Improving Detection of Canine Distemper Virus in Formalin-Fixed, Paraffin-Embed- ded Tissues: Using in situ Hybridization with Integrated Optical Density to Give a Semi-Quantitative Assessment

Enhanced canine distemper virus (CDV) nucleoprotein RNA was applied to paraffinembedded tissues from dogs with spontaneous CDV infections. In addition to proteinase K, the tissues were autoclaved in various solutions as a pre-treatment (Trilogy, TBS S3006, H-3301, and S1700) and then compared. The in situ hybridization (ISH) intensity was assessed using integrated optical density (IOD) and tissue morphology examinations. A combination of proteinase K digestion and autoclaving in a Trilogy solution resulted in optimal ISH signal enhancement of CDV RNA. This modified technique may be useful in retrospective viral studies.