Estimation of Foot-and-Mouth Disease windborne transmission risk from USA beef feedlots

Authors: Arzt, Jonathan; COFFMAN, MEGAN - University Of Kansas; SANDERSON, MICHAEL - University Of Kansas; DODD, CHARLES - University Of Kansas; RENTER, DAVID - University Of Kansas

Submitted to: Preventive Veterinary Medicine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2021
Publication Date: 8/8/2021
Citation: Arzt, J., Coffman, M., Sanderson, M.W., Dodd, C.C., Renter, D.G. 2021. Estimation of Foot-and-Mouth Disease windborne transmission risk from USA beef feedlots. Preventive Veterinary Medicine. https://doi.org/10.1016/j.prevetmed.2021.105453.
DOI: https://doi.org/10.1016/j.prevetmed.2021.105453

Interpretive Summary: Foot-and-mouth disease (FMD) is a viral infection of livestock of critical socioeconomic importance. It is well-known that FMD may be transmitted by aerosol (airborne) spread of FMD virus (FMDV), sometimes over long distances. The current study utilized a modeling approach to estimate the potential impact of aerosol spread of FMDV in typical feedlots in Iowa and Kansas. Important findings include the 8% risk of airborne spread at a distance of 10km from an infected herd. And, risks were greater when exposed herds were larger. This information is important to US agriculture because protecting feedlots from aerosol exposure would be an important aspect of FMD control in the event of an outbreak in the USA.

Technical Abstract: Windborne spread of foot-and-mouth disease (FMD) requires specific epidemiological and meteorological conditions, thus modeling the risk of windborne spread involves integrating epidemiological and meteorological models. The objective of this study was to investigate the potential risk of windborne spread of FMD from an infected US feedlot using an integrated modeling approach, and to identify factors that determine this risk. To address this objective, we integrated a within-herd epidemiological model and an advanced atmospheric dispersion model, and calculated infection risk dependent on exposed herd size. A previously-developed epidemiological model was used to simulate the spread of FMD through a typical U.S. feedlot, while the National Oceanic and Atmospheric Administration’s HYSPLIT atmospheric dispersion model, which has been validated for FMD modeling, was used to model virus dispersion. Infection risk for exposed herds was calculated as a binomial probability accounting 23 for dose and exposed herd size. We modeled risk of windborne spread from a typical 4,000 head feedlot in IA, and a typical 48,000 head feedlot in KS during winter and summer seasons. The risk of windborne spread of FMD varied based on weather/season conditions, estimated average viral shedding rate per head, size of infected herd, and size of exposed herd. In the baseline winter scenario at peak shedding day (highest number of clinicals) for the infected feedlot, the median of the maximum daily risk of infecting a 1,000-head exposed herd located downwind of a KS feedlot ranged from 89.88% at 3km to 8.37% at 10km, and from 48.38% at 3km to 1.13% at 10km for an IA feedlot. Risks were greater when exposed herds were larger. The minimum control area recommended by USDA APHIS in an FMD outbreak is 10 km from the infected premise. Our results indicate that significant risk of windborne spread may extend beyond 10 km in certain situations. This is particularly a concern in areas where there are large feedlots in relatively close proximity, such as in southwestern KS. Our model may be useful as a research tool in the absence of an outbreak, and may help direct surveillance and response efforts in the event of an outbreak.