Relationship between Uveal Inflammation and Viral Detection in 30 Cats with Feline Infectious Peritonitis

Area of Science:

• Veterinary Ophthalmology
• Infectious Diseases
• Molecular Diagnostics

Background:

• Feline infectious peritonitis (FIP) is a significant cause of uveitis in cats.
• Current diagnostic methods for FIP often rely on postmortem examination.
• The influence of inflammatory patterns on viral detection in FIP uveitis is not well understood.

Purpose of the Study:

• To investigate the relationship between histologic inflammatory patterns and viral detection in feline infectious peritonitis (FIP)-induced uveitis.
• To localize FIP viral antigen and RNA within ocular tissues.
• To assess if macrophage-rich or plasma cell-rich inflammation impacts diagnostic yield.

Main Methods:

• Evaluation of 30 cats diagnosed with FIP-induced uveitis.
• Histologic examination to characterize inflammatory patterns (pyogranulomatous vs. plasmacytic).
• Detection of FIP viral antigen and/or RNA using immunohistochemistry, in situ hybridization, and RT-qPCR.

Main Results:

• FIP viral antigen and/or RNA were detected in 11 out of 30 cases, primarily within uveal macrophages.
• Eight of these positive cases were confirmed by RT-qPCR.
• A significant negative correlation was found between plasmacytic inflammation and the likelihood of viral detection.

Conclusions:

• The predominance of plasmacytic inflammation in FIP uveitis cases is associated with a lower probability of detecting FIP virus via antigen or RNA.
• This finding suggests that diagnostic strategies may need to account for inflammatory patterns in FIP cases.
• Further research may explore alternative diagnostic markers or methods for FIP uveitis with predominantly plasmacytic inflammation.