An immuno-epidemiological model for Johne's disease in cattle

Area of Science:

• Veterinary epidemiology
• Infectious disease modeling
• Bovine health

Background:

• Johne's disease, caused by Mycobacterium avium ssp. paratuberculosis (MAP), significantly impacts dairy cattle health and productivity.
• Understanding the transmission dynamics of MAP is crucial for effective disease control strategies.

Purpose of the Study:

• To develop a novel integrated modeling approach linking within-host dynamics of MAP infection with epidemiological transmission patterns in dairy cattle.
• To investigate how within-host bacterial load influences key epidemiological parameters.

Main Methods:

• A within-host model tracking time since infection and infected cell compartments (macrophages, T cells) was developed.
• This within-host model was integrated with an epidemiological model, influencing transmission, mortality, and shedding rates.
• The impact of bacterial load on the epidemiological reproduction number was analyzed.

Main Results:

• The integrated model demonstrates a complex relationship between within-host bacteria load and the epidemiological reproduction number, showing multiple peaks.
• A mechanism explaining shifts in MAP shedding patterns was incorporated into the within-host model.
• The influence of this shedding mechanism on the overall epidemiological reproduction number was observed.

Conclusions:

• Linking within-host and epidemiological models provides a more comprehensive understanding of Johne's disease dynamics.
• Bacterial load and shedding patterns play a critical role in the transmission and spread of Johne's disease in cattle.
• This integrated modeling approach can inform targeted interventions for Johne's disease control.