Evaluation of spleen swabs for sensitive and high-throughput detection of classical swine fever virus

Authors: HOCHMAN, ORIE - Canadian Food Inspection Agency-National Centre For Foreign Animal Disease; GOONEWARDENE, KALHARI - Canadian Food Inspection Agency-National Centre For Foreign Animal Disease; Chung, Chungwon; AMBAGALA, ARUNA - Canadian Food Inspection Agency-National Centre For Foreign Animal Disease

Submitted to: Pathogens
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/27/2025
Publication Date: 8/3/2025
Citation: Hochman, O., Goonewardene, K., Chung, C.J., Ambagala, A. 2025. Evaluation of spleen swabs for sensitive and high-throughput detection of classical swine fever virus . Pathogens. 14(8). Article 767. https://doi.org/10.3390/pathogens14080767.
DOI: https://doi.org/10.3390/pathogens14080767

Interpretive Summary: Classical swine fever (CSF) continues to be a common and ongoing problem in parts of South America, Europe, Asia, and the Caribbean, even though there have been strong efforts to eliminate it. Because of this, there's a growing need for better ways to quickly find and track the disease. Building on previous methods used to detect African Swine Fever (ASF) using spleen swabs, this study aimed to make it easier and faster to test large numbers of pigs for CSF. One of the best tools for detecting CSF is a lab test called real-time reverse PCR, which is fast and accurate. However, it only works well if the genetic material of the virus is properly collected and prepared. While spleen tissue is commonly used to test for diseases in pigs, it usually requires an extra step of breaking down the tissue first. In earlier work, we found that swabbing the spleen was actually better than breaking it down when testing for ASF. So in this study, we wanted to see if spleen swabs would also work well for CSF. We tested both methods --swabs and tissue breakdown --on 49 frozen and 33 fresh spleen samples from pigs that had been infected on purpose for research. The results showed that using spleen swabs was just as effective for detecting CSF as the more time-consuming method. Swabs were even able to detect the virus early in the infection and pick up virus particles. Overall, swabbing is a simpler, faster, and less labor-intensive way to collect samples for CSF testing.

Technical Abstract: Classical swine fever (CSF) has continued to remain a consistent, endemic disease across South America, Europe, Asia and the Caribbean despite intensive eradication methods, increasing the need to develop a highly effective surveillance and detection method. Based on established standard operating procedures and previously a described method for spleen swabbing in African Swine Fever (ASF) detection, we aimed to remove major obstacles for high-throughput screening against CSF. Utilizing real-time reverse polymerase chain reaction (RRT-PCR) is the fastest, most sensitive assay in detection of CSF genomic material but requires efficient nucleic acid sequestering and extraction to achieve this. Splenic tissue is a commonly utilized tissue for detection of pathogens within the swine industry but requires an additional tissue homogenization step prior to extraction. Previously, we described spleen swabs outperformance of tissue homogenization for the detection of ASF and aimed to determine its effectiveness against CSF detection to streamline high-throughput screening of swine herds against these pathogens. In this study, we compared tissue homogenates against spleen swabs using 49 frozen spleen samples and 33 fresh spleen samples collected from experimentally inoculated pigs. The results demonstrated spleen swabs were effective against detection of CSFV in comparison to tissue homogenization. Spleen swabs also shown the ability to detect early CSFV infections along with isolate viral particles from samples. Swabbing as a collection method is convenient and significantly less time and labour-intensive procedure compared to tissue homogenization.