SHIC Enables Test-and-Remove ASF Protocol Study in Vietnam

The Swine Health Information Center (SHIC) is pleased to announce an additional study on African swine fever (ASF) management and control taking place in Vietnam, made possible by a USDA-Foreign Animal Service grant received in 2019. Lessons from this study and others will be valuable if ASF enters the US.  This project is validating protocols for targeted removal of individually housed sows when infected with ASF to move the herd to negative status, one of the many research proposals being funded by the USDA FAS grant received by SHIC, or with the cooperation of the National Pork Board in an effort to gain ASF information. The test-and-remove protocol is based on the premise that ASF, although highly infectious, has relatively slow transmission.

The targeted removal process involves immediate removal of any sow exhibiting clinical signs of ASF, submitting blood for ASF detection by PCR, and if the animal is determined positive, adjacent animals (two up and two down the trough from the sow) are also removed. This project will test sufficiency of this methodology for ASF elimination in the Vietnamese sow herd, while in the process testing four commercially available ASF point-of-care (POC) assays on diagnostic performance for detecting ASF in suspect and non-clinical neighboring animals. Researchers working on this study are from Boehringer Ingelheim, Iowa State University, and Nong Lam University. 

As ASF rapidly spread across China, initial depopulation efforts included dramatic, intensive cleaning and disinfection with downtime requirements. Still, re-breaks after repopulation have been common. Many commercial farms in China have subsequently adopted the test-and-remove protocol. Vietnamese producers have followed China’s lead with use of the test-and-remove protocol, exploring its efficacy. Approximately 20% of sow farms affected by ASF in Vietnam have been unsuccessful in eliminating ASF through depopulation/repopulation, creating interest in the targeted removal protocol.

This study aims to assess, with additional diagnostic testing of non-clinical neighbor animals to those showing ASF clinical signs, the extent to which ASF virus has spread along a row of individually housed animals. The learnings from this testing regimen may lead to improvements in the success rate of test-and-remove, if failures have been due to insufficient culling around the positive animal. During the study, a target of 770 samples will be tested by laboratory standard PCR as well as the four POC PCR or lateral flow assays, creating a significant sample set to better assess field application and utility of POC testing in test-and-remove protocols for ASF control in Vietnam.  

As the world deals with the COVID-19 pandemic, SHIC continues to focus efforts on prevention, preparedness, and response to novel and emerging swine disease for the benefit of US swine health. As a conduit of information and research, SHIC encourages sharing of its publications and research. Forward, reprint, and quote SHIC material freely. SHIC is funded by America’s pork producers to fulfill its mission to protect and enhance the health of the US swine herd. For more information, visit or contact Dr. Sundberg at [email protected].