Quantitative impacts of incubation phase transmission of foot-and-mouth disease virus

Authors: Arzt, Jonathan; BRANAN, MATT - Animal And Plant Health Inspection Service (APHIS); DELGADO, AMY - Animal And Plant Health Inspection Service (APHIS); YADAV, SHANKAR - Oak Ridge Institute For Science And Education (ORISE); MORENO-TORRES, KARLA - Oak Ridge Institute For Science And Education (ORISE); TILDESLEY, MICHAEL - University Of Warwick; STENFELDT, CAROLINA - University Of Minnesota

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/4/2019
Publication Date: 2/25/2019
Citation: Arzt, J., Branan, M., Delgado, A., Yadav, S., Moreno-Torres, K., Tildesley, M., Stenfeldt, C. 2019. Quantitative impacts of incubation phase transmission of foot-and-mouth disease virus. Scientific Reports. https://doi.org/10.1038/s41598-019-39029-0.
DOI: https://doi.org/10.1038/s41598-019-39029-0

Interpretive Summary: Computerized models can be used to predict spread and impact of potential infectious disease outbreaks. For such models to be useful, it is important to have data that describes how specific diseases spread between individuals. In this current investigation, a specific statistical technique known as Bayesian modeling was used to investigate if foot-and-mouth disease (FMD) could spread from infected pigs, before the pigs developed any visible signs of the disease. The result from this investigation was that transmission of disease occurred approximately one day before it was possible to see that the pigs were sick. This data was subsequently used to simulate an outbreak of FMD in the U.S. using an advanced computer model. This modeling showed that if disease transmission occurred one day before the appearance of visible signs of disease, this would lead to a 40% increase in farms that would be affected by the outbreak. The overarching conclusion of this investigation is that it is important to consider the possibility of disease spread from healthy-looking individuals when designing computer models to predict disease outbreaks. This information may be used to protect USA livestock herds from exotic animal diseases such as FMD.

Technical Abstract: The validity of infectious disease modeling is intrinsically dependent upon high quality data for parameterization, and the translation of that data into biologically relevant applications. The current investigation applied a Bayesian modeling approach to a unique experimental transmission study in a natural host species to estimate the occurrence of transmission of foot-and-mouth disease (FMD) during the incubation phase amongst group-housed pigs. The primary outcome was that transmission occurred approximately one day prior to development of visible signs of disease (posterior median 21.0 hours, 95% CI: 1.1-45.0). Updated disease state durations were incorporated into a simulation model to examine the importance of addressing preclinical transmission in the face of robust response measures. Simulation of FMD outbreaks in the U.S. pig production sector with optimal and suboptimal response demonstrated that including a preclinical infectious period of just one day would result in a 40% increase in median farms affected (166 additional farms and 664,912 pigs euthanized) compared to the scenario of no preclinical transmission, assuming suboptimal outbreak response. These findings emphasize the importance of considering transmission of FMD during the incubation phase of infection in modeling and response planning.