Background and Aim: Canine degenerative myelopathy (DM) is an autosomal recessive inherited disease that affects different dog breeds. It has an invariably fatal outcome once the clinical symptoms begin. This study aimed to investigate the population behavior of the mutation superoxide dismutase 1 (SOD1) c.118: G˃A responsible for the high risk of developing DM in two populations of German Shepherd dogs from Uruguay and Paraguay. Materials and Methods: A total of 158 German Shepherd dogs from Uruguay (n = 114) and Paraguay (n = 44) were analyzed. Genomic DNA was extracted from peripheral whole blood. The SOD1 c.118: G˃A mutation was identified by polymerase chain reaction-restriction fragment length polymorphism and subsequently validated using sequencing. Allelic and genotypic frequencies and Hardy–Weinberg equilibrium were calculated for both populations. The rate of clinical progression was evaluated in animals homozygous for the mutation. Results: The frequencies of allele A associated with a higher risk of DM, were 0.15 and 0.23 in Paraguay and Uruguay, respectively. Paraguay’s population was found to be in Hardy–Weinberg equilibrium (p = 1.00), whereas the population of dogs from Uruguay deviated from equilibrium (p = 0.008). When comparing the populations, no significant difference was observed in the distribution of genotypes (p = 0.26). When evaluating the clinical progression rate, all animals aged >10 years showed clinical symptoms compatible with DM. Conclusion: This study demonstrated for the first time the presence of the SOD1:c118 G>A mutation in German Shepherd dogs from Uruguay and Paraguay. The frequency detected in Uruguay was significant. Although the frequency was lower in Paraguay, the allele was present. This demonstrates the need to implement genotyping tests as part of a possible DM control program in both countries studied. Keywords: degenerative myelopathy, genetic disease, German Shepherd dog, superoxide dismutase 1 gene.

Neurobehavioral comorbidities in dogs with idiopathic epilepsy (IE) are increasingly recognized, yet their phenotypic variability and clinical implications remain poorly understood. This study aimed to identify behavioral changes following seizure onset and to explore the feasibility of stratifying patients based on neurobehavioral profiles. Seventy client-owned dogs with IE were enrolled and grouped according to treatment: 29 had drug-resistant epilepsy (DRE), 29 were drug-sensitive (DSE), and 12 remained untreated. Owners completed a modified version of the C-BARQ questionnaire, assessing behaviors before and after seizure onset. Nearly one-third of behavioral items showed significant changes, particularly in attachment and attention-seeking behaviors, separation-related behaviors, eating behavior, and signs of cognitive decline such as reduced trainability and dementia-like signs. Principal component analysis followed by cluster analysis revealed two distinct neurobehavioral profiles: Cognitive and Emotional. The Cognitive cluster was associated with a higher total questionnaire score, poorer seizure control (predominantly DRE), and lower owner-perceived quality of life. In contrast, the Emotional cluster was more frequently observed in dogs with DSE or no treatment and was associated with higher quality of life scores. These findings support the clinical relevance of behavioral stratification in canine epilepsy and underscore the need for individualized, multimodal approaches to improve patient care.

Canine degenerative myelopathy (DM) is a hereditary disease of the spinal cord, characterized by a progressive clinical course, and the death of affected animals. This study aimed to investigate the population distribution of the SODc.118:G˃A mutation responsible for the disease. For this purpose, 131 dogs from both breeds (Pit Bull Terrier, n=64, and Boxer, n=67) were studied. Genomic DNA was extracted from peripheral blood, and the mutation was identified using the PCR-RFLP technique. For each population, the mutant allele frequency, genotypic frequency, and Hardy–Weinberg equilibrium were calculated. The frequency of the DM-related A allele was 0.16 in the Pit Bull Terrier and 0.52 in the Boxer breed. Both populations were in Hardy–Weinberg equilibrium (p > 0.05). The genotypic distribution differed between the two breeds analyzed and also between different populations within each breed (p < 0.05). Simulation of the evolution of the mutant allele frequency under different genetic drift models showed that the variance of the allele frequency increased as the effective population size (Ne) decreased. The frequency detected in the Boxer breed was high, and although it was lower in the Pit Bull Terrier, the allele was still present. These findings support the potential use of genotyping tests for degenerative myelopathy management and provide descriptive population data from dogs of both breeds in Uruguay. A mielopatia degenerativa canina (MD) é uma doença hereditária da medula espinhal, caracterizada por um curso clínico progressivo e pela morte dos animais afetados. Este estudo teve como objetivo investigar a distribuição populacional da mutação SODc.118:G˃A responsável pela doença. Para isso, foram estudados 131 cães de ambas as raças (Pit Bull Terrier, n=64, e Boxer, n=67). O DNA genômico foi extraído do sangue periférico e a mutação foi identificada usando a técnica PCR-RFLP. Para cada população, foram calculadas a frequência do alelo mutante, a frequência genotípica e o equilíbrio de Hardy-Weinberg. A frequência do alelo A relacionado à DM foi de 0,16 na raça Pit Bull Terrier e de 0,52 na raça Boxer. Ambas as populações estavam em equilíbrio de Hardy-Weinberg (p > 0,05). A distribuição genotípica diferiu entre as duas raças analisadas e também entre diferentes populações dentro de cada raça (p < 0,05). A simulação da evolução da frequência do alelo mutante sob diferentes modelos de deriva genética mostrou que a variância da frequência do alelo aumentou à medida que o tamanho efetivo da população (Ne) diminuiu. A frequência detectada na raça Boxer foi alta e, embora fosse menor no Pit Bull Terrier, o alelo ainda estava presente. Esses achados apoiam o uso potencial de testes de genotipagem para o manejo da mielopatia degenerativa e fornecem dados descritivos da população de cães de ambas as raças no Uruguai