Multi-laboratory proficiency assessment for molecular and serological diagnosis of classical and African swine fever in the Americas

Abstract

African swine fever (ASF) and classical swine fever (CSF) are economically significant transboundary viral diseases of pigs and are reportable to the World Organization for Animal Health (WOAH) due to their severe impact on production and international trade. Both diseases present with similar clinical signs; therefore, they cannot be reliably distinguished without laboratory diagnosis. Given that diagnostic assay performance could vary between laboratories, proficiency testing (PT) exercises play a critical role in ensuring the quality and reliability of laboratory results and in helping laboratories to identify and address procedural issues. As one of the WOAH reference laboratories for ASF and CSF, the National Center for Foreign Animal Disease (NCFAD) organized its first PT exercise for ASF and CSF in 2024, targeting the Americas. A total of 16 international laboratories from 11 countries participated in the PT exercise, which focused on front-line molecular and serological diagnostic assays that are essential for laboratory detection of ASF and CSF. The 15-sample molecular panel contained inactivated ASF (6 samples) and CSF (7 samples) viruses, in addition to two negative samples for genome detection. The 20-sample serological panel comprised serum samples containing antibodies to ASF (10 samples) and CSF (5 samples) viruses. The remaining five serum samples contained no antibodies to ASF or CSF viruses. All laboratories correctly identified the ASF virus (ASFV) genome-positive samples; however, only 85.7% of the laboratories correctly identified the CSF virus (CSFV) genome-positive samples. While 80% of participating laboratories accurately identified the ASF-positive serum samples, only 35.7% accurately identified the CSF-positive serum samples. Overall, most laboratories demonstrated high diagnostic accuracy for the molecular detection of ASF and CSF; however, further improvements are needed in the serological detection of ASF and CSF. The PT exercise helped participating laboratories strengthen their testing performance and advance their efforts toward accreditation.