Spleen swabs for sensitive and high-throughput detection of African swine fever virus by real-time PCR

Authors: CAFARIELLO, CHRISTOPHER - 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: Viruses
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2024
Publication Date: 8/18/2024
Citation: Cafariello, C., Goonewardene, K., Chung, C.J., Ambagala, A. 2024. Spleen swabs for sensitive and high-throughput detection of African swine fever virus by real-time PCR. Viruses. 16(8):1316. https://doi.org/10.3390/v16081316.
DOI: https://doi.org/10.3390/v16081316

Interpretive Summary: African swine fever (ASF) is a contagious, lethal hemorrhagic fever that affects both wild and domestic swine leading to huge economic losses in the swine industry as well as increased food insecurity. The causative agent, ASF virus (ASFV), is an enveloped, double-stranded DNA arbovirus now endemic to Sub-Saharan Africa, much of Eastern Europe, Asia and the Central American island of Hispaniola. As the virus spreads across the globe, many countries have increased their surveillance efforts for early detec-tion of ASFV genomic DNA.

Technical Abstract: African swine fever (ASF) continues to spread in Africa, Europe, Asia, and the island of Hispaniola increasing the need to develop more streamlined and highly efficient surveillance and diagnostic capabilities. One way to achieve this is by further optimization of already established standard operating procedures to remove bottlenecks for high-throughput screening. Real-time poly-merase chain reaction (RT-PCR) is the most sensitive and specific assay available for the early detection of ASF, but it requires high quality nucleic acid extracted from the samples. Whole blood from live pigs and spleen tissue from dead pigs are the preferred samples for RT-PCR. Whole blood can be used as is in nucleic acid extraction, but spleen tissues require an additional homogenization step. In this study, we compared the homogenates and swabs prepared from 52 spleen samples collected from pigs experimentally inoculated with highly and moderately virulent ASF virus strains. The results show that not only are the spleen swabs more sensitive when executed with a low-cell-count nucleic acid extraction procedure followed by RT-PCR assays, they also increase the ability to isolate ASFV from positive spleen samples. Swabbing is a convenient, simpler, and less time-consuming alternative to tissue homogenization. Hence, we recommend spleen swabs over tissue homogenates for high-throughput detection of ASFV by real-time PCR.