Foot-and-mouth disease: a highly contagious disease that goes undetected clinically

A study reveals the critical importance of silent transmission of foot-and-mouth disease in cattle. Foot-and-mouth disease is one of the most feared threats to cattle herds and the animal production industry. The disease is characterized by extreme contagiousness, rapid spread, and major economic consequences. While the clinical signs (oral lesions, fever, and decreased production) are well known, one area remains unclear: preclinical transmission—that is, the ability of the foot-and-mouth virus to spread before visible symptoms appear. Scientists have addressed this issue by developing a novel model of spread. Their study demonstrates that neglecting the virus’s silent phase amounts to a serious underestimation of the speed, scale, and complexity of potential outbreaks.  

Models Based on the Biological Reality of Outbreaks

To understand the actual impact of preclinical transmission, the researchers combined in vivo experimental data with spatiotemporal modeling. Their goal: to simulate the progression of a foot-and-mouth disease outbreak in cattle across three major regions of the United States. Two management scenarios were compared. In the first, described as optimal, clinical detection occurs just one day after the first signs appear. In the second, described as suboptimal, the delay increases to four days. These timeframes are crucial: they represent the time needed to identify sick animals, isolate outbreaks, activate emergency plans, and restrict animal movements. The model’s results reveal a troubling reality: even a single day of silent transmission is enough to multiply secondary outbreaks and expand the affected area. The less virulent the strain, the longer the preclinical phase lasts… and the greater the risk of uncontrolled spread.  

A race against time to contain the epidemic

The consequences of this hidden mechanism are severe. When late detection combines with preclinical transmission, outbreaks become longer-lasting, more widespread, and more costly. The study shows that in the eastern and central regions of the United States, where cattle density is high and interstate trade is frequent, the responsiveness of veterinary services plays a decisive role. Conversely, in less densely populated areas, such as the West, the impact remains significant but more limited, underscoring the importance of differentiated regional strategies. These findings are part of a broader observation: traditional risk assessment models, based solely on clinical detection, systematically underestimate the potential spread of the foot-and-mouth disease virus. Health authorities therefore risk experiencing spillover if they fail to take this biological reality into account.  

Major Economic and Strategic Challenges

Foot-and-mouth disease, although rare in the United States, poses a considerable threat to global livestock industries. In Europe, a single outbreak can trigger the culling of thousands of head of livestock and result in colossal economic losses due to halted exports and the closure of international markets. The study highlights the need for proactive surveillance and an ultra-rapid response. In practice, this involves:

• the deployment of early-diagnostic tools capable of identifying the virus before clinical signs appear;
• training livestock farmers and veterinarians to recognize early warning signs;
• updating veterinary emergency plans to incorporate silent transmission into crisis scenarios.

In this context, the researchers call for a rethinking of biosecurity policies and strengthened international cooperation. By incorporating preclinical transmission into predictive models, policymakers gain a more realistic perspective for calibrating vaccine stockpiles, organizing quarantines, and limiting economic impacts.  

Toward a New Generation of Epidemiological Models

This study represents a major methodological breakthrough: it demonstrates that the invisible phase of a virus can, on its own, alter the dynamics of an epidemic. By incorporating this parameter, projections become more reliable, more region-specific, and better adapted to on-the-ground realities. For veterinary services, this presents an opportunity to anticipate developments more quickly and effectively. For livestock farmers, it ensures access to more precise and effective control strategies. Finally, for policymakers, it serves as a wake-up call: investing in early detection is no longer an option, but a necessity.  

A Strong Message for Global Animal Health

Although the foot-and-mouth disease virus is currently absent from many developed countries, the risk of its introduction remains high through international trade. Incorporating preclinical transmission into preparedness policies is therefore not merely a precaution—it is an essential tool for preventing disaster scenarios. Ignoring preclinical transmission can lead to a serious underestimation of the potential impact of foot-and-mouth disease. Rapid detection and regional planning are key to protecting the livestock sector and the economy, which places epidemiological surveillance at the heart of the fight against transboundary diseases.