Study advances CWD detection in preserved lymph node samples

A new study suggests veterinary and wildlife disease teams may be able to get more value from the samples they already have. In Journal of Veterinary Diagnostic Investigation, researchers from the University of Pennsylvania describe an optimized RT-QuIC method for detecting chronic wasting disease prions in preserved retropharyngeal lymph nodes, including formalin-fixed and formalin-fixed paraffin-embedded tissue, with performance approaching that of fresh or frozen samples. In practical terms, it opens the door to using “old nodes” for surveillance questions that previously depended on stricter storage conditions. (journals.sagepub.com)

That matters because current official CWD testing still runs through a split workflow. USDA APHIS says the two approved postmortem tissue types are the medial retropharyngeal lymph nodes and the obex, and the two approved diagnostic tests are immunohistochemistry and ELISA. Those methods are useful, but they rely on different preservation pathways, with ELISA requiring fresh or frozen tissue and IHC relying on formalin-fixed material interpreted by a veterinary pathologist. The new paper is aimed squarely at that operational gap. (aphis.usda.gov)

The Penn team evaluated 201 retropharyngeal lymph nodes from white-tailed deer in Pennsylvania, including 100 CWD-positive and 101 CWD-negative samples previously classified by ELISA and/or IHC at the Pennsylvania Animal Diagnostic Laboratory. The deer came from hunter-harvested animals, clinical suspects, and vehicle-struck deer. Using commercially available reagents and standardized assay conditions, the researchers found that formalin-fixed samples reached up to 96% sensitivity and 100% specificity, while formalin-fixed paraffin-embedded samples reached up to 98% sensitivity and 99% specificity. They also reported no meaningful effect of prion protein genotype on overall assay performance. (journals.sagepub.com)

One notable detail is what the protocol leaves out. The authors say their approach differs from prior FFPE workflows because it does not require xylene, a hazardous solvent commonly used in deparaffinization. That could make the method more attractive for routine laboratory environments, especially if agencies want preserved-tissue testing that is easier to standardize and less burdensome from a safety and waste-disposal standpoint. The study also positions preserved-sample RT-QuIC as a tool for retrospective prevalence work and for reconstructing historical spread from archived tissues. (journals.sagepub.com)

There wasn’t much direct outside commentary on this specific paper in public view, but the broader field is moving in the same direction. A recent inter-laboratory comparison published in Journal of Veterinary Diagnostic Investigation supported RT-QuIC’s reliability for CWD detection in retropharyngeal lymph nodes across multiple U.S. labs, and APHIS recently highlighted the Penn preserved-tissue project in its 2024 wild cervid cooperative agreement summaries. Penn’s Wildlife Futures Program also frames improved diagnostic capability as part of its wildlife surveillance mission with the Pennsylvania Game Commission. Taken together, that suggests this isn’t a one-off technical exercise, but part of a larger push to make prion surveillance more flexible and scalable. (pubmed.ncbi.nlm.nih.gov)

Why it matters: For veterinary professionals, especially those in diagnostic labs, state wildlife health programs, and regulatory surveillance, the study points to a practical way to expand testing options without waiting for ideal sample handling. Preserved lymph nodes are often what’s available in the real world, particularly in field surveillance, retrospective investigations, or cases with autolysis and cold-chain limitations. If RT-QuIC on fixed tissue continues to perform this well, it could help programs recover more actionable information from archived submissions, improve follow-up on discordant ELISA and IHC findings, and support more complete disease mapping. (journals.sagepub.com)

The timing also matters beyond lab workflow. University of Calgary researchers reported in May 2026 that CWD prions could be present and transmissible even in asymptomatic animals in controlled cross-species experiments involving nonhuman primates, while emphasizing that there has still been no confirmed human case of CWD. That doesn’t change immediate public health guidance on its own, but it does reinforce the surveillance argument: better detection, earlier detection, and better use of available tissues all matter when the disease is geographically expanding and biologically hard to contain. (eurekalert.org)

What to watch: The next question is whether preserved-tissue RT-QuIC moves from promising research method to broader validation in APHIS-approved laboratory networks, and whether agencies begin using it for retrospective surveillance, discrepancy resolution, or regions where fresh-sample collection is less practical. (aphis.usda.gov)