Experimentally induced Leptospira interrogans serovar autumnalis infections in young swine.

Leptospira interrogans serovar autumnalis strain 621 was proven to be infective for swine by intranasal and ocular inoculation and by contact exposure. The course of the disease was that of a chronic asymptomatic infection. Throughout the experiment, leptospires were observed in all tissues examined by darkfield microscopy of 10% tissue suspensions and examination by indirect fluorescent antibody technique of frozen tissue sections. Infected pigs had increasing antibody titers, as determined by the microscopic agglutination test. The organism spread from intranasally inoculated pigs to contact controls.