Benjamin, Lisa A. (2009-08). An Environmental Perspective to Decision-making for the Control of Johne's Disease on Beef Ranches. Doctoral Dissertation. | Thesis individual record

Biosecurity practices for Mycobacterium avium subsp. paratuberculosis (Mptb),
the etiologic agent for Johne's disease (JD), are predicated on the fact that fecal-oral is
the major route of infection and that Mptb is present in the environment of affected
farms. The objectives of these studies were to describe perceived benefits of testnegative
Level 4 status in the Voluntary Bovine Johne's Disease Control Program
(VBJDCP), describe producer and veterinarian attitudes towards JD relevant biosecurity
practices, compare 5 JD control options using a Markov model, determine if tangential
flow filtration (TFF) increases the detection sensitivity for Mptb and describe the
distribution of environmental predictors for Mptb survival.
Twenty-five percent and 39% of beef producers in the VBJDCP reported that
they received substantial or marginal benefits (financial and non-financial), respectively,
from program participation. Producers suggested increased marketing opportunities to
improve the VBJDCP. Producers in a cross-sectional mailed survey of attitudes towards biosecurity
practices were more likely than veterinarians to agree that separating JD clinical or
suspects from calves or heifers; acquiring replacements or additions from JD low-risk
herds, testing for JD every 10 to 14 months and test and culling clinical suspects only
were useful for control of JD.
A state transition Markov model, with the environment as the source of Mptb,
was used to compare 6 alternative control strategies for JD. Management and the
probability of Mptb surviving 1 year in the environment were important determinants of
the prevalence of subclinical JD on beef farms under the analyzed control strategies.
Heterogenous distribution of environmental predictors for Mptb survival was observed
in spatial risk maps.
In conclusion, although some beef producers experienced gains from
participation in the VBJDCP, the perceived program benefits could be improved by
increased marketing and education on the advantages of participation. Specific problem
areas should be addressed. The length of time Mptb survived in the environment was an
important parameter in the Markov chain model. Additionally, due to the heterogenous
distribution of environmental predictors, a multiscale approach to sampling and analysis
should be useful.

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