Preclinical transmission of Foot-and-mouth disease virus studied in pigs
Foot-and-mouth disease virus (FMDV) spreads much more aggressively in pigs than previous research suggests, according to a study by U.S. Department of Agriculture (USDA) scientists.
The study, published in Scientific Reports, shows that pigs infected with FMDV were highly contagious to other pigs just 24 hours after infection – long before showing any clinical signs of infection such as fever and blisters.
Jonathan Arzt, lead investigator and veterinary medical officer with USDA’s Agricultural Research Service (ARS), noted that prior to this research, it was believed that transmission of FMDV did not occur during the preclinical phase.
A variety of disease-dynamics models have been developed in recent years to identify critical targets for control efforts, predict impacts and estimate resource requirements for specific outbreak scenarios for FMD, Arzt said. However, none of these models included the impact of preclinical transmission.
Working with scientists at the Center for Epidemiology and Animal Health in USDA’s Animal and Plant Health Inspection Service, Arzt and his team used a mathematical modelling approach to estimate the occurrence of FMD preclinical transmission amongst pigs. They found that transmission occurred approximately one day before development of visible signs of disease.
This updated disease data was then incorporated into a second model that simulates disease spread. The results showed that simulation of FMD outbreaks in the U.S. pig production sector, including a preclinical infectious period of one day, would result in a 40-percent increase in the number of farms affected. That’s 166 additional farms and more than 664,000 pigs euthanized compared to the existing scenario of no preclinical transmission, Arzt added.
Failure to account for information like this could make the difference between a limited, well-controlled FMD outbreak in the United States with a cost of $3 million over two months as opposed to a catastrophic nationwide epidemic with a cost of $20 billion over one year, Arzt added.
Article: Quantitative impacts of incubation phase transmission of Foot-and-mouth disease virus by Jonathan Arzt, Matthew A. Branan, Amy H. Delgado, Shankar Yadav, Karla I. Moreno-Torres, Michael J. Tildesley and Carolina Stenfeldt, published in Scientific Reports (2019) volume 9, article number: 2707, doi: 10.1038/s41598-019-39029-0