Early detection and understanding sources of pseudorabies virus (PRV) are essential to contain spread and prevent economic losses, should the virus arrive in the US. US PRV surveillance now relies on antibody detection. However early response will need to have nucleic acid detection (PCR) to enable detection of the virus right away in clinical tissues sent to veterinary diagnostic labs (VDLs). The National Animal Health Laboratory Network (NAHLN) VDLs currently don’t have the direct ability to detect PRV in submitted clinical tissues with a validated PCR. When this was discovered, the Swine Health Information Center (SHIC) worked with other industry organizations and the National Pork Board (NPB) Swine Health Committee to develop a foundation for action. Availability of a new PCR test, developed with funding from SHIC, to discern classical PRV from the variant high path Chinese strain strengthens the US pork industry’s ability to respond quickly and effectively.
Action on behalf of the pork industry began when a member of the SHIC Monitoring and Analysis Working Group raised concern over the inability of VDLs to run a validated PCR test for PRV. SHIC coordinated with the American Association of Swine Veterinarians, National Pork Board, and National Pork Producers Council to hold a call with NAHLN and the National Veterinary Services Laboratories to initiate a discussion and gather information. They confirmed NAHLN labs don’t currently have a validated PCR test for PRV available to them.
SHIC then shared this information with the NPB Swine Health Committee, which passed a resolution calling for USDA to prepare NAHLN labs for the possibility of PRV infection and outbreak. Citing the need for prompt detection of emerging or newly introduced swine diseases for effective response, the Committee also noted PRV was eradicated from domestic swine in 2004 when vaccination was discontinued, leaving the US herd vulnerable. The virulent strain of PRV in China, different than the version eradicated in the US, emerged in Asia in 2011 where it is causing high morbidity and mortality still today. PRV has also been shown to survive in feed components shipped from China, a potential path for introduction in the US. In their resolution, the Committee said it believes there is a rational urgency for this preparation and calls for providing access to reagents for PRV DNA detection, proficiency testing to assure their reliable use, and validation of their use with swine oral fluids.
In 2016, SHIC funded, at the National Centre for Foreign Animal Disease in Winnipeg, Manitoba, Canada, development of a PCR test able to differentiate between PRV strains – the high path strain circulating in China, the strain eradicated from the US, and the strain still in US feral swine. The newly developed PRV assay is highly sensitive and specific and was able to detect as low as one infectious PRV particle in a sample while discerning between the variant and classical strains.
The assay was validated using nasal swabs, oral swabs, whole blood, serum, and tissues at the Kansas State University Veterinary Diagnostic Laboratory and at the USDA National Veterinary Services Laboratory. Specificity of the assay was further confirmed by testing over 300 clinical samples (serum, tissues, and swabs) collected from Canadian and US herds.
It is a part of SHIC’s mission to protect and enhance the health of the United States swine herd through coordinated global disease monitoring and targeted research investments that minimize the impact of future disease threats. This PCR test was validated using laboratory and clinical samples and will be submitted to NAHLN for consideration by their technical working group for distribution to the labs. While this will be a step-wise process, SHIC proactively contributed to the capability of the industry to address a potential threat through development of the PCR for PRV and taking action on this vulnerability.
In incidents of high or ongoing morbidity or mortality, where an etiology is either not identified or there is a strong suspicion that the identified etiology is not the likely cause of the outbreak, SHIC continues to offer diagnostic fee support after the initial diagnostic workup is completed and paid for by the owner. In these cases, additional support for the fees of further diagnostic workup may help to identify newly introduced or emerging swine diseases. Find a description of the requirements, submission and review process for the Support for Diagnostic Fees Program on the SHIC website.
Funded by America’s pork producers to protect and enhance the health of the US swine herd, the Swine Health Information Center focuses its efforts on prevention, preparedness, and response. As a conduit of information and research, SHIC encourages sharing of its publications and research for the benefit of swine health. Forward, reprint, and quote SHIC material freely. For more information, visit http://www.swinehealth.org or contact Dr. Paul Sundberg at psundberg@swinehealth.org.