Disease eradication on large industrial farms

Area of Science:

• Veterinary Epidemiology
• Mathematical Modeling
• Animal Health

Background:

• Modern industrial farming often uses all-in-all-out (AIAO) systems, where entire livestock groups are replaced simultaneously.
• This practice, while efficient, can facilitate rapid disease transmission within farms.
• Marek's disease is a significant economic concern in poultry farming, known for its indirect transmission routes.

Purpose of the Study:

• To develop a mathematical model for tracking Marek's disease transmission within poultry barns and between successive flocks.
• To identify conditions necessary for disease eradication under AIAO farming conditions.

Main Methods:

• A mathematical model using impulsive differential equations was developed to simulate disease dynamics.
• The model tracks transmission within a single cohort and between sequential cohorts in a barn.
• Conditions for disease eradication were mathematically determined based on transmission rates, cohort size, and cleaning efficacy.

Main Results:

• Disease eradication is achievable if cohort length and/or cohort size are sufficiently reduced for a given transmission level.
• Sufficiently high cleaning effort between cohorts can also lead to Marek's disease eradication.
• Complete disinfection is not essential; eradication is possible with partial cleaning, with less effort required for smaller/shorter cohorts.

Conclusions:

• The study provides a framework for understanding and controlling indirect disease spread in AIAO poultry systems.
• Optimizing cohort management (size and duration) and implementing effective cleaning protocols are key strategies for Marek's disease eradication.
• Mathematical modeling offers valuable insights into disease dynamics and control in intensive animal agriculture.