Olfaction evaluation in dogs with sudden acquired retinal degeneration syndrome

• Published in: Veterinary ophthalmology Vol. 27; no. 2; pp. 127 - 138
• Main Authors: Abrams, Kenneth L., Ward, Daniel A., Sabiniewicz, Agnieszka, Hummel, Thomas
• Format: Journal Article
• Language: English
• Published: England 01.03.2024
• Subjects: Acute Disease; Animals; blindness; Blindness - etiology; Blindness - veterinary; body weight; cell membranes; cyclic nucleotides; Dog Diseases - diagnosis; Dogs; dysosmia; electroretinogram; endocrinopathy; Eugenol; G-proteins; Humans; hyposmia; odor compounds; olfactory disorders; olfactory receptors; olfactory threshold; ophthalmology; Receptors, G-Protein-Coupled; retinal degeneration; Retinal Degeneration - diagnosis; Retinal Degeneration - veterinary; Smell; steroidogenesis; Syndrome; electroretinogram; retinal degeneration; endocrinopathy; olfactory threshold; dysosmia; hyposmia
• DOI: 10.1111/vop.13121
• ISSN: 1463-5216; 1463-5224

Purpose To evaluate olfaction in dogs with sudden acquired retinal degeneration syndrome (SARDS) compared with sighted dogs and blind dogs without SARDS as control groups. Animals Studied Forty client‐owned dogs. Procedure Olfactory threshold testing was performed on three groups: SARDS, sighted, and blind/non‐SARDS using eugenol as the test odorant. The olfactory threshold was determined when subjects indicated the detection of a specific eugenol concentration with behavioral responses. Olfactory threshold, age, body weight, and environmental room factors were evaluated. Results Sixteen dogs with SARDS, 12 sighted dogs, and 12 blind/non‐SARDS dogs demonstrated mean olfactory threshold pen numbers of 2.8 (SD = 1.4), 13.8 (SD = 1.4), and 13.4 (SD = 1.1), respectively, which correspond to actual mean concentrations of 0.017 g/mL, 1.7 × 10−13 g/mL and 4.26 × 10−13 g/mL, respectively. Dogs with SARDS had significantly poorer olfactory threshold scores compared with the two control groups (p < .001), with no difference between the control groups (p = .5). Age, weight, and room environment did not differ between the three groups. Conclusions Dogs with SARDS have severely decreased olfaction capabilities compared with sighted dogs and blind/non‐SARDS dogs. This finding supports the suspicion that SARDS is a systemic disease causing blindness, endocrinopathy, and hyposmia. Since the molecular pathways are similar in photoreceptors, olfactory receptors, and steroidogenesis with all using G‐protein coupled receptors in the cell membrane, the cause of SARDS may exist at the G‐protein associated interactions with intracellular cyclic nucleotides. Further investigations into G‐protein coupled receptors pathway and canine olfactory receptor genes in SARDS patients may be valuable in revealing the cause of SARDS.