Pathological Study on Trigeminal Ganglionitis Among Rabid Dogs in the Philippines

Area of Science:

• Veterinary Pathology
• Neurovirology
• Immunohistochemistry

Background:

• The trigeminal nerve serves as a primary entry point for the rabies virus into the central nervous system.
• Trigeminal neuritis, an inflammation of the trigeminal nerve, is linked to specific clinical manifestations of rabies.
• Understanding trigeminal ganglion pathology is crucial for comprehending rabies pathogenesis in dogs.

Purpose of the Study:

• To investigate the histopathological changes in the trigeminal ganglia of rabid dogs.
• To classify the severity of trigeminal ganglionitis and identify associated cellular responses.
• To correlate viral antigen distribution with pathological findings and immune cell infiltration.

Main Methods:

• Histopathological examination and grading (mild, moderate, severe) of 92 rabid dog trigeminal ganglia.
• Immunohistochemistry using antibodies for lymphocytes (CD3, CD20), glial cells (GFAP), macrophages (Iba-1, HLA-DR), neurons (NF), and Schwann cells (S-100).
• Double-immunofluorescence staining to characterize neuronophagia and Nageotte nodules.

Main Results:

• Trigeminal ganglionitis was graded as mild (13.0%), moderate (56.5%), and severe (30.4%).
• Moderate and severe cases exhibited degenerative necrosis of ganglion cells and axons, replaced by inflammatory infiltrates.
• Viral antigens were abundant in mild cases but decreased in severe cases, while immune cell markers (CD3, CD20, GFAP, Iba-1) and HLA-DR-positive cells in inflammatory lesions increased with severity.

Conclusions:

• The rabies virus invades the trigeminal ganglion, leading to neuropathological alterations that contribute to clinical signs in dogs.
• The progression of trigeminal ganglionitis involves significant inflammatory cell infiltration and neuronal damage.
• Immune responses, characterized by specific cell types, correlate with the severity of rabies-induced trigeminal nerve pathology.