Abstract
Canine cognitive dysfunction syndrome (CCDS) is a progressive neurodegenerative disorder in senior dogs that is mainly associated with decreased ability to learn and respond to stimuli. It is commonly under-diagnosed because behavioral changes are often attributed to the natural process of aging. In the present study, we used for the first time a comprehensive approach enabling early diagnosis of canine patients with mild cognitive disorders (MiCI). We included CAnine DEmentia Scale (CADES) questionnaires, biochemical parameters, and biomarkers in blood serum, and correlated them with post-mortem histopathological changes. The CADES questionnaires enabled us to identify MiCI dogs developing changes mainly in domains corresponding to social interaction and spatial orientation, which seems to be crucial for delineating early cognitive disorders. Biochemical analyses in these dogs showed slightly elevated liver enzyme parameters (AST and ALT) and significantly decreased sodium and chloride levels in blood serum. Furthermore, we describe for the first time a significant increase of neurofilament light chain (NFL) in blood serum of MiCI dogs, compared to normal aging seniors and young controls, but no changes in TAU protein and amyloid-β (Aβ42) peptide levels. In canine brains with cognitive impairment, amyloid plaques of mainly diffuse and dense types were detected. Furthermore, activated microglia with amoeboid body and dystrophic processes occurred, in some cases with spheroidal and bulbous swellings. On the other hand, no TAU pathology or neurofibrillary tangles were detected. These results suggest that a combination of CADES questionnaire mainly with CNS injury biomarker (NFL) and with biochemical parameters (ALT, AST, Na, and Cl) in blood serum may predict CCDS in senior dogs.
Highlights
The population of aging dogs is growing significantly, similar to the increase in senior numbers in the human population
Senior Dogs After blood testing, we found that the patients did not show any remarkable abnormalities in complete blood count (CBC)
The blood biochemistry results revealed some changed values, and we noticed significant elevation of alanine aminotransferase (ALT), gamma glutamyl transferase (GMT, known as GGT), and total protein (TP) in mild cognitive disorders (MiCI) dogs when compared to young control dogs (YC) and normal aging (NA) group, the levels of these parameters were still in the physiological range
Summary
The population of aging dogs is growing significantly, similar to the increase in senior numbers in the human population. There is no doubt that prolonged life expectancy is associated with different age-related systemic diseases, which are Diagnostic Tools for Canine Cognitive Impairment treated at veterinary clinics as per standard treatment procedure (symptomatology-based and anti-inflammatory treatment) [2]. Neurodegenerative features in elderly dogs are manifested by cognitive deficits that could be paralleled with human neurodegenerative symptoms, Alzheimer’s disease (AD) [3]. To understand the similarities and differences between canine and human cognitive impairment, there is a need to include approaches supported by reliable cognitive tests, biomarkers, and pathological changes associated with neurodegeneration. Large-breed dogs are considered to be seniors at 6–7 years of age, whereas in small breeds, it is not until they reach 10 years [1]
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