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[Modelling of prevalence development in a paratuberculosis control program in a dairy herd]
M Beyerbach1, G F Gerlach, L Kreienbrock
1Institut für Biometrie, Epidemiologie und Informationsverarbeitung, Tierärztlichen Hochschule Hannover.
DTW. Deutsche Tierarztliche Wochenschrift
|October 16, 2001
Summary
A six-year paratuberculosis control program model shows that strict adherence to hygiene and culling protocols can significantly reduce disease prevalence in dairy herds. Consistent application of guidelines is key for lasting herd health improvement.
Area of Science:
- Veterinary Epidemiology
- Mathematical Modeling
- Animal Health Management
Context:
- Paratuberculosis (Johne's disease) poses a significant economic threat to dairy industries worldwide.
- Effective control programs are crucial for mitigating disease spread and improving herd productivity.
- Previous control strategies have varied in success, necessitating refined predictive models.
Purpose:
- To develop and validate a mathematical model for predicting the success of a paratuberculosis control program in dairy herds.
- To identify key parameters influencing program efficacy, including diagnostic accuracy, culling compliance, and biosecurity measures.
- To assess the projected impact of a six-year control program on disease prevalence under different initial conditions.
Summary:
- The model incorporates initial prevalence, diagnostic test performance (sensitivity/specificity), culling adherence, herd turnover, replacement strategies, and external disease introduction.
- Calculations based on the Lower Saxony control program indicate that a six-year duration is necessary for sustained herd health improvement, especially with high initial prevalence.
- Strict hygiene and culling of test-positive animals can lead to rapid prevalence reduction in the first year, followed by a temporary increase before a continuous decline from year four onwards.
Impact:
- The model accurately predicts a substantial decrease in paratuberculosis prevalence within six years, reducing it to 3-8% from initial levels of 10-30%.
- The findings support the effectiveness of the Lower Saxony control program's guidelines for managing paratuberculosis in dairy herds.
- While complete eradication is not achieved, the model demonstrates that consistent implementation of control measures significantly enhances herd health and reduces disease burden.