Frequency of superoxide dismutase 1 c.118: G>A mutation associated with canine degenerative myelopathy in German Shepherd dogs from Uruguay and Paraguay

Abstract

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.