Excretion of Mycobacterium bovis by experimentally infected cattle
Neill, S.D.; Hanna, J.; O'Brien, J.J.; McCracken, R.M.
Veterinary Record 123(13): 340-343
1988
ISSN/ISBN: 0042-4900 PMID: 3057717 Document Number: 323301
Three groups, each of five calves, 4-7 months old, were inoculated intranasally with different numbers of Mycobacterium bovis. Infection was established readily in the calves which received an inoculum containing either 106 or 104 colony forming units (cfu). After every infection there was a lag period during which the organisms could not be isolated from specimens of nasal mucus. All the animals excreted M. bovis and the time of commencement, quantity and duration of excretion appeared to be related to the inoculation dose. Excretion continued for many weeks, and for two calves excretion became intermittent over many months. All the calves given inocula of 92 cfu failed to develop the disease and no immunological responses were detected; however, M. bovis was isolated from nasal secretions from one of these animals 100 days after inoculation.