Decrease of Johne's disease prevalence and incidence in six Minnesota, USA, dairy cattle herds on a long-term...

Area of Science:

• Veterinary Epidemiology
• Animal Health Management
• Bovine Infectious Diseases

Background:

• Johne's disease (JD) poses a significant economic threat to dairy herds worldwide.
• Effective control programs are crucial for mitigating JD transmission and impact.
• The Johne's Disease Demonstration Herd Project (JDDHP) aimed to evaluate control strategies in commercial dairy settings.

Purpose of the Study:

• To assess changes in JD seroconversion and fecal shedding prevalence and incidence rates.
• To evaluate the impact of herd management compliance, measured by a risk assessment (RA) score, on JD control.
• To determine the effectiveness of the JDDHP in reducing JD transmission across different age cohorts.

Main Methods:

• Prospective longitudinal field study involving six Minnesota dairy herds from 2000 to 2005.
• Regular testing of adult cows using serum ELISA and fecal culture.
• Logistic and Cox proportional hazards regression analyses to evaluate risk factors and incidence rates.
• Analysis of herd RA scores to correlate management changes with JD outcomes.

Main Results:

• Significant decrease in the proportion of cows testing positive for JD (serum ELISA and fecal culture) over the 5-year study period.
• Cows benefiting from JDDHP interventions at a young age (≤12 months) showed significantly lower risk of seroconversion and fecal shedding.
• Herds with substantial RA score reduction demonstrated better outcomes for cohorts born after program initiation.

Conclusions:

• The JDDHP demonstrated success in reducing JD prevalence and incidence in participating herds.
• Early-life management and reduction of environmental contamination are critical for JD control.
• Improved herd management, reflected in lower RA scores, enhances the efficacy of JD control programs, particularly for young stock.