently unable to result in an epizooty in intensive pig husbandry. According to experimental evidence, Mus musculus can be a potential reservoir of the murine L. pomona biovar in Central Europe.