This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
Researchers Rachel A. Schambow, Michelle L. Schultze, Leticia C. M. Linhares, Bret Crim, Albert Rovira, Hemant K. Naikare, Catherine Lorenz, Cole Vanicek, Rodger G. Main, and Andres M. Perez from the University of Minnesota, Iowa State University and the USDA bring us today’s science page.
Key Findings:
- Sick pig VDL surveillance appears to efficiently rule out ASF/CSF in intensive commercial sick pigs.
- All types and sizes of swine farms are encouraged to submit a compatible sample (spleen, spleen swabs, tonsils, lymph nodes, whole blood, or whole blood swabs) with their regular sick pig cases, which then can be ruled out for ASF/CSF at no cost to producers or veterinarians.
Introduction
The US is currently free of African swine fever (ASF) and classical swine fever (CSF). To improve ASF/CSF detection capabilities, USDA operates a surveillance plan with a component of regular testing of qualifying sick pig cases for ASF/CSF at approved veterinary diagnostic laboratories (VDLs). Cases submitted for diagnosis of endemic swine diseases may qualify for ASF/CSF testing if they have an approved sample type (spleen, spleen swabs, tonsils, lymph nodes, whole blood, or whole blood swabs) and consistent clinical signs, history, and necropsy findings for ASF or CSF. This study aimed to describe the characteristics of ASF/CSF-tested swine cases compared to general swine cases at two major VDLs for swine, University of Minnesota (UMN) VDL and Iowa State University (ISU) VDL, then to engage swine stakeholders to identify gaps and needs regarding ASF/CSF sick pig surveillance in the US.
Methods
Approximately two years of data on swine diagnostic cases (2022-2024) were received from UMN and ISU-VDLs. Submitter information was de-identified. Data were descriptively analyzed to compare between ASF/CSF-tested cases and general cases. Following this, a workshop was organized at the 2024 Leman Swine Conference. 15 public and private swine stakeholders attended. In two moderated focus groups, they discussed findings and strategies for supporting the sick pig VDL surveillance component.
Results & Discussion
Together, UMN and ISU-VDLs ruled out 8,354 cases for ASF/CSF from 39 different states during the study period. About 82% of cases with a compatible tissue at UMN and 63% at ISU were tested. The most commonly tested specimen for ASF/CSF was spleen. As expected, the majority of cases came from states with large intensive commercial populations, including Iowa, Minnesota, North Carolina, Oklahoma, and Indiana. Porcine reproductive and respiratory syndrome virus (PRRSV) was the most commonly tested endemic pathogen for all cases, which is an important differential for ASF and CSF. At the UMN and ISU-VDLs, about 20% and 40% of tissue cases that were tested for PRRSV were also confirmed negative for ASF/CSF, respectively. Most tissue cases were from nursery and growing pigs, and ASF/CSF-tested cases were significantly almost twice as likely to be from pigs under 1 year of age compared to those that were older. At the workshop, swine stakeholders indicated this was consistent with the swine population distribution and disease dynamics. They felt that the results indicated that commercial swine were well-represented with limited potential for significant gains in sample submission and testing. They reported that education and outreach on ASF and CSF surveillance would be beneficial for all parts of the swine industry, including small-scale, niche, and non-commercial swine farmers, and for mixed and small animal veterinarians who see pigs but whose training in recognizing swine foreign animal diseases is not well characterized.
Read more by visiting: https://z.umn.edu/ASFsickpig