Is the U.S. Prepared for an African Swine Fever Outbreak?

Jul 18, 2023

As the specter of African swine fever (ASF) continues to cast a shadow over the swine industry, researchers from North Carolina State University have delved into the potential consequences of an outbreak in the southeastern U.S. Utilizing a computer model, they examined the transmission routes and evaluated existing response plans, shedding light on the readiness of the country to combat this highly contagious viral disease.

ASF poses a significant threat to pigs, with a mortality rate that can reach a devastating 100%. Complicating matters further, infected pigs may not display symptoms before succumbing to the disease, enabling the virus to spread undetected. The potential cost of an ASF outbreak in the U.S. has been estimated at a staggering $80 billion.

To assess the dynamics of a potential outbreak, the researchers employed an epidemiological model called PigSpread. This model incorporated six transmission routes, including between-farm swine movements, vehicle movements, and local spread. Drawing from the Morrison Swine Health Monitoring Project, data from 2,294 swine farms in the southeastern U.S. were analyzed to inform the model.

The simulations conducted by the researchers revealed that between-farm movements accounted for the majority (71%) of disease transmissions, with local spread and vehicular transmission contributing approximately 14% each. Notably, vehicular transmission emerged as a pivotal route for disease spread, highlighting the need for further investigation and understanding.

Implementing a combination of control strategies, such as quarantine, depopulation, movement restrictions, contact tracing, and enhanced surveillance, demonstrated a positive impact in curbing the outbreak. Simulations with these interventions showed an average reduction of up to 79% in secondary infections within the 140-day time frame. In approximately 29% of simulations with all control strategies in place, no further affected farms were observed during that period.

While the results offer promise, the researchers caution that further investigations and refinements are necessary to fully grasp the requirements for effective control. Additionally, they emphasize that the duration of an epidemic may exceed the 140-day timeframe, warranting sustained efforts and vigilance.