A pathological study of the salivary glands of rabid dogs in the Philippines

Abstract

Rabies is a zoonotic disease caused by the rabies virus. While the salivary glands are important as exit and propagation sites for the rabies virus, the mechanisms of rabies excretion remain unclear. Here, we investigated the histopathology of the salivary glands of rabid dogs and analyzed the mechanism of excretion into the oral cavity. Mandibular and parotid glands of 22 rabid dogs and three control dogs were used. Mild to moderate non-suppurative sialadenitis was observed in the mandibular glands of 19 of the 22 dogs, characterized by loss of acinar epithelium and infiltration by lymphoplasmacytic cells. Viral antigens were detected in the mucous acinar epithelium, ganglion neurons and myoepithelium. Acinar epithelium and lymphocytes were positive for anti-caspase-3 antibodies and TUNEL staining. In contrast, no notable findings were observed in the ductal epithelial cells and serous demilune. In the parotid gland, the acinar cells, myoepithelium and ductal epithelium all tested negative. These findings confirmed the path through which the rabies virus descends along the facial nerve after proliferation in the brain to reach the ganglion neurons of the mandibular gland, subsequently traveling to the acinar epithelium via the salivary gland myoepithelium. Furthermore, the observation that nerve endings passing through the myoepithelium were absent from the ductal system suggested that viral proliferation and cytotoxicity could not occur there, ensuring that secretions containing the virus are efficiently excreted into the oral cavity.

Characterization of a 2016 Clinical Isolate of Zika Virus in Non-human Primates

“…Unexpectedly, our results suggest that the parotid gland, besides intestinal tracts and spleen, represents potential major target tissues of ZIKV. The parotid gland serves as the viral replication site and exit portal for the highly neurotropic rabies virus into saliva (Boonsriroj et al, 2016). Although the biological importance of ZIKV replication in parotid gland remains unknown, a probable connection to the persistent excretion of viral RNA in saliva is highly suspected.…”

Statistical analysis of the usefulness of follicle-sinus complexes as a novel diagnostic material for canine rabies

“…The sections were stained with hematoxylin and eosin (HE), and serial sections were subjected to IHC for detecting rabies viral antigen. For the detection of rabies viral antigen in brain tissues and FSCs, sections were stained using the polymer method with rabbit polyclonal rabies anti-phosphoprotein antibody (anti-P) as previously described [4, 12, 14]. Briefly, tissue sections were treated with 0.25% trypsin at RT for 30 min for anti-P antibody.…”

Follicle sinus complexes (FSCs) in muzzle skin as postmortem diagnostic material of rabid dogs

“…For detecting the rabies virus antigen in tissues, sections were stained using the polymer method with rabbit polyclonal rabies anti-phosphoprotein antibody (anti-P) as described previously [4, 23]. To identify cell types that express the virus antigen, double staining of a single tissue section was performed using an immunofluorescent antibody.…”