Affected dogs manifest neurological signs of progressive motor dysfunction from 5–6 months of age and die at 12–18 months after a clearly defined clinical course, which is associated with progressive accumulation of GM1 ganglioside and the subsequent neuronal damage in the central nervous system.
The causative mutation has been identified as a deletion of the cytosine in exon 15 at nucleotide position 1647 in the putative coding region (c.1647delC) of the canine GLB1 gene, thereby enabling molecular diagnosis and/or genotyping with polymerase chain reaction (PCR)-based DNA tests. GM1 gangliosidosis in Shiba Inu dogs was first reported in 2000. GM1 gangliosidosis, a lysosomal storage disease that affects the brain and multiple systemic organs, is caused by an autosomal recessively inherited deficiency in acid β-galactosidase, which is encoded by the GLB1 gene. Therefore, for effective control and prevention of this disease, it is necessary to examine as many breeding dogs as possible from all regions of Japan, especially from kennels located in areas with high prevalence and carrier frequency. This observation suggests that carrier dogs are distributed all over Japan however, kennels in the Kinki district may face an increased risk of GM1 gangliosidosis. Our results showed that the current carrier frequency for GM1 gangliosidosis is on the average 1.02% in Japan and rather high in the Kinki district, which may be related to the high prevalence observed over the past 16 years in this region. Pedigree analysis demonstrated that all the affected dogs and carriers with the pedigree information have a close blood relationship. Of the 23 affected dogs, 12 dogs (52.2%) were from the Kinki district. The retrospective survey revealed 23 affected dogs, among which, 19 dogs (82.6%) were born within the last 7 years. Of the 590 dogs examined, 6 dogs (1.02%, 6/590) were carriers: 3 dogs (2.27%, 3/132) from the Kinki district and the other 3 dogs from the Hokkaido, Kanto, and Shikoku districts. The number and native district of affected dogs identified in 16 years from 1997 to June 2013 were also surveyed retrospectively. The survey was carried out among 590 clinically unaffected Shiba Inu dogs from the 8 districts of Japan, and a genotyping test was used to determine nation-wide and regional carrier frequencies. This molecular epidemiological survey was performed to formulate an effective strategy for the control and prevention of this disease. Therefore, it is important to control and reduce the prevalence of GM1 gangliosidosis for maintaining the quality of this breed and to ensure supply of healthy dogs to prospective breeders and owners. Canine GM1 gangliosidosis is a fatal disease in the Shiba Inu breed, which is one of the most popular traditional breeds in Japan and is maintained as a standard breed in many countries.
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