Real-Time Quaking-Induced Conversion Assay Applied to the Italian Chronic Wasting Disease Monitoring Plan: Comparison...

Area of Science:

• Veterinary Medicine
• Neuroscience
• Prion Diseases

Background:

• Chronic Wasting Disease (CWD) is a transmissible prion disease affecting cervids, with European detection raising surveillance concerns.
• Existing diagnostic methods for bovine and small ruminant surveillance can detect European CWD strains, but their sensitivity in wild cervids requires further evaluation.
• The contagious nature of some CWD strains necessitates robust diagnostic tools for effective surveillance and control.

Purpose of the Study:

• To compare the diagnostic performance of rapid screening tests with the highly sensitive RT-QuIC assay for CWD detection in Italian wild red deer.
• To investigate the presence of CWD prion seeding activity in brainstems and lymph nodes of red deer sampled through the Italian CWD surveillance system.
• To assess the utility of RT-QuIC as a complementary tool for enhancing early detection and diagnostic accuracy in CWD surveillance.

Main Methods:

• A retrospective study analyzed 100 brainstem and medial retropharyngeal lymph node samples from Italian wild red deer.
• Samples were initially tested using the HerdChek BSE-Scrapie Antigen Test, followed by RT-QuIC analysis.
• Positive RT-QuIC results were reconfirmed using different prion protein substrates and batches, alongside alternative diagnostic methods (TeSeE SAP Combi, Western blot, immunohistochemistry).

Main Results:

• The rapid screening test yielded negative results for all tested brainstem and lymph node samples.
• RT-QuIC detected prion seeding activity in only one red deer brainstem sample; all lymph node samples, including from the positive case, were negative.
• The positive brainstem sample consistently showed seeding activity across multiple RT-QuIC analyses and substrates, even at high dilutions, while other diagnostic tests were negative.

Conclusions:

• RT-QuIC demonstrated superior sensitivity in detecting low levels of PrPSc seeding activity compared to classical diagnostic methods in this study.
• The findings suggest RT-QuIC's potential as a valuable complementary tool for strengthening CWD surveillance and early detection in wild cervid populations.
• Further bioassays are recommended to determine the infectivity and definitive disease status of the RT-QuIC positive red deer case.