Rhinitis is defined as an inflammatory disease of the nasal membranes characterized by persistent nasal discharge.
Chronic rhinitis is usually reserved for cases that are refractory to treatment, regardless of cause. Sinusitis can be a sequela in chronic rhinitis.
Rhinitis invariably results in disturbances to nasal vascular control, leading to mucosal congestion may be caused by dilatation of venous sinusoids and/or collecting veins and constriction of outflow veins. The nasal vascular bed is under sympathetic nervous controls. Sympathetic nerve stimulation causes constriction of the resistance vessels via an α-adrenergic and β-adrenoceptors mechanisms and constriction of capacitance vessels occurs via α-adrenergic as well as non-adrenergic and non-cholinergic mechanisms. Toxins such as tetrodotoxin have been shown to temporarily block these actions.
Various forms of nasal discharge have been described associated with this condition, including serous (clear fluid in early stages of infection), catarrhal (less clear), mucopurulent, purulent, fibrinopurulent and fibrinous. The latter forms of discharge are observed in chronic rhinitis associated commonly with chronic foreign bodies, mycotic rhinitis and nasal tumors.
Fibronecrotic and ulcerative rhinitis are manifestations of very severe damage to the nasal mucosa.
A breed predisposition has been reported in dolicocephalic (long-skull) dogs - e.g. Greyhound, Collie, particularly with nasal tumors, possibly due to greater mucous membrane surface area increasing exposure of the nasal mucosa to pollutants, irritants and allergens.
Brachycephalic breeds, which have fewer turbinates and filter less air, are more predisposed to pulmonary 'pollution-induced' tumors.
In dogs, reported causes of rhinitis include, in order of frequency:
- Traumatic rhinitis - traumatic fractures of maxillary and nasal bones due to motor vehicle accidents or dog bites
- Nasal tumors - nasal adenocarcinoma, carcinoma, undifferentiated sarcoma, fibrosarcoma, chondrosarcoma, squamous cell carcinoma
- Lymphocytic-plasmacytic rhinitis - immune-mediated disease
- Mycotic rhinitis - often associated with chronic nasal foreign bodies
- - Aspergillus fumigatus
- - Penicillium spp
- - Cryptococcus spp - predisposition in the Doberman and Great Dane
- - Pseudallescheria boydii
- - Rhinosporidium seeberi
- - Blastomyces dermatitidis
- - nonpathogenic mycotic contaminants - Alternaria spp, Mucorale spp
- Nasal foreign bodies
- Dental disease - periodontitis and carnassial tooth root abscess
- Nasal parasites - Pneumonyssoides spp, Capillaria aerophila, Linguatula serrata
- Stenotic nares, oro-nasal fistula, nasal polyposis (polyps)
- Viral rhinitis
- - catarrhal rhinitis associated with canine distemper
- - canine herpesvirus with secondary bacterial infections, reported in the Irish Wolfhound
- - Canine parainfluenza 2
- Secondary bacterial rhinitis - common
- Primary bacterial rhinitis - rare in dogs, usually chronic
- - Bordetella bronchiseptica (prior history of kennel cough)
- - Pasteurella multocida
- - Streptococcus zooepidemicus (in dogs living near horses)
- Granulomatous rhinitis (Bartonella berkhoffii)
- Cleft palate-associated bacterial rhinitis
- Allergic rhinitis - common in humans, extremely rare in dogs
- Situs inversus totalis
Clinically affected dogs typically present with reverse sneezing, nasal discharge, epistaxis and stertor when breathing.
Diagnosis can be challenging due to the anatomy of the nasal cavity making it difficult to access, requiring use of ancillary diagnostic tests. A presumptive diagnosis can based on presenting clinical signs and endoscopic and radiographic imaging studies as well as computed tomography, magnetic resonance imaging, and culturing for bacteria and fungi and PCR assays for viruses.
Marked radiographic lesions in dogs with rhinitis are more commonly associated with neoplastic or fungal diseases.
A definitive diagnosis requires histological examination of tissue biopsies.
With nasal parasites, nasal flushing may be required to assist identification.
- Vet Specialists
- University of Georgia
- Dog Health Guide
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