Natural Occurrence of Leptospira ballum in Rural House Mice and in an Opossum

Abstract

SummaryIn a search for wildlife carriers of L. pomona, various species of mammals were trapped in an endemic area of bovine leptospirosis. Direct dark-ground microscopic examinations of urine or bladder saline washings disclosed the presence of leptospires in 10 of the 37 house mice examined. Leptospiral cultural isolates were obtained from 9 of these 10 house mice. The recovery of leptospires from 6 additional house mice and from 1 of 2 opossums emphasizes the importance of cultural methods in any survey for leptospirosis. All isolates, serologically typed on the basis of a cross agglutinationlysis pattern, employing 18 type leptospiral immune rabbit serums, belonged to the serotype L. ballum. The failure to detect L. pomona in the rodent and other wild life population in an endemic area of bovine leptospirosis affords ancillary evidence that the natural hosts of L. pomona leptospirosis are to be found primarily in the livestock population. To the authors' knowledge, this is the first report of leptospirosis in the opossum.