Incubation phase transmission of foot-and-mouth disease virus in cattle: experimental evidence and simulated impacts

The capacity of any pathogen to transmit from infected hosts prior to the development of clinical disease substantially impacts the ability to effectively control an outbreak. Foot-and-mouth disease virus (FMDV) is known for its rapid spread and ability to cause severe disease outbreaks amongst susceptible livestock species. In this current investigation, it was demonstrated that cattle infected with FMDV were capable of transmitting infection at least 24 h prior to the development of clinical signs. Additionally, the progression of infection in cattle exposed to infected donors during the early infectious phase was slower than in cattle exposed at later time points, suggesting a dose-dependent effect on infection dynamics in contact-exposed cattle. To quantify the impact, outcomes from the transmission experiment were used to parameterize agent-based simulations at three biological levels, within-host, within-herd, and between-farm. Simulations revealed that outbreaks spread more rapidly and infect more cattle and farms when models account for preclinical transmission. Specifically, including pre-clinical transmission in a between-farm simulation resulted in a 33.7% increase in the number of affected farms, demonstrating that incubation phase infectiousness has important implications for outbreak preparedness and response.