Intrauterine inoculation of Mycobacterium paratuberculosis into guinea pigs and cattle.

Mycobacterium paratuberculosis was inoculated intrauterinely into guinea pigs and cattle near the time of insemination to assess the effect and subsequent distribution of the organisms. Guinea pigs inoculated intrauterinely with 1 of 3 concentrations of M paratuberculosis or not inoculated were caged with male guinea pigs for 10 days. Guinea pigs given the largest dose had the lowest rate of pregnancy when examined. At necropsy, tissues were cultured to determine extent of infection. Abortion followed hypersensitivity reactions to johnin in some highly infected animals. Mycobacterium paratuberculosis was recovered in culture from the body and horns of the uterus of cows necropsied 1, 2, 3, and 7 days after inoculation and from 1 of 3 cows necropsied 2 weeks after inoculation. The organisms were not detected in extrauterine organs of any cattle or in uterine specimens taken at 3 or 4 weeks after inoculation. The evidence indicates that the small numbers of M paratuberculosis sometimes found in semen from paratuberculous bulls probably would be destroyed, rather than leading to systemic infection of the dam or to persistent hypersensitivity.