Objectives—To determine whether vaccination with
a killed vaccine prevents fecal shedding of Mycobacterium
avium subsp paratuberculosis, to compare
effectiveness of a culture and cull program in vaccinated
and nonvaccinated herds, and to compare
paratuberculosis-related preventive management in
vaccinated and nonvaccinated herds.
Design—Cross-sectional study (study A) in vaccinated
(n = 25) and nonvaccinated (29) herds of dairy
cows. Longitudinal study (study B) in vaccinated
(n = 2) and nonvaccinated (2) herds of dairy cows.
Procedure—In study A, fecal samples were obtained
from adult cows in herds with and without a history
of vaccination with a killed vaccine. Management
measures were evaluated. In study B, fecal samples
were obtained 4 times at 6-month intervals from
cows older than 6 months. Cows that had positive
test results were removed from the herd directly after
the outcome of the culture.
Results—In study A, differences were not detected
among the 25 herds that were vaccinated; culture
results were positive for M avium subsp paratuberculosis
in 4.4% of herds. In 29 herds that had not been
vaccinated, culture results were positive in 6.7%. In
study B, the percentage of positive results on culture
decreased from 10.9% and 5.7% to 3.5% and 0%,
respectively in the 2 vaccinated herds. In the 2 nonvaccinated
herds, percentages decreased from 6.1%
and 16.5% to 0% and 2.3%, respectively.
Management practices were different between herds
that were vaccinated and herds that were not; owners
of herds that were not vaccinated followed more
preventive management procedures and practiced
less feeding of raw milk to calves.
Conclusions and Clinical Relevance—Vaccination
of calves with a killed vaccine does not prevent transmission
of M avium subsp paratuberculosis; therefore,
hygienic practices remain essential in herd management.
(Am J Vet Res 2001;62:270–274)