Complex responses to movement-based disease control: when livestock trading helps

Area of Science:

• Epidemiology
• Mathematical Biology
• Veterinary Public Health

Background:

• Livestock disease control strategies frequently rely on managing animal movements between farms.
• Accurate assessment of herd-to-herd transmission is crucial for designing effective disease control measures.
• Existing metapopulation models, like those using R*, do not explicitly incorporate individual animal movements, limiting their application to livestock systems.

Purpose of the Study:

• To develop novel mathematical tools for calculating R* in livestock populations considering individual movements.
• To investigate the impact of livestock movement rates on disease transmission and control efficacy.
• To analyze the implications of movement-based controls in livestock systems.

Main Methods:

• Employed next-generation matrix approaches to explicitly model individual animal movements between herds.
• Developed new methodologies for calculating the metapopulation reproduction number (R*) in systems with coupled populations.
• Simulated disease dynamics under varying livestock movement rates and control scenarios.

Main Results:

• The study introduces novel tools to calculate R* by explicitly accounting for individual movements.
• Depletion of infected individuals in the source herd significantly impacts control strategy efficacy.
• R* demonstrates a peak at intermediate livestock movement rates, suggesting complex disease dynamics under control.

Conclusions:

• Movement-based livestock disease controls can be counterintuitive; reducing movements may increase prevalence at intermediate rates.
• Optimal livestock movement rates for disease control vary, with high rates allowing control but intermediate rates potentially sustaining disease.
• Management of livestock movements requires careful consideration as interventions for one disease may exacerbate another.