If the African swine fever virus was to enter the United States, it would most likely come through the illegal entry of swine products and byproducts, according to the USDA’s recently published “Qualitative Assessment of the likelihood of African swine fever virus entry to the United States: Entry Assessment.” Port inspection and interception data indicates that air passenger baggage and foreign mail are two of the largest illegal pathways and pork, ham and sausage are the products with the highest interception rates.
This week the Swine Health Information Center shared the assessment conducted by the USDA Animal Plant Health Inspection Service Veterinary Service Center for Epidemiology and Animal Health, Risk Assessment Team in Fort Collins, Colo. The purpose of the analysis was to determine the transboundary pathways representing the greatest likelihood of entry for ASF virus into the United States, and to identify pathways where there is limited data or high uncertainty for future investigation.
While the interception data mimics other studies demonstrating the potential entry of ASF virus and other swine diseases through the air passenger pathway, the risk assessment team says there are no studies that look at foreign mail as a pathway for entry of animal disease. According to entry assessment, the estimate of annual volume of packages entering the United States, and the estimate of product concealment in mailed packages indicates that foreign mail is an entry pathway that warrants greater analytical scrutiny.
To conduct the assessment, the team evaluated imports of live animals, animal products and animal feed ingredients occurring through commercial cargo, air passenger baggage, cruise ships, international mail, border crossings, regulated garbage from ships and airliners coming from outside the United States and fomites.
When rating the likelihood of ASF virus entry, the researchers considered the following factors.
- The overall volume of imports in terms of passengers, animals, shipments, etc., that could potentially be contaminated.
- Inspection effort and detection efficiency.
- The number and effectiveness of various regulatory and mitigation actions to reduce disease prevalence/transmission along the pathway such as diagnostic testing, treatment, disinfection, certificates of animal health, compliance agreements, product labeling/traceability, quarantine, regionalization, etc.
- Available research to quantify viral prevalence, survival and/or transmission probabilities by pathway.
The risk assessment team acknowledges that animal feed ingredients and fomites have the potential to be pathways associated with a moderate likelihood of ASF virus entry, but say there is still high uncertainty because of the lack of data on transmission from these sources. They also did not evaluate how the virus may reach susceptible pigs or probability of infection following potential exposure.