Parameterization of the durations of phases of foot-and-mouth disease in cattle

Authors: YADAV, SHANKAR - Orise Fellow; STENFELDT, CAROLINA - University Of Minnesota; BRANAN, MATTHEW - Animal And Plant Health Inspection Service (APHIS); MORENO-TORRES, KARLA - Orise Fellow; HOLMSTROM, LINDSEY - Animal And Plant Health Inspection Service (APHIS); DELGADO, AMY - Animal And Plant Health Inspection Service (APHIS); Arzt, Jonathan

Submitted to: Frontiers in Veterinary Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/8/2019
Publication Date: 8/9/2019
Citation: Yadav, S., Stenfeldt, C., Branan, M.A., Moreno-Torres, K.I., Holmstrom, L., Delgado, A.H., Arzt, J. 2019. Parameterization of the durations of phases of foot-and-mouth disease in cattle. Frontiers in Veterinary Science. https://doi.org/10.3389/fvets.2019.00263.
DOI: https://doi.org/10.3389/fvets.2019.00263

Interpretive Summary: Foot-and-mouth disease (FMD) is an infectious disease that can be economically devastating for the livestock industry. Though this disease has not been detected in the United States since 1929, the presence of FMD in several parts of the world and potential bioterrorism create threats for reintroduction. An introduction of FMD virus would result in an international trade ban on the U.S. livestock commodities and create devastating impacts for the U.S. livestock industry. To predict these affects, mathematical modeling tools are often used to estimate the impacts of an FMD outbreak and benefits of different control options. The purpose of this current study was to use newly available data from laboratory experiments to improve the accuracy of mathematical models for FMD in cattle. Specifically, we determined standardized lengths of the distinct phases of disease for incorporation into downstream models. The ultimate goal of this effort was to improve the ability to predict, prevent, and control FMD outbreaks.

Technical Abstract: The objective of the current study was to update parameterization of mathematical simulation models for foot-and-mouth disease (FMD) in cattle utilizing recent knowledge of FMD-virus (FMDV) pathogenesis and dynamics to estimate the duration of distinct phases of FMD. Specifically, the durations of incubation, latent, and infectious periods were estimated for 3 serotypes of FMDV, individually and collectively (pan-serotypic). Animal-level data were used in Accelerated Failure Time (AFT) models to estimate the duration of the defined phases of infection, while also investigating the influence of factors related to the experimental design on disease progression. The quantity of viral shedding used as a proxy for the onset of infectiousness, virus serotypes, and experimental exposure systems significantly influenced the estimated duration of distinct phases of disease. The use of detection of any viral RNA as a proxy of infectiousness inappropriately lengthened the total infectious period compared to use of threshold-based detection. Additionally, the experimental system used to infect the animals also had significant effects on the duration of distinct phases of disease. Overall, the mean (95%Cl) durations of pan-serotype disease phases in cattle were estimated to be: incubation phase = 3.6 days (2.7, 4.8), latent phase = 1.5 days (1.1, 2.1), subclinical infectious phase = 2.2 days (1.5, 3.5), clinical infectious phase = 8.5 days (6.2, 11.6), and total infectious phase = 10.8 days (8.2, 14.2). This study highlights the importance of identifying appropriate proxy measures to define the onset and duration of infectiousness in FMDV-infected cattle in the absence of actual transmission data. Additionally, it is demonstrated herein that factors associated with experimental design, such as virus exposure methods, may significantly affect disease progression in individual animals and should be considered when data is extrapolated from experimental studies. Pan-serotypic parameterization including all routes of inoculation and threshold-defined infectiousness is recommended as the most robust system for most applications; however various options of stratification are available herein for specialized applications.