INCIDENCE OF PARATUBERCULOSIS AFTER VACCINATION AGAINST MYCOBACTERIUM-PARATUBERCULOSIS IN 2 INFECTED DAIRY HERDS

Vaccination against paratuberculosis of all newborn animals has been p erformed since April 1984 in two dairy herds with a high incidence of clinical cases of paratuberculosis, using a vaccine containing heat-in activated M. paratuberculosis in a water/mineral oil emulsion. Animals slaughtered between April 1984 and January 1991 were included in the study. Histology, bacterioscopy and culture on Smith and modified Lowe nstein-Jensen media were performed using jejunum, ileum and draining l ymph nodes. The animals present on the farm in April 1984 constituted a retrospective non-vaccinated group, giving an indication of the init ial infection rate. After vaccination, the percentage of animals culle d for clinical paratuberculosis decreased significantly (7.8 to 1.8%; P < 0.005), as did the percentage of animals with positive histology ( 11.8% to 5%). The incidence of infected animals, defined by positive r esults in histology and/ or bacterioscopy and/or culture, however, inc reased from 21.8% to 25.9%.